Preoperative facial nerve studies predict paresis following cerebellopontine angle surgery

Facial paresis or paralysis following resection of cerebellopontine angle tumors can occur despite intraoperative cranial nerve monitoring. In an attempt to identify preoperatively those patients at greatest risk for postoperative facial nerve dysfunction, we have prospectively evaluated 30 patients with clinically normal facial function using preoperative facial nerve conduction, electromyography, and the blink reflex. Surgical approach, tumor size, tumor histology, and postoperative facial nerve function were correlated with the preoperative electrophysiologic data to determine the utility of preoperative facial nerve tests as predictors of postoperative facial nerve function. Nineteen patients (Group 1) had normal preoperative facial nerve studies, while 11 patients (Group 2) had abnormal results. Fourteen patients in Group 1 were Grade I immediately after surgery, and five were Grade II. All 19 patients were Grade 1 at 6 months. The 11 patients in Group 2 had immediate postoperative facial nerve function graded as follows: I, three patients; II, five patients; III, one patient; VI, two patients. After 6 months, facial nerve function was graded as follows: I, six patients; II, two patients; III, one patient; VI, two patients. The blink reflex was the single most accurate predictor of facial nerve involvement preoperatively.