Patent Application
20100324355
The invention is in the field of implantable hearing devices, a kit, and methods for the implantation of said hearing devices.
Sounds are perceived in humans by means of a mechanical-neural system distributed over the external ear canal, the middle ear cavity and the cochlea. Sound waves propagate through the external ear canal to reach and vibrate the tympanic membrane. The middle ear ossicles—malleus, incus and stapes—transfer the tympanic membrane vibrations to the footplate of the oval window that seals off the cochlea. Footplate vibrations set up waves of fluid motion within the fluid that is contained in the cochlea. The fluid motions in turn activate hair cells inside the cochlea. The hair cells produce in response electrical nerve impulses that are routed through the spiral ganglion and the auditory nerve to the brain, where they are perceived as sound. The electro-mechanics of the cochlear membranes and hair cells vary gradually along the length of the cochlea, which creates a natural spectral distribution of sensitivity along the cochlea: high-pitch sounds activate the hair cells near the oval window, whereas the lower pitches activate the hair cells further down the cochlea.
Modification and/or amplification of the energy reaching the sensory cells of the inner ear are the basis for treatment of conductive and sensorineural hearing losses. First attempts to improve hearing by making a hole in the wall of the inner ear at the level of the lateral semicircular canal were undertaken in 1914 in a procedure called fenestration. In fenestration, a trough-shaped window is made in the bony wall of the inner ear and is covered with transposed tympanic membrane. This connects the fluid spaces of the human inner ear directly to the outside world bypassing the dysfunctional middle ear. This procedure enables the sound energy to reach directly the membranous part of the inner ear and can result in an improvement of hearing by up to 30 dB.
Currently, when opening of the inner ear space is necessary, other safer and more effective surgical techniques have been developed. In patients with otosclerosis (immobility of the ossicular chain due to fixation of the stapes footplate), a small-hole fenestration in the stapes footplate is made, and a Teflon piston is transposed between the incus and the opening in the footplate after removal of the stapes superstructure. This procedure, albeit quite difficult technically, normalises the functional status of the conductive part of the middle ear and, in most cases, restores hearing to normal or quasi-normal.
The main drawback of the latter technique is that the fenestration of the inner ear remains open, which incurs the risk for inner ear infections. This may lead to meningitis or total hearing loss. A solution is to cover the fenestration with a piece of tissue, however, this has in the long term a tendency to re-ossify, which leads to diminishing results.
Hearing improvement can also be achieved by amplification of the energy reaching the sensory cells of the inner ear, using a variety of hearing aids. All these devices try to compensate for the diminished hearing acuity by amplification of the energy reaching the inner ear. They either amplify air sound waves, vibrate the ossicular chain, or vibrate the bones of the skull. However, application of any one of these devices has a number of important drawbacks including lack of aesthetic appeal, poor performance of conventional hearing aids due to feedback and distortion, limited indications and variable results in implantable hearing aids.
There have also been a few devices described in the literature, which employ a direct energy transfer to or from the inner ear. The advantage of these systems is that relatively little energy is required to achieve substantial amplifications and that the transducers can be very small. Some of these direct energy transfer devices are described below.
The Round Window Electromagnetic device (RWEM) realises coupling to the cochlear fluids through an intact round window membrane, which serves as the natural flexible interface between the middle and the inner ear. The RWEM uses a magnet, surgically placed onto the round window and an electromagnetic coil to induce vibration. This vibration is transmitted through an intact round window membrane to the cochlea's fluids. The RWEM device, however, would compromise the normal compliance of the round window membrane, which could induce a hearing loss.
Leysieffer describes in DE 39 40 632 an implantable hearing aid with either separate electromechanical stimulation or separate electrical stimulation.
Money (U.S. Pat. No. 5,782,744) proposed an implantable microphone encapsulated in a waterproof casing and placed at the round window in contact with the cochlear fluid, immersed in the cochlear fluid or placed in the middle ear and coupled to the inner ear fluid by a conduction tube. Such a microphone transmits the pressure variations induced in the inner ear by acoustic stimulation.
A cochlear implant bypasses the mechanical signal chain altogether, and provides direct electrical stimulation of the auditory neural system using an elongated electrode inserted in and following either the scala tympani or the scala vestibuli.
Hybrid electrical-mechanical systems have been described recently that complement the electrical stimulation of a cochlear implant with mechanical means to induce vibrations in the inner ear fluid. Electrical stimulation complementary to mechanical stimulation can be a significant advantage to certain otological pathologies. In case of locally damaged inner ear structures, mechanical stimulation can be ineffective at related frequencies. For example in patients with presbyacousis where the sensory cells (hair cells) for sensing the high frequencies are damaged and no longer function, the related neural structures are functional and can be electrically stimulated to transfer high-frequency acoustical signals. There are also many pathologies other than presbyacousis pathologies with high-frequency hearing loss. In general, electrical stimulation is necessary whenever “dead frequency regions” are present that cause sound distortion when only stimulated acoustically/mechanically.
Leysieffer (U.S. Pat. No. 6,697,674) describes the combination of a cochlear electrode with an implanted mechanical transducer that vibrates parts of the middle ear. The middle ear vibrations find their natural way to the inner ear via the stapes footplate in the oval window. Harrison (U.S. Pat. No. 6,754,537) describes a hybrid system for patients with severe high-frequency hearing loss but normal or near normal hearing for low frequencies. He combines a cochlear electrode that electrically stimulates the cochlea with the high-frequency audio content, and relies on the patient's natural hearing to pick up the low-frequency audio content. This low-frequency content is then provided mechanically by either a conventional external hearing aid, or a middle-ear mechanical transducer. Leysieffer describes in U.S. Pat. No. 6,565,503 an electrical cochlear electrode modified with miniature mechanical transducers distributed over the electrode's length to generate mechanical vibrations in the inner ear fluid.
A drawback of known hybrid electrical-mechanical devices for hearing aids is that their implantation is a highly invasive procedure causing irreparable damage to the residual hearing the patient may still have. This is because they are configured either as a conventional cochlear electrode in combination with a mechanical device, or as a cochlear electrode modified with intra-cochlear electromechanical converters that generate mechanical vibrations in the inner ear fluid. Both types have an elongated electrode that is inserted in the scala vestibuli or scala tympani. They penetrate deep into the cochlea through a hole in the bony cochlea wall, thereby risking damaging the fine features inside and destroying whatever residual hearing the patient may still have. Shortening and thinning the electrodes to preserve hearing is an area of intensive research. It is technically challenging and experiments have yet to show conclusive and consistent improvements, although full coverage for speech has been demonstrated on some patients with a 16-17 mm outer-wall electrode. More important, implanting short electrodes actually jeopardizes the patient's prospects for later upgrades to longer electrodes, e.g. in cases of progressive hearing loss. This is caused by tissue growth around the electrodes that tears during electrode removal and ruptures the fragile basilar membrane with it.
The present invention aims at overcoming the problems associated with conventional hearing implants, by providing an effective method and device which retains residual hearing.
It also aims to allow the surgeon to implant an electrical and mechanical stimulatory hearing aid in a single procedure, in those cases where he does not have the foreknowledge of which stimulation would be the most effective.
One embodiment of the invention is an implantable device for improving hearing in a subject comprising:
Another embodiment of the invention is an implantable device as described above, wherein the vibration generator comprises:
Another embodiment of the invention is an implantable device as described above, wherein the frame (22) is configured for physical attachment to a wall enclosing the middle ear (6).
Another embodiment of the invention is an implantable device as described above, wherein the frame (22) is configured for physical attachment to
Another embodiment of the invention is an implantable device as described above, wherein the vibrating surface (25) is a flat surface co-operatively connected to the electromechanical actuator (20).
Another embodiment of the invention is an implantable device as described above, wherein the vibrating surface (25) is extended by an elongated member co-operatively connected to the electromechanical actuator (20).
Another embodiment of the invention is an implantable device as described above, wherein the frame (22) comprises a first sub-frame (22a) that supports the electromechanical actuator (20) and a second sub-frame (22b) provided with the output region (19) wherein the vibration energy from the electromechanical actuator (20) is directed to the output region (19) via a vibrational-energy conducting element (80).
Another embodiment of the invention is an implantable device as described above, wherein the conducting element (80) is a tube (84) adapted to contain a non-compressible liquid or gel (81).
Another embodiment of the invention is an implantable device as described above, wherein the conducting element (80) is a cable link, comprising a flexible cable (83) housed in a sleeve (82), which cable (83) is configured to move within the sleeve (82), while maintaining a coaxial relation therewith.
Another embodiment of the invention is an implantable device as described above, wherein the conducting element (80) is a non-flexible, elongated rod (85).
Another embodiment of the invention is an implantable device as described above, wherein the conducting element (80) is an adjustable telescopic slip link (89).
Another embodiment of the invention is an implantable device as described above, wherein the conducting element (80) is an adjustable hinged link (91).
Another embodiment of the invention is an implantable device as described above, wherein the second sub-frame (22b) forms a passage (72) having a receiving end (70) to receive vibrational energy from the conducting element (80), and a transmitting end (71) where vibrational energy is directed towards the inner ear fluid.
Another embodiment of the invention is an implantable device as described above, wherein the second sub-frame (22b) is disposed with the vibrating surface (25) in the passage (72), optionally in a region towards or at the transmitting end (71).
Another embodiment of the invention is an implantable device as described above, wherein the vibrating surface (25) is a flexible or flexibly suspended membrane (73) in sealing connection with the transmitting end (71) of the passage (72), and in hydraulic connection with the electromechanical actuator (20).
Another embodiment of the invention is an implantable device as described above, wherein the vibrating surface (25) is a flexibly suspended plate in mechanical connection with the electromechanical actuator (20)
Another embodiment of the invention is an implantable device as described above, wherein the vibrating surface (25) is formed from a sliding piston (75) in hydraulic or mechanical connection with the electromechanical actuator (20).
