Usefulness of 1000 Hz tone-burst-evoked responses in the diagnosis of acoustic neuroma.

The auditory brain stem response (ABR) has become widely recognized as a sensitive and cost-effective screening modality in neuro-otologic diagnosis. However, the audiometric characteristics of the test ear may obscure the interpretation of the click-evoked ABR, particularly in the face of high-frequency hearing loss. It is often unclear whether latency delays or absent responses are attributable to retrocochlear disease or simply to the magnitude of the patient's hearing loss. The acoustic click stimulus commonly used in ABR testing activates predominantly the basilar membrane in the 2000 to 4000 Hz range. Because many cochlear and retrocochlear processes are associated mainly with hearing loss in this range, we have found it helpful in selected cases to use 1000 Hz tone-burst stimuli to circumvent the effects of elevated hearing thresholds on the ABR. In this article, our experience with the use of 1000 Hz nonlinearly gated tonebursts in 17 patients with acoustic neuroma is presented.