Faculty Bibliography

A major concern regarding multichannel (multi-electrode) cochlear prosthesis usage has been the possibility of long-term deleterious physiological effects such as the degeneration of spiral ganglion cells, neuronal degeneration, and new bone formation. These effects, if present, would become evident in the deterioration of hearing sensation and performance of the cochlear implant recipient on a battery of audiologic tests. To date, five patients using the Australian multi-electrode multichannel cochlear implant have undergone a 1-year evaluation of the device. The assessment includes a check of electrical threshold and comfort levels for each electrode, sound field pure tone and speech thresholds, the MAC battery, vowel and consonant recognition tests, and speech tracking tasks. All results were compared to those obtained postoperatively following stimulation and a 3-month training period. Results to date have shown no deterioration in implant functioning in all patients tested. Periodic extensive monitoring of all implant recipients is advocated in order to evaluate the possibility of long-term effects

A multichannel cochlear prosthesis was evaluated using the method of Connected Discourse Tracking. Data were obtained from five subjects over a 10-week period. Significant learning effects were obtained both with and without the prosthesis. The method of orthogonal polynomials was used to obtain a statistically precise fit for each learning curve. The curves differed both in terms of shape and average rate of learning. The two best subjects showed substantial improvements, reaching tracking rates in excess of 90 words-per-minute. A method for representing prosthesis-based improvements, which takes learning effects into account, is developed and discussed

During 1984, six patients have been implanted with a 22-channel cochlear prosthesis. The device features a programmable wearable speech processor using a speech feature encoding strategy. A strict clinical protocol was followed, and no patients have been lost to follow-up. All patients are regular users of the device and have shown a restoration of hearing sensation in response to acoustic stimuli. Pure tone averages ranged from 20 to 47 dB HL and speech detection thresholds varied from 15 to 32.5 dB HL. All patients have shown a recognition of a large variety of environmental sounds, and an improvement in speech recognition ability when the device is used in conjunction with lipreading. Speech reception thresholds using spondee words without lipreading were obtained in three patients at levels of 27.5 to 55 dB HL and one patient had an open-set speech discrimination score (w-22 word list) of 42% without lipreading. In addition, two of the patients show an ability to have limited interactive conversation without the use of lipreading