Morphometry of structural preservation of tunica media in aged and hypertensive human intracerebral arteries.

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Abstract
Medial smooth muscle cell necrosis has been reported as a lesion that may precede angionecrosis, which is a major cause of not only hypertensive brain hemorrhage but also lacunar infarct. We morphometrically studied a loss of smooth muscle cells in the media of cerebral arteries in relation to clinical risk factors. The lateral striate, ie, perforating arteries and the medullary arteries in the subcortical white matter of the temporal lobe (100 to 400 microns in diameter) were histologically investigated in 121 autopsied brains. Medial area was measured quantitatively, and the number of nuclei of smooth muscle cells in the area was calculated in 1210 cross-sectional arteries of histological sections. The influence on the structural (ie, smooth muscle cell) preservation of the tunica media (ratio of number of smooth muscle cell nuclei to medial area [N-MA ratio]) of age, blood pressure, serum lipids, and presence of absence of extracerebral severe atherosclerosis was investigated. The N-MA ratio decreased slightly with age in both arteries. A reverse correlation between N-MA ratio and age was seen in groups both with and without hypertension. The mean N-MA ratio in the hypertensive group was significantly lower than that of the nonhypertensive group (P < .001) in all decades of life. The mean N-MA ratio of the perforating arteries was slightly lower than that of the medullary arteries in both groups. Severe atherosclerosis of the internal carotid arteries, even with hypertension, mitigated a decrease of the N-MA ratio, which was as slight as that in the nonhypertensive group. Serum cholesterol in this group was higher than in both the conventional hypertensive group (P < .005) and the nonhypertensive group (P < .001). Although both hypertension and age were significant risk factors for medial smooth muscle cell necrosis, hypertension was relatively more significant. Medial smooth muscle cells of the perforating arteries in the basal ganglia were more vulnerable than those of the medullary arteries. Cerebral small arteries in subjects with severe atherosclerosis of the carotid and major cerebral arteries (hypertension in eight of nine subjects) may have been protected from extensive loss of medial smooth muscles presumably because of both high serum cholesterol and decreased wall tensile stress associated with reduced blood perfusion due to severe atherosclerotic stenosis.