WO2025172331A1

WO2025172331A1 - Brain stimulation

Info

Publication number: WO2025172331A1
Application number: PCT/EP2025/053668
Authority: WO
Inventors: Peter Forsell
Original assignee: Implantica Patent Ltd
Current assignee: Implantica Patent Ltd
Priority date: 2024-02-16
Filing date: 2025-02-12
Publication date: 2025-08-21
Anticipated expiration: 2026-08-16

Abstract

A therapeutic brain stimulation system comprises several stimulation signal emitters (I) generating stimulation signals from different positions towards a common target region in a patient's brain. A kit and a method are provided for mounting the system on a patient's head. The kit comprises a support structure (6) to be temporarily mounted on the patient's head as an aid for fixing the signal emitters (I) in the cranial bone structure. The support structure (6) has support legs (13a - 13c) for temporarily fixing the support structure (B) on the patient's head and guide holes (7) for aiding in guiding an orientation pin (0), a driver (3), a drill guide (B), a drill (D), a thread cutter (T) and the signal emitters (I) towards and against the patient's head.

Description

BRAIN STIMULATION Background of the invention _{[001] The present invention relates to the stimulation of regions of a patient’s brain for therapeutic purposes and, in particular,} to a kit for a therapeutic brain stimulation system, a support structure thereof, and a method of mounting such system on the patient’s head. _{[002] It is known to stimulate the human brain electrically by advancing electrodes into a specific brain region to be stimulated.} In micro stimulation therapy, extremely fine glass pipettes are used. These methods are highly invasive. _{[003] Furthermore, a non-invasive therapeutic brain stimulation method is known which is called “transcranial magnetic} stimulation” (TMS). In this method, a circular or figure-eight type coil is used to create an electromagnetic field inside the brain, thereby inducing a current in the brain’s neurons, in particular in those neurons having the axons parallel to the electric field. The position and orientation of the coil as well as the duration and intensity of stimulation can be varied. In so-called repetitive TMS (rTMS) a sequence of stimulus pulses is provided, the pulse length, the time between the pulses, the duration of the stimulation sequence and the number of stimulation sequences being varied to achieve different therapeutic results. A plurality of coils can be used to stimulate different brain regions to achieve a combinatory therapeutic effect. However, as the distance to the coil increases linearly, the intensity of the electromagnetic field decreases exponentially. Also, the heat dissipation close to the patient’s head can cause problems. The application of TMS and rTMS is thus _{limited to the outer areas of the brain, i.e. to the cerebral cortex, in proximity to the parietal and occipital cranial bone structure.} _{[004] It is further known to subject the human brain to ultrasonic waves. Here, the ultrasonic waves are applied to destroy brain} tumours by non-invasive surgery. A complex network of a great number of small ultrasound emitters are applied to the patient’s head from the outside thereof and directed towards a very limited target area of e.g.1 mm in size within the patient’s brain. The little size and equal distribution prevents regions of the brain outside the target area from heating up above a critical cell temperature. _{[005] Alternatively, the target can be irradiated stereo-tactically (DE 196 14 643 A1). In this method, the patient and/or an} irradiation source are rotated relative to a target centre within the patient’s brain. This way, the target is hit from different sides over time, _{the radiation ultimately leading to the destruction of the tumour cells.} _{[006] WO 2009/132855 A1 discloses a system and method to stimulate limited regions inside a patient’s brain for therapeutic} _{purposes without the need to penetrate into the patient’s brain, which permits brain activity to be stimulated in one or more limited brain} _{regions of e.g. depressive or epileptic patients. The system comprises a number of stimulation signal emitters which are directed from} different positions outside the patient‘s brain onto a common target region within the patient’s brain so as to provide an accumulated _{stimulating effect on that target region. The intensity 1of the stimulation signal of each 1of the emitters is adjusted so low that it does not} _{cause stimulation of a brain region other than the target region where the stimulating effects of all signal emitters are accumulated. The} _{intensity of the signals emitted by the signal emitters is adjustable such that the accumulated stimulating signals in the target region do not} negatively affect the anatomic structure of neuronal brain cells. Such arrangement allows non-invasive stimulation of specific target regions deep inside the patient’s brain. _{[007] In a first embodiment, the signal emitters are mounted on a common support structure at positions on opposite sides of the patient’s} _{head. The support structure provides sufficient elasticity and stiffness to hold the signal emitters in contact with the patient’s cranial bone.} _{However, there is a likelihood of a signal emitter being unintentionally displaced.} _{[008] In a second embodiment, the signal emitters are arranged on the support structure with a distance to the patient’s head and pivotal} about one or two pivoting axes so that their stimulating signals can be emitted from different positions of the support structure towards the common target region. The mounting of the support structure on the patient’s cranium can be permanent and, thus, relatively secure against _{unintentional displacement in that support legs of the support structure are fixedly mounted in cranial bone structure. However, the increased} distance of the signal emitters from the brain as compared to the first embodiment may be disadvantageous. _{[009] In a third embodiment, the signal emitters are permanently screwed into the patient’s cranial bone structure and implanted} subcutaneously. Their position relative to each other and relative to the patient’s brain is thereby permanently defined. Here, the signal _{emitters are contained in a mounting tube with screw threads provided on an outer surface thereof, and the orientation of the signal emitter} inside the mounting tube is adjustable. Once the signal emitters have been accurately adjusted to the target region so as to allow for stimulation of a particular brain region whenever need arises, such as in the case of epileptic patients, the patient can continue to live with the signal emitters fixedly mounted in the head. This allows the patient to live a relatively normal life. _{[010] WO 2009/132855 A1 suggests different types of signal emitters. For instance, a current may be induced in or near neuronal brain} cells in the patient’s brain in order to stimulate the brain. The induced electrical current may cause a chemical reaction to occur in the _{neuronal brain cells, thereby achieving the therapeutic effect. With other stimulation signals, such chemical reaction in the neuronal brain} cells can be provoked either directly or in a different manner indirectly. The stimulation signals may likewise comprise electromagnetic _{radiation, sound waves, current inducing electromagnetic fields and others. Where electromagnetic radiation is employed, this may include} _{light waves with a wavelength in the range of between infrared and ultraviolet or waves with a wavelength longer than infrared light. It is also} _{possible to use electromagnetic radiation comprising microwaves. Preferably, the electromagnetic radiation signals are emitted in the form} of beams which are directed to cross each other in the target region. Focusing devices may help to concentrate the beam onto the target _{region. Where sound waves are used as the stimulation signal, these are preferably ultrasonic sound waves. In this case it is advantageous} when sound wave signal emitters are arranged at an equal distance from the target region or at least at a phase-correct distance relative to the target region. Where the signal emitters are adapted to emit the individual stimulation signals in the form of electromagnetic fields, it _{is advantageous when the electromagnet fields overlap each other in a manner such that the current directions of the currents induced in} the target region are co-linear. _{[011] Furthermore, WO 2009/132855 A1 discloses an adjustment device for adjusting the position of the signal emitters relative} _{to the target region in the patient’s brain which includes position adjusting motor mechanically connected to the signal emitter. An external} _{control unit controls the adjustment device to adjust the position of the signal emitter relative to the target region. The position controller is} coordinated with a 3-D brain imaging system by means of an appropriately programmed processing system. The position adjusting motor _{further includes a distance adjusting motor for adjusting the distance between the signal emitter and the target region and an angle adjusting} _{motor for adjusting the orientation of the signal emitters relative to the target region. The control unit further controls the timing, sequence,} _{intensity, frequency and duration of the stimulating signals emitted by the signal emitters, and it may be operable by the patient, including} _{remote control. For further details, reference is made to the specification of WO 2009/132855 A1.} _{[012] Starting out from the disclosure of WO 2009/132855 A1, in particular the above-mentioned third embodiment of WO} 2009/132855 A1, the present invention is concerned with a secure and accurate mounting of the signal emitters in the patient’s cranial bone structure. Summary of the invention _{[013] Accordingly, a kit for a therapeutic brain stimulation system is provided, in particular a support structure thereof which is} _{configured to be temporarily mounted on the patient’s head as an aid for fixing the signal emitters in the cranial bone structure. The} _{therapeutic brain stimulation system is particularly intended for wireless stimulation of neuronal cells in a patient’s brain by means of} _{stimulating signals emitted from different positions towards a common target region in a patient’s brain so as to provide an accumulated} stimulating effect on said target region, same as in WO 2009/132855 A1. For this purpose, the kit includes, in addition to the support structure, two or more stimulation signal emitters which are adapted to be fixed in the cranial bone structure and generate the stimulating signals. The _{shape of the support structure is generally comparable to the support structure known from WO 2009/132855 A1, but the purpose is different} in that such support structure is not supposed to hold the signal emitters relative to the target region but merely to assist in the process of _{fixing the signal emitters in the cranial bone structure. Thereafter, the support structure is removed and, preferably, the skin above the} implanted signal emitters is closed in a conventional way, e.g. by suturing. _{[014] Special aspects of the support structure relate to support legs for temporarily fixing the support structure on the patient’s} head, markers on the support structure for determining the exact position of the support structure in space, and guide holes which are configured for aiding in guiding certain tools of the kit towards and against the patient’s head, namely an orientation pin, a driver, a drill guide, _{a drill, a thread cutter, and, preferably, further for guiding the signal emitters towards and against the patient’s head.} _{[015] As regards the support legs, at least three support legs are provided so as to extend from the support structure towards} and against the patient’s head. The three support legs are needed to define a fixed position of the support structure relative to the patient’s head. More than three support legs may be provided in order to further strengthen the connection between the patient’s head and the support structure. _{[016] Preferably, the support structure is configured to span around a part of the patient’s head. For instance, the support} structure may comprise a curved beam which embraces an angle of curvature of at least about 180°. Two of the at least three support legs _{may be provided at opposite end regions of the support structure, whereas one of the at least three support legs may be provided on the} _{support structure between those two support legs, preferably centrally between those two support legs, in order to achieve an optimum grip} on the patient’s head. The three support legs each have a longitudinal extension with a longitudinal axis, of which preferably at least the longitudinal axes of those two support legs lie in a common plane. In particular, when the support structure has the shape of a beam, the two support legs arranged at the opposite end regions of the support structure may be urged against the patient’s head at respective first and second fixation points, then the support structure may be pivoted about an axis defined by the first and second fixation points, before the third support leg is also urged against the patient’s head at a third fixation point. This way, the support structure may be pivoted into a predetermined position relative to the desired target region, preferably a position in which the desired target region of the patient’s brain lies within a plane defined by the first, second and third fixation points. This pivoting step has the particular advantage that, when the signal _{emitters are mounted in the patient’s cranium using the support structure after it has been pivoted into the predetermined position, as will} _{be described in more detail below, the signal emitters all lie in the same plane as the target region and, therefore, need only be adjusted} (pivoted) in one direction in order to aim at the target region. _{[017] At a later point in the procedure, it may turn out that the target region is not exactly in the plane defined by the three fixation} points. In this case, a fine adjustment may become necessary. For that purpose, the third support leg which is arranged between the two _{other support legs is moveable relative to the support structure in a direction which is perpendicular to a longitudinal axis of the support leg.