Serial neurocognitive and perfusion MR imaging findings are described in the perioperative course of a 48-year-old woman with a superficial temporal artery to middle cerebral artery bypass for right hemispheric ischemia due to moyamoya syndrome. Neurocognitive testing reflected both global and focal cerebrovascular dysfunction, which suggests that perfusion augmentation following surgical revascularization may engender cognitive and neurologic improvement beyond focal regions of established ischemia.