Growth Patterns of Residual Tumor in Preoperatively Growing Vestibular Schwannomas.

To analyze growth of residual vestibular schwannoma (VS) following incomplete tumor resection and determine the influence of residual location and size.  Retrospective case note and scan review.  Tertiary skull base unit.  Patients with residual tumor following primary surgery for medium and large unilateral growing vestibular schwanomas between 2006 and 2009.  Location of residual VS and post-operative growth, comparing those with more (>5%) or less than 5% of tumor residual (<5%).  Fifty-two patients had visible residual tumor left behind at surgery. Twenty had < 5% and 32 had > 5% residual. The residual growth rates were 38% overall, 20% in < 5%, and 50% in > 5% residuals. There was no significant difference in growth rates at different residual locations. Median follow-up was 6.4 years.  There is a greater risk of regrowth of residuals > 5%. All positions of residual tumor can regrow, and the preoperative tumor size plays a role in this. Further data is needed to confirm if residual tumor in the fundus is less likely to grow.