BACKGROUND: Intraoperative brainstem auditory evoked potentials reduced the sensorineural hearing loss (SNHL) after microvascular decompression (MVD) This study was performed to evaluate the validity of BAEP parameters of latency or amplitude to SNHL.

METHODS: 557 patients out of 930 hemifacial spasm patients performed MVD, who were free from hearing impairment preoperatively, were enrolled in this study. Maximal changes of BAEPs wave V latency and amplitude during MVD were retrospectively sought according to postoperative SNHL. Sensitivity, specificity and positive predictability of wave V latency and amplitude were also sought according to the postoperative SNHL with a critical value of 1.0 msec prolongation and 40% decrease, respectively.

RESULTS: Wave V latency of BAEPs prolonged less in patients with normal hearing outcome (0.44 ± 0.63 msec) than in the patients with temporary or permanent SNHL (1.23 ± 0.56 msec, 1.33 ± 0.33 msec). Wave V amplitude also decreased less in the patients with normal hearing outcome (5.4 ± 15.8%) than in the patients with transient or permanent SNHL (42.8 ± 31.7%, 60.0 ± 34.7%). While sensitivity, specificity and predictability of prolongation of wave V latency at a value of 1.0 msec for SNHL, were 52.5%, 76.4% and 14.7%, respectively, those of decrease in the amplitude of wave V for SNHL at a value of 40% were 35.0%, 93.6% and 29.8%, respectively.

CONCLUSIONS: Decrease of the amplitude of wave V seems to have higher specificity, predictability and lower sensitivity for SNHL than the prolongation of wave V latency.