The anatomy of the collateral circulation of the major vessels of the brain has been known since the studies of Willis, but little is known about the ability of these and other anastomotic channels not described by Willis to function in patients who have had spontaneous or surgical occlusion of one or more major arterial trunks. The purpose of this presentation is to describe the findings in a series of such cases studied at the Neurological Institute of the Presbyterian Hospital of New York.
The collateral circulation of the cerebral hemispheres has been clearly demonstrated by cerebral angiography in seriographic films obtained on 42 patients who had had surgical therapy for intracranial aneurysms and on 30 patients who had thrombosis of the internal carotid artery or one of its branches. The potential collateral circulation was found to be very extensive but variable. The first, and most important, source of collateral