Contralateral acute subdural hematoma following moyamoya bypass surgery: a rare complication

BACKGROUND: Moyamoya disease (MMD) is a progressive cerebrovascular disorder characterized by compensatory development of collateral vessels in response to internal carotid artery occlusion. Superficial temporal artery to middle cerebral artery (STA-MCA) bypass combined with encephalomyosynangiosis is a standard surgical intervention, hemorrhagic complications following such procedures are rare, especially in pediatric patients. We present a rare case of contralateral acute subdural hematoma (ASDH) occurring immediately after revascularization surgery in a child with MMD. CASE DESCRIPTION: A 7-year-old girl with a history of left cerebral infarction due to MMD underwent left STA-MCA bypass with encephalomyosynangiosis. Although the bypass was technically successful and the patient showed no new neurological deficits postoperatively, routine computed tomography revealed a contralateral ASDH. The hematoma was promptly evacuated. Intraoperative findings included oozing from the dura near the sphenoid ridge, but no active bleeding source was identified. She recovered well without neurological deterioration. Notably, follow-up digital subtraction angiography at five months postoperatively revealed the formation of a spontaneous transdural anastomosis from the right middle meningeal artery, eliminating the need for further bypass surgery on the contralateral side. CONCLUSION: Cerebral atrophy, intraoperative cerebrospinal fluid drainage, and perioperative aspirin use may have contributed to the development of contralateral ASDH. Surgeons should be aware of this possibility. Prompt recognition and evacuation are essential.