CA1293204C - Implantable hearing aid and method of improving hearing - Google Patents

Abstract

ABSTRACT

In the present application, there is disclosed a method and apparatus for improving the impaired hearing of a subject utilizing a totally implantable device, not requir-ing any percutaneous elements and manifesting a frequency response commensurate with that provided by normal hearing.
In accordance with one aspect of the present invention, the mechanical vibrations effected by the tympanic membrane (ear-drum) are converted into electrical signals which are there-after amplified and converted into mechanical vibrations and communicated to the inner ear. Conversion of mechanical energy to electrical energy is achieved by means of an input transducer which is surgically implanted within the ossi-cular chain, followed by suitable amplification of those electrical signals to account for both the level of hearing impairment suffered by the subject and the electromechanical response of the implanted device, and then the signals are converted to mechanical energy (vibrations) once again by an output transducer, all to achieve the desired level of aural enhancement for the wearer. These transducers and the asso-ciated circuitry thus comprise means for mediating mechanical/electrical energy within the middle ear space.
In all instances the ossicular chain of the subject is inter-rupted to preclude transmission of mechanical vibrations between the tympanic membrane and the inner ear, with the implanted device interposed within the chain to bridge the interruption therein and form an electromechanically inde-pendent link, free from feedback, between the membrane and the inner ear.

Description

IMP~ANTABLE HEARING AID AND METHOD
OF IMPROVXNG HEARING

BACKGROUND OF THE INVENTION

The present invention relates to a device for improving the impaired hearing of a human subject, and more particularly, to a totaLly implantable hearing aid device.

In an anatomically normal human hearing appara tus, sound waves, which represent acoustical energy, are directed into an ear ca~al by the outer ear (pinna) and impinge upon a tympanic membrane (eardrum) interposed, at the terminus of the ear canal, between it and the middle ear space. The pressure of the sound waves effect tympanic vibrations in the eardrum, which then become manifested as mechanical energy. The mechanical energy in the form of tympanic vibrations is communicated to the inner ear by a sequence of articulating bones located in the middle ear space, which are generally referred to as the ossicular chain. The ossicular chain must be intact if acoustical energy existing at the eardrum is to be conducted as mechani-cal energy to the inner ear.

The ossicular chain includes three primary compo-nents, the malleus, the incus and the stapes. The malleus includes respective manibrium, neck and head portions. The manibrium of the malleus attaches to the tympanic membrane .,~

:

~293Z~9~

at a point known as the umbo. The head of the malleus, con-nected to the manubrium by the neck portion, articulates with one end of the incus, which provides a transmission path for the mechanical energy of induced vibrations from the malleus ~o the stapes. The stapes includes a capitulum portion connected to a footplate portion by means of a support crus and is dispo~ed in and against a membrane-covered open-ing to the inner ear referred to as the oval window~ The incus articulates with the capi~ulum of the stapes to complete the mechanical transmission path.
Normally, tympanic vibrations are mechanically conducted through the malleus, incus and stapes, to the oval window and therethrough to the inner ear (cochlea). ~hese mechanical vibrations generate fluidic motion (transmitted as hydraulic energy) within the cochlea. Pressures generated in the cochlea by fluidic motion are accommodated by a second membrane-covered opening between the inner and middle ear, referred to as the round window. The cochlea translates the fluidic motion into neural impulses corresponding to sound perception as interpreted by the brain. However, various disorders of the tympanic mem~rane, ossicular chain and/or inner ear can occur to disrupt or impair normal hearing.
Various passive mechanical ossicular prosthesis and implantation techniques have been developed in connection with recons~ructive surgery of the middle ear. See G.J.
Jako, "8iomedical Engineering in Ear Surgeryn, Otolar~ngolo~ic Clinics of North America, Vol. 5, No. 1, Feb. 1972, and G.J.

