Stapedius reflex and EABR thresholds in experienced users of the Nucleus cochlear implant

Evoked auditory brainstem responses (EABR) and stapedius reflex thresholds were established in 7 experienced users of the Nucleus cochlear implant. Even using biphasic 400 microseconds/phase clicks for the EABR, responses were observed in only 5 patients; no stapedius reflex (SR) was seen in 3 patients, 2 of whom had a history of middle-ear disorder. The EABR threshold varied widely between subjective threshold and uncomfortable loudness level (ULL) for the same stimulus. The average SR threshold was found somewhat more consistently at 66% of the dynamic range between threshold and ULL, but grossly overestimated the most comfortable level (MCL) in most cases. To obtain equal loudness at the same current level we suggest that broad clicks (300 microseconds/phase) be used for EABR measurements, thus compensating for the lower repetition rate of EABR stimulus compared with the device fitting stimulus.