Ann Otol Bhinol LaryngollOO:1991
INEXPENSIVE COCHLEAR IMPLANT DEVICE CHALEE KANCHANARAK, MD NARIN SIRIRATWATANAKUL, MS SEETONE BOONYANUKUL, MA AKACHAI SAENG-IN, MENG TAWANWONG KRAIROJANANAN, PHD CHIANG MAl, THAILAND
We have developed a cochlear implant (CI) device modified from the House/3M cochlear implant device. The cost of raw materials was about $25. We used a new and simple technique for coating the implanted coil. We modified the circuit and removed the amplitudemodulated circuit. With this modification, the device useslesselectricity and fewer transistors. There are slightly more than 3,000 patients using CI devices allover the world. Millions of profoundly deaf patients are poor and cannot afford the CI device that is now commercially available. Any university with well-trained otolaryngologists and physicists or electrical engineers can perform this technique.
KEY WORDS - cochlear implant. trode leads are connected to the coil wires by way of a solder joint, and the coil windings are impregnated with cyanoacrylate glue to fill the voids between the coil turns. The coil and the platinum wires are then insulated with Selleys Super Steel Epoxy Filler/Adhesive (from Selleys Chemical Company, Bankstown, Australia) to increase long-term reliability, as it is water-resistant and a good insulator.
INTRODUCTION
William F. House first implanted a cochlear implant (CI) device in a patient in 1972; it is essentially this same device that is in use today" There are slightly more than 3,000 patients worldwide using these CI devices (C. Dobson, Cochlear Corp, personal communication, 1989). The cost of most CI devices is more than $5,000. The House/3M CI device was considered to be simple and relatively inexpensive and had worldwide established service centers,? but many profoundly deaf patients are poor and cannot afford it. To solve this problem, we tried to make an inexpensive one, and with Dr House's help we modified the circuit from the House/3M CI device. 1,3.4 We made a CI device from raw materials costing $25. We used a new technique for coating the implanted coil. This made the overall expenses low. We modified the circuit and coils and removed the amplitude-modulated circuit. With these modifications, the device uses less electricity and fewer transistors. To our knowledge nobody else has made such a device!
A thin layer of Silastic medical adhesive silicone type A (SMA) is used to coat the outside of the insulated coil and the platinum wires. Reinforced Silastic sheeting (SSB) is used to wrap the coated coil. It adheres to the coated coil through use of SMA. The coated platinum wires are insulated with SMA and silicone rubber tubing (inside diameter, 1.1176 mm; outside diameter, 2.159 mm). A 6-0 nylon suture is used to secure the edges of the SSR to the other SSB, and silicone rubber tubing to the SSB. The CI device is gas-sterilized, and then all edges and the ends of the silicone rubber tubing are sealed with SMA. The SSR is 0.1778 mm thick, and the implanted coil is 23 mm in diameter and 6 mm thick. The electrical properties of the coil exhibit a DC resistance of about 500 O.
MATERIALS AND METHODS
This CI device has been modified from the House/ 3M CI device. 1.3 It consists of an internal coil, an external coil, and an external stimulator.
External Coil. This is made from 1,500 turns of 42-gauge copper wire wound on a ferrite pot core (15 mm in diameter and 6 mm thick). It is also impregnated with cyanoacrylate glue. We coat the external coil with Super Steel Epoxy. The total dimensions of the external coil are 24 mm in diameter and 8 mm in thickness. The electrical characteristic of the coil is a DC resistance of about 200 O. Our way of placing the external coil over the internal coil is by taking away one speaker of a headband set and replacing it with the external coil (Fig 1).
