Four-Channel cochlear system with a passive, non-hermetically sealed implant

• US 5,549,658 A
• Filed: 10/24/1994
• Issued: 08/27/1996
• Est. Priority Date: 10/24/1994
• Status: Expired due to Fees

• Current Assignee: House Ear Institute
• Original Assignee: House Ear Institute, Advanced Bionics Corporation (Sonova Holding AG)
• Inventors: Loeb, Gerald E., Zeng, Fan-Gang, Shannon, Robert V.
• Primary Examiner(s): Kamm, William E.
• Assistant Examiner(s): LAYNO, CARL HERNANDZ
• Application Number:
  US08/328,260
• Time in Patent Office: 673 Days
• Field of Search: 607/55, 607/56, 607/57, 607/116, 607/137
• US Class Current: 607/57
• CPC Class Codes: A61N 1/36038 Cochlear stimulation

Abstract

A low-cost, multichannel cochlear stimulation system utilizes a passive, non-hermetically sealed, implantable receiver/electrode array and an external wearable processor. At one end of the receiver/electrode array, positioned subcutaneously near the surface of skin above the ear, multiple receiving coils are arranged in an appropriate pattern. At the other end, which is adapted for insertion into the spiral-shaped cochlea, electrodes are spaced apart along the spiral. Each electrode is electrically connected to a respective receiving coil in a monopolar or bipolar fashion. The wearable processor senses audible sounds, converts the sensed sounds to corresponding electrical signals, and divides the electrical signals into multiple frequency bands or channels. A continuous interleaved sampling (CIS) speech processing strategy applies the processed signals of each channel to each of multiple external coils, one coil for each channel, as a series of narrow, rapid, biphasic current pulses. The external coils are aligned, using a suitable headpiece, with corresponding coils of the receiver/electrode array. The narrow CIS pulses contain sufficiently high frequency components to inductively couple the biphasic current pulses directly to the aligned implanted coils without having to modulate a high frequency carrier signal with the biphasic pulses. The induced voltage at the implanted coils causes the biphasic current pulse to appear at a respective electrode of the implanted electrode array, thereby providing electrical stimulation at the cochlea as a function of sensed audible sounds.

Claims

1. A low-cost, multichannel cochlear stimulation system comprising:

a passive, non-hermetically sealed, implantable receiver/electrode array comprising;

a carrier in which is embedded a plurality of coil assemblies at a proximal end of the carrier and a plurality of electrodes at a distal end of the carrier, the distal and proximal ends of the carrier being integrally connected together, the distal end of the carrier being adapted for insertion into a human cochlea, whereby the plurality of electrodes may be placed within the cochlea,

the proximal end of the carrier holding the plurality of coil assemblies in a predetermined pattern,

the plurality of coil assemblies and electrodes comprising the only electrical components within the carrier,

the coil assemblies each comprising a sufficient number of turns of a first wire wound to form a coil, one end of the first wire of each coil being electrically connected directly to at least one of the electrodes at the distal end of the carrier and an other end of the first wire of each coil being connected directly to a second electrode, and

implantable alignment means for aligning the plurality of coil assemblies with corresponding external coils; and

an external wearable processor comprising;

microphone means for generating an electrical signal representative of sensed audible sounds,

filter means for dividing the electrical signal into a plurality of frequency bands, thereby creating a corresponding plurality of frequency band signals, the number of frequency bands being the same as the number of implanted coil assemblies, whereby there is an implanted coil assembly for each frequency band,

signal processing means for processing each of the plurality of frequency band signals in accordance with a prescribed speech processing strategy to produce a biphasic stimulation signal for each frequency band, the biphasic stimulation signal comprising a series of narrow biphasic stimulation pulses of varying amplitude having a width of less than 250 μ

sec and a repetition rate of at least 250 Hz,

an external headpiece having a plurality of external coils, each connected to receive the biphasic stimulation signal of one of the plurality of frequency bands, and

external alignment means for aligning each of the external coils of the external headpiece with respective ones of the plurality of coil assemblies of the implantable receiver/electrode array;

whereby the narrow biphasic stimulation pulses received by each of the plurality of external coils are inductively coupled to respective ones of the plurality of implantable coil assemblies, thereby causing an induced biphasic stimulation current to appear at respective ones of the implantable electrodes as a function of sensed audible sounds.

