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

In our series of patients operated on for acoustic neuromas at New York University Medical Center between 1974 and 1983, 13% (17 of 133) had sudden hearing loss. Of these, approximately 23% (four of 17) had recovered auditory function before acoustic neuroma extirpation. Three patients spontaneously recovered, while one improved with steroid therapy. Contrast computerized tomography demonstrated a widened internal auditory canal and evidence of cerebellopontine angle tumor, respectively, in 88% and 59% of patients with sudden hearing loss and acoustic neuroma. Clinical characteristics suggesting acoustic neuroma as the cause of sudden hearing loss with or without auditory recovery could not be identified in our series. Our data support the rationale that patients with unilateral sudden hearing loss, even with recovery, must be evaluated for a possible cerebellopontine lesion

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

Misonidazole, a potent new antitumor agent that selectively increases the effect of ionizing radiations on poorly oxygenated tumor tumor cells, was given to 21 patients at New York University-Bellevue Medical Center. In 11 of the 21 patients, hearing loss developed secondary to drug ingestion. In all cases the hearing loss was sensorineural, of cochlear origin, and at least partially reversible. There did not seem to be a relationship between degree of hearing loss and age, sex, dose, anatomic site of lesion, or prior hearing loss

Dichotic CV recognition at interaural temporal onset asynchronies (lag times) of 0, 30, 60, and 90 ms was investigated in normal hearing young and elderly subjects. The results for the young group were consistent with those reported in previous studies (Studdert-Kennedy et al., 1970; Berlin et al., 1973a). The older group demonstrated a mean right ear advantage (REA) at simultaneity of 12.7%, which was not significantly different from that of the young group (12.4%). This suggests that the processes subserving the REA are not affected by age. However, there was a significant reduction in the total (right ear plus left ear) dichotic scores of the elderly group compared to the young; suggesting an age-associated reduction in the channel capacity of the aging auditory system. Further, there were striking aberrations of the dictotic lag effect in the elderly group compared to the young subjects, consistent with age-related changes in auditory temporal processing. The findings are discussed with respect to the aging auditory system and the nature of dichotic speech processing

This study investigated the effects of two 'frozen' narrow-band waveforms with different waveform envelopes 50 msec in duration and centered at 250 Hz, on temporal masking at short masking intervals and, further, assessed the effects of phase shifts on backward and forward masking. Four normal-hearing experienced Ss detected a monaurally presented 250-Hz tone burst, 12 msec in duration, that either preceded, occurred simultaneously with, or followed a burst of the narrow-band noise. A 2IFC technique was used with a transformed up-down procedure for threshold estimation. The masking intervals from onset of masker to onset of tonal pulse ranged from -30 to +70 msec. The 3 phasic conditions for the signal were in-phase, 90 degrees out-of-phase, and 180 degrees out-of-phase. Results of this experiment substantiated the data of other researchers who have shown greater backward than forward masking at short masking intervals and greater masking was found for all simultaneous conditions than for any of the backward or forward masking conditions. In addition, differences between the two noise waveforms, as well as the phase shifts, had a significant effect on the thresholds obtained for the backward and forward masking conditions, as well as for the simultaneous masking conditions. Criterion change and waveform storage are discussed as possibly having an effect up these variables