Collateral circulation between the external and internal carotid artery.

The most important anastomoses between the arteria carotis externa and interna are discussed, based on a study of several patients with obstruction of the arteria carotis interna. When the arteria carotis interna is obstructed, it is important to determine, as best as possible, the collateral circulation to the vessels distal to the occlusion, since the prognosis can partly depend on it, and because collateral circulation must be taken into account in evaluating operative possibilities.