Medial olivocochlear system and tinnitus: A systematic review

The purpose of the study was to analyze the medial olivocochlear system (MOCS) through the suppression of transient evoked otoacoustic emissions (TEOAEs) in humans with tinnitus. A search across five databases identified 182 articles, of which 25 were selected for full-text analysis based on inclusion and exclusion criteria. Most articles included patients with unilateral and bilateral tinnitus, but few reported tinnitus etiology or classification. The common stimulus for TEOAE suppression was a 60 dB linear click with 260 sweeps, and only a few articles noted a signal-to-noise ratio (SNR) ≥6 dB. MOCS stimulation was contralateral, mainly using 50 dB white noise. Suppression was estimated by comparing conditions with and without MOCS stimulation, showing a lower suppressive effect in tinnitus patients compared to controls. MOCS assessment in tinnitus has varied paradigms, making comparison difficult. A standardized method is needed, though challenging due to the lack of consensus on the MOCS test itself.