Abstract
Brainstem auditory evoked responses (BER) have been studied in 67 supratentorial lesions, 10 midbrain lesions, 23 intrinsic pontine lesions and 27 extrinsic compressions of the pons, including 15 acoustic neurinomas. BER in supratentorial lesions showed completely normal records. In midbrain lesions wave V was specifically altered. As wave I is a far field reflection of the VIII nerve potential and wave V the midbrain potential, waves II to IV can be inferred to originate in the central auditory pathway between the peripheral VIII nerve and the midbrain. Alterations of these waves correlated well with the location and nature of brainstem lesions. The BER in large acoustic neurinomas showed no response to clicks on the affected side and waves of delayed latencies with stimulation on the normal side. In small to medium-sized tumors with preservation of hearing, wave I of normal or delayed latency was recorded and subsequent components were absent in the majority of cases. These alterations of BER are closely related to the size and location of the tumors.