Internal Coil. The electrodes are pure platinum wire with a diameter of 0.2 mm and a 0.5-mm ball at the end. The active lead is 78 mm in length from the edge of the coil body to the ball end, with 6 mm left uninsulated to form the electrode. The ground lead is 68 mm in length, with 50 mm left uninsulated to form the electrode. The implanted coil is wound on a ferrite pot core (15 mm in diameter and 4 mm thick) with 1,800 turns of 45-gauge copper wire. The platinum elec-
External Stimulator. We use a folded aluminum
From the Departments of Otolaryngology (Kanchanarak, Boonyanukul), Physics (Siriratwatanakul), and Electrical Engineering (Saeng-in, Krairojananan), Chiang Mai University, Chiang Mai, Thailand. Presented at the XIV World Congress of Otorhinolaryngology-Head and Neck Surgery, Madrid, Spain, September 10-15, 1989. REPRINTS - Chalee Kanehanarak, MD, Dept of Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
984
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
Kanchanarak et al, Inexpensive Cochlear Implant
985
patients must be able to read and write. They should be postlingually deafened adults who are highly cooperative and in general good health. The ear proposed for implantation must be free from infection and middle ear disorders. The tympanic membrane must be intact. We have implanted devices in six patients since March 26, 1988. Four of them are profoundly deaf from ototoxic drugs, and two from head injuries. All are postlingually deafened adults with poor to good lipreading abilities (ages ranged from 32 to 60 years). We did a promontory stimulation test on all of them to make sure that the hearing pathway beyond the cochlea was still good. We used a transtympanic needle with a biphasic current waveform for the stimulation. The surgical procedures were performed through the facial recess approach to the middle ear as described by House. S After implantation, the auditory performance of these patients was assessed by using pure tone audiometry, speech perception tests, and environmental sounds tests. Speech perception tests consist of 1) spondee words (20 items), 2) consonant-vowel-consonant rhyme discriminations (30 items of initial rhymes and 36 items of final rhymes), and 3) monosyllabic word discriminations (25 items). The tests were prepared in the Thai phonemic system. Words that are commonly used in northern Thai everyday life were selected for the tests. They were tested for standardization in 10 normal subjects. The index of difficulty is 8.4 (moderately difficult) . Fig 1. Inexpensive cochlear implant device consisting of internal coil, external coil (in headbands), and external stimulator.
case with dimensions of 11.6 x 5.9 x 2.8 em. It is powered by two 9-V carbon-zinc batteries. The total weight is 172 g (Fig 1). On the front, there is a condenser microphone and an on-off switch. On the top, there is a volume control knob, a sensitivity control knob, and a plug for the external coil. Signal Flow. The sound enters the microphone with a preamplifier circuit and is routed to a bandpass filter. At the preamplifier circuit, the total gain from the microphone is controlled by a sensitivity circuit. The 3-dB down-points of the filter section are at 200 and 5,000 Hz. From the output of the filter, the signal is routed to a volume control circuit and then to a driver amplifier. Finally, it is routed to the external coil (Fig 2). The electrical stimulus from the internal coil is of a sine waveform.
The patients felt discomfort when the voltage at the external coil was about 15 V peak-to-peak. With the circuit designed, the clipping level is at 15 V peak-to-peak, with new batteries, as in Fig 3. Patients are selected for a CI device if it is determined that they have a profound sensorineural hearing loss and gain no benefit from hearing aids. The
Each item was presented by live voice at normal conversational loudness (about 70 dB sound pressure level [SPL]). The tests were performed in a quiet room under two conditions. First was lipreading only and second was lipreading with the CI device. Under both conditions the subject had to repeat each item. The environmental sounds tests consisted of 10 sounds that are commonly heard in everyday life. All sounds used were readily identified by a group of 10 normal-hearing listeners. The sounds were presented once, and were repeated once if necessary. Subjects were instructed to identify what they heard. RESULTS
The first patient refused to use the CI device, as she was content with her good lipreading ability. Even after a I-year follow-up period, she still refused to use it. She had had high expectations and was disappointed about the sound she perceived through the CI device. She did not like the headbands either. Her internal coil, however, has not been removed. The internal coil of the third patient had to be removed after 4 months of implantation. This was be-
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
Kanchanarak et al, Inexpensive Cochlear Implant
986
C4
vee 0.01-0.e01U
vee \lR2
02
2501-
".
100
.-., ,./
Aided
~~ 80 Coc.hlear
...
-:
~_ '~
Implant
•••
Kanchanarak
oDe
-:
"
~
"
'~ __
.o(>_oO
.----...--_
60
n" 85
House
40
n
=4
n .. 115
Spectrum
20 ,
Ar\SI 1969 0 .... _ _
100
150
500
.__
c>-.-.Q- -
IK
2K
3K
-
.()
6K
10K
Fig 4. Summary of pure tone thresholds obtained from four patients under earphones and with hearing aids prior to implantation and with cochlear implant device. American National Standards Institute (ANSI) standard for 0 dB hearing level and average long-term speech spectrum are included as references.