} In particular, the central support leg may be slideably guided on the support structure in said direction. This way, when the support structure is fixed to the patient’s head by means of the three support legs and the central support leg is moved relative to the support structure in the direction perpendicular to the central support leg’s longitudinal axis, the support structure effectively moves relative to the patient’s head into a position which may serve better the purpose of mounting the signal emitters to the patient’s head with the aid of the support structure. _{[018] In a preferred embodiment, the support legs may each comprise an external screw thread and the support structure may} comprise at least three screw holes configured to mate with the external screw thread of the support legs. This allows for screwing the support legs through the screw holes of the support structure against the patient’s head. Upon screwing the support legs further towards _{the patient’s head, a force builds up between the patient’s head and the support structure by which the support structure is clamped on the} patient’s head. Preferably, the patient’s skin is cut and opened beforehand so as to expose the patient’s cranium at respective positions prior to fixing the support structure on the patient’s head by means of the support legs. _{[019] Advantageously, the support legs may each have a pointed tip end facing towards the patient’s head so as to press into the} cranial bone. _{[020] As regards the markers, of which there are at least three provided on the support structure, they serve to determine the} position of the support structure in space. In combination with 3-D imaging of the patient’s brain, such as by CT or MRI, the proper position of the support structure relative to the patient’s brain can be determined. _{[021] Then, as regards the guide holes in the support structure, there are at least two guide holes. More specifically, the support} _{structure has one guide hole per signal emitter, and may have even further guide holes which may be needed in future applications. That is,} the support structure is reusable. The purpose of the guide holes is to aid in guiding certain items and tools towards and against the patient’s _{head in the course of fixing the signal emitters in the cranial bone structure. The guide holes do not necessarily need to be completely closed} _{about their periphery. However, they need to form through holes all the way through the support structure so as to allow access to the} patient’s head through the guide holes. Preferably, the guide holes are used to guide an orientation pin, a driver, a drill guide, a drill, a thread cutter and, finally, the signal emitters, as will be explained further below. For instance, an outer diameter of the signal emitters may correspond to an inner diameter of the guide holes so that the signal emitters may be guided along a predetermined path towards their final position in the patient’s head. Alternatively, the signal emitters may be mounted in pre-configured holes in the patient’s cranial bone structure without the aid of the support structure after the support structure has been used for preparing such holes and removed. _{[022] In a first embodiment, the guide holes are fixed relative to the support structure, e.g. integrally formed in the support} structure. Accordingly, the mounting holes for the signal emitters, which are created in the cranial bone with the aid of the guide holes of the _{support structure, are more or less predetermined by the position of the guide holes in the support structure. Then, in order for the signal} _{emitters mounted in those mounting holes to be adjusted towards the target region in the patient’s brain, they need to be accordingly} _{adjustable. For instance, the signal emitters disclosed in WO 2009/132855 A1 may be used for this purpose, which include a motor providing} _{two pivoting axes for directing the signal emitter towards the target region. If the guide holes in the support structure are arranged all in one} _{plane and if the position of the support structure has been appropriately adjusted relative to the patient’s head, e.g. in that the fixation points} of the support legs and the desired target region lie within the same plane or in that the position of the support structure relative to the _{desired target region has been fine adjusted as described above, then the signal emitters need to be pivoted about only one axis in order to} direct them towards the target region, which allows employment of a simpler motor. _{[023] According to a preferred aspect, which by itself is considered inventive in relation to the motors for adjusting the signal} _{emitters and/or the adjustment devices, the motor is a piezoelectric motor. Piezoelectric motors are advantageous in that they may have} high precision, low power consumption, may be made small and lightweight, may provide high motion accuracy, and may be made from materials which are relatively immune to interference, such as electromagnetic interference. In particular, piezoelectric motors can be _{manufactured without magnetic and/or metallic parts. Thus, piezoelectric motors can be made MRI-safe, meaning that the patient can undergo} Magnetic Resonance Imaging (MRI) while having the piezo motor implanted. _{[024] Since speed and power is not critical in the present application, the piezo-electric motor may be of different types. According} _{to a first variant, the piezoelectric motor is a piezoelectric inchworm motor. According to a second variant, the piezoelectric motor is a} _{piezoelectric inertial motor. According to a third variant, the piezoelectric motor is a piezoelectric walk-drive motor. According to a fourth} _{variant, the piezoelectric motor is a piezoelectric ultrasonic motor.} _{[025] The piezoelectric motor may be a linear piezoelectric motor, which may operate with at least one of: a speed in the range} _{of 1 mm/s – 10 mm/s, a stroke length of up to 5 mm, and a force in the range of 2 N – 30 N, or the piezoelectric motor may be a rotational} _{piezoelectric motor, which may operate with at least one of: a rotational speed in the range of 1 mrad/s – 100 mrad/s and a torque in the} _{range of 100 Nmm – 900 Nmm.} _{[026] The piezoelectric ultrasonic motor may be a linear piezoelectric ultrasonic motor, which may operate with at least one of:} _{a speed in the range of 4 mm/s – 100 mm/s, a stroke length of up to 5 mm and a force in the range of 0.006 N – 40 N, or it may be a rotational} _{piezoelectric ultrasonic motor which may operate with at least one of: a rotational speed in the range of 10 mrad/s – 10,000 mrad/s, and a} _{torque in the range of 20 Nmm – 450 Nmm. Although piezoelectric motors have a relatively complex structure and control system, they may} feature a linear resolution as low as 0.21 µm. _{[027] According to one sub-aspect, the piezoelectric motor comprises at least one bimorph piezoelectric actuator.} _{[028] The piezoelectric motor according to any one of the variants is preferably substantially non-magnetic and/or non-metallic.} _{[029] In all of the variants, the piezoelectric motor may be a reversible piezoelectric motor.} _{[030] According to a second embodiment, the support structure comprises an adjustment device for each of the guide holes in} order to adjust the associated guide hole relative to the support structure. Then, the guide holes may be adjusted such that a central axis of each of the guide holes is directed through the desired target region in the patient’s brain. Again, when the support structure has been _{appropriately aligned with the target region prior to fixing its position relative to the patient’s head, then the adjustment devices need only be} _{pivotal about a single pivoting axis in order to direct the central axes of their associated guide holes through the target region. This pivoting} axis is therefore preferably perpendicular to the central axis of the respective guide hole. Otherwise, the support structure would need to be pivotal about two pivoting axes. In any case, the effect of such adjustment device is that a central axis of the mounting holes to be created in the cranial bone structure with the aid of the support structure are all oriented towards the target region so that, when the signal emitters have been placed into such mounting holes in the cranium do not need any further adjustment with respect to their angular orientation. _{Accordingly, a motor for changing the angular position of the signal emitter relative to the target region can be dispensed with. This renders} the signal emitters substantially cheaper and smaller. A support structure with such an adjustment device for each of the guide holes is _{therefore preferred over fixed guide holes in the support structure.} _{[031] In addition, the adjustment devices of the guide holes may be mounted on the support structure so as to be displaceable in} a peripheral direction relative to the patient’s head. For instance, where the support structure comprises a beam having a longitudinal extension, the adjustment device may be mounted on the beam so as to be displaceable along said longitudinal extension. This way, it can be _{avoided that certain sensitive areas of the patient’s brain come to lie between the finally implanted signal emitters and the target region.} _{[032] An orientation pin may be used to check the orientation of the guide holes when the support structure is being or has been} fixed to the patient’s head. Preferably, one orientation pin is provided for each of the guide holes where a signal emitter is to be placed in the cranial bone structure. Preferably, the orientation pins have an outer diameter corresponding to an inner diameter of the guide holes so that _{they perfectly fit in the guide holes and can be advanced through the guide holes towards and against the patient’s head. Either now or} _{beforehand, the patient’s skin may be cut at the respective locations so as to expose the cranium. The orientation pins may have a pointed tip} _{end by which they can be pressed against and into an outer area of the cranial bone structure. This way, the tip end marks the point where} the hole for the signal emitter is to be created in the cranial bone. _{[033] Again, the orientation pins may comprise or may even be entirely made of a material which allows for an automatic} _{determination of their orientations, such as by CT or MRI imaging. Thus, in combination with the 3-D imaging of the patient’s brain, it can be} verified by means of the orientation pins whether the guide holes are properly aligned with respect to the desired target region. _{[034] Next, the orientation pins are removed from the guide holes and a drill guide may be inserted into the guide holes instead.} The drill guide has a through hole for guiding a drill towards and against the patient’s head. This way, a mounting hole for the signal emitter _{may be drilled in the cranial bone exactly at the marking left by the orientation pin. Again, the drill guide preferably has an outer diameter} which corresponds to an inner diameter of the guide holes. Furthermore, the outer diameter of the drill should correspond to an inner diameter of the drill guide’s through hole. It may be sufficient to provide a single drill guide and a single drill in the kit because the mounting holes for the signal emitters are usually drilled one after the other. _{[035] In the case that the signal emitters comprise an outer thread for threading the signal emitters into the mounting hole} created in the cranial bone, it may be preferable to cut a thread into the mounting holes in the cranial bone using a thread cutter which is preferably configured to be inserted into the guide holes so as to be guided by the guide holes during the thread cutting process. For this purpose, the outer diameter of the thread cutter preferably corresponds to an inner diameter of the guide holes. _{[036] Once the mounting holes for the signal emitters have been drilled in the cranial bone and possibly provided with an internal} _{thread, the signal emitters need to be mounted in the mounted holes. For this purpose, the kit includes a driver having a front end configured} to contact a rear end of the signal emitters. Preferably, the support structure is still in place on the patient’s head and both the signal emitters and the driver are configured to advance the signal emitters through the guide holes towards and against the patient’s head by means of the _{driver. Again, the outer diameter of the driver preferably corresponds to an inner diameter of the guide holes. This ensures that the signal} emitters reach the cranial bone with a proper angular orientation corresponding to the central axis of the mounting holes in the cranial bone. _{[037] Where the signal emitters are screwed into the mounting holes of the cranial bone, the driver may be a screw driver with} the front end thereof being configured to cooperate with the rear end of the signal emitters. _{[038] Preferably, the signal emitters are fixed in the cranial bone structure so as to penetrate only a part of a hard outer layer} thereof or so as to completely penetrate the cranial bone structure without penetrating into the dura mater of the brain. The signal emitters as such may be the same as the signal emitters disclosed in WO 2009/132855 A1. _{[039] As a final step, the signal emitters may be implanted subcutaneously by closing the patient’s skin over the signal emitters.} _{[040] Furthermore, as is described in WO 2009/132855 A1,} _{- a control unit may be provided and adapted to directly or indirectly control one or more elements of the kit, in particular the signal} emitters, _{- the control unit may include a position controller adapted to control the adjustment of the positions of the signal emitters relative} to a target region to be stimulate, _{- a data processing system may be provided and connected both to the position controller and to a 3-D brain imaging system,} _{- the control unit may include a signal emission controller for controlling the generation of stimulating signals emitted by the signal} emitter, _{- the control unit may be adapted to be operable by the patient,} _{- the control unit may comprise a first part adapted to be mounted to the patient’s cranium along with the signal emitters and a} second part for remote communication with the first part, _{- the second part of the control unit may be adapted to wirelessly transmit control signals to the first part of the control unit,} _{- the first part of the control unit may be programmable via the second part of the control unit,} _{- the second part of the control unit may be adapted to transmit a feedback signal to the first part of the control unit,} _{- galvanic coupling may be provided for data transfer between the control unit and the signal emitters or, alternatively, wireless} remote control may be provided for transmitting data between the control unit and the signal emitters, _{- an energy supply may be provided and galvanically connected to the signal emitters,} _{- at least one energy transformer may be connected to the signal emitters for transforming wireless energy into electric energy and} for supplying the electric energy directly or indirectly to the signal emitters, and _{- an energy transmitter may be provided for wirelessly transmitting energy to the at least one energy transformer.} _{[041] Accordingly, a method of mounting a therapeutic brain stimulation system for wireless stimulation of neuronal cells in a} patient’s brain onto a patient’s head, may comprise at least the following steps: _{- cutting the patient’s skin at first positions and second positions above the patient’s cranial bone structure,} _{- providing a support structure comprising two or more guide holes and further comprising three or more support legs extending from} the support structure towards the patient’s head, _{- fixing the support structure on the patient’s head by means of the support legs at each of the first positions,} _{- preparing the second positions through the guide holes for subsequently mounting signal emitters at the second positions,} _{- mounting at least one of the signal emitters to the patient’s cranial bone structure at each of the second positions, said signal emitters} being adapted to generate stimulating signals which in combination allow for wireless stimulation of neuronal cells in the patient’s brain, and _{- removing the support structure (6) while leaving the signal emitters in place.} Brief description of the drawings _{[042] The invention will now be described in more detail in context with some preferred embodiments of the invention as shown} in the accompanying drawings. _{Figure 1 shows very schematically the general principles of a brain stimulation system,} _{Figures 2A and 2B show a brain stimulation system installed on a patient’s head,} _{Figures 3 shows a first embodiment of a support structure for mounting a brain stimulation system on a patient’s head,} _{Figure 4 shows a cross-sectional view of a lateral fixation point of the support structure of Figure 3,} _{Figure 5 shows a guide hole of the support structure of Figure 3 together with a drill guide and drill,} _{Figure 6 shows the guide hole of Figure 5 together with a thread cutter,} _{Figure 7 shows the guide hole of Figures 5 and 6 together with a signal emitter and screw driver,} _{Figure 8 shows a signal emitter implanted in a patient’s head,} Figure 9 shows a second embodiment of a support structure for mounting a brain stimulation system on a patient’s head, _{Figure 10 shows an adjustable guide hole of the support structure of Figure 9 along with an orientation pin,} Figure 11 shows a cross-sectional view of a central fixation point of the support structure of Figures 3 and 9, respectively, _{Figure 12 shows a plan view of the central fixation pin of Figure 11,} _{Figure 13 shows, schematically, an embodiment of an inchworm motor,} _{Figure 14 illustrates, schematically, an operation cycle of a piezoelectric inchworm motor,} _{Figure 15 shows, schematically, an embodiment of a piezoelectric inertial motor,} _{Figure 16 shows, schematically, an embodiment of a piezoelectric walk-drive motor,} _{Figure 17 illustrates, schematically, an operation cycle of a piezoelectric walk-drive motor,} _{Figure 18 shows, schematically, a Traveling Wave Ultrasonic Motor (TWUSM),} _{Figure 19 shows, schematically, an embodiment of a Standing Wave Ultrasonic Motor (SWUSM), and} _{Figure 20 shows, schematically, an embodiment of a linear ultrasonic motor.