~2~3~

Jako, et al., "Conservative Tympanoplas~y~, American Academy of Opthalmology and Otolarynology, Course 319, presented : Oct. 1, 1966~
, , Miniaturized electronic hearing aid devices which : 5 compensate for hearing disorders are also, in general, well ~ known. Various of such devices are adapted to be en~irely :: .
: received within the ear canal or partly or comple~ely implanted within the skull of a subject. Examples of such devices are those di~closed in U~S. Patents No. 3,170,046, issued to ~; 10 L~ P. Leale on February 16, 1965 No~ 3,712,962 issued to J. M. Epley on January 23, 1973î No. 3,764,748 issued to J. P. Branch et al. on October 9, 1973; No. 3,346,704 and No~

- 3,557,775 issued on October 10, 1967 and ~anuary 26, 1971, respectively to J. L. Mahoney; No. 3,870,B32 issued to J. M.
Fredrickson on March 11, 1975; No~ 4,150,262 issued to H.
Ono on April 17, 1979; and No. ~,28~,856 and No~ 4,357,497 both issued to I. J. Hochmaier et al. on Augu~t 18, 1981 and November 2, 1982, respectively. Further description of such devices is found in T. Ohno, "The Implantabale Hearing Aid"
(Part I) Audecibel, Fall 1984 and Ari~omo et al., "Audiologi-cal Assessment of Vibratory Hearing" presented at 17~h Inter-national Congress of ~udiology meeting, Santa Barbara, CA., Aug. 1984.
Perhaps the mos~ interesting of the aforementioned United States paten~s is the '748 paten~ which concerns :~ implantable hearing aids including those which are configured for disposition principally within the middle ear space.
The approach suggested there provides a transducer, which ~2~3204 may be a piezoelectric crystal transducer, capable of con-verting m~chanical vibrations within the ossicular chain into an output voltage. That output voltage may be applied to the area of the oval window to electrically stimulate it and may include a diode to rectify the variable vol~age out-put of the transducer into a pulsat in~ DC voltage to st imulate the auditory nerve. In another variant, the patentees suggest the incorporation of a piezoelectric crystal in the area of the oval window which receives the variable voltage signals from the ~ransducer and vibrates to stimulate the auditory nerv~. In any of ~hese approaches, however, the proposed system also utilizes what the patentees regard as the natural distortion-~ree transmission of sound through the ossicular - chain wherever poss;ble. They say that, by virtue of leaving the ossicular chain intact, th~ acoustic energy impinging upon the eardrum passes through the ossicular ~hain in a distortion-free manner whereby ~he sound powered hearing aid they describe needs only supply minimal assistance to the hearing process. The description continues in the '748 paten~ to note that, as an alternative, the s~apes may be removed and the hearing aid physically located in its stead where conditions permit. Under those circumstances, where the stapes is removed, the end of thP incus is free-s anding and the hearing aid is physically associated with it, such as by means of crimpable rings or the like. Thus the hearing aid serves as an integral par~ of the mechanical linkage in the transmission of forces from the eardrum to the oval window in all events, whether or not the integrity or continuity of the ossicular chain remains unimpairedO That being the case, ~;~932~
', mechanical feedback through the ossicular chain is a likely consequence, diminishing the overall efficacy of ~he approach suggested there.
Another example of an implantable hearing aid is described in U.S. Patent No. 3,882,285 issued to J. A. Nunley et al. on May 6, 1975 and commonly assigned with the present invention. In accordance with the Nunley et al. invention, a self-contained miniature hearing device is implanted in the skull just behind the ear (pinna). The device includes a transducer, such as a mlcrophone, a microphone p~rt, an amplifier and a transmitter for providing a mehanical re-sponse to the sound received by the microphone. The micro-phone port is positioned in the ear canal. The transmitter of the preferred exemplary embodiment of Nunley et al~ utilizes a piezoelectric crystal connected to the ossicular chain, preferably to the stapes.
The prior art systems, however, admit of room for improvement in that these known devices tend to be suscepti-ble to interference by extraneous sounds and/or distortion of the sound ultimately perceived by the subject. Moreover, certain prior art systems tend ~o either include external or permanent transcutaneous or percu~aneous components. ThosP
with external components are aesthetically displeasing and susceptible to extrinsic forces. Tran~cutaneous elements typically utilize induction coils that are susceptible to misalignment and, urther, consume high levels o~ power.
Percutaneous elements such as a wire or tube protruding through the skin are inherently susceptible to infection.

