Search PubMed⌕ Search

Biomedical subjects

J K Shallop

Publications and source records attributed to J K Shallop.

28 records · Page 2Linked to original sources
PubMed1991

Prediction of behavioral threshold and comfort values for Nucleus 22-channel implant patients from electrical auditory brain stem response test results.

We have studied the prediction of behavioral threshold and comfort values for 11 patients who use the Nucleus 22-channel cochlear implant by means of the results of electrical auditory brain stem response (EABR) procedures. For prediction purposes, EABR and behavioral testing were done in the same electrode mode configuration for three specific electrodes. The results of this investigation suggest that EABR threshold current level is consistently near the behavioral comfort current level, rather than the patient's behavioral threshold level.

Adult↗
PubMed1990

Electrically evoked auditory brain stem responses (EABR) and middle latency responses (EMLR) obtained from patients with the nucleus multichannel cochlear implant.

Electrical auditory brain stem responses (EABR) and electrical middle latency responses (EMLR) were recorded from patients who had received the Nucleus multichannel cochlear implant system. Twenty-five sequential patients had either intraoperative or outpatient EABR testing. We also recorded EMLRs from several outpatients. EABR results were consistent among all patients tested. Wave V mean latencies were the shortest (3.82 msec) for the most apical electrode (E20) and increased slightly for the medial (E12) and basal (E5) electrodes (3.94 and 4.20 msec, respectively). Absolute latencies for all EABR component waves were observed to be 1 to 1.5 msec shorter than typical acoustic auditory brain stem response (ABR) mean latencies. We have examined the relationships between patients' EABR/EMLR and their behavioral responses to electrical stimulation. Generally, the behavioral threshold and comfort current levels were lower than the predicted values based on EABR/EMLR findings. This observation may be due in part to psychophysical loudness differences noted for pulse rates of 10 to 500 pulses per second in some of the patients that we have studied in greater detail.

Adolescent↗
PubMed1990

Characteristics of electrically evoked 'auditory' brainstem responses elicited with the nucleus 22-electrode intracochlear implant.

Electrically evoked auditory brainstem responses (EABRs) were measured in cochlear implant patients fitted with the Nucleus 22 electrode system. The typical response waveform consisted of a series of two to three peaks. The largest peak was similar in form to the wave V of acoustically evoked ABRs and was most prominent for stimulus intensities nearly equal to the patients' maximum comfortable (MC) behavioural stimulus level for the test electrode. The first identifiable wave V amplitude was observed at stimulus levels greater than the patients' psychophysical threshold. With increasing stimulus intensity, wave V amplitude increased rapidly to plateau at a level highly correlated with the patients' MC level at the EABR stimulus rate of 17/s. Wave V peak latency was generally shorter than normal ABRs (4.0 cf. 5.5 ms) and varied with electrode position: apical electrodes had shorter latencies than basal electrodes by approximately 0.4 ms. These results suggest that EABRs can be used as an objective estimate of a patient's electrode-specific MC level, once the correlation of EABR growth functions at 17/s to those at clinically employed rates of 250/s has been determined. EABRs may indicate differences in nerve action potential generation for apical and basal electrodes.

Cochlea↗
PubMed1985

The effect of sleep on the auditory brainstem response (ABR) and the middle latency response (MLR).

The ABR and the MLR were measured without interruption in 4 subjects during a whole night of natural sleep and compared with the awake responses. The conventional EEG activity was monitored during the whole procedure, which permitted a precise rating of the sleep stage during each recording period. Only minor changes were found in the latencies for the ABR during sleep. The MLR responses showed quite dramatic changes in morphology and latencies. Our results appear to indicate that the 40/sec stimulus presentation mode of the MLR will not be very effective during sleep due to the pronounced latency shifts of the different peaks in the MLR. The 40/sec response is based on an inter-peak latency of 25 msec. If this presumption is not fulfilled the different waves in the 40/sec response will not be superimposed and consequently enhanced in the averaging procedure.

Acoustic Stimulation↗
PubMed1983

A comparative study of measurements of SN-10 and the 40/sec middle latency responses in newborns.

Auditory SN-10 responses and summed middle latency responses (40/sec MLR) were obtained from 36 full-term newborns. Wave V latencies from 20-70 dB nHL were in agreement with previous studies. Although the amplitudes of the SN-10 and the 40/sec MLR paradigms were not significantly different, we were able to detect the lowest thresholds with an SN-10 response for unfiltered clicks. The mean threshold for the click evoked SN-10 potential was 5 dB better than the mean threshold for the click evoked 40/sec MLR and 10 dB better than the mean threshold for the 500 Hz toneburst 40/sec MLR. We conclude that both the SN-10 and 40/sec MLR techniques can be useful in the assessment of the hearing of newborns, but that only the 40/sec MLR may be useful in obtaining responses to a 500 Hz toneburst.

Acoustic Stimulation↗
PubMedDate not supplied

Contralateral masking in cochlear implant users with residual hearing in the non-implanted ear.

Contralateral masking was investigated in cochlear implant users with residual hearing in the non-implanted ear. Threshold elevations for acoustic probes were observed when electrical maskers were presented in the opposite ear. Also, threshold elevations for electrical probes were observed when acoustic contralateral maskers were presented. The amount of threshold shift expressed in decibels charge or decibels sound pressure level produced by either contralateral acoustic or electric maskers was within the range found in normal listeners for similar stimuli (i.e. 4-8 dB). There was a correlation between the sensation level of acoustic maskers and the maximum amount of masking observed which is consistent with data for normally hearing subjects. The width of the masking patterns was similar to that expected from forward masking patterns in severely sensorineurally impaired ears and implanted ears. The maximum amount of acoustic masking tended to occur for electrode positions that were more basal than expected from characteristic frequency positions. However, where a relatively high-frequency 4-kHz masker could be used, there was a good match between the characteristic frequency position of the maximum threshold elevation and that of the masker.

Adult↗
PubMedDate not supplied

Objective intraoperative method to record averaged electromyographic stapedius muscle reflexes in cochlear implant patients.

We have developed a procedure to measure the averaged stapedius muscle reflex in response to electrical stimulation (AESR) with a cochlear implant. The AESR, as activated by ipsilateral stimulation with a cochlear implant, was investigated intra-operatively in a series of 12 children. After the cochlear implant was placed into the cochlea and secured by the surgeon, an electromyographic (EMG) needle electrode was gently placed into the stapedius muscle. During stimulation of the cochlear implant, the stapedius reflex was monitored visually (VESR) and as an averaged EMG response (AESR). Consistent AESRs were obtained in 7 of the 12 children. These measures provide a method to obtain stapedius muscle responses that may be helpful in the programming of young children with cochlear implants. Comparative post-operative measures were also obtained, including behavioral threshold levels, behavioral comfort levels, and the contralateral stapedius reflex threshold (ESR) on selected electrodes.

Auditory Threshold↗