We made an inexpensive model by using handmade materials and coating the implanted coil with SSR, SMA, silicone rubber tubing, and 6-0 nylon suture. Using this method, we did not have to invest in high technology and an expensive process for molding medical-grade silicone to coat the coil. The SSR, SMA, and silicone rubber tubing have good biocompatibility." The SMA alone is not strong enough to be used as a coating. The durability and longevity of the implanted coil depend on the coating system. The integrity of the SSR, SMA, silicone rubber tubing, and 6-0 nylon suture coated with SMA is lifelong. Coated with SMA, the silicone adheres to the epoxy coating much more strongly than when coated with silicone elastomer. The potential space between the silicone and epoxy coating for body fluid accumulation should not occur. The SMA is permeable and body fluid can reach the epoxy coating through microporous spaces. The epoxy coating is water-resistant and a good insulator. These characteristics should make the implanted coil lifelong. We used a ferrite pot core and a headband set, as a samarium cobalt magnet was not available, but the ferrite material is about $100 cheaper. Some patients did not like the model as it made them look ACKNOWLEDGMENTS -
The authors thank
987
Our speech processing strategy was modified from House's CI device. 1.3,4 We used coils that had larger dimensions and higher resistance. That put the response signal at a low frequency, and it did not require a carrier frequency in coupling of signals from the external coil to the implanted coil. Hence, we removed the amplitude modulator circuit. With these features, the set used less electricity and fewer transistors. Two 9-V carbon-zinc batteries lasted 120 to 150 hours. Danley and Fretz' reported that the House device used two 9-V alkaline batteries that lasted 40 to 80 hours. If an alkaline battery lasts seven times longer than a carbon-zinc battery, using the same battery, our CI device lasts about 15 times longer than the House/3M device. The results are good in four patients. The threshold of our CI device was relatively high at 250 and 500 Hz, owing to the limitation of the condenser microphone. The differences in lipreading scores after the patients had used the external processors for 1 month are not significant, but the scores on environmental sounds tests were 100%. We chose this circuit as we compared external processors constructed from House's circuit and a few circuits that generated sine, square, and biphasic waveforms, and the patients preferred the sine waveform. All of the patients had a fourth grade education. We did not have a good speech rehabilitation program for the patients, and some of them used the external processors for only a few hours a day. This factor might contribute to poor lipreading scores. We are now in the process of designing a new circuit to improve the threshold and performance. We are starting to look at a more standardized way of evaluating the implant. We are also starting to set up a more comprehensive aural rehabilitation program. Further improvement in appearance of this CI device can be achieved by adding a piece of samarium cobalt magnet to hold the coil instead of using a headband set. CONCLUSION
Manufacturing this CI device is easily accomplished. Coating by hand is the most important step in making it inexpensive. Modifying the coils and circuit makes it use less electricity and fewer transistors. Most of our deaf patients are poor but can afford this model. The authors' aim is to allow all, or as many as possible, to hear.
J. M. Nedzelski, MD, Sou-MooTse, PhD,
and W. F. House, MD, for their kindness.
REFERENCES 1. Danley MJ, Fretz RJ. Design and functioning of the singleelectrode cochlear implant. Ann Otol Rhinol Laryngol 1982; 91(suppl 91):21-6.
Am J Otol 1986;7:244-7. 3. House WF. Cochlear implants. Ann Otol Rhinol Laryngol 1976;85(suppl 27).
2. Belal A. Cochlear implantation in developing countries.
4. Edgerton BJ, House WF, Brimacombe lA, Eisenberg LS.
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
988
Kanchanarak et al, Inexpensive Cochlear Implant
Status of the cochlear implant program at the House Ear Institute. Adv AudioI1984;2:68-89.
tient performance on the MAC battery. Otolaryngol CUn North Am 1983;16:267-80.