~z~a3;~0~

Other prior art systems utilize air-induced microphones dis-posed to ~e responsive to soundwaves for generating an elec-trical signal from which the stimulus to the inner ear is ultimately derived. Air-induced microphones are disadvan-tageous in that the microphone is typically either disposed external to the skull or requires a percutaneous element such as a microphone port or connecting wire. Moreover, the fre~uency response of air-induced microphones tends no~ to provide sufficient Xrequency range for realistic fidelity, and such microphones typically do no~ provide constant fre-quency sensitivity acrQss their frequency band.
In the aforementioned presentation, ~Conservative Tympanoplasty" by Jako et al., it was proposed that a rela-tively large piezoelectric crystal pickup transducer be built into the piace of the tympanic membrane and directly drive a smaller piezoelectric crystal Oll~pUt transducer placed in the oval window. See Jako et al., su~ra, at pages 53-54.
However, the ~ako et al. system has reportedly never been reduced to practice, and the practicability of the system was noted as questionable by the authors ~hemselves (See p.
53).

UMMARY OF T~æ INV~NTION
The present invention provides a method and appa-ratus for improv;ng the impaired hearing of a subject uti-lizing a ~otally implantable device, not requiring any percu~aneous elements and manifesting a frequency response commensurate with that provided by normal hearing. In accor-dance with one aspect of the present invention, the mechanical vibrations effected by the tympanic membrane (eardrum) are 3~

converted into electrical signals which are therPaf~er ampli-fied and converted into mechanical vibrations and communicated to the inner ear. Conversion of mechanical energy to elec-trical energy is achieved by means of an input transducer which is surgically implanted within the ossicular chain, followed by suitable amplification of those electrical signals to account for both the level of hearing impairm~nt suffered by ~he subiect and the electromechanical response of the implanted device, and then the ~ignals are convPrted to mechanical energy (vibra~ions) once again by an output trans-ducer, all to achieve ~he desired level of aural enhancement for the wearer. These transducers and the associated cir-cuitry thus comprise means for mediating mechanical/electrical energy within the middle ear space. In all instances the ossicular chain of the subject is interrupted to preclude transmission of mechanical vibrations between the tympanic membrane and the inner ear, with the implanted device inter-posed within the chain to bridge the interruption therein and form an electromechanically independent link, free from ; ~ 20 Peedback, between the membrane and the inner ear.
In a particularly preferred variant o~ the present invention, the implanted device includes an input transducer means operatively associated wi~h or proximate the eardrum for receiving mechanical t~mpanic vibrations therefrom and converting them in~o electrical signals characteristic of the acoustic eneryy creating those vibrations. ~hose signals are applied to appropriate electronic circuitry ~o amplify ; and perhaps otherwise control or condi~ion them as may be required or found des;rable. An output transducer means is ' ` 1~2633Z~

operatively associated with or proximate the inner ear, pre-ferably at or about the oval window, but perhaps proximate the round window if desired, for receiving amplified elec-trical signals and converting them in~o mechanical vibrations replicating the ~ympanic vibrations representative of the initiating acoustic energy. Those mechanical vibrations are thence processed in the cochlea in precisely the same way as mechanical vibrations would normally have been processed were the ossicular chain functionally complete: the magnitude of the vibrational energy at that juncture being controlled by the degree of amplification built within the to~al implant device. The transducers may be of any convenient and effi-cient design, including piezoelectric film transducers, piezoelectric crystal force transducers, piezoelectric ;: 15 accelerometers, or electromagnetic transducers. Preferred are the piezoelectric transducers, and most preferred is a piezoelectric transducer in an accelerometer configuration.
`:`
BRIE:F DE:SCRIPTION OF 1~1~ DRAWING
~; Preferred exemplary embodiments of the present invention will hereinafter be descri~ed in conjunction with the appended drawing wherein like designations denote like elements and:
Figure 1 is a schematic section through a portion of the skull of a human subject adjacent to the ear showing the disposition of one embodiment cf an implantable hearing aid in accordance with the present invention;
Figures 2-5 are schema~ic illustrations of respec-tive alternative mechanical connections between the trans-ducers and the hearing apparatus of the subject, :`
Figure 6 is a schematic illustration of a further : embodiment of the present invention utilizing polymeric piezo-electri~ film transducers; and ~ ~igure 7 is a schematic illus~ration, p~rtly in : 5 section, of a preferred alternate embodiment, showing a trans-ducer in an accelerometer configuration.

