Collateral Circulation of the Brain with Special Reference to Atherosclerosis of the Major Cervical and Cerebral Arteries

Abstract

Collateral circulation of the brain was studied on 400 autopsied cases aged 60 and over, selected at random, with special reference to atherosclerosis of the cervical and cerebral arteries. 1) Of the arteries branching off from the aortic arch, the lumen of the subclavian and the common carotid was more narrowed on the left side of the body than on the right. 2) Fifteen to 25% of 400 cases examined showed stenosis over 50 % in one or more of the internal carotid and vertebral arteries. Complete occlusion was observed in 9 (2%) and in 24 (6%) cases in the internal carotid and vertebral arteries, respectively; however, in only 2 of the former and 4 of the latter, cerebral infarction was confirmed at autopsy. 3) The incidence of cerebral infarction was not paralleled by the degree of stenosis of the internal carotid, but was significantly correlated to the severity of cerebral atherosclerosis. It was, consequently, concluded that the cerebral infarction was due more to stenotic changes of the cerebral arteries than to those of the cervical arteries. This fact may be important from a clinical point of view in order to interpret angiographic findings. 4) The grade of stenosis of the internal carotid was significantly correlated to that of the vertebral as well as of the external carotid arteries. 5) Anastomoses between the external carotid, the internal carotid, and the vertebral arteries were demonstrated by anatomical and/or radiographical methods. The function of collateral circulation of these anastomoses, however, might not sufficiently be expected in the aged subjects, with already advanced sclerotic changes in these arterial parts. 6) The variations of the basal cerebral arteries were observed in 65% of 400 cases. In the cases with cerebral infarction, the incidence of the right and left caliber difference of the anterior and of the vertebral arteries was significantly higher than in the cases without gross findings in the brain. The embryonic derivation of the posterior cerebral artery from the internal carotid was also found more commonly in the cases with cerebral infarction. The latter type of variation was two or three times more frequent in Japanese than in Americans and in Europeans. An existence of a type of heredity was suggested in the formation of this variation. Clinicopathologic significance of the variations of the basal cerebral arteries was discussed with special emphasis on collateral circulation. 7) Thirty-eight of 67 cases with severe stenosis in the cervical arteries showed recurrent episodes of CVI along with a drop of the blood pressure; in an average, a drop of 76±24mm. Hg, systolic. CVI was frequently observed in febrile conditions with various causes. © 1963, The Japanese Society of Internal Medicine. All rights reserved.