Another embodiment of the invention is an implantable device as described above, wherein the vibrating surface (25) comprises:
Another embodiment of the invention is an implantable device as described above, wherein the first sub-frame (22a) is configured for physical attachment to:
Another embodiment of the invention is an implantable device as described above, wherein the first sub-frame (22a) is incorporated within the housing of a regulating unit (7).
Another embodiment of the invention is an implantable device as described above, wherein the second sub-frame (22b) is configured for attachment at
Another embodiment of the invention is an implantable device as described above, wherein the electromechanical actuator (20) is an electromagnetic, piezoelectric, electrostatic or magnetostrictive actuator.
Another embodiment of the invention is an implantable device as described above, wherein at least part of the frame (22) or at least part of the vibrating surface (25) acts as the proximal electrode (1).
Another embodiment of the invention is an implantable device as described above, wherein the proximal electrode (1) and/or the distal electrode (1) is pin-shaped and is configured to diverge from a longitudinal centreline of a cochlea (4) lumen.
Another embodiment of the invention is an implantable device as described above, wherein the proximal electrode (1), the output region (19) and/or distal electrode (3) is configured to sit flush or recessed with the inside wall of the inner ear (2).
Another embodiment of the invention is an implantable device as described above, wherein the proximal electrode (1), the output region (19) and/or distal electrode (3) is configured to sit flush or recessed with the inside wall of the cochlea (4) lumen.
Another embodiment of the invention is an implantable device as described above, further comprising a regulating unit (7) configured to provide electrical signals to said electrodes and/or vibration generator, which signals represent sound information.
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to provide full audio frequency spectrum to the vibration generator (5).
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to enhance or suppress one or more bands of audio frequency provided to the vibration generator (5).
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to translate sound information into electrical signals for triggering nerves to fire neural signals, which electrical signals are provided to the electrodes (1, 3).
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to translate full audio frequency spectrum into said signals.
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to enhance or suppress one or more bands of audio frequency and translate it into said signals.
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to split sound information into higher frequency signals and lower frequency signals, whereby the higher frequency signals are provided to the electrodes (1, 3) and the lower frequency signals are translated and provided to the vibration generator (5).
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to receive sound information from an internal microphone, an external microphone or a telecoil.
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) is configured to use measurements from a measurement electrode for closed-loop control of electrical and/or vibrational stimulation.
Another embodiment of the invention is an implantable device as described above, wherein the wherein the regulating unit (7) is configured to use readings from the electromechanical actuator (20) operating as a microphone for closed-loop control of electrical and/or vibrational stimulation.
Another embodiment of the invention is an implantable device as described above, wherein the wherein the regulating unit (7) is configured to generate also a static pressure using the vibration generator (5).
Another embodiment of the invention is an implantable device as described above, wherein the electromechanical actuator (20) is configured to act as a pressure sensor.
Another embodiment of the invention is an implantable device as described above, wherein the wherein the regulating unit (7) is configured to control an inner ear (2) pressure using the vibration generator (5).
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) comprises a receiving means configured to receive sound information across a wireless link.
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) comprises a transmitting and/or receiving means, configured to exchange data with an external device across a wireless link.
Another embodiment of the invention is an implantable device as described above, wherein the regulating unit (7) comprises memory storage configured to store patient-specific data.
Another embodiment of the invention is an implantable device as described above, wherein the distal electrode is disposed within the regulating unit (7).
Another embodiment of the invention is a method for improving hearing in a subject comprising the steps of:
Another embodiment of the invention is a method as described above, wherein the vibration generator further comprises:
Another embodiment of the invention is a method as described above, wherein the frame (22) of the vibration generator (5) is attached to the locations defined above.
Another embodiment of the invention is a method as described above, wherein the frame (22) of the vibration generator (5) is attached to a wall enclosing the middle ear (6).
Another embodiment of the invention is a method as described above, wherein the frame (22) of the vibration generator (5) is attached at the interface (28) between the middle (6) and inner ear (2).
Another embodiment of the invention is a method as described above, wherein the frame (22) is embedded in a cavity machined in a bony wall enclosing the middle ear (6), which wall is not an interface (28) between the middle (6) and inner ear (2).
Another embodiment of the invention is a method as described above, wherein said bony wall enclosing the middle ear (6) is the mastoid or temporal bone.
Another embodiment of the invention is a method as described above, wherein the frame (22) of the vibration generator (5) is attached so as to position the output region (19) in a hole drilled all the way through, or drilled partially through the interface (28) between the middle (6) and inner ear (2).
Another embodiment of the invention is a method as described above, wherein the frame (22) of the vibration generator (5) is attached so as to position the output region (19) in a hole drilled all the way through, or drilled partially through a wall enclosing the inner ear (2), preferably interface (28) between the middle (6) and inner ear (2), or preferably the interface between the inner ear (2) and the mastoid region.
Another embodiment of the invention is a method as described above, wherein said hole is in a bony part.
Another embodiment of the invention is a method as described above, wherein the frame comprises a first sub-frame (22a) that supports the electromechanical actuator (20) and a second sub-frame (22b) provided with the output region (19) as defined above.
Another embodiment of the invention is a method as described above, wherein the first sub-frame (22a) is attached to the locations defined above.
Another embodiment of the invention is a method as described above, wherein the first sub-frame (22a) is incorporated within the housing of a regulating unit (7).
Another embodiment of the invention is a method as described above, wherein the second sub-frame (22b) attached the locations defined above.
Another embodiment of the invention is a method as described above, wherein the proximal electrode (1) is implanted at the interface between the middle (6) and inner ear (2).
Another embodiment of the invention is a method as described above, wherein the proximal electrode (1) is implanted where there is a bony part.
Another embodiment of the invention is a method as described above, wherein the proximal electrode (1) is placed in a drilled hole in said bony part, wherein said hole is drilled all the way through, or drilled partially through the bony part.
Another embodiment of the invention is a method as described above, wherein said proximal electrode (1) and output region (19) occupy the same said hole or occupy separately drilled holes.
Another embodiment of the invention is a method as described above, wherein the proximal electrode (1) and/or output region (19) are placed in the oval window.
Another embodiment of the invention is a method as described above, wherein the proximal electrode (1) and/or distal electrode (3) is pin-shaped and is implanted such that a longitudinal axis of the proximal electrode (1) and/or distal electrode (3) diverges from a longitudinal centreline of a cochlea (4) lumen.
Another embodiment of the invention is a method as described above, wherein the proximal electrode (1), vibrating surface (25) and/or distal electrode (3) is implanted such that it is flush or recessed with the inside wall of the inner ear (2).
Another embodiment of the invention is a method as described above, wherein the proximal electrode (1), vibrating surface (25) and/or distal electrode (3) is implanted such that it is flush or recessed with the inside wall of the lumen of the cochlea.
Another embodiment of the invention is a method as described above, wherein the distal electrode (3) is implanted such that the electrical impedance between it and the inner ear fluid at 1kHz is between 10 and 10 000 ohms.
Another embodiment of the invention is a method as described above, wherein the distal electrode (3) is implanted such that the electrical resistance between it and the proximal electrode (1) is between 10 and 10 000 ohms.
Another embodiment of the invention is a method as described above, wherein the distal electrode (3) is implanted such that the electrical impedance between it and the proximal electrode (1) at 1 kHz is between 10 and 10 000 ohms.
Another embodiment of the invention is a method as described above, further comprising the step of implanting a regulating unit (7), and connecting said electrodes (1, 3) and vibration generator (5) to said unit using one or more connecting electrical leads.
Another embodiment of the invention is a method as described above, wherein the proximal electrode, distal electrode, and vibration generator (5) are as defined above.
Another embodiment of the invention is a kit comprising the following components:
Another embodiment of the invention is a as described above, wherein said connecting electrical leads are disposed with connectors for connecting to the proximal electrode (1), distal electrode (3) and/or vibration generator (5).
Another embodiment of the invention is a as described above, wherein said where in the proximal electrode (1), distal electrode (3), and vibration generator (5) are as defined in above.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art. All publications referenced herein are incorporated by reference thereto. All United States patents and patent applications referenced herein are incorporated by reference herein in their entirety including the drawings.
The articles “a” and “an” are used herein to refer to one or to more than one, i.e. to at least one of the grammatical object of the article. By way of example, “an electrode” means one electrode or more than one electrode.
Throughout this application, the term “about” is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.
The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1, 2, 3, 4 when referring to, for example, a number of electrodes, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, a measurement).
The present invention relates to a method and device for improving hearing of a subject, based on the finding by the inventors that a significant improvement in hearing is achieved by:
Because the electrodes do not pass along the scala tympani 42, scala vestibuli 40 or the scala media 41, the procedure is much less invasive than a traditional cochlea electrode, where the electrode enters and penetrates these areas.
In the present invention, a pair of electrodes can be attached anywhere near the cochlea, preferably outside the scala tympani 42, scala vestibuli 40 or the scala media 41 of the cochlea, to provide electrical stimulation of the cochlea. The electrodes in combination with mechanical (vibrational) stimulation of the inner ear, especially the cochlea improve hearing, while maintaining residual natural hearing in a less invasive surgical procedure.
The inventors have found that the electrodes can be placed in any configuration which provides electrical stimulation to the cochlea. In a preferred configuration, stimulation is achieved using a proximal electrode in physical (mechanical or actual) contact with a wall of the inner ear, and a distal (counter) electrode in electrical contact with the cochlea, more specifically the auditory nerve. Thus, a proximal electrode may be attached to a wall enclosing the inner ear, and a distal electrode may be attached or be sufficiently close to the auditory nerve to provide electrical contact.
Reference is made in the description below to the drawings which exemplify particular embodiments of the invention; they are not at all intended to be limiting. The skilled person may adapt the device and method, and substituent components and features according to the common practices of the person skilled in the art.
Device
With reference to
Proximal Electrode
The proximal electrode 1 is placed proximal to the output region 19 of the vibration generator 5 and is configured for physical attachment to a wall enclosing the inner ear 2.