D~l'AI L13D D~3SCRIPTION OF A
PREFER~E:D l~ BODIM13NT
_ .
Referring to Figure 1, a first embodimen~ 10 of an implantable hearing device in accordance wi~h ~he present invention is shown disposed in a surgically developed antrum 12 in the mastoid bone of the subject's skull 1~, communi-cating with the subject's middle ear space 16. Device 10 in . ~his embodiment is comprised of a power source 18, an ampli ier 20, a mechanical to electrical input transducer 22 and . an electrical to mechanical output transducer 24.
: ` Referring briefly to Figure 2, input transducer 22 and output transducer 24 suitably each comprise a piezoelec-tric element 202 cooperating with a resilient diaphram 204.
A connecting member 208, mounted on and maintained by diaphram 204, is opera~ively coupled to piezoelectric element 202.
Connecting member 208 advantageously is a 0.005 inch diameter stainless steel wire. (The respective wires 208 associated with input transducer ~2 and output transducer 24 will be referenced as 208A and 208B, respectively.) A sleeve 206, mounted to housing 204, and slideable retaining wire 208 may be employed to prevent la~eral movement and dampen any spurio~ls vibrations.

~ 33~

Input transducer 22 cooperates with tympanic mem-brane 26 and converts tympanic vibrations corresponding to sound into electrical signals. Input transducer 22, in effect, utilizes tympanic membrane 26 in a manner similar to the diaphram of a microphone. ~ith reference now to Figures 1 and 2, the input transducer 22 is mechanically coupled to ~ympanic membrane 26, suitably by connecting stiff wire 208A
to the subject's malleus 30. Connecting wire 208A may be affixed to malleus 30 u~ilizing sur~ical technique~ similar to those used in ossicular reconstructive surgery, or by other desirable techni~ues or mechanisms. Examples of con-nection mechanisms will be described in conjunction with Figures 3 5. When sound waves, generally indicated as 60, impinge upon tympanic membrane 26, corresponding tympanic vibrations are inikiated. The vibrations are transmitted to malleus 30, and therefrom, through wire 208A to input trans-ducer 22~ The mechanical vibrations are converted by piezo-electric element 202 (F'igure 2) to electrical signals. The electrical ~ignals are then applied as input slgnals to ampli-fier 20.
The use of the tympanic membrane as an operative por~ion of the input transducer is particularly advantageous.
Permanently percutaneous elements, e.~O wires, ports to the ear canal, etc., typically associated with other input mecha-nisms such as air-induced microphones, are avoided. Further, the frequency response of the input ~ransducer is in main part determined by the tympanic membrane and other character-istics of the indiYidual subject's hearing mechani~m and ~293ZO~

thu~ tends to more nearly approximate the frequency response of ~he subject'~ normal aural apparatus.
Amplifier 20 opera~es on the input transducer elec-trical output signals to generate corresponding amplified input signals to output transducer which are of sufficient magnitude to drive the output transducer element 202, and which compensate for deficiencles in the frequency sensi-tivity of the subject. AmpliXier 20 is typically of the : thin film typ~ and suitably comprises any conventional ampli-~; 10 f ieF circuit having input and output electrical impedences in accordance with the.electrical impedences of transducers.
The frequency response of the amplifier circuit is shaped, as is well known in the art, to compensate for frequency ; sensitivity deficiencies of the subject. The magnitude of the output signals from amplifier 20 is also limited to a predetermined maximum value ~o prevent possible injury (acoustic tral~a) to the inner ear. The power source 18 for amplifier 20 is preferably a lony li~e lithium-type battery.
Output transducer 2~ i~ utilized to convert the amplified electrical signals representing the tympanic vibra tions into mechanical vibration~ for application to the inner : ear 28 of the subject. The amplified electrical signals are applied as inpu~ signals to the piezoelectric elemen~ 202 of output transducer 24 and are converted into corresponding mechanical vibrations. The vibrations are communicated to the inner ear by a mechanical connection ~etween wire 208B
and the oval window 50 or round window 56, and therethrough .~ to the cochlea 51. The connection between wire 208B and the inner ear can be made in a manner similar to techniques employed in reconstructive surgery using passive mechanical :

