Reflex "delay" in sensorineural hearing-loss.

Abstract

Delay of the acoustic reflex is concerning the latency and the rise-time of the response. The magnitude of these parameters is correlated with the stimulus characteristics but it is also modified by the instrumentation. Normative data obtained with commercial instruments demonstrate statistically meaningful differences of latency depending on age groups, ipsi-or contralateral recording, monophasic or biphasic deflection, which is also a normal response in about 12% of ears. The value are comprised within 150 ms for ipsilateral recording and 200 ms for the contralateral recording. The interaural latency difference (ILD) is not exceeding 40 ms. In cochlear deafness (50 cases with Ménière's disease and 50 cases with acoustic or ototoxic lesions) the latency values are slightly shorter than normal in 25% of the cases. This is better demonstrated when ILD can be evaluated with the normal ear. Also rise-time is similarly reduced. In retrocochlear lesions, when a cochlear involvement is not superimposed latency and rise-time are lengthened. Also in these cases ILD values are very important. It must be recalled that an acoustic reflex delay has been observed also in cases of brain-stem involvement.