5. House WF. Surgical considerations in cochlear implantation. Ann Otol Rhinol LaryngoI1982;91(suppI91):15-20. 6. Rosen S, Ball U. Speech perception with the Vienna extracochlear single-channel implant: a comparison of two approaches to speech coding. Br J AudioI1986;20:61-83.
9. Schindler RA, Kessler DK, Rebscer SK, Yanda JL. The University of California:San Francisco/Storz cochlear implant program. Otolaryngol Clin North Am 1986;19:287-305.
7. Rose DE, Facer GW, King AM, Fabry DA. Results using 3M/Vienna extracochlear implant in five patients. Ann Otol Rhinal Laryngol 1987;96(suppl 128):114-7. 8. Edgerton BJ, Prietto A, Danhauer J. Cochlear implant pa-
10. Clark GM. The University of Melbourne/Cochlear Corporation (Nucleus) program. Otolaryngol Clin North Am 1986; 19:329-54. 11. Clark GM, Blamey PI, Brown AM, et al, The biocompatibility of materials. Adv OtorhinolaryngoI1987;38:22-32.
SEVENTH INTERNATIONAL SYMPOSIUM ON THE FACIAL NERVE The Seventh International Symposium on the Facial Nerve will take place June 9-14, 1992, in Cologne, Germany. For further information, please contact the Congress Secretary, Klinik und Poliklinik fUr HNO, Universitat zu Koln, Kongressburo, Joseph-StelzmannStrasse 9, D-5000 Koln, Germany; 49-221-478-6190.
CONFERENCE ON ASSISTIVE LISTENING DEVICES GENERAL ANNOUNCEMENT AND CALL FOR PAPERS A Conference on Assistive Listening Devices, Tutorials, Applications, and Research will be held June 12-14, 1992, at The University of Iowa, Iowa City, Iowa. For information on registration and accommodation, contact the Conference Center, University of Iowa, Memorial Union, Iowa City, IA 52242; (319) 335-3231, Fax (319) 335-3407. For information on Call for Papers, contact Regina Tisor (319) 356-2471, Fax (319) 356-4547. We have applied for Continuing Education Units from ASHA and HAIC.
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
INEXPENSIVE COCHLEAR IMPLANT DEVICE CHALEE KANCHANARAK, MD NARIN SIRIRATWATANAKUL, MS SEETONE BOONYANUKUL, MA AKACHAI SAENG-IN, MENG TAWANWONG KRAIROJANANAN, PHD CHIANG MAl, THAILAND
We have developed a cochlear implant (CI) device modified from the House/3M cochlear implant device. The cost of raw materials was about $25. We used a new and simple technique for coating the implanted coil. We modified the circuit and removed the amplitudemodulated circuit. With this modification, the device useslesselectricity and fewer transistors. There are slightly more than 3,000 patients using CI devices allover the world. Millions of profoundly deaf patients are poor and cannot afford the CI device that is now commercially available. Any university with well-trained otolaryngologists and physicists or electrical engineers can perform this technique.
KEY WORDS - cochlear implant. trode leads are connected to the coil wires by way of a solder joint, and the coil windings are impregnated with cyanoacrylate glue to fill the voids between the coil turns. The coil and the platinum wires are then insulated with Selleys Super Steel Epoxy Filler/Adhesive (from Selleys Chemical Company, Bankstown, Australia) to increase long-term reliability, as it is water-resistant and a good insulator.
INTRODUCTION
William F. House first implanted a cochlear implant (CI) device in a patient in 1972; it is essentially this same device that is in use today" There are slightly more than 3,000 patients worldwide using these CI devices (C. Dobson, Cochlear Corp, personal communication, 1989). The cost of most CI devices is more than $5,000. The House/3M CI device was considered to be simple and relatively inexpensive and had worldwide established service centers,? but many profoundly deaf patients are poor and cannot afford it. To solve this problem, we tried to make an inexpensive one, and with Dr House's help we modified the circuit from the House/3M CI device. 1,3.4 We made a CI device from raw materials costing $25. We used a new technique for coating the implanted coil. This made the overall expenses low. We modified the circuit and coils and removed the amplitude-modulated circuit. With these modifications, the device uses less electricity and fewer transistors. To our knowledge nobody else has made such a device!