The wall of the inner ear 2 refers to the tissues that enclose the inner ear 2 to form a fluid filled space. The inner ear 2 includes the cochlea with its scala vestibuli, scala typani and the various membranes and neural elements, the vestibulum and the semi-circular canals; such meaning is well understood in the art. The inner ear 2 may be regarded as the cavity bound by the cochlea 4 and the interface between the inner ear and the middle ear. Preferably, the proximal electrode 1 is configured for attachment to the outside of the wall enclosing the inner ear, i.e. on the non-fluid-filled side of the wall. Preferably, the proximal electrode is configured for attachment at the interface between the middle 6 and inner ear 2; the interface may include the promontorium. Preferably, the proximal electrode 1 is configured for attachment at the interface between the middle 6 and inner ear 2, where there is a bony part. Preferably, the proximal electrode 1 is configured for attachment at the interface between the middle 6 and inner ear 2, on the bony wall accessing the scala vestibuli 40 or the scala tympani 42. Preferably, the proximal electrode 1 is configured for attachment to an artificially drilled hole in the bony wall accessing the scala vestibuli (
The shape of a proximal electrode 1 can be any that permits implanting proximal to the vibration generator. Examples of shapes include, but are not limited to the following:
The proximal 1 electrode may be provided with a measuring electrode for measuring the fluid or tissue voltage at the electrode interface. Such electrodes may be provided in a coaxial configuration whereby a tubular outer member provides the stimulation and a central pin measures the fluid or tissue voltage. The tubular outer member may have a smooth surface or may be threaded for screwing into a bony wall. An alternative configuration of the measuring electrode is where it is provided in the metal wall of the vibration generator, for example, as a pin, but electrically insulated therefrom; the metal wall of the vibration generator acts as the proximal electrode and stimulates the acoustic nerve while the pin is used to measure the fluid or tissue voltage at the electrode interface. Another alternative of the measuring electrode is where it is provided as part of the vibration generator as a coaxial arrangement with the proximal electrode; a coaxial electrode embedded in the metal wall of vibration generator, but electrically insulated from it. The outer coaxial sleeve is electrically driven to stimulate the acoustic nerve, and where the central pin is used to measure the fluid or tissue voltage right at the electrode interface.
Such a measurement can be part of a control loop that may automatically adjust the stimulation current on the proximal electrode to obtain a desired neural response and/or be used to control the vibrational stimulation. One embodiment of the invention, therefore, is a device as described herein, wherein the regulating unit 7 is configured to use measurements from a measuring electrode for closed-loop control of the electrical and/or vibrational stimulation.
According to one embodiment of the invention, the proximal electrode 1 penetrates a lumen of the cochlea 4 (e.g. the scala tympani 42, scala vestibuli 40 or the scala media 41) and contacts the fluid of the lumen. Where the electrode is pin-shaped, a longitudinal axis of the electrode may be divergent from a longitudinal centreline of a cochlea 4 lumen. In other words, a pin-shaped electrode may not lie along the passage of a lumen of the cochlea 4. The longitudinal axis and centreline may preferably be about perpendicular. This configuration is distinct from the prior art (e.g.
Where the proximal electrode 1 penetrates a lumen of the cochlea 4 (e.g. the scala vestubuli 40, scala media 41 or scala tympani 42) and contacts the fluid therein, the electrode may or may not extend into a lumen. Where it does not, the electrode may be flush with the inside wall of a lumen, or recessed with the inside wall. Where it does, it may only extend by amount so as not to damage the fragile basilar and Reissner membranes, the spiral organ, the organ of Corti, or the sensory hair cells of the cochlea. According to one embodiment of the invention, the proximal electrode 1 extends into a lumen of the cochlea, by a distance less than or equal to 2 mm, 1.8 mm, 1.6 mm, 1.4 mm, 1.2 mm, 1 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm, 0.1 mm, 0.08 mm, 0.06 mm, 0.04 mm, 0.02 mm, or by an amount in the range between any two of the aforementioned values. Preferably the distance is between 0.1 and 0.5 mm.
In one embodiment of the invention, the proximal electrode is a short intracochlear electrode that extends into the a lumen of the cochlea 4, without damage to the fragile basilar and Reissner membranes, the spiral organ, the organ of Corti, or the sensory cells (hair cells). According to one aspect, an intracochlear electrode extends into a lumen of the cochlea 4 by a distance less than or equal to 15 mm, 14 mm, 12 mm, 10 mm, 8 mm, 6 mm, 4 mm, 3 mm, or by an amount in the range between any two of the aforementioned values. Preferably the distance is between 3 and 15 mm.
The proximal electrode 1 is configured for physical attachment to a wall enclosing the inner ear 2. This means it is implantable. As such, it should fulfil the requirements for an implant such as biocompatibility, stability, and be of suitable shape and size for attachment. The proximal electrode 1 may be made from any suitable biocompatible conducting material such as surgical steels, or platinum, iridium, titanium, gold, silver, nickel, cobalt, tantalum, molybdenum, or their biocompatible alloys. The skilled person may employ material as known in the prior art, for example as described in Venugopalan R. and R. Ideker, “Bioelectrodes,” in Biomaterial Science—An Introduction To Materials in Medicine, Eds. B. D. Ratner, A. S. Hoffman, F. J. Schoen and J. E. Lemons, Elsevier Academic Press, ISBN 0-12-582463-7, pp. 648-657. The proximal electrode may be coated with a substance that lowers its DC and/or AC impedance. Examples of suitable impedance lowering substances include porous platinum coating, titanium nitride coating with or without carbon, iridium coating, iridium oxide coating, titanium nitride coating with iridium oxide, tantalum-based coatings. The number of proximal electrodes may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. The number of proximal electrodes may equal the number of distal electrodes.
According to one aspect of the invention, a proximal electrode 1 is configured to attach to a wall enclosing the inner ear 2, in close proximity to the output region 19 of the vibration generator 5. This configuration means the output region 19 and the proximal electrode 1 are close together, so making implantation easier. The proximal electrode 1 may be attached to the surface of the wall, adjacent to the output region 19; this embodiment is seen, for example, in
Distal Electrode
The distal electrode 3 is separate from the proximal electrode 1, and is placed apart therefrom. The distal electrode 3 is configured to make electrical contact with the auditory nerve 32. It may or may not be in physical (mechanical) contact with the auditory nerve 32 to achieve this. Where it is in physical contact with the auditory nerve 32, it may be attached thereto.
Where the distal electrode 3 is not in physical contact with the auditory nerve 32, it may be attached to a wall enclosing the cochlea 4. In which case, the distal electrode 3 is preferably configured for attachment to the outside of the wall enclosing the cochlea 4, i.e. on the non-fluid-filled side of the wall. The distal electrode 3 may attach either to the surface of the wall, to a small hole drilled partially through the wall, or through a small hole drilled all the way through the wall.
According to one embodiment of the invention, the distal electrode 3 is configured for attachment at the interface between the middle 6 and inner ear 2. The distal electrode 3 may be configured for attachment at the interface between the middle 6 and inner ear 2, where there is a bony part; the interface may include the promontorium. The distal electrode 3 may be configured for attachment at the interface between the middle 6 and inner ear 2, on the bony wall accessing the scala vestibuli or the scala timpani. The distal electrode 3 may be configured for attachment to an artificially drilled hole in the bony wall accessing the scala vestibuli or to the oval window. The distal electrode 3 may be configured for attachment to a walled interface between the inner ear 2 and mastoid region. The distal electrode 3 may be configured for attachment to a walled interface between the inner ear 2 and mastoid region where there is a bony part.
According to one embodiment of the invention, the distal electrode 3 penetrates a lumen of the cochlea 4 (e.g. the scala tympani 42, scala vestibuli 40 or the scala media 41) and contacts the fluid of the lumen. Where the electrode is pin-shaped, a longitudinal axis of the electrode may be divergent from a longitudinal centreline of a cochlea 4 lumen. In other words, a pin-shaped distal electrode 3 may not lie along a passage of a lumen of the cochlea 4. The longitudinal axis and centreline may preferably be about perpendicular. This configuration is distinct from the prior art (e.g.
Where the distal electrode 3 penetrates a lumen of the cochlea 4 and contacts the fluid of the lumen, the electrode may or may not extend into the lumen. Where it does not, the electrode may be flush with the inside wall of the lumen, or recessed with the inside wall. Where it does, it may only extend by amount not to damage the fragile basilar and Reissner membranes, the spiral organ, the organ of Corti, or the sensory cells (hair cells) inside the cochlea. According to one embodiment of the invention, the distal electrode 3 extends into the lumen by a distance less than or equal to 2 mm, 1.8 mm, 1.6 mm, 1.4 mm, 1.2 mm, 1 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm, 0.1 mm, 0.08 mm, 0.06 mm, 0.04 mm, 0.02 mm, or by an amount in the range between any two of the aforementioned values. Preferably the distance is between 0.1 and 0.5 mm.
Where the distal electrode 3 is not in physical contact with the auditory nerve 32, it is sufficiently close thereto to retain electrical contact with the auditory nerve 32 or the neural elements inside the cochlea. This means the auditory nerve or the neural elements inside the cochlea can be electrically stimulated by passing electrical current between said distal electrode 3 and proximal electrode 1. This may also mean that the electrical impedance between the distal electrode 3 and the inner ear fluid at 1 kHz may be less than or equal to 100 000 ohms, 80 000 ohms, 60 000 ohms, 40 000 ohms, 20 000 ohms, 10 000 ohms, 8 000 ohms, 5 000 ohms, 2 000 ohms, 1000 ohms, 800 ohms, 600 ohms, 400 ohms, 200 ohms, 100 ohms, 50 ohms, or a value in the range between any two of the aforementioned values. Preferably the impedance is between 10 and 10 000 ohms.
According to one aspect of the invention, the distal electrode 3 is positioned such that the electrical resistance between it and the proximal electrode 1 is less than or equal to 100 000 ohms, 80 000 ohms, 60 000 ohms, 40 000 ohms, 20 000 ohms, 10 000 ohms, 8 000 ohms, 5 000 ohms, 2 000 ohms, 1000 ohms, 800 ohms, 600 ohms, 400 ohms, 200 ohms, 100 ohms, 50 ohms, or a value in the range between any two of the aforementioned values. Preferably the resistance is between 10 and 10 000 ohms.
