Embolization of segments of the circle of Willis and adjacent branches for management of certain inoperable cerebral arteriovenous malformations.

Most large cerebral arteriovenous malformations (AVM's) in the territories of the penetrating arteries arising from the circle of Willis, including the proximal anterior, middle, and posterior cerebral arteries, have been considered untreatable. However, the pattern of collateral circulation which accompanies these lesions presents the possibility of completely occluding certain segments of the circle of Willis and adjacent major branches without producing infarction distally in the cerebral hemisphere or in the critical areas occupied by the AVM itself. The ensuing reduction of arterial pressure within the AVM may reduce the likelihood of hemorrhage or progressive enlargement. Four patients in whom this was accomplished in whole or in part by embolization are described. In one patient, infarction did ensure but the potential for collateral circulation had been restricted by the passage of emboli into the pericallosal artery. In the others, angiographic filling of the lesion was considerably reduced without worsening of their neurological deficits. One patient had recovery of neurological loss following the procedure, and another was slightly improved. Over follow-up periods of up to 28 months there have been no recurrent hemorrhages or further progression of neurological deficits. However, final assessment of the efficacy of this procedure will require longer follow-up intervals and additional patients.