Assessing the threshold for vestibular schwannoma resection and the behavior of residual tumor

In vestibular schwannoma surgery postoperative facial nerve function is generally described as being related to tumor size, with 20 mm extrameatal diameter suggested as the threshold at which facial nerve function deteriorates. Near-total resection is accepted if the risk to nerve function becomes unacceptably high. We sought to review outcomes of vestibular schwannoma resection and follow residual tumor fragments. Second, we pooled data to quantify the risk of regrowth and need for subsequent intervention.

Prospectively collected data on all patients undergoing microsurgical removal of vestibular schwannoma by the senior author over the past 15 years.

Approximately 247 patients were identified, the spread of tumors was 74 intracanalicular, 120 15 mm or lesser, 57 between 16 and 30 mm, and 6 greater than 30 mm. Overall, 91.5% recovered to House-Brackmann Grade 1 or 2, with no difference between the groups with 15 mm or lesser and greater than 15 mm (p > 0.05); 26 had incomplete resection, and 3 showed regrowth. Pooled data: 193 near total resections with 12% regrowing; 181 subtotal resections with 30% regrowing. Of 108 growing fragments, 78% had intervention.

The present series suggests that the threshold for preservation of good facial nerve function may be moved to a tumor of 30-mm extrameatal diameter. Although historically tumor fragments were felt to have a low growth potential, the cumulative data would suggest that a significant proportion of fragments do grow and may need intervention.