Cerebral ischemia owing to compression of the brain by swollen temporal muscle used for encephalo-myo-synangiosis in moyamoya disease

Compression of the brain by swollen temporal muscle used for indirect pial synangiosis is a rare complication after the revascularization surgery for moyamoya disease, and its mechanism and clinical presentation are undetermined. A 26-year-old woman, who had been suffering transient ischemic attack (TIA), underwent superficial temporal artery-middle cerebral artery anastomosis with encephalo-myo-synangiosis (EMS) on the affected hemisphere. The ¹²³I-IMP-SPECT 1 day after surgery demonstrated an improvement of cerebral blood flow (CBF) on the operated hemisphere. Two days later, however, she suffered fluctuating aphasia when computed tomography scan revealed marked swelling of the temporal muscle used for EMS. The ¹²³I-IMP-SPECT 4 days after surgery showed significant decrease in CBF by the compression of the brain. Then, we performed revision of EMS. The base of the temporal muscle was markedly compressed by the edge of the free bone flap, which resulted in swelling of the entire temporal muscle used for EMS. We drilled out the edge of the free bone flap for decompression. Her aphasia disappeared postoperatively, and CBF normalized 7 days after the initial surgery. Her TIA disappeared, and there was no deterioration during the follow-up period. The STA-MCA bypass has been patent since the initial surgery. Surgical revascularization including EMS has a substantial risk for cerebral ischemia owing to compression of the brain by temporal muscle swelling. Relative wide bone window for temporal muscle insertion is necessary to avoid this rare complication. Once the flow compromise is confirmed, we recommend early decompression by the revision of EMS.