Peri-ictal hyperperfusion via external carotid–middle cerebral artery bypass with radial artery graft after trapping of giant internal carotid artery aneurysm revealed by arterial spin labeling perfusion imaging

A 51-year-old woman developed focal to bilateral tonic-clonic seizures, 5 years after trapping of a giant right internal carotid artery aneurysm, following placement of a high-flow cervical external carotid artery-to-middle cerebral artery bypass using a radial artery graft. Peri-ictal magnetic resonance imaging (MRI), including arterial spin labeling (ASL) perfusion imaging, revealed prominent hyperperfusion supplied through the bypass, with a close anatomical relationship to a postoperative infarction in the right frontal lobe. Electroencephalography (EEG) performed 2 hours later revealed periodic discharges of approximately 1.2 Hz in the right frontal region. To our knowledge, peri-ictal hyperperfusion supplied by bypass has not been previously documented using ASL. Although this is a single case report, further use of peri-ictal MRI, including ASL, in addition to EEG in neurological emergency settings, will help elucidate the pathogenesis of epilepsy after bypass surgery.