The Recurrence of Cyst Formation Following Gamma Knife Surgery for Arteriovenous Malformation

Cyst formation is a well-known complication of gamma knife surgery for the treatment of arteriovenous malformation (AVM). Surgical treatment for cysts is widely performed, but there is no common procedure for the surgery. We report a case of cyst recurrence after partial resection of a nodule that exhibited enhancement on magnetic resonance imaging (MRI). A 44-year-old man underwent surgery for a cyst that formed after gamma knife surgery for an AVM performed 5 years earlier. MRI performed after the surgery revealed an enhancing nodule. Six months later, a cyst formed around the nodule and grew steadily. Because of the cyst, the patient had a seizure. We decided to perform an operation to resect the cyst and nodule. After the second operation, enhanced MRI showed there was no remaining nodule. The patient had no recurrence until 15 months after surgery. The findings from this case suggest that total resection of the enhancing nodules must be performed during surgery for cysts that form after gamma knife surgery for AVM.