} Detailed description of the drawings _{[043] Figure 1 schematically shows the general principals of a brain stimulation system. The brain stimulation system that is} _{shown here includes six signal emitters 1, as an example. The signal emitters 1 are adapted to emit electromagnetic radiation in the form of} beams 2. A lens system 3 is schematically shown as a focusing means for each of the signal emitters 1 and is displaceable along the axis of the beam 2 so as to concentrate the radiation on a common target region 4 within the patient’s brain 5. Each of the signal emitters 1 is individually adjustable so that it can be directed to any desired location within the patient’s brain 5. The pivoting axis, longitudinal displacement _{axis and rotational axis along which the signal emitters 1 can be displaced are indicated by arrows in respect of only one of the signal emitters} _{1. Shown by dotted lines and designated with reference numeral 1’ is a signal emitter that has been displaced so as to direct the corresponding} beam 2’ onto a different region in the patient’s brain 5. _{[044] Figure 2A shows a specific embodiment of a brain stimulation system in which the signal emitters 1 are permanently fixed} in the patient’s cranial bone structure 8 subcutaneously under the skin 10. As shown in a detailed view in Figure 2B, the signal emitters 1 are adjustably mounted in a mounting tube 9. Accordingly, they are mounted pivotally on a pivot axis substantially parallel to the patient’s cranium, they are further rotatable about a rotating axis perpendicular to the pivot axis and, possibly, they are also axially displaceable along the _{rotating axis. This allows the signal emitters 1 to be directed onto the common target region 4 within the patient’s brain 5. The mounting tube} _{9 has a thread 12 on its outside by which it is threaded into and through the cranial bone structure 8 so as to completely penetrate the cranial} bone up to the dura mater 11 of the brain 5, without damaging the dura mater 11. The mounting tube 9 is relatively short and the remainder thereof not penetrating the patient’s cranium 8 is covered by the patient’s skin 10. _{[045] Figure 3 shows a first embodiment of a support structure 6 for mounting the brain stimulation system of Figures 2A, 2B on} a patient’s head. The support structure 6 comprises a beam having a longitudinal extension and provided with spaced-apart guide holes 7. There may be more or less than the eight guide holes 7 shown in Figure 3. The guide holes 7 are arranged all in one plane with a central axis 7a thereof also lying in the same plane. The position and orientation of the guide holes 7 are fixed relative to the support structure 6. The _{guide holes 7 are configured for aiding and guiding an orientation pin O, a driver S, a drill guide G, a drill D, a thread cutter T and the signal} emitters 1, as will be described in more detail below. _{[046] Three support legs 13a, 13b and 13c are provided on the support structure 6, namely a first support leg 13a and a second} support leg 13c arranged at opposite end regions of the support structure 6 and a third support leg 13b arranged centrally between the first and second support legs 13a, 13c. The support legs 13a to 13c support the support structure 6 on and fix the support structure 6 in relation _{to the patient’s head. There may be more than the three support legs 13a to 13c.} _{[047] A preferred embodiment of a support leg 13a is shown in more detail as a cross sectional view in Figure 4. Accordingly, the} _{support leg 13a comprises an external screw thread and the support structure comprises a corresponding screw hole which mates with the} external screw thread of the support leg. By screwing each of the support legs 13a to 13c through corresponding screw holes of the support structure 6 towards and against the patient’s head, the support structure 6 is securely held in a fixed position relative to the cranial bone structure 8. A pointed tip end of the support legs 13a to 13c help anchoring the support structure 6 on the patient’s head. Preferably, the _{patient’s skin 10 is cut open so as to expose the cranium prior to advancing the support legs 13a to 13c against the cranial bone structure 8.} _{[048] As is shown in Figure 3, three markers M are provided on the support structure so as to permit the determination of the} position of the support structure 6 in space once the support structure 6 has been fixed on the patient’s head by means of the support legs 13a to 13c. Verification of proper placement of the support structure 6 relative to the patient’s brain 5 may be done by 3-D imaging of the brain, such as by CT or MRI imaging, with the support structure 6 fixedly mounted on the patient’s head. _{[049] Figure 5 shows the guide hole 7 of the support structure 6 of Figure 3 together with a drill guide G and a drill D. The outer} diameter Do of the drill guide G corresponds to an inner diameter Di of the guide hole 7. Furthermore, the drill guide G has an inner diameter which corresponds to an outer diameter of the drill D. When the drill guide G is positioned in the guide hole 7, the drill D may be guided through the drill guide G to a defined position of the cranial bone structure 8. Again, the patient’s skin 10 is cut open prior to the drilling process so as to expose the patient’s cranium. _{[050] After the drill guide G has been removed from the guide hole 7, as is shown in Figure 6, a thread cutter T is inserted into} and through the guide hole 7 in order to cut an internal thread into the mounting hole 14 which was previously drilled into the cranial bone structure 8. Again, the outer diameter Do of the thread cutter T corresponds to the inner diameter Di of the guide hole 7. _{[051] Once an internal thread 15 has been cut into the cranial bone structure 8, as is shown in figure 7, the signal emitter 1 is} _{mounted in the mounting hole 14 of the cranial bone structure 8. This is preferably done with the aid of the support structure 6. Accordingly,} the signal emitter 1 has a mounting tube 9 with an outer threading 12 which is configured to mate with the internal thread 15 of the mounting _{hole 14 in the cranial bone structure 8. An outer diameter Do of the mounting tube 9 preferably corresponds to the inner diameter Di of the} _{guide hole 7. A screw driver S has a front end configured to cooperate with a rear end of the signal emitter 1 so as to allow screwing of the} signal emitter 1 into the cranial bone structure 8. Again, the driver S has an outer diameter Do which corresponds to the inner diameter Di for proper guidance of the driver S along the central axis 7a of the guide hole 7. _{[052] After the signal emitter 1 has been implanted in the cranial bone structure 8, the patient’s skin 10 is closed over the signal} _{emitter 1 so that the signal emitter 1 is arranged subcutaneously. A corresponding suture 16 with sewing thread 17 is shown in Figure 8.} _{[053] Then, the signal emitters 1 may be adjusted such that their stimulating signals are emitted from their respective positions} towards the common target region 4 in the patient’s brain 5 so as to generate the accumulated stimulating effect on that target region 4. For this purpose, the signal emitters (meaning the relevant parts thereof) are pivoted about two axes so that their stimulating signals emit towards the common target region 4. Actually, since the longitudinal axes 7a of the guide holes 7 and, therefore, also the orientation axes of the implanted signal emitters 1 are arranged all in one plane, it is sufficient to pivot the signal emitters 1 about a single axis, namely an axis which is perpendicular to the such plane. An angle adjusting motor (not shown) is provided for this purpose in the mounting tube 9. In addition, _{the angle adjusting motor may be configured to further adjust a distance of the effective parts of the signal emitter 1 relative to the common} _{target region 4.} _{[054] In the embodiment shown in Figure 8, a wiring provides energy and data to the signal emitters 1. The wiring may be arranged} subcutaneously, as is shown in Figure 8, but may likewise be mounted directly on the patient’s skin 10. Accordingly, each of the signal emitters 1 is connected to a control unit C which is conveniently arranged in the patient’s neck area. An energy source E is also connected to the control unit C to provide the control unit C and the signal emitters 1 with energy. A processing unit P remote from the control unit C and energy source E is used to wirelessly provide control data to the control unit C and energy to the energy source E. The control unit C may send feedback data to the processing unit P, the feedback data relating to functional parameters of the system, such as position data of the signal emitters 1. In this context, the system further comprises position sensors (not shown) to sense the positions of the relevant parts of the individual signal emitters 1. In addition, a physical parameter sensor (also not shown) for sensing a physical parameter of the patient is connected to the control unit C, wherein the feedback data sent to the processing unit P may further comprise such physical data of the patient. Altogether, the control unit and its various functions and structure corresponds to that disclosed in WO 2009/132855 A1. _{[055] Figure 9 shows a second embodiment of a support structure 6 for mounting the brain stimulation system on a patient’s} head. The support structure 6 according to the second embodiment differs from that of the first embodiment only in that the position and _{orientation of the guide holes 7 are not fixed relative to the support structure 6, but that the support structure 6 comprises an adjustment} device 20 associated to each of the guide holes 7 by which the guide holes 7 may be adjusted relative to the support structure such that the central axis 7a of the associated guide hole 7 is directed through the target region 4 in the patient’s brain 5. Since the guide holes 7 are arranged all in one plane, it is sufficient that the support structure 6 has a single pivoting axis 21 for each of the adjustment devices 20 which _{is perpendicular to the plane in which the central axes 7a of the guide holes 7 are arranged. Conclusively, when the holes 14 are drilled into} the cranial bone structure 8 through the guide holes 7 in the properly adjusted adjustment device 20, a central axis of such mounting hole 14 _{is oriented through the desired target region 4 in the patient’s brain 5. Any signal emitter 1 mounted in such mounting hole 14 of the cranial} bone structure 8 needs no further angular adjustment relative to the target region 4 so that a respective angle adjusting motor may be dispensed with. _{[056] Figure 10 shows an orientation pin O which has an outer diameter Do that corresponds to an inner diameter Di of the guide} _{holes 7. The orientation pin O is used to properly adjust the central axis 7a of the guide hole 7 in the adjustment device 20 relative to the} _{desired target region 4 in the patient’s brain 5. For this purpose, the orientation pin is made of a material which allows for automatic} _{determination of the orientation of the orientation pin O, such as by CT or MRI imaging. Once the proper orientation has been found, the} adjustment device 20 is fixed (not shown) relative to the support structure 6 so that the orientation of the guide hole’s 7 central axis 7a is _{maintained for the subsequent steps of drilling the mounting hole 14 in the cranial bone structure 8, cutting the internal screw thread 15 in} _{such mounting hole 14 and inserting the signal emitter 1 through the guide hole 7 into the mounting hole 14 in the cranial bone structure 8.} _{[057] Figures 11 and 12 show an improved variant of the central support leg 13b which may be employed in the first embodiment of} the support structure 6 as well as in the second embodiment of the support structure 6 and which allows for the fine adjustment of the _{support structure’s position relative to the patient’s head. Accordingly, the support leg 13b is provided in a section 6’ of the support structure} _{6 which is slidable relative to the support structure 6 in a direction which is substantially parallel to the patient’s head. Or in other words,} _{the section 6’ is slidable in a direction which is perpendicular to both a central axis of the support leg 13b and a longitudinal extension of the} support structure 6. _{[058] As can be seen in the cross sectional view shown in Figure 11, the section 6’ of the support structure 6 engages with the} _{support structure 6 via two wings 6”. This is further illustrated in the top view shown in Figure 12. The section 6’ is held in a central position} relative to the support structure 6 by means of two coil springs 18a, 18b acting on opposite sides of the section 6’. In addition, two adjustment _{screws 19a, 19b are provided to displace the section 6’ against the force of the coil springs 18a, 18b relative to the support structure 6. In use,} once the support structure 6 has been fixed to the patient’s head by means of the support legs 13a to 13c, as described above, the position of the support structure 6 relative to the patient’s head may be fine adjusted using the adjustment screws 19a, 19b. Namely, when the orientation _{of the support structure 6 relative to the patient’s head is verified. e.g. by means of the markers M on the support structure 6, and it turns} out that the support structure 6 is misaligned relative to the desired target region 4, the section 6’ may be displaced relative to the support structure 6 using one of the two adjustment screws 19a, 19b and fixed in the displaced position by means of the respective other one of the _{adjustment screws 19a, 19b. This way, since the central support leg 13b is fixed on the patient’s head by its pointed end, the support structure} _{6 pivots about the two fixation points at which the first and second support legs 13a, 13b are fixed to the patient’s head by their respective} pointed ends. _{[059] The electric motor or motors of the signal emitters for adjusting the angular and/or the linear displacement of the signal} emitters, or relevant parts thereof, preferably comprise a piezo-electric motor. _{[060] The piezoelectric effect is a property of certain solid materials to generate an electrical voltage in response to an applied} mechanical stress (so-called direct piezoelectric effect) and to deform elastically in response to an applied electrical voltage (so-called _{inverse piezoelectric effect). The piezoelectric effect is a reversible process, meaning that materials exhibiting the direct piezoelectric effect} also exhibit the inverse piezoelectric effect. _{[061] Materials exhibiting the piezoelectric effect are denoted as piezoelectric materials. Examples of piezoelectric materials} comprise: crystalline materials, such as lithium niobate, lithium tantalate and quartz; ceramics, such as lead zirconate titanate, potassium _{niobate and barium titanate; polymers, such as polyvinylidene fluoride.} _{[062] Piezoelectric coefficients are a fundamental property of piezoelectric materials. A given piezoelectric material is} characterized by a set of piezoelectric coefficients, wherein a piezoelectric coefficient is a measure of the relationship between the applied mechanical stress along a first direction and the generated electric charge along a second direction. Piezoelectric coefficients are usually expressed in units of picocoulombs per newton (pC/N). The value of piezoelectric coefficients may strongly vary depending on the piezoelectric material and piezoelectric coefficient being considered. For example, the ^_^^ piezoelectric coefficient is commonly reported for piezoelectric materials and quantifies the electric charge generated along a given direction in response to the mechanical stress applied along the same direction. _{[063] A piezoelectric motor or piezo motor is a type of electric motor that uses the inverse piezoelectric effect to generate} _{mechanical motion, typically linear or rotatory motion. Piezo motors are often used in applications where precise positioning and fine control} of movement are required. Piezo motors have the advantage of providing high motion accuracy, being possible to miniaturize and being relatively immune to interference, such as electromagnetic interference. Piezoelectric motors can also be manufactured without magnetic and/or metallic parts, and instead be manufactured from ceramics or certain composites. This feature is particularly advantageous in medical _{and biotechnology applications with strong magnetic fields. Piezoelectric motors can thus be made MRI-safe, meaning that the patient can} undergo Magnetic Resonance Imaging (MRI) while having the piezo motor implanted. MRI is a medical imaging technique used to form pictures of the anatomy and the physiological processes of the body using strong magnetic fields. Conventional implantable electromagnetic motors prevent the use of MRI as the strong magnetic field risks damaging both the patient and the implant. _{[064] Also, compared to classical electromagnetic motors, piezo motors may have a simpler structure and smaller footprint.