A thin layer of Silastic medical adhesive silicone type A (SMA) is used to coat the outside of the insulated coil and the platinum wires. Reinforced Silastic sheeting (SSB) is used to wrap the coated coil. It adheres to the coated coil through use of SMA. The coated platinum wires are insulated with SMA and silicone rubber tubing (inside diameter, 1.1176 mm; outside diameter, 2.159 mm). A 6-0 nylon suture is used to secure the edges of the SSR to the other SSB, and silicone rubber tubing to the SSB. The CI device is gas-sterilized, and then all edges and the ends of the silicone rubber tubing are sealed with SMA. The SSR is 0.1778 mm thick, and the implanted coil is 23 mm in diameter and 6 mm thick. The electrical properties of the coil exhibit a DC resistance of about 500 O.
MATERIALS AND METHODS
This CI device has been modified from the House/ 3M CI device. 1.3 It consists of an internal coil, an external coil, and an external stimulator.
External Coil. This is made from 1,500 turns of 42-gauge copper wire wound on a ferrite pot core (15 mm in diameter and 6 mm thick). It is also impregnated with cyanoacrylate glue. We coat the external coil with Super Steel Epoxy. The total dimensions of the external coil are 24 mm in diameter and 8 mm in thickness. The electrical characteristic of the coil is a DC resistance of about 200 O. Our way of placing the external coil over the internal coil is by taking away one speaker of a headband set and replacing it with the external coil (Fig 1).
Internal Coil. The electrodes are pure platinum wire with a diameter of 0.2 mm and a 0.5-mm ball at the end. The active lead is 78 mm in length from the edge of the coil body to the ball end, with 6 mm left uninsulated to form the electrode. The ground lead is 68 mm in length, with 50 mm left uninsulated to form the electrode. The implanted coil is wound on a ferrite pot core (15 mm in diameter and 4 mm thick) with 1,800 turns of 45-gauge copper wire. The platinum elec-
External Stimulator. We use a folded aluminum
From the Departments of Otolaryngology (Kanchanarak, Boonyanukul), Physics (Siriratwatanakul), and Electrical Engineering (Saeng-in, Krairojananan), Chiang Mai University, Chiang Mai, Thailand. Presented at the XIV World Congress of Otorhinolaryngology-Head and Neck Surgery, Madrid, Spain, September 10-15, 1989. REPRINTS - Chalee Kanehanarak, MD, Dept of Otolaryngology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.
984
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
Kanchanarak et al, Inexpensive Cochlear Implant
985
patients must be able to read and write. They should be postlingually deafened adults who are highly cooperative and in general good health. The ear proposed for implantation must be free from infection and middle ear disorders. The tympanic membrane must be intact. We have implanted devices in six patients since March 26, 1988. Four of them are profoundly deaf from ototoxic drugs, and two from head injuries. All are postlingually deafened adults with poor to good lipreading abilities (ages ranged from 32 to 60 years). We did a promontory stimulation test on all of them to make sure that the hearing pathway beyond the cochlea was still good. We used a transtympanic needle with a biphasic current waveform for the stimulation. The surgical procedures were performed through the facial recess approach to the middle ear as described by House. S After implantation, the auditory performance of these patients was assessed by using pure tone audiometry, speech perception tests, and environmental sounds tests. Speech perception tests consist of 1) spondee words (20 items), 2) consonant-vowel-consonant rhyme discriminations (30 items of initial rhymes and 36 items of final rhymes), and 3) monosyllabic word discriminations (25 items). The tests were prepared in the Thai phonemic system. Words that are commonly used in northern Thai everyday life were selected for the tests. They were tested for standardization in 10 normal subjects. The index of difficulty is 8.4 (moderately difficult) . Fig 1. Inexpensive cochlear implant device consisting of internal coil, external coil (in headbands), and external stimulator.
case with dimensions of 11.6 x 5.9 x 2.8 em. It is powered by two 9-V carbon-zinc batteries. The total weight is 172 g (Fig 1). On the front, there is a condenser microphone and an on-off switch. On the top, there is a volume control knob, a sensitivity control knob, and a plug for the external coil. Signal Flow. The sound enters the microphone with a preamplifier circuit and is routed to a bandpass filter. At the preamplifier circuit, the total gain from the microphone is controlled by a sensitivity circuit. The 3-dB down-points of the filter section are at 200 and 5,000 Hz. From the output of the filter, the signal is routed to a volume control circuit and then to a driver amplifier. Finally, it is routed to the external coil (Fig 2). The electrical stimulus from the internal coil is of a sine waveform.
