Temporary neurological deterioration caused by hyperperfusion after extracranial-intracranial bypass--case report and study of cerebral hemodynamics.

A 64-year-old female with occlusion of the left internal carotid artery (ICA) developed temporary neurological deterioration after superficial temporal artery to middle cerebral artery anastomosis. Preoperative single photon emission computed tomography (SPECT) showed marked reduction of the cerebral perfusion reserve in the left ICA territory. She suddenly developed aphasia 18 hours after operation. Follow-up SPECT revealed temporary hyperperfusion in the left temporal lobe, strongly suggesting that this unusual complication resulted from bypass flow into the brain tissue with chronic severe ischemia and impaired autoregulation.