} Piezo motors may offer improved positioning accuracy and simpler design, as linear motion may be obtained directly, without the need of mechanical coupling elements otherwise required to convert the rotary motion of classical electromagnetic motors to linear motion. The fact that linear motion can be obtained directly may improve the positioning accuracy. _{[065] An additional advantage of piezoelectric motors is that they usually feature higher energy-efficiency and less power} consumption compared to conventional electromagnetic motors. _{[066] As discussed in more detail below, inchworm motors, inertial motors, walk-drive motors and ultrasonic motors are four} _{suitable types of piezoelectric motors.} _{[067] Fig. 13 shows an embodiment of an inchworm motor MO configured to generate linear motion. The inchworm motor MO} comprises a first lateral piezoelectric actuator 801a and second lateral piezoelectric actuator 801b. The first lateral piezoelectric actuator _{801a is laterally connected to a first clutching actuator 802a’ and a second clutching actuator 802a’’. The second lateral piezoelectric actuator} _{801b is laterally connected to a third clutching actuator 802b’ and a fourth clutching actuator 802b’’. The inchworm motor MO is configured} _{to impart a linear motion to a movable member 805. The movable member 805 is configured to be attached to the load or mechanism to be} moved, for instance to a signal emitter (1) or a relevant part thereof. _{[068] Fig. 14 illustrates an operation cycle of the piezoelectric inchworm motor MO wherein the movable member 805 is linearly} moved in a direction to the right in the illustration by sequentially controlling the first and second piezoelectric actuators 801a, 801b and the _{clutching actuators 802a’, 802a’’, 802b’, 802b’’. In an initial relaxation state, the movable member 805 is detached from all the clutching} _{actuators 802a’, 802a’’, 802b’, 802b’’. The inchworm motor MO is subsequently brought into an initialization state by electrically activating} the second and fourth clutching actuators 802a’’, 802b’’. As a result, the clutching actuators 802a’’, 802b’’ extend and clutch the movable member 805. _{[069] In step 1, the first and second lateral actuators 801a, 801b extend in response to an applied electrical voltage. As a result,} the movable member 805 undergoes a first linear displacement with a distance equal to half the distance of the extension of the lateral actuators 801a, 801b. _{[070] In step 2, the first and third clutching actuators 802a’, 802b’ are electrically activated. As a result, the first and third} clutching actuators 802a’, 802b’ extend and clutch the movable member 805. _{[071] In step 3, the electrical voltage applied to the third and fourth clutching actuators 802a’’, 802b’’ is decreased as compared} to the initialization state. As a result, the third and fourth clutching actuators 802a’’, 802b’’ detach from the movable member 805. _{[072] In step 4, the electrical voltage applied to the first and second lateral actuators 801a, 801b is decreased as compared to} _{step 1. As a result, the first and second lateral actuators 801a, 801b contract and the movable member 805 undergoes a second linear} displacement with a distance equal to half the distance of the contraction of the lateral actuators 801a, 801b. _{[073] In step 5, the second and fourth clutching actuators 802a’’, 802b’’ are electrically activated such that they extend and} clutch the movable member 805. _{[074] In step 6, the electrical voltage applied to the first and second clutching actuators 802a’, 802b’ is decreased as compared} to step 2. As a result, the first and second clutching actuators 802a’, 802b’ contract and detach from the movable member 805. _{[075] The steps from 1 to 6 may be repeated a number oftimes in the sequence illustrated above in order to move the movable} member 805 by a desired distance. _{[076] This configuration of an inchworm piezoelectric motor MO creating a linear motion can be used to generate the linear motion} _{of the signal emitters 1, for instance, in order to synchronize phases of electromagnetic waves emitted from each of the signal emitters 1 with} _{respect to the common target region 4. In the embodiment shown in Fig. 14, the inchworm motor is configured to generate a linear motion at} _{a speed in the range of 1 mm/s to 10 mm/s, a stroke length of up to 5 mm and a force in the range of 2 N – 30 N.} _{[077] In another embodiment, the movable member 805 may be replaced with a rotary module (not shown) such that the inchworm} _{motor can be used to generate a rotary motion. At least one and possibly two of such a rotating inchworm motor can be used as a rotational} _{electrical motor of the signal emitters 1 in order to adjust the angular orientation of the signal emitters 1 so as to direct them towards the} _{common target region 4. Likewise, at least one and possibly two of such a rotating inchworm motor can be used as a rotational electrical} motor of the adjustment devices 20 in order to adjust the angular orientation of the adjustment devices 20 so as to direct them towards the _{common target region 4. An inchworm motor configured to generate rotary motion may have a rotational speed in the range of 0.5 mrad/s} _{to about 70 mrad/s and a torque ranging from about 100 Nmm to about 900 Nmm.} _{[078] Fig. 15 illustrates an embodiment of a piezoelectric inertial motor MO configured to generate linear motion. The motor MO} comprises a movable member 805, a piezoelectric actuator 801, a recoiling member 804 and a base 806. The movable member 805 is attached to the piezoelectric actuator 801. The piezoelectric actuator 801 is attached to the recoiling member 804. The movable member 805 is in contact with the base 806. The movable member 805 is configured to be attached to the load or mechanism to be moved, for instance to a signal emitter (1) or a relevant part thereof. _{[079] An operation mode of the piezoelectric inertial motor MO described in Fig.15 comprises two steps. In step 1, the piezoelectric} _{actuator 801 slowly elongates in response to an applied voltage. Due to the static friction between the movable member 805 and the base} 806, the movable member 805 does not move. In step 2, the piezoelectric actuator 801 rapidly contracts in response to a change in the _{applied voltage. As a result of the recoil produced by the recoiling member 804, the movable member 805 moves by a distance Δx to the left} in the illustration of Fig.15. By reversing the operation cycle, the piezoelectric inertial motor MO generates motion in the opposite direction. _{[080] In the embodiment shown in Fig. 15, the piezoelectric inertial motor MO is configured to generate linear motion and may} _{feature a speed in the range of 1 mm/s – 10 mm/s, a stroke length of up to 5 mm and a force in the range of 2 N – 30 N.} _{[081] This configuration of a piezoelectric inertial motor MO creating a linear motion can be used to generate the linear motion} of the signal emitters 1, for instance, in order to synchronize phases of electromagnetic waves emitted from each of the signal emitters 1 with respect to the common target region 4. _{[082] In alternative embodiments of piezoelectric inertial motors (not shown), the movable member 805 may be replaced with a} rotary module such that the piezoelectric inertial motor is configured to generate rotary motion. At least one and possibly two of such a piezoelectric inertial motor creating a rotary movement can be used as a rotational electrical motor of the signal emitters 1 in order to adjust _{the angular orientation of the signal emitters 1 so as to direct them towards the common target region 4. Likewise, at least one and possibly} _{two of such a piezoelectric inertial motor creating a rotary movement can be used as the rotational electrical motor of the adjustment devices} 20 in order to adjust the angular orientation of the adjustment devices 20 so as to direct them towards the common target region 4. _{Piezoelectric inertial motors configured to generate rotary motion may have a rotational speed in the range of 1 mrad/s – 100 mrad/s and a} _{torque in the range of 100 Nmm – 900 Nmm.} _{[083] Yet another design of a piezoelectric motor suitable for use in the implantable medical device described herein is the walk-} drive motor. Walk-drive motors take their name from the fact that their working principle essentially resembles a walk. Linear motion is achieved through the coordinated and sequential action of a number of piezoelectric actuators acting as legs. _{[084] Fig. 16 shows an embodiment of a piezoelectric walk-drive motor MO. The piezoelectric walk-drive motor MO comprises a} _{number of piezoelectric actuators 801a – 801d attached to a supporting member 800. The piezoelectric actuators 801a – 801d may be divided} into a first set 801a, 801c and a second set 801b, 801d. The first and second set 801a, 801c and 801b, 801d of piezoelectric actuators may be controlled independently. The piezoelectric walk-drive motor MO is configured to impart a linear motion to a movable member 805 by _{sequentially controlling the piezoelectric actuators 801a – 801d. The movable member 805 is configured to be attached to the load or} mechanism to be moved, for instance to a signal emitter (1) or a relevant part thereof. _{[085] A piezoelectric walk-drive motor 805 may be operated in various operation modes, each offering specific advantages in} terms of performance. _{[086] Fig. 17 illustrates an operation cycle of a piezoelectric walk-drive motor MO according to one embodiment. In this} embodiment, the first set of piezoelectric actuators 801a, 801c is controlled by a first electrical voltage ^_^. The second set of piezoelectric actuators 801b, 801d is controlled by a second electrical voltage ^_^. The cycle comprises a number of steps. _{[087] In step 1, in response to a change in ^^, the first set of piezoelectric actuators 801a, 801c stretch and make contact with} the movable member 805. When in contact, the first set of piezoelectric actuators 801a, 801c are bended sideways in a direction opposite to _{the motion direction D. Conversely, the second set of piezoelectric actuators 801b, 801d detach from the movable member 805 in response} to a change in ^_^. _{[088] In step 2, the first set of piezoelectric actuators 801a, 801c maintain contact with the movable member 805 and bend in the} _{motion direction D in response to a change in ^^. The second set of piezoelectric actuators 801b, 801d remain detached from the movable} member 805. As a result of the friction between the first set of piezoelectric actuators 801a, 801c and the movable member 805, the movable member 805 is moved in the motion direction D. _{[089] In step 3, in response to a change in ^^, the second set of piezoelectric actuators 801b, 801d stretch and make contact with} the movable member 805. When in contact, the second set of piezoelectric actuators 801b, 801d are bended in a direction opposite to the motion direction D. Conversely, the first set of piezoelectric actuators 801a, 801c detach from the movable member 805 in response to a change in ^_^. _{[090] In step 4, the second set of piezoelectric actuators 801b, 801d maintain contact with the movable member 805 and bend in} _{the motion direction D in response to a change in ^^. The first set of piezoelectric actuators 801a, 801c remain detached from the movable} member 805. As a result of the friction between the second set of piezoelectric actuators 801b, 801d and the movable member 805, the movable member 805 is moved in the motion direction D. _{[091] The piezoelectric actuators 801a – 801d in Fig. 14 and Fig. 15 may be bimorph piezoelectric actuators. A bimorph actuator} comprises at least two piezoelectric layers bonded together and oppositely responding to a given applied voltage. E.g., one layer extends and _{the other contracts. As a result, the bimorph actuator may stretch and bend. Alternatively, any of the piezoelectric actuators 801a – 801d in} _{Fig. 14 and Fig. 15 may comprise a top part (illustrated as 801a’ in Fig. 14), configured to be attached to the supporting member 800, and a} bottom part (exemplified by illustration as 801a’’ in Fig.14). The top part 801a’ is configured to deform perpendicularly to the motion direction D in response to the voltage applied to the piezoelectric actuator 801a. The bottom part 801a’’ is configured to deform parallelly to the motion direction D in response to the voltage. As a result, the piezoelectric actuator 801a may stretch and bend. _{[092] By reversing the operation cycle, the piezoelectric walk-drive motor MO generates motion in the opposite direction.} _{[093] In the embodiment shown in Figs. 14 and 15, the piezoelectric walk-drive motor MO is configured to generate linear motion} _{at a speed in the range of 1 mm/s to 10 mm/s and a force in the range of 2 N – 30 N. As the maximum stroke is limited by the length of the} _{movable member 805 (also called a runner), there is no set limit for the maximum stroke.} _{[094] This configuration of a piezoelectric walk-drive motor MO creating a linear motion can be used to generate the linear motion} of the signal emitters 1, for instance, in order to synchronize phases of electromagnetic waves emitted from each of the signal emitters 1 with respect to the common target region 4. _{[095] In alternative embodiments of the piezoelectric walk-drive motor (not shown), the movable member 805 may be replaced} with a rotary module such that the piezoelectric walk-drive motor is configured to generate rotary motion. At least one and possibly two of such piezoelectric walk-drive motor configured to generate rotary motion can be used as a rotational electrical motor of the signal emitters 1 in order to adjust the angular orientation of the signal emitters 1 so as to direct them towards the common target region 4. Likewise, at least one and possibly two of such a piezoelectric walk-drive motor configured to generate rotary motion can be used as a rotational electrical _{motor of the adjustment devices 20 in order to adjust the angular orientation of the adjustment devices 20 so as to direct them towards the} _{common target region 4. Piezoelectric walk-drive motors configured to generate rotary motion may have a rotational speed in the range of} _{0.5 mrad/s to about 70 mrad/s and a torque ranging from about 100 Nmm to about 900 Nmm.