Patent Application
20130018216
The present application relates generally to cochlear implants and methods of improving the hearing of a subject using such implants. More particularly, the application relates to cochlear implants that are fully-implantable and microphoneless and methods of improving the hearing of a subject using such fully-implantable, microphoneless implants.
In an anatomically normal human hearing apparatus, sound waves, which represent acoustical energy, are directed into an ear canal by the outer ear (pinna) and impinge upon a tympanic membrane (eardrum) interposed, at the terminus of the ear canal, between the ear canal 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 mechanical energy to the inner ear. The ossicular chain includes three primary components, the malleus, the incus, and the stapes. The malleus includes respective manubrium, neck, and head portions. The manubrium of the malleus attaches to the tympanic membrane at a point known as the umbo. The head of the malleus, connected 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 to the stapes. The stapes includes a capitulum portion connected to a footplate portion by means of a support crus and is disposed in and against a membrane-covered opening to the inner ear, referred to as the oval window. The incus articulates the capitulum 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 through to the inner ear (cochlea). These 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 membrane, ossicular chain and/or inner ear can occur to disrupt or impair normal hearing.
Hearing loss, which may be due to many different causes, is generally of two types, conductive and sensorineural. Of these types, conductive hearing loss occurs where the normal mechanical pathways for sound to reach the hair cells in the cochlea are impeded, for example, by damage to the ossicles. Conductive hearing loss may often be helped by use of conventional hearing aids, which amplify sound so that acoustic information does reach the cochlea and the hair cells. Other times, conductive hearing loss can be helped by the use of a middle ear implant, which essentially augments or bypasses the mechanical conduction of the ossicular chain. Some examples of such a middle ear implant can be found in U.S. Pat. Nos. 4,729,366 and 4,850,962 to Schaefer.
In many people who are profoundly deaf, however, the reason for deafness is sensorineural hearing loss. This type of hearing loss is due to the absence of, or destruction of, the hair cells in the cochlea which transduce acoustic signals into nerve impulses. These people are thus unable to derive suitable benefit from conventional hearing aid or middle ear implant systems, because there is damage to or absence of the mechanism for nerve impulses to be generated from sound in the normal manner.
It is for the purpose of helping these profoundly deaf people that cochlear implant systems have been developed. Such systems bypass the hair cells in the cochlea and directly deliver electrical stimulation to the auditory nerve fibers, thereby allowing the brain to perceive a hearing sensation resembling the natural hearing sensation normally delivered to the auditory nerve. U.S. Pat. No. 4,532,930 provides a description of one type of traditional cochlear implant system.
A typical system includes an external microphone, signal processor and transmitter, and an implanted receiver and electrode. The microphone transponds normal sound waves, converting this acoustic or mechanical sound energy into electrical energy representative thereof. The processor amplifies the electrical energy, filters it and sends it to the transmitter, which changes the electrical signals into magnetic signals. Transcutaneous magnetic currents cross the skin and are received by the implanted receiver, a coil for example, and the signal travels to the cochlea via a wire electrode. Current flows between this active electrode and a nearby ground electrode, preferably disposed in the Eustachian tube, to stimulate nerve fibers present in the cochlea. The brain interprets this stimulation as sound. See T. Kriewall, “Why Combine Multichannel Processing With a Single Electrode,” Hearing Instruments, June 1985; W. House, D. Bode, and K. Berliner, “The Cochlear Implant: Performance of Deaf Patients,” Hearing Instruments, September 1981.
The implanted stimulator/receiver has typically included the antenna receiver coil that receives the coded signal and power from the external processor component and a stimulator that processes the coded signal and outputs a stimulation signal to an intracochlea electrode assembly, which applies the electrical stimulation directly to the auditory nerve producing a hearing sensation corresponding to the original detected sound. As such, the implanted stimulator/receiver device has been a relatively passive unit that has relied on the reception of both power and data from the external unit to perform its required function. The external componentry of the cochlear implant has been traditionally carried on the body of the subject, such as in a pocket of the subject's clothing, a belt pouch, or in a harness, while the microphone has been mounted on a clip mounted behind the ear or on a clothing lapel of the subject. As such, traditional systems have required a large amount of external componentry and electrical leads to enable the system to function properly.
