A case report: An increased oxygen extraction fraction in remote ischemic lesions after revascularization for moyamoya disease with a progression of posterior cerebral artery stenosis

The cerebral metabolism, such as the oxygen extraction fraction (OEF), in remote ischemic lesions following revascularization for moyamoya disease (MMD) has not yet been fully elucidated. We herein report a patient with an increased OEF in a remote ischemic lesion after revascularization in a case of adult-onset MMD. A 21-year-old woman suffered from a left parietal lobe infarction due to MMD. At 2 months after onset, left superficial temporal artery (STA)–middle cerebral artery (MCA) bypass and encephalo-myo-synangiosis (EMS) were performed. The postoperative course was uneventful. 15O-positron emission tomography (PET) performed at 2 months after the first operation revealed an increased OEF in the contralateral (right) frontal lobe that was suspected of being possible remote ischemia. The patient underwent right STA-MCA bypass and EMS. 15O-PET at 14 days after the second operation revealed an increased OEF in the contralateral (left) occipital lobe that was suspected of potentially being remote ischemia caused by a watershed shift. Two years after the second surgery, left occipital artery (OA)–posterior cerebral artery (PCA) anastomosis and EMS were performed due to transient right hemianopsia. Neither rebleeding nor ischemic complications occurred 2 years after the third surgery. We need to be alert for the possible progression of PCA stenosis in MMD after revascularization. It might induce remote ischemia after revascularization. OA–PCA bypass is therefore considered to be an effective treatment option in such cases.