2. The cochlear stimulation system of claim 1 wherein the narrow biphasic stimulation pulses produced by the signal processing means have a width of less than approximately 100 μ

sec and a repetition rate of at least 500 Hz.

3. The cochlear stimulation system of claim 1 wherein the number of coil assemblies within the implantable receiver/electrode array and the number of frequency bands into which the filter means of the wearable processor divides the electrical signal comprises four.

4. The cochlear stimulation system of claim 3 wherein the four frequency bands comprise a low frequency band for frequencies up to approximately 700 Hz, a first intermediate frequency band for frequencies between approximately 700 Hz and 1400 Hz, a second intermediate frequency band for frequencies between approximately 1400 Hz and 2800 Hz, and an upper frequency band for frequencies greater than approximately 2800 Hz.

5. The cochlear stimulation system of claim 1 wherein the external alignment means comprises at least one permanent magnet mounted within the external headpiece, and the implantable alignment means includes at least one magnetic member embedded within the carrier.

6. The cochlear stimulation system of claim 1 wherein the microphone means of the external wearable processor comprises

a microphone,

a preamplifier coupled to the microphone,

pre-emphasis filter means for equalizing the energy content of an output signal received from the preamplifier, and

automatic gain control means for adjusting an output signal from the pre-emphasis filter means to compensate for differences in loudness of different audible sounds sensed by the microphone.

7. The cochlear stimulation system of claim 1 wherein the signal processing means within the external wearable processor includes a plurality of rectifier circuits for rectifying the corresponding frequency band signals;

and a plurality of low pass filter means connected to receive an output from one of the plurality of rectifier circuits, respectively, for deriving an instantaneous envelope signal of the content of the respective frequency band signals.

8. The cochlear stimulation system of claim 7 wherein the signal processing means within the external wearable processor further includes means for sampling the instantaneous envelope signal of the respective frequency band signals, and mapping the sampled signal to an appropriate biphasic stimulation amplitude, on a continuous interleaved sampled (CIS) basis, with only one envelope signal being sampled, and hence with only one biphasic stimulation signal being generated, at any instant of time.

9. The cochlear stimulation system of claim 8 further including loudness mapping means coupled to the means for sampling and mapping for applying a logarithmic function between the instantaneous envelope signal and the biphasic stimulation amplitude of the resulting biphasic stimulation signal.

10. The cochlear stimulation system of claim 1 wherein the carrier comprises an elongate carrier made from silicone rubber.

11. The cochlear stimulation system of claim 10 wherein the distal end of the carrier is formed in the shape of a spiral to match the basal turn of a human cochlea, with the plurality of electrodes being spaced apart along an inner radius of the spiral.

12. The cochlear stimulation system of claim 1 wherein a first end of the first wire from which the coil of each coil assembly is made is bonded to a second biocompatible wire that extends the length of the carrier inside of the carrier to a respective electrode at the distal end of the carrier.

13. The cochlear stimulation system of claim 12 wherein each electrode at the distal end of the carrier comprises a ball formed at a distal end of the second biocompatible wire, a portion of which ball is exposed through the surface of the carrier.

14. The cochlear stimulation system of claim 13 wherein the second wire is made from approximately 90% platinum and 10% iridium.

15. The cochlear stimulation system of claim 1 wherein a second end of the first wire from which the coil of each coil assembly is made is bonded to a third biocompatible wire that extends to another electrode exposed at the surface of the carrier.

16. The cochlear stimulation system of claim 15 wherein the third wire is made from approximately 90% platinum and 10% iridium.