More recently, due in the main to improvements in technology, the physical dimensions of the speech processor have been reduced, thereby allowing the external componentry to be housed in a small unit capable of being worn behind the ear of the subject. This unit has allowed the microphone, power unit, and the speech processor to be housed in a single unit capable of being discreetly worn behind the ear. Despite the development of these behind-the-ear (BTE) units, there still exists the need for an external transmitter coil to be positioned on the side of the subject's head to allow for the transmission of the coded sound signal from the speech processor and power to the implanted stimulator unit. This need for a transmitter coil further requires leads and additional componentry, which have added to the complexity and conspicuousness of such systems. Nevertheless, the introduction of a combined unit capable of being worn behind the ear has greatly improved the visual and aesthetic aspects for cochlear implant subjects.
While traditional cochlear implants have proven very successful in restoring hearing sensation to many people, the construction of the conventional implant with its external electronic components has limited the circumstances in which the implant can be used by a subject. For example, subjects cannot wear the devices while showering or engaging in water-related activities. Most implantees also do not use the devices while asleep due to discomfort caused by the presence of the BTE unit. With the increasing desire of cochlear implant implantees to lead a relatively normal life, there exists a need to provide a system which allows for total freedom with improved simplicity and reliability.
Because of this need, fully implantable systems that do not require external componentry for operation for at least some of their operating life, have been postulated, although none have as yet been commercially available.
An example of one type of system which has been proposed is described in U.S. Pat. No. 6,067,474 by Advanced Bionics Corporation and Alfred E. Mann Foundation for Scientific Research. This system attempts to provide all system components implanted in the subject and includes a microphone placed in the ear canal which communicates with a conventionally positioned receiver unit via a conventional RF link. There is further described a battery unit which can be integrated with the receiver unit or separate therefrom. Such a system provides further complications as it requires surgical implantation of a number of components and hence complicates the surgical procedure. The system also maintains the need for a RF link during normal operation between implanted components, which increases overall power requirements of the system, and thus often rapidly drains the internal battery supply.
Another proposed device is described in International Patent Application No. WO 01/39830 to EPIC Biosonics Inc. This system also employs a microphone positioned in the ear canal and an extendible lead connecting the microphone to the implanted stimulator. This proposed system therefore inherits many of the drawbacks of the system mentioned above.
Also, both of these proposed implants rely on the use of a microphone. Microphones do not provide sound quality on par with that of sound measured as it is naturally amplified by the pinna and ear canal, or as it is sensed by the ossicular chain. Also, all of the above-mentioned implants would require full explantation if any component needed updating or replacement.
With the above background in mind, there is a need to provide a totally implanted cochlear implant that does not require external componentry to operate at least for a specific period of time. Preferably, the implant will use sound input as received by the ossicular chain, whether that chain is intact or not, rather than relying on a microphone. Also preferably, the implant will allow some components, namely the processor, to be easily replaced without requiring full explantation.
Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.
The present invention is directed toward a fully-implantable cochlear implant and method for improving the hearing of a subject using such a fully-implantable cochlear implant. In accordance with one aspect of the present invention the mechanical vibrations that would, if a subject is anatomically normal, impinge on the tympanic membrane and subsequently be transmitted to the ossicular chain of the middle ear are sensed by a sensor in operative contact with the tympanic membrane or one or more of the bones of the middle ear. The sensor can convert the mechanical vibrations into electrical signals, which signals are then interpreted and manipulated by a processor. The processor then sends an output electrical signal to the cochlea via a cochlear electrode where the output electrical signals are ultimately interpreted by the subject as auditory information. This implant is an improvement over the prior art because it is microphoneless. The auditory information of sounds picked up by a microphone has lower quality than sounds that have traveled through the subject's ear canal. Directionality and amplification of useful frequencies are generally improved in sounds that have traveled through the ear canal. Thus, the inventive implant will provide superior results compared to those of other currently available or proposed cochlear implants.
