Temporary neurological deterioration after extracranial-intracranial bypass.

Five patients who experienced temporary neurological deterioration after extracranial to intracranial bypass procedures are reported in detail. These patients suffered transient ischemic attacks or more prolonged deficits usually of a different nature than the preoperative symptoms. All patients had a good outcome and the spells ceased; the neurological deficits improved within a maximum of 2 weeks. Obvious causes of deterioration such as intra- or extracerebral hematomas, occlusion of a previously stenotic vessel, or graft occlusion were ruled out by computed tomography and angiography in each case. Intraoperative causes of neurological deterioration such as anesthetic effect, hypotension, and temporary occlusion of the cortical vessel or sacrifice of its small branches were not likely to be the cause of the deficits because in each case, the patient awoke satisfactorily and deterioration occurred hours to days later. In each case, postoperative angiography showed good perfusion of at least one major division of the middle cerebral territory. Anticoagulation with heparin in three patients did not change the clinical course. In one patient who was not anticoagulated, embolism could have been responsible for a single prolonged ischemic event, but in the other patients thromboembolism does not seem likely to have been responsible for the deficits. The cause of the deterioration in these patients remains unexplained. We speculate that hyperperfusion of chronically ischemic brain tissue and shifts in the watershed region resulting from the new flow pattern after bypass grafting are two mechanisms that may have been of importance in the etiology of these deficits.