CRANIAL NERVE PRESENTATION AFTER STEREOTAXIC RADIOSURGERY FOR SMALL ACOUSTIC TUMORS

Objective: To assess those factors associated with and predictive of c ranial nerve preservation after stereotactic radiosurgery in patients with small acoustic tumors identified by magnetic resonance imaging. D esign: We performed a retrospective analysis of our experience with 31 patients with preserved hearing and acoustic tumors measuring 10 mm o r smaller (pons-to-petrous dimension). All patients underwent clinical and, audiologic evaluations varying from 6 to 48 months (mean, 20 mon ths) after stereotactic radiosurgery performed with use of the 201 sou rce cobalt 60 gamma unit. Results: Stabilization or reduction in tumor volume was achieved in 29 of 31 patients. One patient required delaye d microsurgical resection. Useful hearing (pure tone average less than or equal to 50 dB and speech discrimination score greater than or equ al to 50%) preservation was achieved in 10 of 10 patients immediately postoperatively, eight of 10 patients at 6 months, six of 10 patients at 1 year, and five of 10 at 2 years. Preservation of some measurable bearing was possible in all patients immediately after radiosurgery, i n 84% and in more than half of patients at 2 years. Preoperative facia l nerve function was preserved in 19 of 20 patients at 2 years after r adiosurgery. All patients returned to their preoperative employment st atus within 2 to 5 days after radiosurgery. Conclusion: Stereotactic r adiosurgery performed with current technology (multiple radiation isoc enters and magnetic resonance imaging guidance) is a safe and effectiv e management strategy for patients with small acoustic tumors. The ris k of facial and trigeminal neuropathy after gamma knife radiosurgery i s low, and useful hearing can be preserved in up to 5O% of patients wi th useful preoperative hearing. Stereotactic radiosurgery is a valuabl e alternative strategy to surgical removal for many patients with newl y diagnosed small acoustic tumors.