Chronic Encapsulated Expanding Hematoma After Gamma Knife Thalamotomy for Essential Tremor.

There have been no previous reports of chronic encapsulated expanding hematoma after Gamma Knife thalamotomy. The present case underwent Gamma Knife thalamotomy for essential tremor at the age of 78 years. Three- and 12-month posttreatment magnetic resonance imaging (MRI) showed small T2 high-intensity lesions on the target and along with the internal capsule. Hemiparesis developed 17 months after the treatment. Twenty months post treatment, T2-MRI showed a hypointense mass across the target and internal capsule. Gradual expansion of the mass was confirmed on MRI at 26-38 months. A 54-month posttreatment MRI showed marked expansion of the mass with multiple cysts surrounded by a T2-hypointense rim. Gadolinium-enhanced T1-MRI showed partial enhancement of the mass. MRI findings suggested a radiation-induced cavernoma. Hemiparesis, dysesthesia, and pain on the right side of the body persisted even after steroid therapy for several months. Long-term careful observation is necessary after Gamma Knife thalamotomy.