Hearing preservation in microvascular decompression for trigeminal neuralgia.

OBJECTIVE/HYPOTHESIS: Sensorineural hearing loss is a disturbing complication of microvascular decompression (MVD) for trigeminal neuralgia with an incidence of 1% to 23.8%. Cerebellar retraction with increasing I-V interpeak latency (IPL) during intraoperative brainstem auditory evoked potentials (BAEP) has been identified as the chief cause of acoustic injury. This study was designed to eliminate cerebellar retraction by a modification of the standard suboccipital craniectomy.

STUDY DESIGN: Nine consecutive patients undergoing surgery for trigeminal neuralgia were prospectively selected for this study between 1994 and 1995.

METHODS: Preoperative and postoperative audiograms were obtained. Preoperative and intraoperative BAEPs were performed. The surgical modification describes initiating a partial mastoidectomy to enhance early recognition and delineation of the sigmoid and transverse sinuses crucial to maximizing the lateral extent of the craniectomy. The additional exposure gained by this technique allows for improved visualization of the brainstem without cerebellar retraction.

RESULTS: All patients were relieved of neuralgic pain. Postoperative IPL values were not significantly different from preoperative values (4.9+/-0.6 vs. 4.7+/-0.3 ms). Maintaining IPL of less than 1.5 ms is considered critical for preventing injury to the auditory nerve. In this study the average increase in postoperative IPL was 0.25 ms for the ipsilateral ear and 0.1 ms for the contralateral ear.

CONCLUSIONS: The authors offer a surgical modification of the standard suboccipital craniectomy and furnish intraoperative neurophysiologic data to demonstrate how cerebellar compression can be eliminated and hearing preserved in MVD for trigeminal neuralgia.