Cerebrovascular disease

Abstract

The large arteries along the base of the brain all have relatively similar structure consisting of a well defined internal elastic membrane, a well developed muscular media, and a collagenous adven-titia. Regardless of the size of these vessels, the internal elastic membrane almost always measures 5 [mu] thick and the adventitia, 35 to 40 u thick. The media usually is 1/10 the thickness of the vessel''s diameter, although thickness varies, depending on the size of the vessel. In the smaller arteries along the base of the brain, the chief degenerative change consists of an intimal connective tissue increase which may or may not narrow the vessel lumen. The larger arteries reveal not only an intimal connective tissue increase but also show changes within the elastica and fatty deposits within the intima which produce the typi-cal atherosclerotic plaques. Atherosclerotic lesions were most frequent and severe on the internal carotid artery just anterior to the bifurcation and along the upper portion of the basilar artery. Less intense changes were observed along the middle and lower basilar artery and the middle cerebral, the posterior cerebral, and the vertebral arteries. In cases of severe atherosclerosis, the anterior basilar, the internal carotid at and before the bifurcation, and the 1st portion of the middle and anterior cerebral arteries were always implicated. Frequency and severity of the atherosclerotic process definitely increase with age. Atherosclerotic lesions first appear on the larger intracranial arteries in the 2d decade of life. Of all subjects in the 6th decade and over, 17% will show no degenerative arterial lesions. Sex plays no role in the atherosclerotic process. Men and women were equally affected.