A further advantage of the current invention is that the ossicular chain of the middle ear may not have to be disarticulated. Disarticulation is usually required when sensing mechanical vibrations at the tympanic membrane or ossicular chain because of feedback issues. The present implant, however, does not rely on transmitting the sound information through mechanical vibrations. Instead it relies on electrical stimulation of the cochlea and, thus, as long as the sensing portion of the implant is electrically isolated (vs. mechanically isolated), there should be no feedback or interference issues. Being able to leave the ossicular chain intact is an advantage because it simplifies the surgical procedure.
To ensure the cochlear implant device is fully-implantable, the present invention also contemplates a long-lasting, rechargeable battery. The battery is chargeable by telemetry and, as a result, an inductive coil is part of the fully-implantable cochlear implant. A separate battery charger for the implanted battery can also be envisaged. This separate charger can charge the implanted battery through use of the inductive link provided by internal and external coils. A separate charger allows the implanted power source to be recharged when required.
In one embodiment of the invention, at least the cochlear electrode is attached to the processor with a removable lead, whereby if for some reason, the processor needed to be replaced or updated, the cochlear electrode could remain in position inside the subject. Being able to leave the electrode in place is advantageous because the cochlear tissue is fragile and can be damaged by insertion or removal of an electrode. Having the cochlear tissue be as intact as possible is important to retain any natural hearing function the subject may have and to allow for the cochlea to function as needed to stimulate the auditory nerve, which a subject will interpret as auditory information. Also, a further advantage of a removable lead is that the cochlea may ossify after implantation making replacement difficult or outright impossible. The invention also contemplates that all the implanted electrodes of the device may be attached to the processor by removable leads, conferring the same advantage of being able to easily remove the processor without having to disturb any other portions of the fully-implantable cochlear implant. In addition, this invention contemplates that the processor may be attached to a sensor that has been previously implanted for use with another hearing restoration system, such as the ESTEEM™ implant (Envoy Medical Corporation, St. Paul, Minn.). This is advantageous because the subject can have a cochlear implant implanted without replacing the sensor if the subject's hearing changes due to, for example, progressive hearing loss. Being able to leave the sensor in place is advantageous because the surgical procedure to properly place the sensor may be challenging and time consuming.
In another embodiment of the invention, the cochlear electrode is marked with a radioactive compound. Such marking is advantageous because it allows for ease in determining the correct placement of the electrode during implantation procedures. It is also advantageous because it allows for ease in determining if the electrode has moved out of position after implantation is complete, for example, when trying to diagnose why an implant no longer functions as intended.
In still another embodiment of the invention, the cochlear electrode is relatively short and does not require navigating the turns of the cochlea conch shape. Being able to avoid navigating such turns is advantageous because it reduces the risk of damaging the tissue of the cochlea.
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:
Referring to
The implant in this embodiment is composed of: a processor 112, a first lead 114 connecting the sensor 120 to the processor 112, a sensor 120, shown here touching the malleus 122 (but could also touch the tympanic membrane 106, the incus 124, or the stapes 126), and a combination lead 115 attached to the processor 112, wherein combination lead 115 contains both a ground electrode 118 and a cochlear electrode 116.
Referring to
Referring to
Referring to
The sensor housing 304 of the sensor 120 may be made of a biocompatible material. In one embodiment, the biocompatible material may be titanium or gold. In another embodiment, the sensor 120 may be similar to the sensor described in U.S. Pat. No. 7,524,278 to Madsen et al., or available sensors, such as that used in the ESTEEM™ implant (Envoy Medical, Corp., St. Paul, Minn.), for example.
In alternative embodiments, the sensor 120 may be an electromagnetic sensor, an optical sensor, or an accelerometer. Accelerometers are known in the art, for example, as described in U.S. Pat. No. 5,540,095.
Referring to
Referring to
In another mode of operation, the coil 208 receives telemetry from the external device or transmission coil 250, and can deliver controller information to the TPM circuit 218. The TPM circuit 218 then delivers the controller information to the controller 220. The controller 220 can then communicate the controller information to the amplifier 216 to make adjustments in the operation of the electronics unit 204 (e.g., make it louder, make it softer, etc.).
