Stapedius reflex in multiple sclerosis.

The stapedius reflex (StR) was studied in humans by impedance audiometry. Ipsilateral and contralateral reflexes, obtained from 48 multiple sclerosis (MS) patients and 26 controls, were analysed. MS patients showed smaller reflex amplitudes, longer onset latencies and higher contralateral reflex thresholds. Using onset latencies, 33% of all MS patients had at least two abnormal ipsi- and/or contralateral StRs. If the diagnosis was MS of the definite type, this figure was 39%. The StR is therefore a useful tool for detecting a subclinical lesion in the brainstem and can contribute to the early diagnosis of MS.