The patients felt discomfort when the voltage at the external coil was about 15 V peak-to-peak. With the circuit designed, the clipping level is at 15 V peak-to-peak, with new batteries, as in Fig 3. Patients are selected for a CI device if it is determined that they have a profound sensorineural hearing loss and gain no benefit from hearing aids. The
Each item was presented by live voice at normal conversational loudness (about 70 dB sound pressure level [SPL]). The tests were performed in a quiet room under two conditions. First was lipreading only and second was lipreading with the CI device. Under both conditions the subject had to repeat each item. The environmental sounds tests consisted of 10 sounds that are commonly heard in everyday life. All sounds used were readily identified by a group of 10 normal-hearing listeners. The sounds were presented once, and were repeated once if necessary. Subjects were instructed to identify what they heard. RESULTS
The first patient refused to use the CI device, as she was content with her good lipreading ability. Even after a I-year follow-up period, she still refused to use it. She had had high expectations and was disappointed about the sound she perceived through the CI device. She did not like the headbands either. Her internal coil, however, has not been removed. The internal coil of the third patient had to be removed after 4 months of implantation. This was be-
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
Kanchanarak et al, Inexpensive Cochlear Implant
986
C4
vee 0.01-0.e01U
vee \lR2
02
2501-
".
100
.-., ,./
Aided
~~ 80 Coc.hlear
...
-:
~_ '~
Implant
•••
Kanchanarak
oDe
-:
"
~
"
'~ __
.o(>_oO
.----...--_
60
n" 85
House
40
n
=4
n .. 115
Spectrum
20 ,
Ar\SI 1969 0 .... _ _
100
150
500
.__
c>-.-.Q- -
IK
2K
3K
-
.()
6K
10K
Fig 4. Summary of pure tone thresholds obtained from four patients under earphones and with hearing aids prior to implantation and with cochlear implant device. American National Standards Institute (ANSI) standard for 0 dB hearing level and average long-term speech spectrum are included as references.
We made an inexpensive model by using handmade materials and coating the implanted coil with SSR, SMA, silicone rubber tubing, and 6-0 nylon suture. Using this method, we did not have to invest in high technology and an expensive process for molding medical-grade silicone to coat the coil. The SSR, SMA, and silicone rubber tubing have good biocompatibility." The SMA alone is not strong enough to be used as a coating. The durability and longevity of the implanted coil depend on the coating system. The integrity of the SSR, SMA, silicone rubber tubing, and 6-0 nylon suture coated with SMA is lifelong. Coated with SMA, the silicone adheres to the epoxy coating much more strongly than when coated with silicone elastomer. The potential space between the silicone and epoxy coating for body fluid accumulation should not occur. The SMA is permeable and body fluid can reach the epoxy coating through microporous spaces. The epoxy coating is water-resistant and a good insulator. These characteristics should make the implanted coil lifelong. We used a ferrite pot core and a headband set, as a samarium cobalt magnet was not available, but the ferrite material is about $100 cheaper. Some patients did not like the model as it made them look ACKNOWLEDGMENTS -
The authors thank
987
Our speech processing strategy was modified from House's CI device. 1.3,4 We used coils that had larger dimensions and higher resistance. That put the response signal at a low frequency, and it did not require a carrier frequency in coupling of signals from the external coil to the implanted coil. Hence, we removed the amplitude modulator circuit. With these features, the set used less electricity and fewer transistors. Two 9-V carbon-zinc batteries lasted 120 to 150 hours. Danley and Fretz' reported that the House device used two 9-V alkaline batteries that lasted 40 to 80 hours. If an alkaline battery lasts seven times longer than a carbon-zinc battery, using the same battery, our CI device lasts about 15 times longer than the House/3M device. The results are good in four patients. The threshold of our CI device was relatively high at 250 and 500 Hz, owing to the limitation of the condenser microphone. The differences in lipreading scores after the patients had used the external processors for 1 month are not significant, but the scores on environmental sounds tests were 100%. We chose this circuit as we compared external processors constructed from House's circuit and a few circuits that generated sine, square, and biphasic waveforms, and the patients preferred the sine waveform. All of the patients had a fourth grade education. We did not have a good speech rehabilitation program for the patients, and some of them used the external processors for only a few hours a day. This factor might contribute to poor lipreading scores. We are now in the process of designing a new circuit to improve the threshold and performance. We are starting to look at a more standardized way of evaluating the implant. We are also starting to set up a more comprehensive aural rehabilitation program. Further improvement in appearance of this CI device can be achieved by adding a piece of samarium cobalt magnet to hold the coil instead of using a headband set. CONCLUSION
Manufacturing this CI device is easily accomplished. Coating by hand is the most important step in making it inexpensive. Modifying the coils and circuit makes it use less electricity and fewer transistors. Most of our deaf patients are poor but can afford this model. The authors' aim is to allow all, or as many as possible, to hear.
