Cyst formation after gamma knife radiosurgery for trigeminal schwannoma. A case report

Radiosurgery for small vestibular schwannomas is an established and effective treatment, and it has been used for trigeminal schwannoma recently. Delayed cyst formation is well recognized as complication after gamma knife radiosurgery for arteriovenous malformation. We encountered a case of delayed cyst formation after gamma knife radiosurgery for trigeminal schwannoma. An 81-year-old male presented with abducens palsy and ataxia 6 years after gamma knife radiosurgery for trigeminal schwannoma. A cyst development in the posterior fossa was identified, and the brain stem was compressed by the cyst. The cyst was removed and the abducens palsy and ataxia improved within a month. Histological findings revealed variable tumor tissue in the cyst wall. Delayed cyst formation should be recognized as a complication after radiosurgery for schwannoma. (author)