According to one aspect of the invention, the distal electrode 3 is placed such that the electrical impedance between it and the proximal electrode 1 at 1 kHz is less than or equal to 100 000 ohms, 80 000 ohms, 60 000 ohms, 40 000 ohms, 20 000 ohms, 10 000 ohms, 8 000 ohms, 5 000 ohms, 2 000 ohms, 1000 ohms, 800 ohms, 600 ohms, 400 ohms, 200 ohms, 100 ohms, 50 ohms, or a value in the range between any two of the aforementioned values. Preferably the impedance is between 10 and 10 000 ohms.
The circuit formed by the proximal electrode 1 and distal electrode 3 is shown in
According to one embodiment of the invention, the distal electrode 3 is configured for attachment in the vicinity of the inner ear 2. As mentioned above, it may be in contact with the cochlea 4, on the non-fluid-filled side of the wall. It may make contact with the auditory nerve. For instance, it may be implanted in a hole accessing the singular nerve (posterior ampullary nerve) canal that passes vestibular nerve fibres to the auditory brain stem, providing a low-impedance connection to the auditory nerve. Alternatively, the distal electrode 3 may be remote from the cochlea 4. According to one aspect of the invention, it may be disposed within an implanted regulating unit 7. For example, it may be disposed as an electrically conductive patch on the exterior housing of the regulating unit 7. Alternatively, the distal electrode may be the casing itself of the regulating unit 7.
The distal electrode 3 is implantable. As such, it should fulfil the requirements for an implant such as biocompatibility, stability, and be of suitable shape and size for attachment. The distal electrode 3 may be made from any suitable biocompatible conducting material such as surgical steels, or platinum, iridium, titanium, gold, silver, nickel, cobalt, tantalum, molybdenum, or their biocompatible alloys. The distal electrode may be coated to lower its DC and/or AC impedance; examples of suitable coatings include porous platinum, titanium nitride with or without carbon, iridium, iridium oxide, titanium nitride with iridium oxide, or tantalum-based coatings. The number of distal electrodes may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more. The number of distal electrodes may equal the number of proximal electrodes.
The shape of a distal electrode 3 can be any that permits implanting to make electrical contact with an auditory nerve 32. Examples of shapes include, but are not limited to the following:
The distal electrode 3 may be provided with a measuring electrode for measuring the tissue voltage at the electrode interface. Such electrodes may be provided in a coaxial configuration whereby a tubular outer member provides the stimulation and an central pin measures the tissue or fluid voltage. The tubular outer member may have a smooth surface or may be threaded for screwing into a bony wall. An alternative configuration of the measuring electrode is where it is provided in the metal wall of the vibration generator, for example, as a pin, but electrically insulated therefrom; the metal wall of the vibration generator acts as the distal electrode and stimulates the acoustic nerve while the pin is used to measure the tissue or fluid voltage at the electrode interface. Another alternative of the measuring electrode is where it is provided as part of the vibration generator as a coaxial arrangement with the distal electrode; a coaxial electrode embedded in the metal wall of vibration generator, but electrically insulated from it. The outer coaxial sleeve is electrically driven to stimulate the acoustic nerve, and where the central pin is used to measure the tissue or fluid voltage right at the electrode interface.
Vibration Generator
The vibration generator 5 according to the invention comprises a vibrating output region 19 configured to apply vibrational stimulation to the inner ear fluid.
An electrical lead 9 with lead wires 24 generally connects the electromechanical actuator 20 to a regulating unit 7. The lead wires 24 carry processed sound information to the vibration generator 5. The sound information may be full audio spectrum sound. Alternatively, the sound information may be processed, for example, low-frequency filtered, high-frequency filtered or multi-band processed. A vibrating surface 25 of the electromechanical actuator 20 vibrates according to the signal on the lead wires, and causes mechanical vibrations 26 that propagate in the inner ear fluid. The mechanical vibration generator 5 thus comprises an electromechanical actuator 20 that converts the electrical signals transmitted by the lead wires 24 to mechanical vibrations 26, which are coupled to the inner ear fluid ultimately by the vibrating surface 25.
According to one aspect of the invention, a frame 22 holds the electromechanical actuator 20 and also formed to provide an output region 19 that may be an aperture in the frame 22 through which vibrational energy is directed. The frame 22 may be composed of a single element; this is shown, for example, in
The frame 22 of the vibration generator 5 may be configured for physical attachment to a wall enclosing the middle ear 6. The wall is usually solid tissue (e.g. bone). Preferably, the frame 22 of vibration generator 5 is configured for attachment to the outside of the wall enclosing the inner ear 2, i.e. on the non-fluid-filled side of the wall; this configuration is shown, for example, in
According to another embodiment of the invention, the frame 22 is configured for attachment to a wall enclosing the middle ear 6, which wall is not an interface 28 between the middle 6 and inner ear 2. This is exemplified in
According to yet another embodiment of the invention, the frame 22 is configured for embedding in a cavity machined in a bony wall enclosing the inner ear, e.g. in the mastoid or temporal bone.
According to yet another embodiment of the invention, the frame 22 is configured for attachment at the interface between the inner ear 2 and the mastoid region. According to yet another embodiment of the invention, the frame 22 is configured for attachment at the interface between the inner ear 2 and the mastoid region where there is a bony part. According to yet another embodiment of the invention, the frame 22 is configured for embedding in a bony wall between the vestibule and the mastoid region. The mastoid region contains mastoid cells that are air-filled pockets in the mastoid process that connect to the middle ear. In implanting the frame 22, the mastoid cells are removed when a skilled practitioner e.g. surgeon carves out the mastoid to create access to the vestibulum. This surgical procedure is called a mastoidectomy. We have recently found that the inner-ear vestibule can be accessed surgically from behind the ear via the mastoid, so allowing convenient implantation.
The frame 22 is implantable. As such, it should fulfil the requirements for an implant such as being form from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The parts of the frame 22 in contact with tissue and/or fluid may be made from any suitable biocompatible material, for example, surgical steels, or platinum, iridium, titanium, gold, silver, nickel, cobalt, tantalum, molybdenum, or their biocompatible alloys.
Vibration Generator—Subframes
According to another aspect of the invention, the frame 22 comprises at least two distinct parts; a remote, first sub-frame 22a that supports and holds in place the electromechanical actuator 20 and a second sub-frame 22b configured for attachment at the interface between the middle 6 and inner ear 2, and which provides the output region 19. The first subframe 22a is configured to position the electromechanical actuator 20 so as to direct the vibrational energy therefrom to the output region 19 present in the second sub-frame 22b. Vibration energy from the electromechanical actuator 20 is directed to the output region 19 via a vibrational-energy conducting element 80, which may be, for example, a liquid filled tube, a cable connection, or a rod link, which conducting elements are elaborated below. The two-part frame allows the electromechanical actuator 20 advantageously to be positioned remote from the output region 19, for example, in circumstances where the physiology of the subject does not allow the implant of a single-frame vibration generator 5.
Vibration Generator—First Sub-Frame
The first sub-frame 22a comprises a housing for the electromechanical actuator 20; such housing may protect the actuator from exposure to fluids present in the middle ear 6 or elsewhere. According to one aspect of the invention, the first sub-frame 22a of the vibration generator 5 is configured for physical attachment in the middle ear cavity. Preferably, the first sub-frame 22a of the vibration generator 5 is configured for physical attachment to a supporting wall enclosing the middle ear 6 as shown, for example, in
According to another aspect of the invention, the first sub-frame 22a of the vibration generator 5 is configured for placement in a cavity 100 as shown, for example, in
According to yet another embodiment of the invention, the first sub-frame 22a is configured for embedding in a cavity machined in a bony wall enclosing the inner ear, e.g. in the mastoid or temporal bone.
According to yet another embodiment of the invention, the first sub-frame 22a is configured for attachment to a bony wall of a cavity created in the mastoid region.
According to yet another embodiment of the invention, the first sub-frame 22a is configured for embedding in a bony wall between the vestibule and the mastoid region. The mastoid region contains mastoid cells that are air-filled pockets in the mastoid process that connect to the middle ear. In implanting the first sub-frame 22a, the mastoid cells are removed when a skilled practitioner e.g. surgeon carves out the mastoid to create access to the vestibulum. This surgical procedure is called a mastoidectomy. As already mentioned, we have found that the inner-ear vestibule can be accessed surgically from behind the ear via the mastoid, so allowing convenient implantation. According to another yet another aspect of the invention, the first sub-frame 22a of the vibration generator 5 is incorporated within the housing of the regulating unit 7, as shown, for example, in
The first sub-frame 22a is implantable. As such, it should fulfil the requirements for an implant such as being form from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The parts of the first sub-frame 22a in contact with tissue and/or fluid may be made from any suitable biocompatible material, for example, surgical steels, or platinum, iridium, titanium, gold, silver, nickel, cobalt, tantalum, molybdenum, or their biocompatible alloys.
Vibration Generator—Second Sub-Frame
The second sub-frame 22b may be configured for attachment to a walled interface between the middle 6 and inner ear 2; the interface may include the promontorium. Preferably, the second sub-frame 22b is configured for attachment at the interface between the middle 6 and inner ear 2, where there is a bony part. The second sub-frame 22b of the vibration generator 5 may be configured for physical attachment to a walled interface between the between the middle 6 and inner ear 2. Preferably, the second sub-frame 22b is configured for attachment at the interface between the middle 6 and inner ear 2, on the bony wall accessing the scala vestibuli 40 or the scala tympani 42. Preferably, the second sub-frame 22b may access the scala vestibule 40, the scala tympani 42, or the vestibulum. Preferably, the second sub-frame 22b is configured for attachment to an artificially drilled hole in the bony wall accessing the scala vestibuli, or to the oval window 12. The second sub-frame 22b may attach either to the surface of the wall, to a small hole drilled partially through the wall, or to a small hole drilled all the way through the wall. The second sub-frame 22b may be configured for attachment to a walled interface between the inner ear 2 and the mastoid region. The second sub-frame 22b may be configured for attachment to a walled interface between the inner ear 2 and the mastoid region where there is a bony part. Preferably, the second sub-frame 22b is configured for attachment to a bony wall of the middle ear cavity, or for attachment to a bony wall in the mastoid region, or for embedment in a cavity created in the mastoid region.
