Surgery after radiosurgery for acoustic neuromas: surgical strategy and histological findings.

Objective: To retrospectively review the authors' experience with surgical resections after failed radiosurgery for acoustic neuromas.
Methods: The study group consisted of six patients with acoustic neuromas. The median age was 61 years (range, 18-72 yr). The median marginal radiation dose was 11 Gy (range, 10-12.5 Gy). The median interval between radiosurgery and surgical resection was 28 months (range, 4-74 mo). The operative indications were cerebellar ataxia and symptoms associated with increased intracranial pressure. The median follow-up period was 36 months (range, 11-72 mo) after surgical resection.
Results: The tumors were subtotally removed (> or = 80%) in four patients and partially removed (< 80%) in the other two patients. Three patients had intratumoral bleeding. Preexisting facial nerve palsy improved in two patients and deteriorated in one patient, and one patient experienced new facial palsy. No other new neurological deficits emerged after surgery. Histological features were typical of acoustic schwannoma, and some tumors were associated with foamy macrophages, myxoid degeneration, and necrosis attributed to radiation effects. At follow-up, the residual tumor was decreased in five patients and increased in one patient with an expanding intratumoral hematoma.
Conclusion: Surgical resection after radiosurgery is indicated in the presence of such symptoms as cerebellar ataxia and increased intracranial pressure. It must be carefully considered because of the natural regression of transient tumor swelling over time. Surgical resection should be limited to subtotal removal for functional preservation. In patients with tumor enlargement several years after radiosurgery, the possibility of chronic intratumoral bleeding resulting from delayed radiation injury must be considered.