J. M. Nedzelski, MD, Sou-MooTse, PhD,
and W. F. House, MD, for their kindness.
REFERENCES 1. Danley MJ, Fretz RJ. Design and functioning of the singleelectrode cochlear implant. Ann Otol Rhinol Laryngol 1982; 91(suppl 91):21-6.
Am J Otol 1986;7:244-7. 3. House WF. Cochlear implants. Ann Otol Rhinol Laryngol 1976;85(suppl 27).
2. Belal A. Cochlear implantation in developing countries.
4. Edgerton BJ, House WF, Brimacombe lA, Eisenberg LS.
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
988
Kanchanarak et al, Inexpensive Cochlear Implant
Status of the cochlear implant program at the House Ear Institute. Adv AudioI1984;2:68-89.
tient performance on the MAC battery. Otolaryngol CUn North Am 1983;16:267-80.
5. House WF. Surgical considerations in cochlear implantation. Ann Otol Rhinol LaryngoI1982;91(suppI91):15-20. 6. Rosen S, Ball U. Speech perception with the Vienna extracochlear single-channel implant: a comparison of two approaches to speech coding. Br J AudioI1986;20:61-83.
9. Schindler RA, Kessler DK, Rebscer SK, Yanda JL. The University of California:San Francisco/Storz cochlear implant program. Otolaryngol Clin North Am 1986;19:287-305.
7. Rose DE, Facer GW, King AM, Fabry DA. Results using 3M/Vienna extracochlear implant in five patients. Ann Otol Rhinal Laryngol 1987;96(suppl 128):114-7. 8. Edgerton BJ, Prietto A, Danhauer J. Cochlear implant pa-
10. Clark GM. The University of Melbourne/Cochlear Corporation (Nucleus) program. Otolaryngol Clin North Am 1986; 19:329-54. 11. Clark GM, Blamey PI, Brown AM, et al, The biocompatibility of materials. Adv OtorhinolaryngoI1987;38:22-32.
SEVENTH INTERNATIONAL SYMPOSIUM ON THE FACIAL NERVE The Seventh International Symposium on the Facial Nerve will take place June 9-14, 1992, in Cologne, Germany. For further information, please contact the Congress Secretary, Klinik und Poliklinik fUr HNO, Universitat zu Koln, Kongressburo, Joseph-StelzmannStrasse 9, D-5000 Koln, Germany; 49-221-478-6190.
CONFERENCE ON ASSISTIVE LISTENING DEVICES GENERAL ANNOUNCEMENT AND CALL FOR PAPERS A Conference on Assistive Listening Devices, Tutorials, Applications, and Research will be held June 12-14, 1992, at The University of Iowa, Iowa City, Iowa. For information on registration and accommodation, contact the Conference Center, University of Iowa, Memorial Union, Iowa City, IA 52242; (319) 335-3231, Fax (319) 335-3407. For information on Call for Papers, contact Regina Tisor (319) 356-2471, Fax (319) 356-4547. We have applied for Continuing Education Units from ASHA and HAIC.
Downloaded from aor.sagepub.com at DALHOUSIE UNIV on June 25, 2015