~932~
pros~hesis devices or by any other suitable mechanism.
Exemplary connections will be described in connection with Figures 3-5.
As noted above, the mechanical connections between input transducer 22 and tympanic membrane 26 and between output transducer 24 and inner ear 23 are effected utilizin~
sur~ical techniques similar ~o those used in ossicular recon-structive surgery, or by o~her desired methodsO The connec-tions are sui~ably made by affixing the distal end of s~iff wire 208 to an appropriate portion of the ossicular chain, and a por~ion of the ossicular chain is then util~zed as an inte~ral part of the mechanical connection.
With respect to input transducer 22, the distal end of wire 208A is shown to be affixed to the subject's malleus 30, preferably to the head 34 of malleus 30. For example, as shown in Figure 3, a small hole 36 may be drilled in the malleus head 34 and the distal end of wire 208A re-ceived and secured in hole 36. Wire 20BA may be secured by suitable biocompatible cement such as an acrylate ester or fibrin cement. In some instances, wire 208A may be fixed to :~ malleus head 34 solely through use of a biocompatible cement without the necessity of hole 36. Al~ernatively, as sche-matically shown in Fiyure g, the coupling to malleus 30 can be effected ~hrough use of an intermediary fitting (cap~ 38, articulating with malleus head 34. It may, however, be desirable in some circumstances to affix wire 208A to portions of ~he malleus 30 other than head 34. For example, as shown in the embodiment of Figure 1, the distal end of wire 20BA
may be looped about the neck 32 of malleus 30. Alternatively, wire 208A may be coupled to the tip of the manubrium 42 of ~93204 malleus 30O Such a connection is schematically shown in Figure 5. The attachment is preferably effected utilizing ` biocompatible cement as noted above, or by drilling a hole in manubrium 42 for receiving the distal end of wire 208A.
With respect to output transducer 24, the distal end of wire 208B is suitably affixed to the subject's stapes 52. As schematically shown in Figure l, the distal end of wire 208B may be looped about the capitulum 54 of stapes 52, or, as schematically shown in Figure 4, an intermediate fitting 56 articulating with capitulum 54 may be employed.
Likewise, the connection can ~e effected utilizing biocom-patible cement. In some instances, it may be desirable to effect a connection between 208B and the crus or ~ootplate portions of the stapes or directly to the oval window in accordance with well known reconstructive surgical techniques.
It may, however, be desirable in some circumstances, to effect a connection between wire 208B and the round window 5h rather than to the oval window. A direct connection to .
the round window input to the cochlea may be effected uti-lizing a device fashioned from biocompatible materials simu-lating a footplate disposed over the round window membrane, ; to which wire 208B is at~ached.
In accordance with another embodiment of the present inven~ion, one or both of input transducer 22 and output transducer 24 can be formed from a polymeric pie7oelectric film such as polyvinylidene fluouride (PVDF) disposed directly on an appropriate element of the subject's physical hearing apparatus and electrically connected to amplifier 20O One such embodiment of the present invention is illustrated in ~Z9~

Figure 6, wherein respective PYDF films 622 and 624 are uti-lized as the input and output transducers, respectively.
Input transducer PVDF film 622 is disposed on the inner sur-face of tympanic membrane 26, underlying the manubrium 42 of malleus 30. Alternatively, PVDF film 622 could be disposed on malleus 30, preferably on the underside of the manubrium or otherwise interposed between the tympanic membrane 26 and the underside of the manubrium of malleus 30. Film 622 is : electrically ~onnected to ~he input terminals of amplifier 20.
Input transducer PVDF film 624 is disposed on stapes ~2, or direc~ly on oval window 50 or round window 56, and is electrically connected to the output terminals of amplifier j.
20. When soundwaves impinge on kympanic membrane 26 and generate t~mpanic vibrations, such vibrations are sensed by film 622 and converted into electrical signals ~or application to amplifier 20. The amplified electrical signals are then ~: applied to output transducer film 62~ which converts the amplified signals into mechanical vibrations for transmission to the inn~r ear.
The ossicular chain is broken in implementing the presen~ invention to prevent positive esdback of the ampli-: fied vibrations ~o the input transducers from occurring.
The break would typically be e~fected by removing at least one of the component parts of the ossicular chain, typically ~he incus. It is desirable to main~ain the malleus and stapes in normal anatonomical position with muscle and ~endon intact to maintain the subject's natural defense mechanism against acoustic trauma.

32~
.

