Hearing prognosis and intraoperative guidance of brainstem auditory evoked potential in microvascular decompression.

Intraoperative monitoring of brainstem auditory evoked potential (BAEP) was done in 34 patients submitted to microvascular decompression (MVD). Seventeen of these patients had trigeminal neuralgia, and 17 had hemifacial spasm. Transitory postoperative hearing loss was observed in 6 (18%) of the patients, and permanent hearing loss was observed in 2 (6%) of the patients. Wave I-V interpeak latency (IPL) was calculated during each step of the MVD procedure in order to identify the dangerous steps of the surgery. Wave I-V IPL abnormalities occurred more frequently during cerebellar retraction. Of the 6 patients who had total loss of BAEP lasting throughout the surgery, 1 (17%) had definitive deafness. Ten of the 34 patients had an absence or partial diminution of BAEP without total normalization before the end of surgery. Among these 10 patients, 2 had transitory hearing loss and 1 had permanent hearing loss.