As mentioned above, the proximal electrode may be incorporated into the vibration generator 5; where the vibration generator 5 is formed from a multi-element-frame as described above, the proximal electrode 1 may be comprised in the second-sub frame 22b or in the vibrating surface 25.
The second sub-frame 22b is implantable. As such, it should fulfil the requirements for an implant such as being form from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The parts of the second sub-frame 22b in contact with tissue and/or fluid may be made from any suitable biocompatible material, for example, surgical steels, or platinum, iridium, titanium, gold, silver, nickel, cobalt, tantalum, molybdenum, or their biocompatible alloys.
The second sub-frame 22b is preferably disposed with a passage 72, essentially cylindrical in shape, having a receiving end 70 to receive vibrational energy from the conducting element 80, and a transmitting end 71 where vibrational energy is directed towards the inner ear fluid. The passage 72 may be at least partly linear, though other shapes are envisaged including curved or angular. A region towards or at the transmitting end 71 may be disposed with the vibrating surface 25 (e.g. membrane, a plate, piston) that is able to vibrate responsive to vibrations generated by the electromechanical actuator 20 and which surface is in physical contact with the inner ear fluid.
In
In
It is also within the scope of the invention that the passage 72 is devoid of a vibrating surface 25, such as the membrane 105, pin 101 or piston 75; this is depicted in
Conducting Elements
As already mentioned above, vibration energy generated by the electromechanical actuator 20 present in the first sub-frame 22a is carried to the output region 19 present in the second sub-frame 22b via a conducting element 80, which may be, for example, a fluid containing tube, a cable connection, or a rod link; these conducting elements are elaborated below.
Fluid-Containing Tube
According to one aspect of the invention, the conducting element 80 is a tube 84 adapted to contain a fluid, which carries vibrational energy via the non-compressible liquid medium 81. Such aspect is depicted in
The tube 84 should fulfil the requirements for an implant such as being formed from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The tube 84 is preferably made from a flexible or malleable, non-expandable, material. The tube 84 is preferably water impermeable to the extent that it is able to retain fluid under hydraulic pressure, without significant leakage through the tube detrimental to hydraulic transmission. The parts of the tube 84 in contact with tissue and/or fluid may be made from any suitable biocompatible material having these properties, for example, PTFE tubing, polypropylene tubing, braid-reinforced silicone or polyimide tubing, polyketone (e.g. polyetheretherketone or PEEK™) tubing, or poly-ethylene tubing.
Cable Link
According to another aspect of the invention, the conducting element 80 is a flexible cable link, comprising a flexible cable 83 covered by a flexible sleeve 82, which cable 83 is configured to move within the sleeve 82, for example a rotation or a displacement, while maintaining a coaxial relation with the sleeve 82. Such aspect is depicted in
The cable 83 and sleeve 82 should fulfil the requirements for an implant such as being formed from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The cable 83 is preferably made from a flexible, non-stretchable material. The parts of the cable 83 in contact with tissue and/or fluid may be made from any suitable biocompatible material having these properties stainless steel, stainless steel alloy, titanium, nickel or any suitable material. The sleeve 82 is preferably made from a flexible, non-compressible material. The parts of the sleeve 82 in contact with tissue and/or fluid may be made from any suitable biocompatible material having these properties stainless steel, stainless steel alloy, titanium, nickel, PTFE, polypropylene, silicone, polyimide, polyketone (e.g. polyetheretherketone or PEEK™), or poly-ethylene.
Fixed Length Rod Link
According to one aspect of the invention, the conducting element 80 is a non-flexible elongated member, such as a rod 85 of fixed length. Such aspect is depicted in
The rod 85 should fulfil the requirements for an implant such as being formed from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The rod 85 is preferably made from a rigid material, having the requisite compression and tensile properties i.e. able to resist compression and stretching in normal use. The parts of the rod 85 in contact with tissue and/or fluid may be made from any suitable biocompatible material having these properties stainless steel, stainless steel alloy, titanium, nickel, PTFE, polypropylene, polyimide, polyketone (i.e. polyetheretherketone or PEEK™), poly-ethylene or any suitable material.
Telescopic Slip Link
According to another aspect of the invention, the conducting element 80 is an adjustable telescopic slip link 89 whose length can be increased or decreased in a telescopic manner by the application of tensile or compression force to the ends of the link 89. Such aspect is depicted in
In a preferred embodiment, the first rigid elongated member 89a comprises at one end, an elongated channel 98 to receive the second elongated member 89b. The channel 98 is disposed along the longitudinal axis of the first rigid elongated member 89a, and is preferably dimensioned to allow a close coupling of the second elongated member 89b. The channel 90 is of a maximum depth that allows the shortest length of the adjustable slip link 89.
The slip link 89 is attached at one end to the electromechanical actuator 20 by a joint 86, and at the other end to the vibrating surface 25, more particularly, the plate 74, by another joint 87. Said joints 86, 87 accommodate small angular misalignments between the subframes 22a, 22b, and are preferably ball joints.
The slip link 89 should fulfil the requirements for an implant such as being formed from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The slip link 89 is preferably made from a rigid material, having the requisite compression and tensile properties i.e. able to resist compression and stretching in normal use. The parts of the slip link 89 in contact with tissue and/or fluid may be made from any suitable biocompatible material having these properties stainless steel, stainless steel alloy, titanium, nickel, PTFE, polypropylene, polyimide, polyketone (e.g. polyetheretherketone or PEEK™), poly-ethylene or any suitable material.
Hinged Link
According to another aspect of the invention, the conducting element 80 is an adjustable hinged link 91 whose angle can be increased or decreased by the application of tensile or compression force to the ends of the link. Adjustment to the angle thus alters the linear distance between the ends of the link 91. Such aspect is depicted in
A controlled friction can be created by when the revolute joint 88 comprises two surfaces 92, 93 (
The hinged link 91 is attached at one end to the electromechanical actuator 20 by a joint 86, and at the other end to the vibrating surface 25, more particularly, the plate 74, by another joint 87. Said joints 86, 87 accommodate small angular misalignments between the subframes 22a, 22b, and are preferably a ball joints.
The hinged link 91 should fulfil the requirements for an implant such as being formed from or coated with a biocompatible and stable material, and be of suitable shape and size for insertion and placement. The hinged link 91 is preferably made from a rigid material, having the requisite compression and tensile properties i.e. able to resist compression and stretching in normal use. The parts of the hinged link 91 in contact with tissue and/or fluid may be made from any suitable biocompatible material having these properties stainless steel, stainless steel alloy, titanium, nickel, PTFE, polypropylene, polyimide, polyketone (e.g. polyetheretherketone or PEEK™), poly-ethylene or any suitable material.
The conducting element 80 of the above embodiments, will be of sufficient length to connect the electromechanical actuator 20 in remotely placed first sub-frame 22a with the vibrating surface 25 or output region 19 of second sub-frame 22b. The skilled person will understand that the ideal position for the placement of the first sub-frame 22a will vary from subject to subject, consequently, the length of the conducting element 80 will differ accordingly. For example, a placement of the first sub-frame 22a in the mastoid will require a shorter conducting element 80 compared with its placement in the middle ear cavity. For guidance only, the conducting element may be of a length, or may be configured to connect a distance of 3 mm, 4 mm, 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, 13 mm, 14 mm, 15 mm, 16 mm, 17 mm, 18 mm, 19 mm, 20 mm, 21 mm, 22 mm, 23 mm, 24 mm, 25 mm, 26 mm, 27 mm, 28 mm, 29 mm, 30 mm, 31 mm, 32 mm, 33 mm, 34 mm, 35 mm, 36 mm, 37 mm, 38 mm, 39 mm, 40 mm, 41 mm, 42 mm, 43 mm, 44 mm, 45 mm, 46 mm, 47 mm, 48 mm, 49 mm, 50 mm or a value in the range between any two of the aforementioned values; preferably between 5 and 50 mm.
Vibrating Surface
The vibrating surface 25 of the generator 5 provides vibrational energy to the output region 19. The vibrating surface 25 may be co-operatively connected (e.g. rigidly, flexibly or semi-flexibly) to the electromechanical actuator 20, or it may be extended from the electromechanical actuator 20 by a rigid, semi rigid, or fluid connection of vibration-transmitting material. The former configuration is shown, for example in
Output Region
The output region 19 of the vibration generator 5 transmits vibrational energy to the fluid of the inner ear. The output region 19 may enter the inner ear 2. Alternatively it may contact the interface 28 between the middle ear 6 and inner ear 2 e.g. stimulate a bone in the interface 28. Alternatively it may contact the wall of the inner ear 2 e.g. stimulate a bone in the wall of the inner ear.
The output region 19 may be an aperture in the frame 22 through which vibrational energy is directed. This is shown, for example, in
Alternatively, the output region 19 may be may the vibrating surface 25 of the vibration generator 5. This may be the case when the vibrating surface 25 contacts the fluid of the inner ear or contacts the interface 28 between the middle ear 6 and inner ear 2, or contact the wall of the inner ear 2. This is shown in
According to one embodiment of the invention, at least a part of the vibrating surface 25 penetrates a lumen of the cochlea 4 (e.g. scala tympani 42, scala vestibuli 40 or the scala media 41); this is seen for example in
The vibration generator 5 is configured for physical attachment to a wall enclosing the inner ear 2. This means it is implantable. As such, it should fulfil the requirements for an implant such as biocompatibility, stability, and be of suitable shape and size for attachment. The parts of the vibration generator 5 in contact with tissue and/or fluid (e.g. frame 22, vibrating surface 25) may be made from any suitable biocompatible material. Where it acts as a proximal electrode 1, the conducting parts may be made from, for example, surgical steels, or platinum, iridium, titanium, gold, silver, nickel, cobalt, tantalum, molybdenum, or their biocompatible alloys. They may also be coated to lower their DC and/or AC impedance; examples of suitable coatings include porous platinum, titanium nitride with or without carbon, iridium, iridium oxide, titanium nitride with iridium oxide, or tantalum-based coatings.
