A 37-year-old man presenting with subarachnoid hemorrhage was admitted to our hospital. Emergent cerebral angiography demonstrated moyamoya disease associated with a wide-necked basilar trunk aneurysm. We performed bilateral extracranial-intracranial bypass surgeries prior to stent-assisted coil embolization of the aneurysm after the acute phase. No complication occurred and the patient was discharged with no neurological deficit. Follow-up digital subtraction angiography (DSA) performed 6 months after the surgery showed that all the anastomosises were patent and bilateral collateral vascular compensation was fully established with no recanalization of the basilar trunk aneurysm post embolization.We also found that high-flow bypass did not contribute to cerebral revascularization as imagined despite the good patency.

Combined extracranial-intracranial bypass surgery with endovascular treatment proved to be an efficient therapeutic modality for moyamoya disease with aneurysms located in the posterior circulation. High-flow bypass surgery was not essential due to the inefficiency and the high risk of postoperative cerebral hyperperfusion syndrome. Keywords : Extracranial-intracranial bypass, Coil embolization, Moyamoya disease, Basilar trunk aneurysm