17. A low-cost, four-channel cochlear stimulation system comprising:

a passive, non-hermetically sealed, implantable receiver/electrode array; and

an external wearable processor;

wherein the implantable receiver/electrode array consists of;

an elongate carrier in which is embedded four coil assemblies at a proximal end of the carrier and four electrodes at a distal end of the carrier, with the distal end of the carrier being formed to fit within a human cochlea, and with the proximal end of the carrier holding the four coil assemblies in a predetermined pattern, and

implantable alignment means for aligning the plurality of coil assemblies with corresponding external coils, and wherein

each coil assembly comprises a multiplicity of turns of a first wire wound to form a coil, with a first end of the first wire of each coil being bonded to a second wire that extends the length of the elongate carrier inside of the carrier to a respective electrode at the distal end of the carrier, and with a second end of the first wire of each coil being bonded to a third wire that extends to another electrode exposed at the surface of the carrier, and wherein the second and third wires are each made from a biocompatible conductive material, and further wherein

each electrode comprises a ball formed from the wire extending thereto, with a portion of the ball being exposed through the surface of the carrier; and

wherein the external wearable processor comprises;

microphone means for generating an electrical signal representative of sensed audible sounds,

filter means for dividing the electrical signal into four frequency bands, thereby creating four corresponding frequency band signals, whereby there is an implanted coil assembly and corresponding electrode for each frequency band,

a signal processor that includes means for processing each of the plurality of frequency band signals in accordance with a prescribed speech processing strategy to produce a biphasic stimulation signal for each frequency band, the biphasic stimulation signal comprising a series of narrow biphasic stimulation pulses of varying amplitude having a width of less than 250 μ

sec and a repetition rate of at least 250 Hz, and

an external headpiece having four external coils, each connected to receive one of the respective biphasic stimulation signals,

external alignment means for positioning the external headpiece in alignment with the implantable alignment means to align each of the external coils of the external headpiece with respective ones of the plurality of coil assemblies of the implantable receiver/electrode array;

whereby the narrow biphasic stimulation pulses received by each of the four external coils are inductively coupled to respective ones of the four implantable coil assemblies, thereby causing an induced biphasic stimulation current to appear at respective ones of the implantable electrodes as a function of sensed audible sounds.

18. A passive, non-hermetically sealed, implantable receiver/electrode array for use with a four-channel cochlear stimulation system consisting of:

a carrier in which is embedded four coil assemblies at a proximal end of the carrier and four electrodes at a distal end of the carrier, with the distal end of the carrier being formed to fit within a human cochlea, and with the proximal end of the carrier holding the four coil assemblies in a predetermined pattern, and

implantable alignment means for aligning the plurality of coil assemblies with corresponding external coils, and wherein

each coil assembly comprises a multiplicity of turns of a first wire wound to form a coil, with a first end of the first wire of each coil being bonded to a second wire that extends the length of the carrier inside of the carrier to a respective electrode at the distal end of the carrier, and with a second end of the first wire of each coil being bonded to a third wire that extends to another electrode exposed at the surface of the carrier, and wherein the second and third wires are each made from a biocompatible conductive material, and further wherein

each electrode comprises a ball formed from the wire extending thereto, with a portion of the ball being exposed through the surface of the carrier.

19. A method of directly stimulating a human cochlea with electrical signals representative of sensed audio sounds, thereby imparting the sensation of hearing to a deaf patient, the method comprising the steps of:

(a) implanting a receiver/electrode array into the patient, the receiver/electrode array comprising a non-hermetically sealed carrier in which is embedded a plurality of coil assemblies at a proximal end of the carrier and a corresponding plurality of electrodes at a distal end of the carrier, with each electrode at the distal end of the carrier being electrically connected to a respective one of the coil assemblies at the proximal end of the carrier, and with the distal end of the carrier being inserted into the human cochlea, and with the proximal end of the carrier being positioned just beneath the skin of the patient above an ear of the patient;

(b) generating an electrical signal representative of sensed audible sounds,

(c) dividing the electrical signal into a plurality of frequency bands, the plurality of frequency bands being the same number as the plurality of implanted coil assemblies within the receiver/electrode array, whereby there is an implanted coil assembly and corresponding electrode for each frequency band,

