Observations on electric brain-stem responses in retrocochlear hearing loss: a preliminary report.

Far-field recorded electric brain-stem responses on acoustic stimulation (BSER) were recorded in 29 patients with 31 verified cerebellopontine angle tumors. The responses were compared with the normal response and with responses in cochlear hearing loss by visual observation, considering reproducibility and (supra-liminal) configuration in the first place. There were established (a) obvious differences in response pattern between cochlear and retrocochlear lesions. (b) In the retrocochlear cases, BSER appeared to be more consistent that conventional audiometry, as demonstrated in ears ipsilateral to the lesion, with residual hearing and cochlear or inconsistent auditory findings. (c) BSER also proved able to offer additional diagnostic information by way of the ear contralateral to a retrocochlear lesion, not only in cases where the tumor caused a radiologically visible dislocation of the brain stem.