} _{[096] An ultrasonic motor is another type of piezoelectric motor. In ultrasonic motors, a first component of the motor, the stator,} _{supports mechanical vibrations in the ultrasonic frequency range – from tens to hundreds of kHz. The stator comprises a number of} piezoelectric actuators. Ultrasonic mechanical vibrations are excited in the stator in response to an electrical voltage applied to the piezoelectric actuators. The stator is configured to transfer the ultrasonic vibrations to a second component of the motor, such as a rotor or slider depending on the scheme of operation. Depending on the scheme of operation, various types of motion, such as linear or rotary, may be imparted to the second component. _{[097] A rotary ultrasonic motor is a piezoelectric ultrasonic motor configured to generate rotary motion. Rotary ultrasonic} motors comprise traveling wave ultrasonic motors (TWUSM) and standing wave ultrasonic motor (SWUSM). In TWUSMs the stator vibrates according to a travelling wave pattern. In SWUSMs the stator vibrates according to a standing wave pattern. _{[098] Fig. 18 shows an embodiment of a TWUSM MO. The TWUSM MO comprises a ring-shaped stator 810 with a top and a bottom} surface. The stator 810 is configured to engage with a ring-shaped rotor 811. The stator 810 comprises a ring-shaped member 810’, a first _{number of piezoelectric actuators 801a and a second number of piezoelectric actuators 801b. The piezoelectric actuators 801a, 801b are} attached to the ring-shaped member 810’. An alternating electrical voltage VA may be applied from a first voltage generator 812a (typically a _{controller connected to an energy source) to the piezoelectric actuators 801a. An alternating electrical voltage VB, phase-shifted with respect} _{to VA, may be applied from a second voltage generator 812b to the second number of piezoelectric actuators 801b. The ring-shaped member} 810’ may comprise a number of teeth 813. The rotor 811 is configured to be attached to the load or mechanism to be moved. _{[099] The first number of piezoelectric actuators 801a deform in response to the voltage VA such that they induce a first vibration} _{pattern in the stator 810. The second number of piezoelectric actuators 801b deform in response to the voltage VB such that they induce a} second vibration pattern in the stator 810. The interference of the first and second vibration pattern excites a travelling wave 814 in the stator _{810. The travelling wave 814 has a given propagation direction D1, either clock-wise or counter-clockwise. The regions of maximum} _{displacement – so-called antinodes – and regions of no displacement – so-called nodes – of the travelling wave pattern oscillate transversely} with respect to the top and bottom surface of the stator 810, but they also travel circumferentially along the stator 810 perimeter. _{[100] The propagation of the travelling wave 814 makes the stator vibrate accordingly. As a result, the stator 810 imparts a} _{rotatory motion to the rotor 811 in a rotation direction D2, opposite to the travelling wave 814 propagation direction D1. The teeth 813 facilitate} the motion transmission from the stator 810 to the rotor 811 by enhancing the friction between the rotor 811 and the stator 810. _{[101] The frequency and amplitude of the applied electrical voltages may be controlled and adjusted to tune the performance of} the TWUSM MO, including speed, direction and accuracy of motion. _{[102] In contrast to TWUSMs, a standing wave ultrasonic motor (SWUSM) requires only a single alternating electrical voltage to} operate. In response to this applied voltage, the piezoelectric actuators 801a, 801b of the stator 810 make the stator 810 vibrate according to a standing wave pattern. A standing wave is characterized by antinodes and nodes that do not travel in space. As a result, a standing wave does not have a propagation direction. The stator 810 vibrates in a way that antinodes and nodes oscillate transversely with respect to the top and bottom surface of the stator. However, antinodes and nodes do not travel circumferentially along the stator. _{[103] Fig. 19 shows an embodiment of a SWUSM. The SWUSM MO comprises a ring-shaped stator 810 with a top and a bottom} surface. The stator 810 is configured to engage with a ring-shaped rotor 811. The stator 810 comprises a first set of piezoelectric actuators 801a and a second set of piezoelectric actuators 801b. An alternating electrical voltage may be selectively and exclusively applied to either set of piezoelectric actuators 801a, 801b while the other set is left floating. In such a case, the set to which the voltage is applied is referred to as active, while the other set is referred to as free. The stator 810 comprises a number of protrusions 815. The stator 810 is configured to _{engage with the rotor 811 via the protrusions 815. The rotor 811 is configured to be attached to the load or mechanism to be moved.} _{[104] A standing wave vibration pattern may be excited in the stator 810 in response to the applied voltage. As a result, the} _{protrusions 815 oscillate at a first angle with respect to the top surface of the stator 810 when the piezoelectric actuators 801a are active.} The protrusions 815 oscillate at a second angle with respect to the top surface of the stator 810 when the piezoelectric actuators 801b are active, with the second angle different from the first angle. The first angle is such that the stator 810 imparts a clockwise rotary motion to the rotor 811. The second angle is such that the stator 810 imparts a counter-clockwise rotary motion to the rotor 811. _{[105] In the embodiment shown in Fig. 19, the rotary ultrasonic motor MO has a rotational speed in the range of 10 mrad/s –} _{10,000 mrad/s. and produces a torque in the range of 20 Nmm – 450 Nmm.} _{[106] Rotary ultrasonic motors, such as the SWUSM or TWUSM, configured to generate rotary motion, can be used as the rotational} _{electrical motor. At least one and possibly two of such a rotary ultrasonic motor configured to generate rotary motion can be used as a} rotational electrical motor of the signal emitters 1 in order to adjust the angular orientation of the signal emitters 1 so as to direct them towards the common target region 4. Likewise, at least one and possibly two of such a rotary ultrasonic motor configured to generate rotary _{motion can be used as a rotational electrical motor of the adjustment devices 20 in order to adjust the angular orientation of the adjustment} devices 20 so as to direct them towards the common target region 4. _{[107] Fig. 20 shows an embodiment of a linear ultrasonic motor MO. The linear ultrasonic motor MO comprises a piezoelectric} actuator 801, a pushing member 816, and a movable member 805 (or slider). The piezoelectric actuator 801 vibrates at its resonance frequency in response to an applied alternating voltage. The piezoelectric actuator 801 is attached to the pushing member 816. As a result of the vibrations in the piezoelectric actuator 801, the pushing member 816 alternatively contacts the movable member 805 and makes it move linearly by frictional coupling. _{[108] In the embodiment shown in Fig. 20, the linear ultrasonic piezo motor MO is configured to generate linear motion with a} _{speed in the range of 4 mm/s to 100 mm/s and a force in the range of 0.5 N – 30 N. As the maximum stroke is limited by the length of the} _{movable member 805 (also called a slider), there is no set limit for the maximum stroke.} _{[109] This configuration of a linear ultrasonic piezo motor MO can be used to generate the linear motion of the signal emitters 1,} _{for instance, in order to synchronize phases of electromagnetic waves emitted from each of the signal emitters 1 with respect to the common} target region 4. LIST OF ASPECTS KIT: ACCUMULATED STIMULATION IN TARGET REGION 1_{. A kit for a therapeutic brain stimulation system for wireless stimulation of neuronal cells in a patient’s brain by means of} stimulating signals emitted from different positions towards a common target region (4) in a patient’s brain so as to provide an accumulated stimulating effect on said target region, said kit comprising: -_{two or more signal emitters (1) adapted to be fixed in cranial bone structure and generate the stimulating signals and} _{- a support structure (6) configured to be temporarily mounted on a patient’s head as an aid for fixing the signal} emitters (1) in the cranial bone structure. SUPPORT LEGS 2_{. The kit of aspect 1, wherein the support structure (6) comprises three or more support legs (13a – 13c) which extend from} the support structure (6) towards and against the patient’s head for temporarily fixing the support structure (6) on the patient’s head. 3_{. The kit of aspect 2, wherein the support legs (13a – 13c) each comprise an external screw thread and the support structure} _{(6) comprises three or more screw holes configured to mate with the external screw thread of the support legs (13a – 13c).} _{4. The kit of aspect 2 or 3, wherein the support legs (13a – 13c) each have a pointed tip end facing towards the patient’s head.} _{5. The kit of any one of aspects 2 to 4, wherein the support structure (6) is configured to span around a part of the patient’s} head and further configured so as to arrange two of the support legs (13a, 13c) at opposite end regions of the support structure (6) and one of the support legs (13b) between said two of the support legs (13a, 13c), preferably centrally between said two of the support legs (13a, 13c). 6_{. The kit of aspect 5, wherein said one of the support legs (13b) arranged between said two of the support legs (13a, 13c) is} movable relative to the support structure (6) in a direction which is perpendicular to a longitudinal axis of the at least one of the support legs (13b). 7_{. The kit of aspect 6, wherein said at least one of the support legs (13b) is slidably guided relative to the support structure} (6) in said direction which is perpendicular to the longitudinal axis of the at least one of the support legs (13b). MARKER 8_{. The kit of any one of aspects 1 to 7, wherein at least three markers (M) are provided on the support structure (6) which} permit determination of a position of the support structure (6) in space. GUIDE HOLES 9_{. The kit of any one of aspects 1 to 8, wherein the support structure (6) has two or more guide holes (7), wherein each of the} guide holes (7) is configured for aiding in guiding one or more of the following items towards and against the patient’s head: an orientation pin (O), a driver (S), a drill guide (G), a drill (D), a thread cutter (T), and the signal emitters (1). 1_{0. The kit of aspect 9, wherein an outer diameter (Do) of the one of the signal emitters (1) corresponds to an inner diameter} (Di) of the guide holes (7). 1_{1. The kit of aspect 9 or 10, wherein either a position and orientation of the guide holes (7) are fixed relative to the support} structure (6) or the support structure (6) comprises an adjustment device (20) associated to each of the guide holes (7), wherein the a_{djustment device (20) is configured for adjusting the associated guide hole (7) relative to the support structure (6).} _{12. The kit of aspect 11, wherein the adjustment device (20) is configured for adjusting the associated guide hole (7) relative to} _{the support structure (6) such that a central axis (7a) of the associated guide hole (7) is directed through the target region (4).} _{13. The kit of aspect 11 or 12, wherein the adjustment device (20) is mounted on the support structure (6) so as to be pivotal} about at least one, preferably about only one, pivoting axis (21). 1_{4. The kit of aspect 13, wherein the only one pivoting axis (21) is perpendicular to a plane in which the central axes (7a) of the} guide holes (7) are arranged on the support structure (6). _{15. The kit of any one of aspects 11 to 14, wherein the support structure (6) comprises a beam having a longitudinal extension,} wherein the adjustment device (20) is mounted on the beam so as to be displaceable along said longitudinal extension. _{16. The kit of aspect 15, wherein the beam is curved and embraces an angle of curvature of at least about 180°.} ORIENTATION PIN _{17. The kit of any one of aspects 9 to 16, comprising at least one of the orientation pin (O), the orientation pin (O) having an} outer diameter (Do) which corresponds to an inner diameter (Di) of the guide holes (7). _{18. The kit of aspect 17, wherein the orientation pin (O) has a pointed tip end.} _{19. The kit of aspect 16 or 17, wherein the orientation pin (O) is made of or comprises a material which allows for an automatic} determination of an orientation of the orientation pin (O), such as by CT or MRI imaging. DRILL GUIDE, DRILL and THREAD CUTTER _{20. The kit of any one of aspects 9 to 19, comprising the drill guide (G), the drill guide (G) configured to be inserted into the} guide holes (7), the drill guide having a through hole for guiding a drill (D) towards and against the patient’s head when the drill guide (G) is inserted in one of the guide holes (7). _{21. The kit of aspect 20, wherein an outer diameter (Do) of the drill guide (G) corresponds to an inner diameter (Di) of the guide} holes (7). _{22. The kit of aspect 20 or 21, comprising the drill (D), wherein an outer diameter of the drill (D) corresponds to an inner} diameter of the through hole of the drill guide (G). _{23. The kit of any one of aspects 9 to 22, comprising the thread cutter (T), the thread cutter (T) configured to be inserted into} the guide holes (7). _{24. The kit of aspect 23, wherein an outer diameter (Do) of the thread cutter (T) corresponds to an inner diameter (Di) of the} guide holes (7). SCREW DRIVER _{25. The kit of any one of aspects 9 to 24, comprising the driver (S), the driver (S) having a front end configured to contact a} rear end of the signal emitters (1) and further configured to advance the signal emitters (1) through the guide holes (7) towards and against the patient’s head. _{26. The kit of aspect 25, wherein the driver (S) is a screw driver, wherein the front end of the driver (S) and the rear end of} the signal emitters (7) are configured to cooperate so as to screw the signal emitters (1) into the cranial bone structure by means of the driver (S). _{27. The kit of aspect 25 or 26, wherein an outer diameter (Do) of the driver (S) corresponds to an inner diameter (Di) of the} guide holes (7). SIGNAL EMITTERS _{28. The kit of any one of aspects 1 to 27, wherein the stimulation signal is adapted to perform one or more of the following:} _{- induce a current in or near neuronal brain cells in a patient’s brain,} _{- stimulate a chemical reaction in neuronal brain cells,} _{- emit the stimulation signals in the form of electromagnetic radiation, preferably comprising one or more of: light waves} with a wavelength in the range of between infrared and ultraviolet, waves with a wavelength longer than infrared light and microwaves, and/or wherein the signal emitters (1) are adapted to emit the stimulation signals in one or more of the following forms: _{- beams, said beams being directed or directable to cross each other in the target region, the kit preferably further} comprising focusing devices for focusing the beams onto the target region, _{- sound waves, the sound waves preferably comprising ultrasonic sound waves,} _{- electromagnetic fields, wherein the signal emitters are preferably adjustable so that their respective electromagnetic fields} overlap each other with collinear induced current directions in the target region. _{29. The kit of any one of aspects 1 to 28, wherein the signal emitters (1) comprise one or more screw threads (12) for fixation} _{in cranial bone structure.} _{30. The kit of aspect 29, wherein each of the signal emitters (1) is contained in a mounting tube (9) with the one or more screw} threads (12) provided on an outer surface of the mounting tube (9). _{31. The kit of any one of aspects 1 to 30, wherein the signal emitters (1) are adapted to be implanted subcutaneously so as not} to penetrate patient’s skin (10) after implantation. _{32. The kit of any one of aspects 1 to 31, wherein the signal emitters (1) are pivotable about at least two axes so that their} stimulating signals can be emitted towards the common target region (4) in the patient’s brain so as to provide said accumulated stimulating effect on that common target region (4). MOTOR _{33. The kit of aspect 32, comprising at least one angle adjusting motor for adjusting an angle of the signal emitters (1) relative} to said common target region (4). CONTROL UNIT _{34. The kit of any one of aspects 1 to 33, further comprising a control unit (C) adapted to directly or indirectly control one or} more elements of the kit. POSITION CONTROLLER _{35. The kit of aspect 34, wherein the control unit (C) includes a position controller adapted to control the adjustment of the} positions of the signal emitters (1) relative to a target region to be stimulated. _{36. The kit of aspect 35, further comprising a data processing system connected both to the position controller and to a 3-D} brain imaging system. SIGNAL EMISSION CONTROLLER _{37. The kit of any one of aspects 34 to 36, wherein the control unit (C) includes a signal emission controller for controlling the} generation of stimulating signals emitted by the signal emitters (1). OPERATION OF CONTROL UNIT _{38. The kit of any one of aspects 34 to 37, wherein the control unit (C) is adapted to be operable by the patient.} _{39. The kit of any one of aspects 34 to 38, wherein the control unit (C) comprises a first part adapted to be mounted to the} patient’s cranium along with the signal emitters (1) and a second part for remote communication with the first part. _{40. The kit of aspect 39, wherein the second part of the control unit (C) is adapted to wirelessly transmit control signals to the} first part of the control unit (C). _{41. The kit of aspect 39 or 40, wherein the first part of the control unit (C) is programmable via the second part of the control} unit (C). _{42. The kit of any one of aspects 39 to 41, wherein the second part of the control unit (C) is adapted to transmit a feedback} signal to the first part of the control unit (C). GALVANIC / WIRELESS DATA TRANSFER _{43. The kit of any one of aspects 34 to 42, comprising galvanic coupling for data transfer between the control unit (C) and the} signal emitters (1). _{44. The kit of any one of aspects 34 to 42, comprising wireless remote control for transmitting data between the control unit} (C) and the signal emitters (1). GALVANIC ENERGY SUPPLY _{45. The kit of any one of aspects 1 to 44, comprising an energy supply galvanically connected to the signal emitters (1).