The electromechanical actuator 20 may be based on any electromechanical conversion mechanism such as electromagnetic, piezoelectric, electrostatic or magnetostrictive. These mechanisms are known in the art, and some are briefly elaborated below.
An electromagnetic actuator 20 operates in a manner similar to a magnetic loudspeaker driver; the signal transmitted through lead wires 24 causes an electrical current in an actuator coil that is suspended in a magnetic field inside the actuator and mechanically coupled to an elastically suspended membrane or plate that has a vibrating surface 25 that may be in contact with the inner ear 2 fluid. The coil current in the magnetic field produces a mechanical, so-called Lorentz force on the coil, which is mechanically coupled to the elastically suspended membrane or plate and which moves the vibrating surface 25.
A piezoelectric actuator relies on the piezoelectric properties of certain crystals which, when subjected to an externally applied voltage, change shape by a small amount. Many materials like quartz, lead zirconate titanate (PZT), barium titanate, zinc oxide, and even certain polymers exhibit piezoelectricity, also called ferroelectricity, due to a charge asymmetry in the crystal structure causing a microscopic electric dipole moment. Dipoles near each other tend to be aligned in regions called Weiss domains. The domains are usually randomly oriented, but can be aligned during poling, a process by which a strong electric field is applied across the material, usually at elevated temperatures. Mechanical deformations due to piezoelectricity are typically very small, less than 0.1%. Actual applications often require additional mechanical arrangements, like bi-morphs, to amplify the deformations to more useful magnitudes. The disk bender arrangement is an example of such a mechanical amplifier well suited for the electromechanical actuator in the vibration generator 5. The disk bender comprises a thin metal plate attached along its perimeter to a generator housing and with its vibrating surface 25 exposed to the inner ear fluid. A thin piezoelectric disk is attached to the inner plate surface. One of the lead wires 24 attaches to the thin metal plate. The other lead wire attaches to a metal contact applied to the inner surface of the piezoelectric disk. An electric voltage between the metal plate and the metal contact, applied by the implanted electronic processing unit 7 through the lead wires 24, sets up an electric field in the piezoelectric disk and compresses the disk thickness. The disk bender bulges as a result, since the mechanical Poison effect in the piezoelectric material forces the disk to expand laterally, whereas the metal plate does not deform directly under the electric field. The plate bulging effect amplifies the translation distances. The deflection distance in the plate centre is typically orders of magnitude larger than the piezoelectric disk deformations.
An electrostatic actuator derives its actuation force from the electrostatic attraction between two plates at different voltages. A first plate may be formed by a thin metal plate elastically suspended along its perimeter to a generator housing and with its vibrating surface 25 exposed to the inner ear fluid. A second conductive plate is held inside the generator housing at close distance and parallel with the first plate. One of the lead wires 24 attaches to the first plate. The other lead wire attaches to the second plate. The implanted regulating unit 7 applies an electric voltage between the metal plates through the lead wires 24, which creates the electrostatic attraction force and moves the first plate with respect to the housing.
A known property of the aforementioned vibration actuators is that, besides converting electrical to mechanical energy, they may also perform the reverse operation, i.e. convert mechanical to electrical energy. That means that the vibration actuator may also be used as a microphone, for example, to sense inner-ear vibrations. Such a microphone can be part of a control loop that may automatically adjust the electrical and/or mechanical stimuli to obtain a desired vibration. This microphone feature may also enable the measurement of otoacoustic emissions directly at the cochlea producing higher fidelity measurement data compared to the current measurements in the external ear canal. Otoacoustic emissions are the acoustic response of the cochlear system to mechanical or electrical stimuli. They reflect the fundamental workings of the inner ear (Kemp D. T., “Stimulated acoustic emissions from the human auditory system,” J. Acoust. Soc. Am., vol. 64, pp. 1386-1391, 1978) and can be a powerful diagnostic and optimization tool.
Another embodiment of the invention, therefore, is a device as described herein, wherein the regulating unit 7 is configured to use readings from the electromechanical actuator 20 operating as a microphone for closed-loop control of the electrical and/or vibrational stimulation.
Certain piezoelectric, magnetostrictive and electrostatic vibration actuators, in casu the actuators that can produce a static pressure, are also sensitive to static pressure. This feature can be important in diagnostic and treatment applications. An example of such application is Ménière's Disease where the inner ear develops a slowly fluctuating static pressure that may cause fluctuating (episodic) hearing loss, vertigo, tinnitus, or aural fullness (a sense of pressure in the middle ear), for reasons that are not well understood. This static pressure can be measured with and compensated for by the vibration actuator if it is able to produce static pressures.
One embodiment of the invention, therefore, is a device as described herein, wherein the regulating unit 7 is configured to generate also a static pressure using the vibration generator 5, or more specifically the electromechanical actuator 20.
Another embodiment of the invention is a device as described herein, wherein the electromechanical actuator 20 is configured to act as a pressure sensor.
Yet another embodiment of the invention is a device as described herein, wherein the regulating unit 7 is configured to control the inner ear pressure using the vibration generator 5, or more specifically the electromechanical actuator 20.
Regulating Unit
The device may also comprise a regulating unit 7 configured to provide electrical signals for the electrodes 1, 3 and/or vibration generator 5. The regulating unit 7 may receive sound information from any type of source. These include any of the usual sources for external hearing aids, such as for example, through a wireless or wired external microphone or a Telecoil (T-coil) coupler. In one embodiment of the invention, the sound information is received through an implanted microphone. The sound information is converted by the regulating unit 7 to electrical signals for the electrodes 1, 3 and vibration generator 5. These electrical signals may be amplified. The regulating unit 7 comprises the necessary electronic components (e.g. integrated circuits, digital to analogue converts, digital signal processors, switches etc) for performing the conversion of sound information into electrical signals, which components and configurations thereof are known in the art.
The regulating unit 7 may comprise a power source either directly housed in the unit, or electrically or magnetically connected thereto. The power source may be a disposable battery, preferably a long life battery (e.g. alkaline, lithium based). The power source may be a rechargeable battery (e.g. nickel cadmium, nickel metal hydride or lithium based). The battery may be recharged by externally accessible contacts, or by an induction coil. The power source may be an induction coil; this may be coupled with an externally worn complementary coil.
It is an aspect of the invention that the regulating unit 7 may incorporate the first sub-frame 22a of the vibration generator 5, as shown, for example, in
The regulating unit 7 is preferably implantable. As such, it should fulfil the requirements for an implant such as biocompatible and stable housing, and be of suitable shape and size for insertion and placement. The parts of the regulating unit 7 in contact with tissue and/or fluid may be made from any suitable biocompatible material. Where it acts as a distal electrode 3, the conducting parts may be made from, for example, surgical steels, or platinum, iridium, titanium, gold, silver, nickel, cobalt, tantalum, molybdenum, or their biocompatible alloys. They may also be coated to lower their DC and/or AC impedance; examples of suitable coatings include porous platinum, titanium nitride with or without carbon, iridium, iridium oxide, titanium nitride with iridium oxide, or tantalum-based coatings.
The regulating unit 7 may be configured to perform some sound processing tasks. In one embodiment of the invention, the regulating unit 7 processes received sound information and translates it into electrical signals carried by the proximal 1 and distal 3 electrodes, which are able to trigger nerves to fire neural signals (i.e. action potentials). Although the electrical signals are derived from sound, they do not resemble audio signals. Electrical signals may be, but not limited to, bursts of short bi-phasic pulses i.e. positive current pulse followed by an equal charge negative pulse. Typically, these pulses have a higher amplitude when the sound information is louder. They are typically 10-100 μs long with ps edge transients, i.e. much shorter than audio signals. Such signals and processing thereto is known in the art, and the present method encompasses any processing tasks which convert sound information into signals suitable for stimulation of the auditory nerve.
According to one aspect of the invention, the regulating unit 7 is configured to translate sound information into electrical signals able to trigger nerves to fire neural signals, which electrical signals are provided to the electrodes 1, 3. According to another aspect of the invention, the regulating unit 7 is configured to translate full audio frequency spectrum into said electrical signals. According to one aspect of the invention, the regulating unit 7 is configured to enhance or suppress one or more bands of frequency within said full audio frequency (multi-band filtering), prior to translation.
In one embodiment of the invention, the regulating unit 7 processes received sound information and converts it into signals for sending to the vibration generator 5 which in turn produces the corresponding mechanical vibrations in the inner ear fluid. The signal may be amplified. Such signals may represent full audio spectrum sound. Alternatively, the regulating unit 7 processes may provide only sound in a narrow spectrum e.g. provide only higher (e.g. higher than 2500 Hz) frequency or lower (e.g. less than 2500 Hz) frequency sound to the vibration generator 5, which frequency ranges are exemplified below.
According to one aspect of the invention, the regulating unit 7 processes received sound information for the vibration generator using a multi-band filtering and processing; this many mean the vibration generator will receive full audio spectrum whereby certain frequency band frequencies are be enhanced or suppressed e.g. a limited number of high frequency bands enhanced.
According to one aspect of the invention, the regulating unit 7 is configured to provide full audio frequency spectrum to the vibration generator 5. According to another aspect of the invention, the regulating unit 7 is configured to enhance or suppress one or more bands of frequency within said audio frequency spectrum (multi-band filtering).