(d) processing each of the plurality of frequency band signals to produce a biphasic stimulation signal for each frequency band, the biphasic stimulation signal comprising a series of narrow biphasic stimulation pulses of varying amplitude having a width of less than 100 μ

sec and a repetition rate of at least 500 Hz, and

(e) applying the biphasic stimulation signal of each frequency band to a respective external coil;

(f) aligning each of the plurality of external coils with a corresponding one of the plurality of implanted coil assemblies such that there is a distance at least equal to the thickness of the patient'"'"'s skin separating the external coils from the implanted coil assemblies, whereby the narrow biphasic stimulation pulses received by each of the plurality of external coils are inductively coupled to respective ones of the plurality of coil assemblies, thereby inducing a biphasic stimulation current in the implanted coil assemblies that appears at a respective one of the electrodes at the distal end of the carrier as a function of sensed audible sounds.

20. A low-cost, multichannel cochlear stimulation system comprising:

a passive, non-hermetically sealed, implantable receiver/electrode array comprising;

a carrier in which is embedded a plurality of coil assemblies at a proximal end of the carrier and a corresponding plurality of electrodes at a distal end of the carrier, the distal end of the carrier being adapted for insertion into a human cochlea, whereby the plurality of electrodes are placed within the cochlea,

the proximal end of the carrier holding the plurality of coil assemblies in a predetermined pattern,

the coil assemblies each comprising a sufficient number of turns of a first wire wound to form a coil, one end of each coil being electrically connected directly to at least one of the electrodes at the distal end of the carrier and an other end of each coil being connected directly to a second electrode, and

implantable alignment means for aligning the plurality of coil assemblies with corresponding external coils; and

an external wearable processor comprising;

microphone means for generating an electrical signal representative of sensed audible sounds,

filter means for dividing the electrical signal into a plurality of frequency bands, thereby creating a corresponding plurality of frequency band signals, the number of frequency bands being the same as the number of implanted coil assemblies, whereby there is an implanted coil assembly for each frequency band,

signal processing means for processing each of the plurality of frequency band signals in accordance with a prescribed speech processing strategy to produce a biphasic stimulation signal for each frequency band, the biphasic stimulation signal comprising a series of narrow biphasic stimulation pulses of varying amplitude having a width of less than approximately 50 μ

sec and a repetition rate of at least 1000 Hz,

an external headpiece having a plurality of external coils, each connected to receive the biphasic stimulation signal of one of the plurality of frequency bands, and

external alignment means for aligning each of the external coils of the external headpiece with respective ones of the plurality of coil assemblies of the implantable receiver/electrode array;

whereby the narrow biphasic stimulation pulses received by each of the plurality of external coils are inductively coupled to respective ones of the plurality of implantable coil assemblies, thereby causing an induced biphasic stimulation current to appear at respective ones of the implantable electrodes as a function of sensed audible sounds.

21. The cochlear stimulation system of claim 20 wherein the prescribed signal processing strategy comprises a continuous interleaved sampling (CIS) strategy wherein only one biphasic stimulation pulse is produced at any given time.

22. The cochlear stimulation system of claim 20 wherein the number of coil assemblies within the implantable receiver/electrode array and the number of frequency bands into which the filter means of the wearable processor divides the electrical signal comprises four.

23. The cochlear stimulation system of claim 22 wherein the four frequency bands comprise a low frequency band for frequencies up to approximately 700 Hz, a first intermediate frequency band for frequencies between approximately 700 Hz and 1400 Hz, a second intermediate frequency band for frequencies between approximately 1400 Hz and 2800 Hz, and an upper frequency band for frequencies greater than approximately 2800 Hz.

24. The cochlear stimulation system of claim 20 wherein the external alignment means comprises at least one permanent magnet mounted within the external headpiece, and the implantable alignment means includes at least one magnetic member embedded within the carrier.

25. The cochlear stimulation system of claim 20 wherein the microphone means of the external wearable processor comprises

a microphone,

a preamplifier coupled to the microphone,

pre-emphasis filter means for equalizing the energy content of an output signal received from the preamplifier, and

automatic gain control means for adjusting an output signal from the pre-emphasis filter means to compensate for differences in loudness of different audible sounds sensed by the microphone.

