Recurrent transient ischemic episodes after anticoagulation or bypass operation. Hemodynamic or embolic mechanism.

Three patients who suffered delayed transient ischemic episodes despite adequate anticoagulation or successful extracranial-intracranial (EC-IC) bypass anastomosis were studied. A hemodynamic mechanism was prominent in 1 patient with moderate orthostatic hypotension. After adequate anticoagulation he had further episodes of transient ischemia, which were finally controlled by an EC-IC bypass. Cerebral blood flow studies revealed flow changes with progression of the arterial lesion from stenosis to occlusion. The bypass was patent postoperatively, which suggested that the ischemia in this patient had been hemodynamic in origin. In the other patient the cerebral ischemic symptoms showed a remarkable improvement after the bypass operation. However, ischemia recurred after the operation until anticoagulants were started. Postoperative cerebral ischemia suggested microemboli, whereas preoperatively, it was presumably a hemodynamic phenomenon. In another patient where microembolism was more apparent, anticoagulation controlled the recurrent ischemia after a bypass operation. A hemodynamic as well as embolic mechanism needs to be considered in a cerebral ischemia which recurs after treatment.