Multivariate Analysis of Factors Influencing Facial Nerve Outcome following Microsurgical Resection of Vestibular Schwannoma.
OBJECT The object of this study was to evaluate long-term postoperative facial nerve (FN) function in patients undergoing vestibular schwannoma (VS) surgery. METHODS The authors retrospectively reviewed the clinical course of patients affected by isolated VSs with normal preoperative FN function, with no previous surgical or radiotherapeutic treatment, and who underwent surgery between 1987 and 2007. Facial nerve function was clinically evaluated according to the House-Brackmann (HB) scale. The minimum postoperative follow-up was 12 months. RESULTS Among the 1550 patients surgically treated at the authors' center, 1151 matched inclusion criteria for the present study. The FN was anatomically interrupted in 48 cases (4.2%), and 51 patients (4.4%) underwent subtotal tumor removal and were considered separately. Among the 1052 patients with anatomically preserved FNs and total tumor removal, 684 (65%) enjoyed postoperative HB Grade I or II and 309 (29.4%) enjoyed Grade III, with the remaining 59 cases (5.6%) suffering unsatisfactory results (HB Grades IV-VI). As expected, FN function results deteriorated in cases of larger tumors. CONCLUSIONS The main factor influencing postoperative FN function was tumor size. Although there was a progressive deterioration in FN function outcome in relation to tumor size, a cutoff point between satisfactory and unsatisfactory results could be identified at around 2 cm in maximum extrameatal tumor diameter, with the "optimal size" for surgery identified at < 1 cm. This finding emphasizes the importance of an early diagnosis and should be kept in mind when selecting the correct timing for VS removal. For small lesions, the results following a middle cranial fossa approach were significantly worse as compared with those following the translabyrinthine and retrosigmoidretrolabyrinthine approaches.