26. The cochlear stimulation system of claim 20 wherein the signal processing means includes a plurality of rectifier circuits for rectifying the corresponding frequency band signals;

and a plurality of low pass filter means connected to receive an output from one of the plurality of rectifier circuits, respectively, for deriving an instantaneous envelope signal of the content of the respective frequency band signals.

27. The cochlear stimulation system of claim 26 wherein the signal processing means further includes means for sampling the instantaneous envelope signal of the respective frequency band signals, and mapping the sampled signal to an appropriate biphasic stimulation amplitude, on a continuous interleaved sampled (CIS) basis, with only one envelope signal being sampled, and hence with only one biphasic stimulation signal being generated, at any instant of time.

28. A low-cost, multichannel cochlear stimulation system comprising:

a passive, non-hermetically sealed, implantable receiver/electrode array comprising;

a carrier in which is embedded a plurality of coil assemblies at a proximal end of the carrier and a corresponding plurality of electrodes at a distal end of the carrier, the distal end of the carrier being adapted for insertion into a human cochlea, whereby the plurality of electrodes are placed within the cochlea,

the proximal end of the carrier holding the plurality of coil assemblies in a predetermined pattern,

the coil assemblies each comprising a sufficient number of turns of a first wire wound to form a coil, one end of each coil being electrically connected directly to at least one of the electrodes at the distal end of the carrier and an other end of each coil being connected directly to a second electrode, and

implantable alignment means for aligning the plurality of coil assemblies with corresponding external coils; and

an external wearable processor comprising;

microphone means for generating an electrical signal representative of sensed audible sounds,

filter means for dividing the electrical signal into a plurality of frequency bands, thereby creating a corresponding plurality of frequency band signals, the number of frequency bands being the same as the number of implanted coil assemblies, whereby there is an implanted coil assembly for each frequency band,

signal processing means for processing each of the plurality of frequency band signals in accordance with a prescribed speech processing strategy to produce a biphasic stimulation signal for each frequency band, the biphasic stimulation signal comprising a series of narrow biphasic stimulation pulses of varying amplitude having a width of less than 250 μ

sec and a repetition rate of at least 250 Hz, the signal processing means comprising

a plurality of rectifier circuits for rectifying the corresponding frequency band signals,

a plurality of low pass filter means connected to receive an output from one of the plurality of rectifier circuits, respectively, for deriving an instantaneous envelope signal of the content of the respective frequency band signals,

means for sampling the instantaneous envelope signal of the respective frequency band signals, and mapping the sampled signal to an appropriate biphasic stimulation amplitude, on a continuous interleaved sampled (CIS) basis, with only one envelope signal being sampled, and hence with only one biphasic stimulation signal being generated, at any instant of time, and

loudness mapping means coupled to the means for sampling and mapping for applying a linear function between the instantaneous envelope signal and the biphasic stimulation amplitude of the resulting biphasic stimulation signal,

an external headpiece having a plurality of external coils, each connected to receive the biphasic stimulation signal of one of the plurality of frequency bands, and

external alignment means for aligning each of the external coils of the external headpiece with respective ones of the plurality of coil assemblies of the implantable receiver/electrode array;

whereby the narrow biphasic stimulation pulses received by each of the plurality of external coils are inductively coupled to respective ones of the plurality of implantable coil assemblies, thereby causing an induced biphasic stimulation current to appear at respective ones of the implantable electrodes as a function of sensed audible sounds.

