[Dysfunction of medial olivocochlear system and its audiological test].

The function of medial olivocochlear system (MOC) in patients with three kinds of auditory diseases was tested in order to investigate the relationship between MOC and retrocochlear impairment. Suppressive effect of evoked otoacoustic emissions (OAEs) by contralateral white noise was used as the indicator to evaluate the function of MOC in patients with: (1) sensorineural deafness with definite otoacoustic emissions, (2) hyperacusis and (3) tinnitus. Dysfunction of MOC was found in nine cases out of sixteen patients with sensorineural deafness and six cases out of fifteen patients with tinnitus. Two cases of hyperacusis also showed MOC dysfunction. It was concluded that MOC dysfunction may exist in some patients with sensorineural hearing loss and tinnitus, and in patients with hyperacusis as well. It seemed likely that dysfunction of MOC may played a role in causing tinnitus and hyperacusis in these patients. Testing the function of MOC may provide a helpful way for differential diagnosis of cochlear and retrocochlear impairment in auditory system.