~igure 7 illustrates an alternate and highly pre-ferred e~bodiment of an implantable hearing aid 700 in accor-dance with the present invention. The hearing aid 700 is : comprîsed of paired transducer means for mediating elec~ricalJ
: 5 mechanical signals, in this instance a first or input trans-ducer means designated generally as 702 and a second or output transducer means designated generally as 704. The transducers are powered by 2 power supply 706 disposed within an antrum formed in the bony structure pro~;mate the e~r of ~he subject receiving the implant. The input transducer 702 is opera-tively associated with the head 34 of th~ maleus 30 which vibrates in response to movemen~ of the eardrum as acoustical energy impinges upon it. The transducer 702 in this embodi-ment is shown to be in the configuration of a piezoelectric : 15 accelerometer, comprised of a piezoelectric bimorph 708 having ; a first piezoelectric crystal element 710 lying in generally face-to-face relationship with an opposed crystal 712. The bimorph 708 is cantilevered at its first end 714 from an enveloping structure or implanting shield 716, the terminal edges of which are secured to the head 34 of malleus 30 by means of a suitable biocompatible adhesive or other suryically acceptable means. The accelerometer configuration is achieved in this embodiment by a structural weight 718 secured to one of the crystals such as crystal 712 at the end opposite that cantilevered from the implantiny shield 716. In this con-figura~ion, when the malleus vibrates coincident with tympanic vibrations the weight 718 imparts an inertial response to the bimorph 708 which will itself then vibrate in a mechanical pattern replicating the vibration of the malleus. Recognizing 3~

that the forces extant the tympanic membrane have been deter-mined to be extraordinarily intense, beyond that previously appreciated, the accelerometer configuration offers enhanced efficiency. Then too, since the bimorph 708 is cantilevered or otherwise anchored directly from the mounting structure, the problems inherent in the placement of these ~ypes of elements within a mucous membrance environment are greatly allevia~ed.
Vibrations in the accelerometer are converted to electrical signals as a consequence of the inherent charac-teristics of piezoelectric crystals. These electric signals are applied via signal leads 720 to an amplifi2r 722.
Depending upon the characteristics of the amplifier 722, a suitable or sufficient gain may be realized allowing those electric signals to be applied directly to ~he output or ~econd transducer 704; otherwise the amplifier 722 may be used as a preamp and a separate amplifier associated with the transducer 704 will be provided. Regardless, the signals from amplifier 722 are routed ~hrough ~he middle ear space via signal lines 724 for ultima~e application to th~ output transducer. In this context, the signal leads along with the a~sociated amplifier circuitry thus constitute trans-mission means for communicating between the input and output ~ransducers in lieu of communica~ion through the ossicular chain~
The output transducer of this embodiment is a bimorph piezoelectric crystal structure comprised of a pair of piezo-electric crystals 726 and 728 cantilevered at a first end from a support element 730. The support element 730 is mounted on an arm 732 secured to a bony region of the subject ~2~32 ~'.
by means of fixture elements 734, such as surgical screws.
-This fixturing approach is conceived ~o be most reliable physically-and functionally due to the difficulty of implant-ing devices in the mucous membrane environment of the middle ear. The mounting member 732 thus places the output trans-ducer 704 in proximate contact with the stapes 22 whereby vibrations in the output ~ransducer 704 are communicatively coupled thereto. Depending upon the electrical characteris-tics of the a~plifier 722 as noted above~ an optional ampli-fier 736 may be provided for driving the output transducer 70g. These are ~atters, however, which can be tailored at the time th~ device and its associated circuitry are designed.
As is evident from the description of the structure in Figure 7, it can be seen that the transducers 702 and 704 are surgic~lly int~rposed within the ossicular chain in replacemen~, in this instance, of the incus. The ~ransducers and associated circuitry bridge the interruption in the ossicular chain resultant from removal of the incus to form an independent link between the t~npanic membrane and the inner ear. In this fashion the potential for mechanical feedback is entirely eliminated, resulting in both improved efficiencies and comfort to ~he subj~c~. And, when it is ~he incus which is removed in order to interrupt the ossicu-lar chain and prevent transmission of mechanical vibrations, ~ 25 the skeletomuscular network of the subject maintains the ;~ natural defense mechanism against acoustic trama should exces-sively loud n~ises be encountered.
It will be understood that the above descript;on is of preferrsd exemplary embodiments of the present invention and that the invention is not limited to the specific forms ` 17-~2~3;~

shown. For example, it is not necessary that each of the components in the embodiment of Fi~ure 1 be disposed in a unitary housing. Rather, the various components can be physi-cally s~parated. Further, the respective components may in S some instances be disposed in the natural middle ~ar space of the su~ject, rather than in a surgically developed antrum.
~-~ These and other modifications may be made in the design and arrangement of the components without departing from the spirit of ~he invention as expressed in the appended claims.

