A ruptured middle cerebral artery aneurysm originating from the site of anastomosis 20 years after extracranial-intracranial bypass for moyamoya disease:case report

In patients with moyamoya disease who have undergone extracranial-intracranial bypass surgery, progressive hemodynamic stress may cause the formation of de novo aneurysms after a postoperative period of several decades. Imaging examinations should therefore be performed periodically for follow-up, and a de novo aneurysm should be suspected in a patient who has an unusual ICH.