FACIAL-NERVE PRESERVATION AND TUMOR-CONTROL AFTER GAMMA-KNIFE RADIOSURGERY OF UNILATERAL ACOUSTIC TUMORS

To assess the long-term risk of facial nerve dysfunction after unilate ral acoustic tumor stereotactic radiosurgery, we retrospectively analy zed our initial experience in 98 unilateral acoustic tumor patients wh o were evaluated at least 2 years after treatment. This observation in terval permits an analysis of both the risk of onset and the potential for recovery of facial nerve function. The overall risk of developing any degree of delayed transient or permanent postoperative facial neu ropathy was 21.4% (21 of 98 patients). Only one patient undergoing rad iosurgery alone had poor residual facial nerve dysfunction worse than House-Brackmann grade III. Normal facial nerve function (House-Brackma nn grade I) was preserved in 95% of patients with small tumors (10 mm or less petrous-pons dimension) and in 90% of patients who had useful hearing and normal facial function preoperatively. Normal facial funct ion was preserved in all patients with intracanalicular acoustic tumor s. The risk of delayed facial neuropathy was reduced by performing rad iosurgery when tumors were small (1000 mm3 or less), by enclosing the tumor within the 50% isodose volume, by using multiple small radiation isocenters, and by detailed identification of the tumor volume using stereotactic magnetic resonance imaging.