`' '

Claims (35)

1. An implantable apparatus (10) for use in a hearing impaired subject, said subject being of the type normally having a tympanic membrane (26) configured to generate mechanical tympanic vibrations in response to sound waves impinging thereon, and an ossicular chain disposed to communicate said tympanic vibrations to the inner ear (28) of said subject, said apparatus comprising electromechanical transducer means (22,24) for converting said sound waves into electrical signals representative thereof and for converting said electrical signals into mechanical vibrations applied to said inner ear (28), improved wherein:

said apparatus (10) is disposed in said subject in a manner which interrupts said ossicular chain and establishes a mechanically independent link between said tympanic membrane (26) and said inner ear (28), said electromechanical transducer means (22,24) comprising first transducer means (22), cooperating with said tympanic membrane (26), for receiving mechanical tympanic vibrations therefrom and converting the same into said electrical signals characteristic thereof, second transducer means (24), cooperating with said inner ear (28), for receiving said electrical signals and converting the same into mechanical vibrations representative of said tympanic vibrations, and transmission means for communicating between said first (22) and second (24) transducer means in lieu of said ossicular chain or portion thereof.

2. The apparatus of claim 1, wherein at least one of said first and second transducer (22,24) means comprises a piezoelectric film transducer.

3. The apparatus of claim 1, wherein at least one of said transducer means (22,24) comprises a piezoelectric crystal force transducer.

4. The apparatus of claim 1, wherein at least one of said transducer means (22,24) comprises a piezoelectric accelerometer.

5. The apparatus of claim 1, wherein at least one of said transducer means (22,24) comprises an electromagnetic transducer.

6. The apparatus of claim 1, further comprising means (208A) for effecting mechanical communication between said tympanic membrane and said first transducer means.

7. The apparatus of claim 6, wherein said ossicular chain is broken intermediate the malleus (30) and said inner ear (28), and said means (208A) for effecting mechanical communication comprises:

a stiff connecting member having a first end mechanically linked to said first transducer means (22); and means for coupling said connecting member (208A) to said malleus (30) such that said connecting member (208A) moves in accordance with movement of said malleus (30).

8. The apparatus of claim 1, further comprising an amplifier (20) configured to receive signals from said first transducer means (22) and to apply amplified signals to said second transducer means (24).

9. In an apparatus of the type including means (22) for generating electrical signals indicative of soundwaves impinging on an ear of a subject and means (24), responsive to said electrical signals, for generating mechanical vibrations for transmission to the inner ear (28) of said subject, the improvement wherein:

said means (22) for generating electrical signals comprises a mechanical to electrical transducer connected to the malleus (30) of said subject such that said transducer is mechanically driven by said malleus (30) and is responsive to vibrations effected by sound waves impinging on the tympanic membrane of the subject.

10. An implantable apparatus for improving the hearing of a hearing impaired subject, said subject having a hearing apparatus which if anatomically normal, comprises a tympanic membrane intended for generating mechanical tympanic vibrations in response to sound waves impinging thereon, and an ossicular chain intended to communicate said tympanic vibrations to the inner ear of said subject, said apparatus comprising input and output transducer means for mediating mechanical/electrical signal having controlled amplification characteristics, configured for bridging disposition in an interrupted ossicular chain of a subject as an electro-mechanically independent link between the tympanic membrane and inner ear of said subject, comprised of first transducer means for operative association with said tympanic membrane for receiving mechanical tympanic vibrations therefrom and converting the same into electrical signals characteristic.
thereof, second transducer means for operative association with said inner ear for receiving said electrical signals and converting the same into mechanical vibrations replicating said tympanic vibrations and transmission means for communi-cating between said first and second transducer means in lieu of said ossicular chain of portion thereof.

11. The apparatus of claim 10 , wherein said first transducer means is adapted for disposition in communication with the middle ear space of said subject, said apparatus further comprising means for effecting a mechanical connection between said tympanic membrane and said first transducer.

12 . The apparatus of claim 11 , wherein said ossicular chain is broken medial to the malleus of said ossicular chain and said means for effecting a mechanical connection comprises a stiff connecting member having a first end thereof mechanically linked to said first transducer; and means for coupling said connecting member to said malleus such that said connecting member moves in accordance with movement of said malleus.

