ABR in eighth-nerve and brain-stem disorders.

Auditory brain-stem response (ABR) results are reported on three cases of acoustic tumors and two cases with brain-stem lesions. These cases highlight several considerations in the clinical use of ABR. The sensitivity of ABR to retrocochlear involvement in light of normal pure-tone hearing and cochlear hearing loss is shown in the first two cases. The third case shows the advantage of "contralateral" ABR testing and a unique effect of stimulus polarity. The use of an intensity function and high presentation rate procedures are shown to be helpful diagnostic procedures in case four. Case five shows bilateral ABR effects which correlate well with the degree of brain-stem involvement. In addition to the ABR data, audiologic, radiologic, and medical findings on these patients are also discussed.