Extracranial-intracranial bypass to reduce the risk of ischemic stroke.

Extracranial-intracranial bypass surgery is an operative procedure in which the superficial temporal artery is anastomosed to the middle cerebral artery. The operation, first described in 1969, was employed to circumvent otherwise surgically inaccessible atherosclerotic lesions high in the internal carotid system or in the middle cerebral artery. This assessment compares the findings from 13 surgical series of EC-IC (1,464 patients) with those reported in the only prospective, randomized, cooperative trial of this procedure (1,377 patients). Analysis of the outcomes in the 1,464 patients included in the surgical series produced insufficient evidence to support a conclusion that post-EC-IC bypass stroke rates were lower than the rates of either the medically or surgically treated groups in the controlled clinical trial. In the absence of reliable, objective evidence of the existence of a group of patients in whom surgical intervention is superior to medical treatment in reducing the frequency of stroke, the results of the single controlled clinical trial, which demonstrated no benefit of bypass, must be accepted as the best evidence currently available.