13. The apparatus of claim 12, wherein said means for coupling comprises a fitting adapted to receive the head of said malleus such that said fitting articulates with said malleus, said apparatus further comprising means for mechanically coupling said connection member to said fitting.

14. The apparatus of claim 12, wherein said means for coupling comprises a loop formed in the end of said con-necting member adapted to at least partially circumscribe the neck of said malleus between the manubrium and the head of said malleus.

15. The apparatus of claim 10 , wherein said first transducer means comprises;
a polymeric mechanical to electrical transducer film disposed on said tympanic membrane, said apparatus fur-ther comprising means for communicating electrical output signals generated by said input transducer film to said output trans-ducer.

16. The apparatus of claim 14 , wherein said trans-mission means comprises:
an amplifier, receptive as input signals of said first transducer electrical output signals, and electrically coupled to said second transducer means.

17. The apparatus of claim 15, wherein aid first transducer means polymeric film comprises polyvinylidene fluoride.

18. The apparatus of claim 15, wherein said second transducer means comprises:
a polymeric electrical to mechanical transducer film, disposed in mechanical connection with said inner ear, land receptive of as input signals thereto, said first trans-ducer means electrical output signals.

19. The apparatus of claim 16, wherein said second transducer means comprises a polymeric electrical to mechani-cal transducer film, disposed in mechanical connection with said inner ear, and receptive of, as input signals thereto, said first transducer means electrical output signals.

20. The apparatus of claim 17 , wherein said second transducer means comprises a polymeric electrical to mechani-cal transducer film, disposed in mechanical connection with said inner ear, and receptive of, as input signals thereto, said first transducer means electrical output signals.

21. The apparatus of claim 15, wherein said second transducer means comprises a polymeric electrical to mechani-cal transducer film, disposed in mechanical connection with said inner ear, and receptive of, as input signals thereto, said first transducer means electrical output signals.

22. The apparatus of claim 18, wherein said second transducer polymeric film is disposed on the stapes of said ossicular chain.

23. The apparatus of claim 19, wherein said second transducer polymeric film is disposed on the stapes of said ossicular chain.

24. The apparatus of claim 19, wherein said second transducer polymeric film is disposed on the oval window membrane.

25. The apparatus of claim 19, wherein said second transducer polymeric film is disposed on the round window membrane.

26. The apparatus of claim 10, wherein said second transducer means comprises:
an electrical to mechanical output transducer adapted for disposition in communication with the middle ear space of said subject, said apparatus further comprising means for transmitting mechanical vibrations from said second transducer to said inner ear.

27. The apparatus of claim 26, wherein said trans-mission means comprises:
a stiff output connecting member, coupled at a first end thereof to said second transducer; and means for mechanically coupling said connecting member to said inner ear.

28. The apparatus of claim 26, wherein said means for mechanically coupling comprises means for coupling said output connecting member to the stapes of said ossicular chain.

29. The apparatus of claim 27, wherein said means for mechanically coupling comprises a fitting adapted to receive the subject's stapes capitulum such that said stapes articulates with said fitting, said apparatus further com-prising means for linking said output connecting member to said fitting.

30. The apparatus of claim 11, wherein said means for mechanically coupling comprises a fitting adapted to receive the subject's stapes capitulum such that said stapes articulates with said fitting, said apparatus further com-prising means for linking said output connecting member to said fitting.

31. The apparatus of claim 10, wherein at least one of said transducer means is a piezoelectric film trans-ducer.

32. The apparatus of claim 10, wherein at least one of said transducer means is a piezoelectric crystal force transducer.

33. The apparatus of claim 10, wherein at least one of said transducer means is a piezoelectric accelerometer.

34. The apparatus of claim 10, wherein at least one of said transducer means is an electromagnetic trans-ducer.

35. In an apparatus of the type including means for generating electrical signals indicative of soundwaves impinging on the ears of said subject and means, responsive to said electrical signals, for generating mechanical vibra-tions for transmission to the inner ear of said subject, the improvement wherein said means for generating electrical signals comprises a mechanical to electrical transducer dis-posed in operative connection with the malleus of said subject such that said transducer is mechanically driven by said malleus, and responsive to vibrations effected by sound waves impinging on the tympanic membrane of the subject.