Transient-evoked otoacoustic emissions and contralateral suppression in patients with unilateral tinnitus

Transient-evoked otoacoustic emissions (TEOAE) have been recorded from 20 patients with unilateral tinnitus and symmetrical hearing up to 2000Hz. Responses were digitally low-pass filtered at 2000Hz. The function of the medial olivocochlear system (MOC) was examined by contralateral acoustic stimulation (CAS) with broadband noise at 50 and 70 dB SPL. Emission amplitude was significantly lower in tinnitus ears in the 10-15ms part of the response. No difference in contralateral suppression of amplitude could be found. The latency shifts were small and were not helpful in separating tinnitus from non-tinnitus ears. Analysis on different parts of the response window may be a useful tool for separating tinnitus from non-tinnitus ears. The lack of efferent effect differences could result from influence of stimuli on tinnitus mechanisms.