Topographical study on arteriosclerotic lesions at the bifurcations of human cerebral arteries.

We have studied the topographical distribution of arteriosclerotic lesions at the bifurcation of the internal carotid-anterior cerebral-middle cerebral arteries (internal carotid bifurcation) and of the middle cerebral artery-first temporal branch (first bifurcation of M.C.A.) in humans. The arteriosclerotic lesions showed a distinct pattern with a high incidence on the outer walls of the daughter vessels and at the inner curvatures in the bifurcations where wall shear stress was believed to be relatively low. However, there were differences in the distribution of the lesions between the internal carotid bifurcations and the first bifurcations of M.C.A.. The former are considered to be three-dimensionally unsymmetrical and curved, and the latter symmetrical and straight. The present study suggests that lower shear stress is of considerable importance in both the initiation and localization of arteriosclerotic lesions, and that study of the three-dimensional blood vessel architecture and blood flow patterns needs to be done to clarify the role of hemodynamic forces in atherogenesis.