Surgery for large vestibular schwannoma: residual tumor and outcome.

OBJECTIVE: To evaluate clinical outcome with regard to the amount of residual tumor after surgery for large vestibular schwannoma. PATIENTS: Between January 2000 and December 2005, 51 large vestibular schwannoma tumors with extrameatal diameter of 2.6 cm or greater (mean, 32 mm; median, 30 mm; range, 26-50 mm) were operated using the translabyrinthine approach. The extent of the resection was intraoperatively estimated as complete, near, and subtotal. The amount of residual tumor was measured, and the shape and localization was scored on gadolinium-enhanced magnetic resonance imaging (MRI). Correlation between intraoperative and MRI assessment was performed using the Fisher's exact test. Potential growth of residual tumor was documented with frequent MRI follow-up. Postoperative facial nerve function was classified according to the House-Brackmann classification.
RESULTS: Complete resection was performed in 26% of the patients, near-total resection in 58%, and subtotal resection in 16%. Magnetic resonance imaging showed residual tumor in 46% of patients (mean, 16.7 mm; SD, +/-8, range, 5-36 mm). Postoperative facial nerve function was House-Brackmann Grades I to II in 78% of the patients. The intraoperative assessment of near-total resection did not correlate with postoperative MRI (p = 0.25). Postoperative MRI showed either no residual tumor or residue that should actually have been classified as a subtotal resection. After a follow-up of 4 years (49 mo; mean, 48 mo), 94% of patients did not show changes on MRI.
CONCLUSION: Tumor control with good facial nerve function could be obtained in most patients. Intraoperative assessment did not correlate with the amount of residual tumor on postoperative MRI. Objective documentation with postoperative MRI to measure the extent of removal is therefore mandatory.