Arteriographic Demonstration of External-Internal Carotid c Anastomosis Through the Ophthalmic Arteries

Abstract

In arteriograms obtained months after carotid occlusion in the neck, it has been possible to demonstrate anastomosis between the internal and external carotid arteries by way of the ophthalmic artery. It is the purpose of the present paper to report 3 cases in which these anastomotic pathways have been demonstrated arteriographically following ligation of the internal carotid artery in the neck for intracranial aneurysms and 1 case following spontaneous thrombosis of the artery. In most cases, after ligation or thrombosis of the internal carotid artery, circulation in the ipsilateral hemisphere is established through the anastomotic channels of the circle of Willis. The study of that type of collateral circulation is not within the scope of this paper and will be the subject of a subsequent report. In the literature, references to collateral circulation through the ophthalmic artery are found in papers by Seaman, Page and German (6), by Torkildsen and Koppang (8), and by Denny-Brown (2). Each of these contributions refers to 1 case with this finding. All 3 patients suffered from spontaneous carotid thrombosis. Anatomy It is a known anatomical fact that small anastomotic branches exist between the external and the internal carotid arteries. Four groups of anastomotic vessels have been described (Fig. 1): (a) Branches of the superficial temporal artery anastomose with the lacrimal and palpebral branches of the ophthalmic artery. (b) The angular artery (terminal branch of the external maxillary artery) anastomoses with the inferior palpebral and the dorsonasal branch of the ophthalmic artery. (c) Orbital branches of the middle meningeal pass through the superior orbital fissure, or sometimes through separate canals in the greater wing of the sphenoid, and anastomose with the lacrimal or other branches of the ophthalmic artery. (d) The infra-orbital branch of the internal maxillary anastomoses with the dorsonasal branch of the ophthalmic artery. These anastomotic branches are small and normally contribute very little to the circulation of the brain. Shenkin, Harmel and Kety (7) reported that only 2.7 per cent of the blood in the internal jugular vein normally comes from extracerebral sources and asserted that in man the external carotid system does not participate in the blood supply of the brain. On the other hand, Dandy (1) has pointed out that reduction of the lumen of the internal carotid artery to one-half or less forces the collateral channels of the circle of Willis to enlarge and carry an additional load to the brain. It is reasonable to assume that similar enlargement of the anastomotic branches between the internal and external carotid systems by way of the ophthalmic artery may take place. Poppen (5) considers this a likely possibility.