Early life-threating enlargement of a vestibular schwannoma after gamma knife radiosurgery.

Stereotactic gamma knife radiosurgery (GKS) may induce a transient enlargement of vestibular schwannomas (VS). This phenomenon, known as pseudoprogression or swelling, starts at about 3 months following GKS, peaks at about 6 months, and typically subsides thereafter, usually without significant neurological deterioration. We describe a 34-year-old female who developed an aggressive enlargement of a VS 1 month after GKS. The patient was treated with an immediate external ventricular drainage and surgical resection via retrosigmoid approach for an acute neurological deterioration due to hydrocephalus and brainstem compression. Histopathological examination revealed a VS with abundant intratumoral thrombosis and necrosis, suggesting that its rapid expansion could be related to massive radiation-induced tumor necrosis. The present case indicated that rapid life-threating enlargement of a VS may occur as an early complication following GKS.