Recurrence of Vestibular Schwannoma after Subtotal and Near-Total Resection

Objective Treatment of vestibular schwannomas remains controversial. Many previously reported surgical series prioritized gross total resections (GTR), though an increasing number of surgeons are opting for lesser resections to minimize risk of cranial nerve injury. The strategy of subtotal resection aims to debulk enough tumor to relieve symptoms caused by mass effect and provide a more favorable target size for radiosurgery. Our institutional philosophy is to maximize resection with the goal being microscopic GTR, and reserve subtotal (STR) or near-total resection (NTR) for those tumors that, because of cranial nerve adherence, defy further removal. We aim to assess the progression-free survival of vestibular schwannomas treated with STR or NTR, as well as rates of facial nerve injury.

Methods A retrospective analysis of a prospectively maintained database was queried for all patients undergoing subtotal (STR) or near-total resection (NTR) of vestibular schwannoma at our institution between 2013 until 2016. NTR is defined as tumor remnant no more than 5 × 5 × 2 mm along the facial nerve or brainstem. All other incomplete resections were defined as STR. Primary outcome is identified as progression-free survival while facial nerve injury is a secondary outcome. In agreement with most largely reported case series, we defined recurrence was defined as tumor growth of >2 mm on follow-up imaging. Patient demographics, extent of tumor resection, facial nerve injury, and the need for gamma knife radiosurgery (GKRS) were gathered for analysis. Inclusion criteria required at least 1 year follow-up with available magnetic resonance imaging (MRI) to assess tumor regrowth. Facial nerve injury was quantified by House-Brackmann (HB) scores.

Results Our institution performed a total of 242 surgeries for vestibular schwannomas between 2013 and 2016. Of these, we excluded 176 cases achieving GTR, and 27 cases that did not have at least 1 year of follow-up, leaving a total of 39 cases for analysis. Follow-up duration ranged from12 to 43 months, with a mean of 19.6 months and median of 16.1 months. Twenty patients were classified as STR and 19 were NTR. The STR cohort demonstrated regrowth in two patients (10%), both of which were noted within the first postoperative year and underwent subsequent GKRS. The NTR cohort did not experience tumor recurrence. Postoperative HB scores of I to II were observed in the majority of patients in both cohorts (78.9% NTR, 60% STR) at the time of last follow-up.

Conclusion Optimal treatment of vestibular schwannomas remains controversial. While it is clear that extent of resection plays a major role in progression-free survival, more aggressive resections are commonly associated with higher morbidity profiles including risk of facial nerve injury. Among our patients, only 2 of 39 were found to have tumor regrowth in the short term, both belonging to the STR cohort. Facial nerve deficits were similar among both cohorts. Our findings are suggestive that microscopic GTR with excellent facial nerve outcomes is still the gold standard. Maximizing resections to NTR status should continue to be the surgical goal so long as facial nerve outcomes are remain acceptable.