[The collateral circulation due to cerebral arterio-venous malformation and occlusions of major cranial vessels (author's transl)].

Arteriovenous malformations (AVM) of the brain are diagnosed mostly in the early adult life. With the come up of Computerized Tomography (CT) which often is done without the strong indications as postulated for the conventional neuroradiologic examinations, asymptomatic AVM in the elderly population may be found. Since May 1977 4 asymptomatic arteriovenous malformations were diagnosed in our institution using CT. 2 of these patients had severe degenerative changes of the great cerebral vessels and an unusual collateral circulation developed probably because of the steal-phenomenon in the vascular malformation. These 2 cases allow to study all possibilities of cerebral collateral circulation. Uncommon in one of the cases was a capillary anastomotic network through the thalami, in the other case an extensive dural rete mirabile developed. The problems of collateral circulation are discussed.