29. A low-cost, multichannel cochlear stimulation system comprising:

a passive, non-hermetically sealed, implantable receiver/electrode array comprising;

a carrier in which is embedded a plurality of coil assemblies at a proximal end of the carrier and a plurality of electrodes at a distal end of the carrier, the distal end of the carrier being adapted for insertion into a human cochlea, whereby the plurality of electrodes are placed within the cochlea,

the proximal end of the carrier holding the plurality of coil assemblies in a predetermined pattern,

the coil assemblies each comprising a sufficient number of turns of a first wire wound to form a coil, one end of each coil being electrically connected directly to at least one of the plurality of electrodes at the distal end of the carrier and an other end of each coil being connected directly to a second electrode; and

an external wearable processor comprising;

microphone means for generating an electrical signal representative of sensed audible sounds,

filter means for dividing the electrical signal into a plurality of frequency bands, thereby creating a corresponding plurality of frequency band signals, the number of frequency bands being the same as the number of implanted coil assemblies, whereby there is an implanted coil assembly for each frequency band,

signal processing means for processing each of the plurality of frequency band signals in accordance with a prescribed speech processing strategy to produce a biphasic stimulation signal for each frequency band, the biphasic stimulation signal comprising a series of narrow biphasic stimulation pulses of varying amplitude having a width of less than approximately 50 μ

sec and a repetition rate of at least 1000 Hz,

an external headpiece having a plurality of external coils, each connected to receive the biphasic stimulation signal of one of the plurality of frequency bands, and

external alignment means for aligning each of the external coils of the external headpiece with respective ones of the plurality of coil assemblies of the implantable receiver/electrode array;

whereby the narrow biphasic stimulation pulses received by each of the plurality of external coils are inductively coupled to respective ones of the plurality of implantable coil assemblies, thereby causing an induced biphasic stimulation current to appear at respective ones of the implantable electrodes as a function of sensed audible sounds.

30. A low-cost, multichannel cochlear stimulation system comprising:

a passive, non-hermetically sealed, implantable receiver/electrode array comprising;

a carrier in which is embedded a plurality of coil assemblies at a proximal end of the carrier and a plurality of electrodes at a distal end of the carrier, the distal end of the carrier being adapted for insertion into a human cochlea, whereby the plurality of electrodes are placed within the cochlea,

the proximal end of the carrier holding the plurality of coil assemblies in a predetermined pattern,

the coil assemblies each comprising a sufficient number of turns of a first wire wound to form a coil, one end of each coil being electrically connected directly to at least one of the plurality of electrodes at the distal end of the carrier and an other end of each coil being connected directly to a second electrode; and

an external wearable processor comprising;

microphone means for generating an electrical signal representative of sensed audible sounds,

filter means for dividing the electrical signal into a plurality of frequency bands, thereby creating a corresponding plurality of frequency band signals, the number of frequency bands being the same as the number of implanted coil assemblies, whereby there is an implanted coil assembly for each frequency band,

signal processing means for processing each of the plurality of frequency band signals in accordance with a prescribed speech processing strategy to produce a biphasic stimulation signal for each frequency band, the biphasic stimulation signal comprising a series of narrow biphasic stimulation pulses of varying amplitude having a width of less than 250 μ

sec and a repetition rate of at least 250 Hz, the signal processing means comprising

a plurality of rectifier circuits for rectifying the corresponding frequency band signals,

a plurality of low pass filter means connected to receive an output from one of the plurality of rectifier circuits, respectively, for deriving an instantaneous envelope signal of the content of the respective frequency band signals,

means for sampling the instantaneous envelope signal of the respective frequency band signals, and mapping the sampled signal to an appropriate biphasic stimulation amplitude, on a continuous interleaved sampled (CIS) basis, with only one envelope signal being sampled, and hence with only one biphasic stimulation signal being generated, at any instant of time, and

loudness mapping means coupled to the means for sampling and mapping for applying a linear function between the instantaneous envelope signal and the biphasic stimulation amplitude of the resulting biphasic stimulation signal,

an external headpiece having a plurality of external coils, each connected to receive the biphasic stimulation signal of one of the plurality of frequency bands, and

external alignment means for aligning each of the external coils of the external headpiece with respective ones of the plurality of coil assemblies of the implantable receiver/electrode array;

whereby the narrow biphasic stimulation pulses received by each of the plurality of external coils are inductively coupled to respective ones of the plurality of implantable coil assemblies, thereby causing an induced biphasic stimulation current to appear at respective ones of the implantable electrodes as a function of sensed audible sounds.