Any device which can transmit power and telemetry can be used as the external device or coil 250. Such devices are known in the art. It is well within the knowledge of one of ordinary skill in the art, given the present disclosure, to design and program the electronics unit of the present invention.
The signal from the sensor 120 (
The system according to the present invention includes a power source. The power source provides power for the processor means, electrode array and any other electrical or electronic componentry of the implant system.
The power source can be a battery. The battery is preferably rechargeable. The battery should have a high charge density and be rechargeable over a considerable number of charge/discharge cycles.
The rechargeable battery 206 can be, but does not have to be, any rechargeable battery known in the hearing aid, hearing implant, or medical implant arts.
Preferably the rechargeable battery 206 is a lithium-ion battery. Also preferably, the rechargeable battery 206 is rechargeable by telemetry. The rechargeable battery 206 provides power to electronics unit 204 through connections standard in the art, such as those found in the in the ESTEEM™ implant (Envoy Medical Corp., St. Paul, Minn.), although any available suitable method of connecting the rechargeable battery 206 to the electronics unit 204 may be used without exceeding the scope of this disclosure.
Referring to
Also included in first conductor 550 is a radioactive marker 350. The radioactive marker 350 may be part of the coating 356, or it may be separate. It may be made with of the same material as coating 356, or it may be made with a different material. The radioactive marker may be placed at the point on the cochlear electrode 116 where the coating 356 ends, or it may be placed at another point along the cochlear electrode 116 or at another point along first conductor 550.
Alternatively, the radioactive marker may be part of the cochlear electrode 116 itself. The invention contemplates using any known radioactive isotope as the marker, but preferably a radioactive isotope known and used in the medical arts, and more preferably barium sulfate or tungsten. In one preferable embodiment, the invention contemplates using a radioactive imbued plastic, such as those offered commercially as RADIOPAQUE™ (RTP Company, Winona, Minn.).
Second conductor 552 is composed of a ground electrode 118 coated in a second coating 354, which may be the same as coating 356. The second coating 354 of second conductor 552 ends at a point along the ground electrode 118 distal to the site of attachment to the processor 112 (
Shown in
In a preferred embodiment, the marker 350 is shown in
Also shown in
The casing 352 is an electrically insulating material. The coatings 356 and 354 on first conductor 550 and second conductor 552, respectively, are also electrically insulating materials. The electrically insulating materials used may be the same in all instances, or may be different in all instances, or any combination. In one embodiment, the electrically isolating material is a biocompatible silicone. In alternative embodiments, the electrically isolating material is a biocompatible polyurethane. Similar casings and coatings may be used for any other leads, wires, or electrodes of the invention, for example, leads 114 and 115 (shown at least in
Referring to
The processor 112 is preferably hermetically sealed. The embodiment of
Signals 300 are shown being directed at incus 124, and being reflected back from the incus 124 to the sensor 120. The signals can be sonic, ultra-sonic, IR, RF, or laser signals in various embodiments. Transceiver or sensor 120 can be coupled to processor 112 via wires 306 and 308.
In some embodiments, some signal pre-processing is done remotely from processor 112, for example, near or in sensor 120. Also contemplated is a method of improving the hearing of a subject by using fully-implantable, microphoneless implants described above. The method may include the step of implanting the fully-implantable, microphoneless cochlear implant into a hearing impaired subject, thereby improving the hearing of the subject.
The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” The phrase “or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases.
In accordance with the provisions of the patent statutes, the present invention has been described in what is considered to represent its preferred embodiments. However, it should be noted that the invention can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.
This application is claiming the benefit, under 35 U.S.C. §119 (e), of the provisional application, filed on Jul. 13, 2011, under 35 U.S.C. §111 (b), which was granted Ser. No. 61/507,320. This provisional application is fully incorporated herein by reference. Application Ser. No. 61/507,320 is pending as of the filing date of the present application.
| Number | Date | Country | |
|---|---|---|---|
| 61507320 | Jul 2011 | US |
