The relationship between EAP and EABR thresholds and levels used to program the nucleus 24 speech processor: data from adults.
OBJECTIVE
The objective of this study was to determine the relationship between electrically evoked whole nerve action potential (EAP) and electrical auditory brain stem response (EABR) thresholds and MAP threshold (T-level) and maximum comfort level (C-level) for subjects who use the Nucleus 24 cochlear implant system.


METHODS
Forty-four adult Nucleus 24 cochlear implant users participated in this study. EAP thresholds were recorded using the Neural Response Telemetry System developed by Cochlear Corporation. EABR thresholds were measured for a subset of 14 subjects using standard evoked potential techniques. These physiologic thresholds were collected on a set of five electrodes spaced across the cochlea, and were then compared with behavioral measures of T-level and C-level used to program the speech processor.


RESULTS
EAP thresholds were correlated with MAP T- and C-levels; however, the correlation was not strong. A technique for improving the correlation by combining measures of T- and C-levels made on one electrode with the EAP thresholds was presented. Correlations between predicted and measured T- and C-levels using this technique were 0.83 and 0.77, respectively. Similar results were obtained using the EABR thresholds for a smaller set of subjects. In general, EABR thresholds were recorded at levels that were approximately 4.7 programming units lower than EAP thresholds.


CONCLUSIONS
Either EAP or EABR thresholds can be used in combination with a limited amount of behavioral information to predict MAP T- and C-levels with reasonable accuracy.
Brown
C J
CJ
Department of Speech Pathology and Audiology, University of Iowa, Iowa City 52242-1012, USA.
Hughes
M L
ML
Luk
B
B
Abbas
P J
PJ
Wolaver
A
A
Gervais
J
J
D000161:Acoustic Stimulation / Q000295:instrumentation; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001309:Auditory Threshold / Q000502:physiology; D019929:Cochlear Implantation; D003056:Cochlear Nerve / Q000502:physiology; D003638:Deafness / Q000601:surgery*; D004867:Equipment Design; D005071:Evoked Potentials / Q000502:physiology*; D016057:Evoked Potentials, Auditory, Brain Stem / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010470:Perceptual Masking; D013067:Speech Perception / Q000502:physiology*