In one embodiment of the invention, the regulating unit processes received sound information by splitting it into two frequency bands—one comprising higher frequency signals and one comprising lower frequency signals. The crossover frequency may be between 500 Hz and 5 kHz depending on the patient's condition. The higher frequency signals may be equal to or greater than 500 Hz, 600 Hz, 700 Hz, 800 Hz, 900 Hz, 1 kHz, 2 kHz, 3 kHz, 4 kHz, 5 kHz, 6 kHz, 7 kHz, 8 kHz, 9 kHz, 10 kHz, 11 kHz, 12 kHz, 13 kHz, 14 kHz, 15 kHz, 16 kHz, 17 kHz, 18 kHz, 19 kHz, 20 kHz, or a value in the range between any two of the aforementioned values. Preferably the higher frequency signals are between 2 kHz and 14 kHz. The lower frequency signals may be equal to or less than 500 Hz, 400 Hz, 300 Hz, 200 Hz, 100 Hz, 80 Hz, 60 Hz, 40 Hz, 20 Hz, 10 Hz. Preferably the lower frequency signals are between 100 Hz and 500 kHz. The low-frequency sound information may be processed by the regulating unit 7, and provided as a signal to the vibration generator 5 which in turn produces the corresponding mechanical vibrations in the inner ear fluid. The high-frequency sound information may be processed by the regulating unit 7, and provided as electrical signals for triggering neuronal signalling to the electrodes 1, 3 for electrical stimulation of the cochlea. The high-frequency sound information may be processed according to techniques known in the art as mentioned already. This may involve signal rectification, amplitude envelope detection, compression and translation (i.e. translation of the band-filtered and compressed audio into bursts of microsecond pulses) to create electrical stimulation.
As mentioned above, the extent of mechanical and electrical stimulation will depend on the condition of the subject. Some will benefit from simultaneous mechanical and electrical stimulation, others may only need mechanical stimulation, and others only electrical stimulation. Some patients will benefit from full-audio vibration stimulation, other will require enhancement of certain frequencies. Some patients may need complex multi-band audio processing. The precise requirement of each subject may be adjusted and maintained by the regulating unit.
According to one aspect of the invention, the regulating unit 7 is programmable so that the sound-processing configuration (e.g. split between mechanical and electrical stimulation, processing algorithms are used in the mechanical and the electrical signal path, threshold levels, gain settings, filter parameters, compression parameters, electrode selection etc) can be changed depending on how the unit is programmed. The programming can be prepared to suit the patient's condition. The unit 7 may comprise a memory storage device for storing such programmable configurations. The regulating unit 7 comprises the necessary electronic components (e.g. integrated circuits, memory chips, etc) for performing programmability, which components and configurations thereof are known in the art.
The programmable configuration may be entered into the regulating unit 7 via a wireless link. This wireless link can be, for example, an inductive-powering link by means of field modulation or backscattering, a dedicated radio link, a dedicated induction link separate from the powering link, or an infrared link. The regulating unit 7 comprises the necessary electronic components (e.g. integrated circuits, digital signal processors, antennas, etc) for performing the conversion of sound information into signals, which components and configurations thereof are known in the art.
The processing tasks, wireless capability and optional programmability functions are performed using an arrangement of components disposed within the regulating unit 7.
The digitised sound information is further processed in a microcontroller 52 (pC). The microcontroller 52 contains a read-only-memory area S0 which cannot be overwritten, in which the instructions and parameters necessary for “minimum operation” of the system are stored, and storage areas S1 and S2 in which the operating software of the intended function or functions of the regulating unit 7 are stored. The rewriteable program storages S1 and S2 for storing the operating software can be based on EEPROM or on static RAM cells, and in the latter case, provisions may be made within the regulating unit for this RAM area to always be powered.
The digital output signals of the microcontroller 52 are converted using digital-analog converters (D/A) 53 into analogue signals and amplified and then supplied to the stimulating electrodes 1, 3 and the vibration generator 5.
The microcontroller 52 executes the intended function of the hearing implant. This includes audio signal processing described above and optionally also signal generation in the case of a system with additional tinnitus masker or noiser function. Furthermore, the microcontroller 52 may contain software modules which provide for dual control of the stimulating electrodes 1, 3 and the vibration generator 5 in such a manner that the spectral, time, amplitude- and phase-referenced transducer or stimulating electrode signal properties are configured such that optimum hearing success is achieved for the pertinent patient. These software modules can be designed to be static and dynamic. A static design is intended to mean that the software modules, based on scientific findings, are stored once in the program storage of the microcontroller 52 and remain unchanged. Dynamic means that these software modules are “able to learn”, in order to approach as optimally as possible the desired hearing result in a time iterative manner. This means that the software modules can be designed to be adaptive, and parameter matching is done by training by the implant wearer and optionally using other aids such as rehabilitation programs. Furthermore, a software module can be provided which approximates hearing supply as optimum as possible based on an adaptive neural network. Training of this neural network can take place again by the implant wearer and/or using other external aids.
According to one aspect of the invention, the microcontroller 52 communicates via a bidirectional data bus 55 and a telemetry system (TS) 56 wirelessly (for example, via inductive coupling) through the closed skin indicated at 57 with an external programming system (PS) 58. The programming system 58 can be a PC-based system with corresponding programming, processing, display and administration software. Via this telemetry interface, the operating software of the regulating unit 7 which is to be changed or completely replaced is transmitted. Thus, for example, simple verification of software transmission can be done by a reading process via the telemetry interface before the operating software or the corresponding signal processing portions of this software are transmitted into the program storage areas S1 and S2 of the microcontroller 52 via a data bus 55. Furthermore, the working program for the microcontroller 52 can be changed or replaced in whole or in part via the telemetry interface using the external unit 58.
According to another aspect of the invention, the microcontroller 52 controls within the regulating unit 7, via the bidirectional data bus 60, the ND converters 51 of the sensor preprocessing, the D/A converters 53 for control of the stimulating electrodes 1, 3 and the vibration generator 5. The D/A converters 53 can also be partially or entirely omitted when there are digitally controlled power sources for the stimulating electrodes and/or, in case a vibration generator 5 is used, for example, a pulse width-modulated serial digital output signal of the microcontroller 52 is transmitted directly to the vibration generator 5. Via the data bus 60, program parts or entire software modules can also be transferred between an external unit and the microcontroller 52.
The regulating unit 7 may also comprise a primary or secondary battery cell 59 that supplies the individual components with electrical operating energy.
According to one embodiment if the invention, the regulating unit 7 may have a measurement amplifier which can read electrode voltages (distal and proximal) which can be used by the implant in a feedback loop to automatically adjust the stimulation signals:
Other Components
The device may also comprise other components as would be understood by the person skilled in the art. For example, it may comprise electrical leads 8, 9, 10, 23, 24 that connect the electrodes 1, 3 and vibration generator 5 to a regulating unit 7. Connectors may be included on the electrodes 1, 3, vibration generator 5 and/or regulating unit 7 to allow the replacement of these components while leaving the electrical leads 8, 9, 10, 23, 24 in situ. Connectors may be included in the leads 8, 9, 10, 23, 24 to allow easier replacement of the electrodes 1, 3, vibration generator 5 and/or regulating unit 7 while leaving sections of the electrical leads 8, 9, 10, 23, 24 in situ.
The device may take advantage of wireless connectivity, for example, to pass information between the microphone and the regulating unit 7. Alternatively, or in addition, the device may also use wireless connectivity to transfer data between the regulating unit 7 and an external device. The external device may be capable of programming the regulating unit 7, receiving data from the regulating unit, or controlling the regulating unit.
The wireless link can be, for example, an inductive-powering link by means of field modulation or backscattering, a dedicated radio link, a dedicated induction link separate from the powering link, an infrared link or any wireless link known in the art. It can adopt a technical standard for data transfer such as Wi-fi, ZigBee or Bluetooth.
Configurations
The electrodes, vibration generator, and regulating means, described above, can be implement in a variety of configurations, which are within the knowledge of the skilled artisan. Variations include the configurations of the proximal electrode 1 and vibration generator 5 which are elaborated below.
In
In
The frame 22 is fixed to the solid tissue (e.g. bone) surrounding the said hole 21, and holds the vibration generator 5 and therefore the output region 19 in place and aligned to the small hole 21.
In
In
In
In
In
When electrical stimulation is applied across the distal 3 and proximal electrodes 1, the inner ear neural structures are stimulated. When electrical stimulation is combined with vibrational stimulation, there is a significant improvement in hearing experienced by a subject. Unlike with conventional pure electrical cochlea stimulation, or with hybrid stimulation using elongated electrodes inserted in the cochlea, the improvement produced by the present invention is complemented by no or reduced loss in residual hearing. This can be a significant advantage to certain otoacoustical pathologies.
The invention also allows the specialist (e.g. surgeon) to implant an electrical and a mechanical stimulatory hearing aid in a single procedure, when he does not have the foreknowledge of which stimulation would be the most effective. After the surgery, parameters such as the balance between mechanical and electrical stimulation, the signal processing algorithms and settings, can be carefully tuned to the pathology of the specific patient, and retuned periodically over the lifetime of the implant in cases with progressing hearing loss. For example, in case of locally damaged inner ear structures, mechanical stimulation can be greatly impaired. In patients with presbyacousis where the sensory cells (hair cells) for sensing the high frequencies are damaged, the underlying neural structures may still be functional and can be electrically stimulated to transfer high frequency acoustical information. Thus, the invention would provide both electrical and vibrational stimulation, these would be tested by the specialist (e.g. audiologist), and the proportions of electrical and vibrational stimulation adjusted according to the extent of the damage.
Kit
One embodiment of the present invention is a kit comprising one or more of the following components:
As mentioned elsewhere, the proximal electrode and vibration generator may be comprised in a single unit.
The kit may also comprise surgical tools and instructions for use.
The kit may provide components specific to a particular size of implant. Alternatively, it may provide a range of different sizes, to accommodate different attachment sites.
Method
The present invention also relates to a method for improving hearing of a subject, by:
One embodiment of the present invention is a method for improving hearing in a subject comprising:
The description above in respect of the device applies also to the present method embodiments, and is elaborated below.