} WIRELESS ENERGY SUPPLY _{46. The kit of any one of aspects 1 to 44, comprising at least one energy transformer connected to the signal emitters (1) for} transforming wireless energy into electric energy and for supplying the electric energy directly or indirectly to the signal emitters (1). _{47. The kit of aspect 46, comprising an energy transmitter for wirelessly transmitting energy to the at least one energy} transformer. METHOD OF MOUNTING THE SYSTEM _{48. A method of mounting a therapeutic brain stimulation system for wireless stimulation of neuronal cells in a patient’s brain} onto a patient’s head, comprising the steps of: -_{cutting the patient’s skin (10) at first positions and second positions above the patient’s cranial bone structure (8),} _{- providing a support structure (6) comprising two or more guide holes (7) and further comprising three or more} _{support legs (13a – 13c) extending from the support structure (6) towards the patient’s head,} _{- fixing the support structure (6) on the patient’s head by means of the support legs (13a – 13c) at each of the first} positions, -_{preparing the second positions through the guide holes (7) for subsequently mounting signal emitters (1) at the second} positions, -_{mounting at least one of the signal emitters (1) to the patient’s cranial bone structure (8) at each of the second} positions, said signal emitters (1) being adapted to generate stimulating signals which in combination allow for wireless stimulation of neuronal cells in the patient’s brain, and -_{removing the support structure (6) while leaving the signal emitters (1) in place.} SUPPORT LEGS _{49. The method according to aspect 48, wherein each of the support legs (13a – 13c) comprises an external screw thread and} the support structure (6) comprises three or more screw holes configured to mate with the external screw thread of the support legs _{(13a – 13c), wherein the method comprises the step of screwing the support legs (13a – 13c) through the screw holes against the cranial} _{bone structure (8) so as to attach the support structure (6) to the p atient’s head.} _{50. The method according to aspect 48 or 49, wherein the support structure (6) spans around a part of the patient’s head and} has two of the support legs (13a, 13c) arranged at opposite end regions of the support structure (6) and one of the support legs (13b) arranged between said two of the support legs (13a, 13c), wherein the method comprises the steps of: -_{urging said two of the support legs (13a, 13c) against the patient’s head at respective first and second fixation points,} _{- pivoting the support structure (6) about an axis defined by the first and second fixation points and} _{- urging said one of the support legs (13b) against the patient’s head at a third fixation point,} wherein the step of pivoting the support structure (6) is carried out such that a desired target region of the patient’s brain lies within a plane defined by the first, second and third fixation points. _{51. The method according to aspect 50, wherein the method comprises the step of moving said one of the support legs (13b)} relative to the support structure (6) in a direction which is perpendicular to a longitudinal axis of the at least one of the support legs (13b), thereby moving the support structure (6) relative to the patient’s head. MARKER _{52. The method according to any one of aspects 48 to 51, wherein at least three markers (M) are provided on the support} structure (6), wherein the method comprises the step of determining a position of the support structure (6) in space. GUIDE HOLES ADJUSTMENT _{53. The method according to any one of aspects 48 to 52, wherein the support structure (6) comprises an adjustment device} (20) for each of the guide holes (7), wherein the method comprises the step of adjusting the guide holes (7) relative to the support structure (6) by means of the adjustment devices (20) such that a central axis of each of the guide holes (7) is directed through the target region (4). _{54. The method according to aspect 53, wherein the support structure (6) comprises a beam having a longitudinal extension,} wherein the method comprises the step of displacing the adjustment device (20) on the beam along said longitudinal extension. ORIENTATION PIN _{55. The method according to any one of aspects 48 to 54, wherein the method comprises the step of placing an orientation pin} (O) in each of the guide holes (7) in order to determine an orientation of the guide holes (7) by means of the orientation pin (O). _{56. The method according to aspect 55, wherein determining the orientation of the orientation pin (O) is made using CT or MRI} imaging. DRILL GUIDE, DRILL and THREAD CUTTER _{57. The method according to any one of aspects 48 to 56, wherein the method comprises the steps of inserting a drill guide (G)} into the guide holes (7), guiding a drill (D) through a through hole of the drill guide (G) towards and against the patient’s head, and drilling holes (14) into the cranial bone structure (8). _{58. The method according to aspect 57, wherein the method comprises the steps of inserting a thread cutter (T) through the} guide holes (7) into the holes (14) of the cranial bone structure (8) and cutting internal screw threads (15) into the holes of the cranial bone structure (8). SCREW DRIVER _{59. The method according to any one of aspects 48 to 58, wherein the method comprises the step of advancing the signal} emitters (1) through the guide holes (7) towards and against the patient’s head by means of a driver (S). _{60. The method according to aspect 59, wherein the signal emitters (1) comprise one or more screw threads (12), wherein the} method comprises the step of screwing the signal emitters (1) into the cranial bone structure (8) using the driver (S). _{61. The method according to any one of aspects 48 to 60, wherein the method comprises the step of fixing the signal emitters} (1) in the cranial bone structure (8) so as to penetrate only a part of a hard outer layer thereof or so as to completely penetrate the cranial bone structure (8) without penetrating into the dura mater of the brain. CLOSING _{62. The method according to any one of aspects 48 to 61, wherein the method comprises the step of implanting the signal} emitters (1) subcutaneously by closing the patient’s skin (10) over the signal emitters (1). EMITTER ADJUSTMENT _{63. The method according to any one of aspects 48 to 62, wherein the method comprises the step of adjusting the signal} _{emitters (1) such that their stimulating signals are emitted from said second positions towards a common target region (4) in the} _{patient’s brain (5) so as to provide an accumulated stimulating effect on that target region (4).} _{64. The method according to aspect 63, wherein the method comprises the step of pivoting the signal emitters (1) about at least} two axes so that their stimulating signals emit towards the common target region (4) in the patient’s brain (5) so as to provide said accumulated stimulating effect on the common target region (4). SUPPORT STRUCTURE _{65. A support structure (6) for use in fixing signal emitters (1) of a therapeutic brain stimulation system in cranial bone} _{structure of a patient’s head, wherein the support structure (6) comprises} _{- three or more support legs (13a – 13c) which extend from the support structure (6) towards and against the patient’s} head for temporarily fixing the support structure (6) on the patient’s head and -_{two or more guide holes (7) configured for aiding in guiding one or more of the following items towards and against} the patient’s head: an orientation pin (O), a driver (S), a drill guide (G), a drill (D), a thread cutter (T), the signal emitters (1). _{66. The support structure (6) of aspect 65, wherein the support legs (13a – 13c) each comprise an external screw thread and} the support structure (6) comprises three or more screw holes configured to mate with the external screw thread of the support legs _{(13a – 13c).} _{67. The support structure (6) of aspect 65 or 66, wherein the support legs (13a – 13c) each have a pointed tip end facing} towards the patient’s head. _{68. The support structure (6) of any one of aspects 65 to 67, wherein the support structure (6) is configured to span around a} _{part of the patient’s head and further configured so as to arrange two of the support legs (13a, 13c) at opposite end regions of the} support structure (6) and one of the support legs (13b) between said two of the support legs (13a, 13c). _{69. The support structure (6) of aspect 68, wherein said one of the support legs (13b) is arranged centrally between said two} of the support legs (13a, 13c). _{70. The support structure (6) of any one of aspects 65 to 69, wherein at least one of the support legs (13b), preferably said} one of the support legs (13b) mentioned in aspect 67, is movable relative to the support structure (6) in a direction which is perpendicular to a longitudinal axis of the at least one of the support legs (13b). _{71. The support structure (6) of aspect 70, wherein said at least one of the support legs (13b) is slidably guided relative to the} support structure (6) in said direction which is perpendicular to the longitudinal axis of the at least one of the support legs (13b). MARKER _{72. The support structure (6) of any one of aspects 65 to 71, wherein at least three markers (M) are provided on the support} structure (6) which permit determination of a position of the support structure (6) in space. GUIDE HOLES _{73. The support structure (6) of any one of aspects 65 to 72, wherein an outer diameter (Do) of the signal emitters (1)} corresponds to an inner diameter (Di) of the guide holes (7). _{74. The support structure (6) of any one of aspects 65 to 73, wherein the position and orientation of the guide holes (7) are} fixed relative to the support structure (6). _{75. The support structure (6) of any one of aspects 65 to 73, wherein the support structure (6) comprises an adjustment device} (20) for each of the guide holes (7), wherein the adjustment device (20) is configured for adjusting the associated guide hole (7) relative to the support structure (6) _{76. The support structure (6) of aspect 75, wherein the adjustment device (20) is configured for adjusting the associated guide} hole (7) relative to the support structure (6) such that a central axis of the associated guide hole (7) is directed through the target region (4). _{77. The support structure (6) of aspect 75 or 76, wherein the adjustment device (20) is mounted on the support structure (6)} so as to be pivotal about at least one, preferably about only one, pivoting axis (21). _{78. The support structure (6) of aspect 77, wherein the only one pivoting axis (21) is perpendicular to a plane in which the} central axes (7a) of the guide holes (7) are arranged on the support structure (6). _{79. The support structure (6) of any one of aspects 75 to 78, wherein the support structure (6) comprises a beam having a} _{longitudinal extension, wherein the adjustment device (20) is mounted on the beam so as to be displaceable along said longitudinal} extension. _{80. The support structure (6) of aspect 79, wherein the beam is curved and embraces an angle of curvature of at least about} 180°. PIEZOELECTRIC MOTOR _{81. The support structure (6) of any one of aspects 75 to 80, comprising at least one piezoelectric motor.} _{82. The support structure (6) of aspect 81, wherein each of the adjustment devices (20) comprises one or two, preferably} exactly one, of the at least one piezoelectric motor configured to generate rotary motion to the adjustment devices (20). _{83. The kit of any one of aspects 1 to 47, comprising at least one piezoelectric motor.} _{84. The kit of aspect 83, wherein each of the signal emitters (1) comprises one or two, preferably exactly one, of the at least} one piezoelectric motor configured to generate rotary motion to the signal emitters (1). _{85. The kit of aspect 83 or 84, wherein each of the signal emitters (1) comprises one of the at least one piezoelectric motor} configured to generate linear motion to the signal emitters (1). _{86. A kit for a therapeutic brain stimulation system for wireless stimulation of neuronal cells in a patient’s brain by means of} stimulating signals emitted from different positions towards a common target region (4) in a patient’s brain so as to provide an accumulated stimulating effect on said target region, preferably a kit according to any one of aspects 1 to 47, said kit comprising two or more signal emitters (1) adapted to be fixed in cranial bone structure and generate the stimulating signal, comprising at least one piezoelectric motor. _{87. The kit of aspect 86, wherein each of the signal emitters (1) comprises one or two, preferably exactly one, of the at least} one piezoelectric motor configured to generate rotary motion to the signal emitters (1). _{88. The kit of aspect 86 or 87, wherein each of the signal emitters (1) comprises one of the at least one piezoelectric motor} configured to generate linear motion to the signal emitters (1). _{89. The kit of any one of aspects 86 to 88, including aspect 13, wherein each of the adjustment devices (20) comprises one or} two, preferably exactly one, of the at least one piezoelectric motor configured to generate rotary motion to the adjustment devices (20). _{90. The support structure (6) or kit of any one of aspects 81 to 89, wherein the at least one piezoelectric motor comprises a} piezoelectric inchworm motor. _{91. The support structure (6) or kit of any one of aspects 81 to 89, wherein the at least one piezoelectric motor comprises a} piezoelectric inertial motor. _{92. The support structure (6) or kit of any one of aspects 81 to 89, wherein the at least one piezoelectric motor comprises a} piezoelectric walk-drive motor. _{93. The support structure (6) or kit of any one of aspects 90 to 92, wherein the piezoelectric motor is a linear piezoelectric} motor which operates with at least one of: -_{a speed in a range of 1 mm/s to 10 mm/s,} _{- a stroke length of up to 5 mm, and} _{- a force in a range of 2 N – 30 N.} _{94. The support structure (6) or kit of any one of aspects 90 to 92, wherein the piezoelectric motor is a rotational piezoelectric} motor which operates with at least one of: -_{a rotational speed in a range of 1 mrad/s – 100 mrad/s, and} _{- a torque in a range of 100 Nmm – 900 Nmm.} _{95. The support structure (6) of aspect 81 or 82 or kit of any one of aspects 83 to 89, wherein the at least one piezoelectric} motor comprises a piezoelectric ultrasonic motor. _{96. The support structure (6) or kit of aspect 95, wherein the piezoelectric ultrasonic motor is a traveling wave ultrasonic} motor. _{97. The support structure (6) or kit of aspect 95, wherein the piezoelectric ultrasonic motor is a standing wave ultrasonic} motor. _{98. The support structure (6) or kit of any one of aspects 95 to 97, wherein the piezoelectric ultrasonic motor is a rotational} piezoelectric ultrasonic motor which operates with at least one of: -_{a rotational speed in a range of 10 mrad/s – 10,000 mrad/s, and} _{- a torque in a range of 20 Nmm – 450 Nmm.} _{99. The support structure (6) or kit of any one of aspects 95 to 97, wherein the piezoelectric ultrasonic motor is a linear} piezoelectric ultrasonic motor which operates with at least one of: -_{a speed in a range of 4 mm/s – 100 mm/s,} _{- a stroke length of up to 5 mm, and} _{- a force in a range of 0.5 N – 30 N.} _{100. The support structure (6) or kit of any one of aspects 81 to 99, wherein the at least one piezoelectric motor comprises at} least one bimorph piezoelectric actuator. _{101. The support structure (6) or kit of any one of aspects 81 to 100, wherein the at least one piezoelectric motor is substantially} non-magnetic. _{102. The support structure (6) or kit of any one of aspects 81 to 101, wherein the at least one piezoelectric motor is substantially} non-metallic. _{103. The support structure (6) or kit of any one of aspects 81 to 102, wherein the at least one piezoelectric motor is a reversible} piezoelectric motor.

