Otoacoustic Emissions V. EOAE and Neurinoma of theAcoustic Nerve and Retrocochlear Lesions

Overview

The authors evaluated findings of evoked otoacoustic emissions (EOAE) in 27 patientswith organic and inorganic retrocochlear hearing disorders. The retrocochlear lesion was diagno-sed electrophysiologically (BERA) and/or by means of CT/NMR examination implemented in allpatients of the group. Positive EOAE were found in 16 patients (59 %) independent on the hearingloss. In seven patients of the group (44 %) an organic process in the internal auditory meatus orposterior cranial fossa was involved (5 times a neurinoma of the acoustic nerve, once a congenitalcholesteatoma and once congenital malformation of the cerebellum). In one female patient probablyan attack of demyelinating disease of the multiple sclerosis type was involved. In the remainingeight cases CT/NMR were negative. In the group of 11 subjects where EOAE could not be obtainedin two patients neurinomas of the acoustic nerve were found (18 %), in the remainder CT/NMR werenegative. In three patients with retrocochlear pathology (once CT/NMR negative, once a demyeli-nating process, once a neurinoma of the acoustic nerve) and elicited EOAE the authors observedspontaneous significant improvement of hearing or restoration to normal. In the remaining patientshearing did not improve. In six patients examinations of contralateral acoustic suppression of EOAEwas made. Reduction or disappearance of contralateral acoustic suppression of EOAE on the sideof the retrocochlear disorder could not be confirmed in six examined patients. The authors considerEOAE examination in retrocochlear hearing disorders a useful and simple test which may be relatedto the prognosis and selected therapy. It was not found however that supplementation of audiolo-gical tests by EOAE extends the possibilities of audiology as regards differentiation of tumourousand non-tumourous etiology of retrocochlear hearing disorders. The usefulness of tests of contrala-teral EOAE suppression in retrocochlear lesions remains the subject of clinical research.

Key words:
otoacoustic emissions, retrocochlear pathology, neurinoma of the acoustic nerve.