TRANSITORY-EVOKED OTOACOUSTIC EMISSIONS I N PATIENTS WITH ACOUSTIC NEUROMAS

Click-evoked transitory otoacoustic emissions (TEOAE) were recorded in 34 patients suspected of having an acoustic neuroma with consequent h earing loss. Measurements took place one day prior to transtemporal re moval of tumor. The evoked otoacoustic emissions were compared to hear ing thresholds of the pure-tone audiogram. In 31 of the 34 patients te sted, the spectrum of the emissions corresponded to the audiogram, in that an emission was not detectable at frequencies with a hearing loss exceeding 30 dB HL. Three patients showed good emissions in spite of a demonstrable hearing loss. This can be expected when only retrocochl ear lesions are present. These results suggest that in most cases the hearing loss accompanying a retrocochlear process is combined with sec ondary lesions of the cochlea and is rarely due to isolated retrocochl ear malfunction.