Claims

1. A kit for a therapeutic brain stimulation system for wireless stimulation of neuronal cells in a patient’s brain by means of stimulating signals emitted from different positions towards a common target region (4) in a patient’s brain so as to provide an accumulated stimulating effect on said target region, said kit comprising: -_{two or more signal emitters (1) adapted to be fixed in cranial bone structure and generate the stimulating signals and} _{- a support structure (6) configured to be temporarily mounted on a patient’s head as an aid for fixing the signal emitters (1) in the} cranial bone structure. _{2. The kit of claim 1, wherein the support structure (6) comprises three or more support legs (13a – 13c) which extend from the support} structure (6) towards and against the patient’s head for temporarily fixing the support structure (6) on the patient’s head. _{3. The kit of claim 2, wherein the support legs (13a – 13c) each comprise an external screw thread and the support structure (6)} _{comprises three or more screw holes configured to mate with the external screw thread of the support legs (13a – 13c).} _{4. The kit of claim 2 or 3, wherein the support legs (13a – 13c) each have a pointed tip end facing towards the patient’s head.} _{5. The kit of any one of claims 2 to 4, wherein the support structure (6) is configured to span around a part of the patient’s head and} further configured so as to arrange two of the support legs (13a, 13c) at opposite end regions of the support structure (6) and one of the support legs (13b) between said two of the support legs (13a, 13c), preferably centrally between said two of the support legs (13a, 13c). _{6. The kit of claim 5, wherein said one of the support legs (13b) arranged between said two of the support legs (13a, 13c) is movable} relative to the support structure (6) in a direction which is perpendicular to a longitudinal axis of the at least one of the support legs (13b). _{7. The kit of claim 6, wherein said at least one of the support legs (13b) is slidably guided relative to the support structure (6) in said} direction which is perpendicular to the longitudinal axis of the at least one of the support legs (13b). _{8. The kit of any one of claims 1 to 7, wherein at least three markers (M) are provided on the support structure (6) which permit} determination of a position of the support structure (6) in space. _{9. The kit of any one of claims 1 to 8, wherein the support structure (6) has two or more guide holes (7), wherein each of the guide holes} (7) is configured for aiding in guiding one or more of the following items towards and against the patient’s head: an orientation pin (O), a driver (S), a drill guide (G), a drill (D), a thread cutter (T), and the signal emitters (1). _{10. The kit of claim 9, wherein an outer diameter (Do) of the one of the signal emitters (1) corresponds to an inner diameter (Di) of the} guide holes (7). _{11. The kit of claim 9 or 10, wherein either a position and orientation of the guide holes (7) are fixed relative to the support structure (6)} or the support structure (6) comprises an adjustment device (20) associated to each of the guide holes (7), wherein the adjustment device (20) is configured for adjusting the associated guide hole (7) relative to the support structure (6). _{12. The kit of claim 11, wherein the adjustment device (20) is configured for adjusting the associated guide hole (7) relative to the support} structure (6) such that a central axis (7a) of the associated guide hole (7) is directed through the target region (4). _{13. The kit of claim 11 or 12, wherein the adjustment device (20) is mounted on the support structure (6) so as to be pivotal about at least} one, preferably about only one, pivoting axis (21). _{14. The kit of claim 13, wherein the only one pivoting axis (21) is perpendicular to a plane in which the central axes (7a) of the guide holes} (7) are arranged on the support structure (6). _{15. The kit of any one of claims 11 to 14, wherein the support structure (6) comprises a beam having a longitudinal extension, wherein the} adjustment device (20) is mounted on the beam so as to be displaceable along said longitudinal extension. _{16. The kit of claim 15, wherein the beam is curved and embraces an angle of curvature of at least about 180°.} _{17. The kit of any one of claims 9 to 16, comprising at least one of the orientation pin (O), the orientation pin (O) having an outer diameter} (Do) which corresponds to an inner diameter (Di) of the guide holes (7). _{18. The kit of claim 17, wherein the orientation pin (O) has a pointed tip end.} _{19. The kit of claim 16 or 17, wherein the orientation pin (O) is made of or comprises a material which allows for an automatic} determination of an orientation of the orientation pin (O), such as by CT or MRI imaging.

_{20. The kit of any one of claims 9 to 19, comprising the drill guide (G), the drill guide (G) configured to be inserted into the guide holes (7),} the drill guide having a through hole for guiding a drill (D) towards and against the patient’s head when the drill guide (G) is inserted in one of the guide holes (7). _{21. The kit of claim 20, wherein an outer diameter (Do) of the drill guide (G) corresponds to an inner diameter (Di) of the guide holes (7).} _{22. The kit of claim 20 or 21, comprising the drill (D), wherein an outer diameter of the drill (D) corresponds to an inner diameter of the} through hole of the drill guide (G). _{23. The kit of any one of claims 9 to 22, comprising the thread cutter (T), the thread cutter (T) configured to be inserted into the guide} holes (7). _{24. The kit of claim 23, wherein an outer diameter (Do) of the thread cutter (T) corresponds to an inner diameter (Di) of the guide holes} (7). _{25. The kit of any one of claims 9 to 24, comprising the driver (S), the driver (S) having a front end configured to contact a rear end of} the signal emitters (1) and further configured to advance the signal emitters (1) through the guide holes (7) towards and against the patient’s head. _{26. The kit of claim 25, wherein the driver (S) is a screw driver, wherein the front end of the driver (S) and the rear end of the signal} emitters (7) are configured to cooperate so as to screw the signal emitters (1) into the cranial bone structure by means of the driver (S). _{27. The kit of claim 25 or 26, wherein an outer diameter (Do) of the driver (S) corresponds to an inner diameter (Di) of the guide holes} (7). _{28. The kit of any one of claims 1 to 27, wherein the stimulation signal is adapted to perform one or more of the following:} _{- induce a current in or near neuronal brain cells in a patient’s brain,} _{- stimulate a chemical reaction in neuronal brain cells,} _{- emit the stimulation signals in the form of electromagnetic radiation, preferably comprising one or more of: light waves with a} wavelength in the range of between infrared and ultraviolet, waves with a wavelength longer than infrared light and microwaves, and/or wherein the signal emitters (1) are adapted to emit the stimulation signals in one or more of the following forms: -_{beams, said beams being directed or directable to cross each other in the target region, the kit preferably further comprising} focusing devices for focusing the beams onto the target region, -_{sound waves, the sound waves preferably comprising ultrasonic sound waves,} _{- electromagnetic fields, wherein the signal emitters are preferably adjustable so that their respective electromagnetic fields} _{overlap each other with collinear induced current directions in the target region.} _{29. The kit of any one of claims 1 to 28, wherein the signal emitters (1) comprise one or more screw threads (12) for fixation in cranial} bone structure. _{30. The kit of claim 29, wherein each of the signal emitters (1) is contained in a mounting tube (9) with the one or more screw threads} (12) provided on an outer surface of the mounting tube (9). _{31. The kit of any one of claims 1 to 30, wherein the signal emitters (1) are adapted to be implanted subcutaneously so as not to penetrate} patient’s skin (10) after implantation. _{32. The kit of any one of claims 1 to 31, wherein the signal emitters (1) are pivotable about at least two axes so that their stimulating} signals can be emitted towards the common target region (4) in the patient’s brain so as to provide said accumulated stimulating effect on that common target region (4). _{33. The kit of claim 32, comprising at least one angle adjusting motor for adjusting an angle of the signal emitters (1) relative to said} common target region (4). _{34. The kit of any one of claims 1 to 33, further comprising a control unit (C) adapted to directly or indirectly control one or more elements} of the kit. _{35. The kit of claim 34, wherein the control unit (C) includes a position controller adapted to control the adjustment of the positions of} the signal emitters (1) relative to a target region to be stimulated.