The properties of the proximal electrode 1 are described above. Preferably, the proximal electrode 1 is attached to the outside of the wall enclosing the inner ear, i.e. on the non-fluid-filled side of the wall. Preferably, the proximal electrode is attached at the interface between the middle 6 and inner ear 2; the interface may include the promontorium. Preferably, it is attached at the interface between the middle 6 and inner ear 2, where there is a bony part. Preferably, the proximal electrode 1 is attached at the interface between the middle 6 and inner ear 2, the bony wall accessing the scala vestibuli 40 or the scala timpani 42. Preferably, the proximal electrode 1 is attached to an artificially drilled hole in the bony wall accessing the scala vestibuli 40 (
According to one embodiment of the invention, the proximal electrode 1 penetrates a lumen of the cochlea 4 (e.g. the scala tympani 42, scala vestibuli 40 or the scala media 41) and contacts the fluid of the lumen. Where the electrode is pin-shaped, a longitudinal axis of the electrode may be divergent from a longitudinal centreline of a cochlea 4 lumen. In other words, a pin-shaped electrode may not lie along the passage of a lumen of the cochlea 4. The longitudinal axis and centreline may preferably be about perpendicular. This configuration is distinct from the prior art (e.g.
Where the proximal electrode 1 penetrates the lumen of the cochlea 4 and contacts the fluid of the lumen, the electrode may or may not extend into the lumen. Where it does not, the electrode may be flush with the inside wall of the lumen, or recessed with the inside wall. Where it does, it may only extend by amount not to damage the fragile basilar and Reissner membranes, the spiral organ, the organ of Corti, or the sensory cells (hair cells) inside the cochlea. According to one embodiment of the invention, the proximal electrode 1 extends into the lumen by a distance less than or equal to 2 mm, 1.8 mm, 1.6 mm, 1.4 mm, 1.2 mm, 1 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm, 0.1 mm, 0.08 mm, 0.06 mm, 0.04 mm, 0.02 mm, or by an amount in the range between any two of the aforementioned values. Preferably the distance is between 0.1 and 0.5 mm.
The number of proximal electrodes attached may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more. The number of proximal electrodes may equal the number of distal electrodes.
According to one aspect of the invention, a proximal electrode 1 is attached to a wall enclosing the inner ear 2, in close proximity to the output region 19 of the vibration generator 5. This configuration means the output region 19 of the vibration generator 5 and proximal electrode 1 are close together, so making implantation easier. The proximal electrode 1 may be attached to the surface of the wall, adjacent to the output region 19 of the vibration generator 5; this embodiment is seen, for example, in
The properties of the distal electrode are described above. The distal electrode 3 is placed apart from the proximal electrode 1, and is implanted to make electrical contact with the auditory nerve 32. It may or may not be in physical contact with the auditory nerve 32 to achieve this. Where it is in physical contact with the auditory nerve 32, it may be attached thereto.
Where it is not in physical contact with the auditory nerve 32, it may be attached to a wall enclosing the cochlea 4. In which case, the distal electrode 3 is preferably configured for attachment to the outside of the wall enclosing the cochlea 4, i.e. on the non-fluid-filled side of the wall. The distal electrode 3 may attach either to the surface of the wall, to a small hole drilled partially through the wall, or through a small hole drilled all the way through the wall.
According to one embodiment of the invention, the distal electrode 3 is attached to the cochlea 4 so that it penetrates a lumen of the cochlea 4 (e.g. scala tympani 42, scala vestibuli 40 or the scala media 41) and contacts the fluid of the lumen. In this embodiment the longitudinal axis of the implanted electrode may be divergent from a longitudinal centreline of a cochlea 4 lumen. This is distinct from the prior art (e.g.
Where the distal electrode 3 penetrates a lumen of the cochlea 4 and contacts the fluid of the inner ear, the electrode may or may not extend into the lumen. Where it does not, the electrode may be flush with the inside wall of the lumen, or recessed with the inside wall. Where it does, it may only extend by amount not to damage the fragile basilar and Reissner membranes, the spiral organ, the organ of Corti, or the sensory cells (hair cells) inside the cochlea. According to one embodiment of the invention, the distal electrode 3 extends into the lumen by a distance less than or equal to 2 mm, 1.8 mm, 1.6 mm, 1.4 mm, 1.2 mm, 1 mm, 0.8 mm, 0.6 mm, 0.4 mm, 0.2 mm, 0.1 mm, 0.08 mm, 0.06 mm, 0.04 mm, 0.02 mm, or by an amount in the range between any two of the aforementioned values. Preferably the distance is between 0.1 and 1.0 mm.
Where the distal electrode 3 is not in physical contact with the cochlea 4, it is implanted so as to retain electrical contact with the auditory nerve or the neural elements inside the cochlea 4. This may mean the cochlea 4 can be electrically stimulated by said distal electrode 3. This may also mean that the distal electrode 3 is implanted so that electrical impedance between the distal electrode 3 and the inner ear fluid 4 at 1 kHz is less than or equal to 100 000 ohms, 80 000 ohms, 60 000 ohms, 40 000 ohms, 20 000 ohms, 10 000 ohms, 8 000 ohms, 5 000 ohms, 2 000 ohms, 1 000 ohms, 800 ohms, 600 ohms, 400 ohms, 200 ohms, 100 ohms, 50 ohms, or a value in the range between any two of the aforementioned values. Preferably the impedance is between 10 and 10 000 ohms.
According to one aspect of the invention, the distal 3 and/or proximal 1 electrodes are implanted so that the electrical impedance between the distal electrode 3 and proximal electrode 1 at 1 kHz is less than or equal to 100 000 ohms, 80 000 ohms, 60 000 ohms, 40 000 ohms, 20 000 ohms, 10 000 ohms, 8 000 ohms, 5 000 ohms, 2 000 ohms, 1 000 ohms, 800 ohms, 600 ohms, 400 ohms, 200 ohms, 100 ohms, 50 ohms, or a value in the range between any two of the aforementioned values. Preferably the impedance is between 10 and 10 000 ohms.
According to one aspect of the invention, the distal 3 and/or proximal 1 electrodes are implanted so that the electrical resistance between the distal electrode 3 and the proximal electrode 1 is less than or equal to 100 000 ohms, 80 000 ohms, 60 000 ohms, 40 000 ohms, 20 000 ohms, 10 000 ohms, 8 000 ohms, 5 000 ohms, 2 000 ohms, 1 000 ohms, 800 ohms, 600 ohms, 400 ohms, 200 ohms, 100 ohms, 50 ohms, or a value in the range between any two of the aforementioned values. Preferably the resistance is between 10 and 10 000 ohms.
According to one embodiment of the invention, the distal electrode 3 is attached in the vicinity of the inner ear 2. As mentioned above, it may be in contact with the cochlea 4, on the non-fluid-filled side of the wall. It may make contact with the auditory nerve. For instance, it may be implanted in a hole accessing the singular nerve (posterior ampullary nerve) canal that passes vestibular nerve fibres to the auditory brain stem, providing a low-impedance connection to the auditory nerve. Alternatively, the distal electrode 3 may be remote from the cochlea 4. According to one aspect of the invention, the distal electrode 3 may be disposed within an implanted regulating unit 7 as described above. For example, it may be disposed as an electrically conductive patch on the exterior housing of the regulating unit 7. Alternatively, the distal electrode may be the casing itself of the regulating unit 7.
The number of distal electrodes attached may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more. The number of distal electrodes may equal the number of proximal electrodes.
The vibration generator 5 is implanted such that its' output region is located in a wall enclosing the inner ear, and can apply vibrational stimulation to the inner ear fluid. The frame 22, or second subframe 22b where present, of the vibration generator 5 is generally attached to a wall enclosing the middle ear 6. The wall is usually solid tissue (e.g. bone). Preferably, the frame 22, more particularly, the second subframe 22b is attached to the outside of the wall enclosing the inner ear 2, i.e. on the non-fluid-filled side of the wall. Preferably, the frame 22, more particularly, the second subframe 22b of the vibration generator is attached at the interface between the middle 6 and inner ear 2. Preferably, the frame 22, more particularly, the second subframe 22b of the vibration generator 5 is attached at the interface between the middle 6 and inner ear 2, where there is a bony part. Preferably, the frame 22, more particularly, the second subframe 22b is attached at the interface between the middle 6 and inner ear 2, on the bony wall accessing the scala vestibuli 40 or the scala tympani 42. Preferably, the frame 22, more particularly, the second subframe 22b of the vibration generator 5 is attached to an artificially drilled hole in the bony wall accessing the scala vestibuli (
According to one embodiment of the invention, the frame 22, more particularly, the first subframe 22a is attached to a wall enclosing the middle ear 6, which wall is not an interface 28 between the middle 6 and inner ear 2. This is exemplified in
According to one embodiment of the invention, the frame 22 more particularly, the first subframe 22a, is embedded in a cavity machined in a bony wall enclosing the middle ear 6, which wall is not an interface 28 between the middle 6 and inner ear 2, e.g. in the mastoid bone.
According to another aspect of the invention, the frame 22 more particularly, the first subframe 22a, is embedded in a cavity 100 as shown, for example, in
According to one embodiment of the invention, vibration generator 5 is attached such that at least a part of the vibrating surface 25 penetrates a lumen of the cochlea 4 (e.g. scala tympani 42, scala vestibuli 40 or the scala media 41) and contacts the fluid of the lumen); this is seen for example in
The present invention may further comprise the step of implanting a regulating unit, and connecting said electrodes and vibration generator to said unit using one or more wire cables. The properties of a regulating unit are described above, one or more of which may be implemented into the present method.
The method of the present invention includes the steps which lead to implantation of the configurations depicted in
It will be within the competence of the skilled person to carry out the steps of method or construct the above described device. Those skilled in the art will recognise, or be able to ascertain using no more than routine substitutions, many equivalents to the specific embodiments of the invention described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT EP2006 012532 | Dec 2006 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2007/064462 | 12/21/2007 | WO | 00 | 6/26/2009 |