_{36. The kit of claim 35, further comprising a data processing system connected both to the position controller and to a 3-D brain imaging} system. _{37. The kit of any one of claims 34 to 36, wherein the control unit (C) includes a signal emission controller for controlling the generation} of stimulating signals emitted by the signal emitters (1). _{38. The kit of any one of claims 34 to 37, wherein the control unit (C) is adapted to be operable by the patient.} _{39. The kit of any one of claims 34 to 38, wherein the control unit (C) comprises a first part adapted to be mounted to the patient’s} _{cranium along with the signal emitters (1) and a second part for remote communication with the first part.} _{40. The kit of claim 39, wherein the second part of the control unit (C) is adapted to wirelessly transmit control signals to the first part} of the control unit (C). _{41. The kit of claim 39 or 40, wherein the first part of the control unit (C) is programmable via the second part of the control unit (C).} _{42. The kit of any one of claims 39 to 41, wherein the second part of the control unit (C) is adapted to transmit a feedback signal to the} first part of the control unit (C). _{43. The kit of any one of claims 34 to 42, comprising galvanic coupling for data transfer between the control unit (C) and the signal} emitters (1). _{44. The kit of any one of claims 34 to 42, comprising wireless remote control for transmitting data between the control unit (C) and the} signal emitters (1). _{45. The kit of any one of claims 1 to 44, comprising an energy supply galvanically connected to the signal emitters (1).} _{46. The kit of any one of claims 1 to 44, comprising at least one energy transformer connected to the signal emitters (1) for transforming} wireless energy into electric energy and for supplying the electric energy directly or indirectly to the signal emitters (1). _{47. The kit of claim 46, comprising an energy transmitter for wirelessly transmitting energy to the at least one energy transformer.} _{48. A method of mounting a therapeutic brain stimulation system for wireless stimulation of neuronal cells in a patient’s brain onto a} patient’s head, comprising the steps of: -_{cutting the patient’s skin (10) at first positions and second positions above the patient’s cranial bone structure (8),} _{- providing a support structure (6) comprising two or more guide holes (7) and further comprising three or more support legs (13a} _{– 13c) extending from the support structure (6) towards the patient’s head,} _{- fixing the support structure (6) on the patient’s head by means of the support legs (13a – 13c) at each of the first positions,} _{- preparing the second positions through the guide holes (7) for subsequently mounting signal emitters (1) at the second positions,} _{- mounting at least one of the signal emitters (1) to the patient’s cranial bone structure (8) at each of the second positions, said} signal emitters (1) being adapted to generate stimulating signals which in combination allow for wireless stimulation of neuronal cells in the patient’s brain, and -_{removing the support structure (6) while leaving the signal emitters (1) in place.} _{49. The method according to claim 48, wherein each of the support legs (13a – 13c) comprises an external screw thread and the support} structure (6) comprises three or more screw holes configured to mate with the external screw thread of the support legs (13a – 1_{3c), wherein the method comprises the step of screwing the support legs (13a – 13c) through the screw holes against the cranial} bone structure (8) so as to attach the support structure (6) to the p23atient’s head. _{50. The method according to claim 48 or 49, wherein the support structure (6) spans around a part of the patient’s head and has two of} the support legs (13a, 13c) arranged at opposite end regions of the support structure (6) and one of the support legs (13b) arranged between said two of the support legs (13a, 13c), wherein the method comprises the steps of: -_{urging said two of the support legs (13a, 13c) against the patient’s head at respective first and second fixation points,} _{- pivoting the support structure (6) about an axis defined by the first and second fixation points and} _{- urging said one of the support legs (13b) against the patient’s head at a third fixation point,} wherein the step of pivoting the support structure (6) is carried out such that a desired target region of the patient’s brain lies within a plane defined by the first, second and third fixation points.

_{51. The method according to claim 50, wherein the method comprises the step of moving said one of the support legs (13b) relative to} _{the support structure (6) in a direction which is perpendicular to a longitudinal axis of the at least one of the support legs (13b),} thereby moving the support structure (6) relative to the patient’s head. _{52. The method according to any one of claims 48 to 51, wherein at least three markers (M) are provided on the support structure (6),} wherein the method comprises the step of determining a position of the support structure (6) in space. _{53. The method according to any one of claims 48 to 52, wherein the support structure (6) comprises an adjustment device (20) for} each of the guide holes (7), wherein the method comprises the step of adjusting the guide holes (7) relative to the support structure (_{6) by means of the adjustment devices (20) such that a central axis of each of the guide holes (7) is directed through the target} region (4). _{54. The method according to claim 53, wherein the support structure (6) comprises a beam having a longitudinal extension, wherein the} _{method comprises the step of displacing the adjustment device (20) on the beam along said longitudinal extension.} _{55. The method according to any one of claims 48 to 54, wherein the method comprises the step of placing an orientation pin (O) in each} of the guide holes (7) in order to determine an orientation of the guide holes (7) by means of the orientation pin (O). _{56. The method according to claim 55, wherein determining the orientation of the orientation pin (O) is made using CT or MRI imaging.} _{57. The method according to any one of claims 48 to 56, wherein the method comprises the steps of inserting a drill guide (G) into the} guide holes (7), guiding a drill (D) through a through hole of the drill guide (G) towards and against the patient’s head, and drilling holes (14) into the cranial bone structure (8). _{58. The method according to claim 57, wherein the method comprises the steps of inserting a thread cutter (T) through the guide holes} (7) into the holes (14) of the cranial bone structure (8) and cutting internal screw threads (15) into the holes of the cranial bone structure (8). _{59. The method according to any one of claims 48 to 58, wherein the method comprises the step of advancing the signal emitters (1)} through the guide holes (7) towards and against the patient’s head by means of a driver (S). _{60. The method according to claim 59, wherein the signal emitters (1) comprise one or more screw threads (12), wherein the method} comprises the step of screwing the signal emitters (1) into the cranial bone structure (8) using the driver (S). _{61. The method according to any one of claims 48 to 60, wherein the method comprises the step of fixing the signal emitters (1) in the} cranial bone structure (8) so as to penetrate only a part of a hard outer layer thereof or so as to completely penetrate the cranial bone structure (8) without penetrating into the dura mater of the brain. _{62. The method according to any one of claims 48 to 61, wherein the method comprises the step of implanting the signal emitters (1)} subcutaneously by closing the patient’s skin (10) over the signal emitters (1). _{63. The method according to any one of claims 48 to 62, wherein the method comprises the step of adjusting the signal emitters (1) such} that their stimulating signals are emitted from said second positions towards a common target region (4) in the patient’s brain (5) so as to provide an accumulated stimulating effect on that target region (4). _{64. The method according to claim 63, wherein the method comprises the step of pivoting the signal emitters (1) about at least two axes} so that their stimulating signals emit towards the common target region (4) in the patient’s brain (5) so as to provide said accumulated stimulating effect on the common target region (4). _{65. A support structure (6) for use in fixing signal emitters (1) of a therapeutic brain stimulation system in cranial bone structure of a} patient’s head, wherein the support structure (6) comprises -_{three or more support legs (13a – 13c) which extend from the support structure (6) towards and against the patient’s head for} temporarily fixing the support structure (6) on the patient’s head and -_{two or more guide holes (7) configured for aiding in guiding one or more of the following items towards and against the patient’s} head: an orientation pin (O), a driver (S), a drill guide (G), a drill (D), a thread cutter (T), the signal emitters (1). _{66. The support structure (6) of claim 65, wherein the support legs (13a – 13c) each comprise an external screw thread and the support} structure (6) comprises three or more screw holes configured to mate with the external screw thread of the support legs (13a –

_{67. The support structure (6) of claim 65 or 66, wherein the support legs (13a – 13c) each have a pointed tip end facing towards the} patient’s head. _{68. The support structure (6) of any one of claims 65 to 67, wherein the support structure (6) is configured to span around a part of the} patient’s head and further configured so as to arrange two of the support legs (13a, 13c) at opposite end regions of the support structure (6) and one of the support legs (13b) between said two of the support legs (13a, 13c). _{69. The support structure (6) of claim 68, wherein said one of the support legs (13b) is arranged centrally between said two of the} support legs (13a, 13c). _{70. The support structure (6) of any one of claims 65 to 69, wherein at least one of the support legs (13b), preferably said one of the} support legs (13b) mentioned in claim 67, is movable relative to the support structure (6) in a direction which is perpendicular to a longitudinal axis of the at least one of the support legs (13b). _{71. The support structure (6) of claim 70, wherein said at least one of the support legs (13b) is slidably guided relative to the support} structure (6) in said direction which is perpendicular to the longitudinal axis of the at least one of the support legs (13b). _{72. The support structure (6) of any one of claims 65 to 71, wherein at least three markers (M) are provided on the support structure} _{(6) which permit determination of a position of the support structure (6) in space.} _{73. The support structure (6) of any one of claims 65 to 72, wherein an outer diameter (Do) of the signal emitters (1) corresponds to an} inner diameter (Di) of the guide holes (7). _{74. The support structure (6) of any one of claims 65 to 73, wherein the position and orientation of the guide holes (7) are fixed relative} to the support structure (6). _{75. The support structure (6) of any one of claims 65 to 73, wherein the support structure (6) comprises an adjustment device (20) for} each of the guide holes (7), wherein the adjustment device (20) is configured for adjusting the associated guide hole (7) relative to the support structure (6) _{76. The support structure (6) of claim 75, wherein the adjustment device (20) is configured for adjusting the associated guide hole (7)} relative to the support structure (6) such that a central axis of the associated guide hole (7) is directed through the target region (4). _{77. The support structure (6) of claim 75 or 76, wherein the adjustment device (20) is mounted on the support structure (6) so as to be} pivotal about at least one, preferably about only one, pivoting axis (21). _{78. The support structure (6) of claim 77, wherein the only one pivoting axis (21) is perpendicular to a plane in which the central axes} (7a) of the guide holes (7) are arranged on the support structure (6). _{79. The support structure (6) of any one of claims 75 to 78, wherein the support structure (6) comprises a beam having a longitudinal} extension, wherein the adjustment device (20) is mounted on the beam so as to be displaceable along said longitudinal extension. _{80. The support structure (6) of claim 79, wherein the beam is curved and embraces an angle of curvature of at least about 180°.} _{81. The support structure (6) of any one of claims 75 to 80, comprising at least one piezoelectric motor.} _{82. The support structure (6) of claim 81, wherein each of the adjustment devices (20) comprises one or two, preferably exactly one, of} the at least one piezoelectric motor configured to generate rotary motion to the adjustment devices (20). _{83. The kit of any one of claims 1 to 47, comprising at least one piezoelectric motor.} _{84. The kit of claim 83, wherein each of the signal emitters (1) comprises one or two, preferably exactly one, of the at least one} piezoelectric motor configured to generate rotary motion to the signal emitters (1). _{85. The kit of claim 83 or 84, wherein each of the signal emitters (1) comprises one of the at least one piezoelectric motor configured to} generate linear motion to the signal emitters (1). _{86. A kit for a therapeutic brain stimulation system for wireless stimulation of neuronal cells in a patient’s brain by means of stimulating} signals emitted from different positions towards a common target region (4) in a patient’s brain so as to provide an accumulated s_{timulating effect on said target region, preferably a kit according to any one of claims 1 to 47, said kit comprising two or more signal} emitters (1) adapted to be fixed in cranial bone structure and generate the stimulating signal, comprising at least one piezoelectric motor.

_{87. The kit of claim 86, wherein each of the signal emitters (1) comprises one or two, preferably exactly one, of the at least one} piezoelectric motor configured to generate rotary motion to the signal emitters (1). _{88. The kit of claim 86 or 87, wherein each of the signal emitters (1) comprises one of the at least one piezoelectric motor configured to} generate linear motion to the signal emitters (1). _{89. The kit of any one of claims 86 to 88, including claim 13, wherein each of the adjustment devices (20) comprises one or two, preferably} exactly one, of the at least one piezoelectric motor configured to generate rotary motion to the adjustment devices (20). _{90. The support structure (6) or kit of any one of claims 81 to 89, wherein the at least one piezoelectric motor comprises a piezoelectric} inchworm motor. _{91. The support structure (6) or kit of any one of claims 81 to 89, wherein the at least one piezoelectric motor comprises a piezoelectric} inertial motor. _{92. The support structure (6) or kit of any one of claims 81 to 89, wherein the at least one piezoelectric motor comprises a piezoelectric} walk-drive motor. _{93. The support structure (6) or kit of any one of claims 90 to 92, wherein the piezoelectric motor is a linear piezoelectric motor which} operates with at least one of: -_{a speed in a range of 1 mm/s to 10 mm/s,} _{- a stroke length of up to 5 mm, and} _{- a force in a range of 2 N – 30 N.} _{94. The support structure (6) or kit of any one of claims 90 to 92, wherein the piezoelectric motor is a rotational piezoelectric motor} which operates with at least one of: -_{a rotational speed in a range of 1 mrad/s – 100 mrad/s, and} _{- a torque in a range of 100 Nmm – 900 Nmm.} _{95. The support structure (6) of claim 81 or 82 or kit of any one of claims 83 to 89, wherein the at least one piezoelectric motor comprises} _{a piezoelectric ultrasonic motor.} _{96. The support structure (6) or kit of claim 95, wherein the piezoelectric ultrasonic motor is a traveling wave ultrasonic motor.} _{97. The support structure (6) or kit of claim 95, wherein the piezoelectric ultrasonic motor is a standing wave ultrasonic motor.} _{98. The support structure (6) or kit of any one of claims 95 to 97, wherein the piezoelectric ultrasonic motor is a rotational piezoelectric} ultrasonic motor which operates with at least one of: -_{a rotational speed in a range of 10 mrad/s – 10,000 mrad/s, and} _{- a torque in a range of 20 Nmm – 450 Nmm.} _{99. The support structure (6) or kit of any one of claims 95 to 97, wherein the piezoelectric ultrasonic motor is a linear piezoelectric} ultrasonic motor which operates with at least one of: -_{a speed in a range of 4 mm/s – 100 mm/s,} _{- a stroke length of up to 5 mm, and} _{- a force in a range of 0.5 N – 30 N.} _{100. The support structure (6) or kit of any one of claims 81 to 99, wherein the at least one piezoelectric motor comprises at least one} bimorph piezoelectric actuator. _{101. The support structure (6) or kit of any one of claims 81 to 100, wherein the at least one piezoelectric motor is substantially non-} magnetic. _{102. The support structure (6) or kit of any one of claims 81 to 101, wherein the at least one piezoelectric motor is substantially non-} metallic. _{103. The support structure (6) or kit of any one of claims 81 to 102, wherein the at least one piezoelectric motor is a reversible piezoelectric} motor.