Ultrastructural morphometry of hypertensive medial damage in lenticulostriate and other arteries.

Characteristic medial damage occurs in the distal lenticulostriate arteries in patients with hypertensive cerebral hemorrhage. Medical changes were studied in the proximal and distal lenticulostriate arteries and cortical circumflex arterioles. Additionally, intramyocardial coronary, gastric submucosal and renal interlobular arterioles were examined in hypertensive patients. Hypertensive medial damage consisted of irregular atrophy and paucity of smooth muscle with accumulation of nonfatty debris and basement membranes. These changes were diffuse, extensive and not uniform, and were unrelated to atherosclerosis or bifurcation. By electron microscopic morphometry smooth muscle occupied 28% of the media in the distal lenticulostriate arteries of hypertensive patients as compared with 80% in controls. The proximal lenticulostriate and cortical branches in hypertensive patients showed values higher than 50%, as did the coronary, gastric and renal arterioles. Massive primary hemorrhages are prevalent in the area supplied by the distal lenticulostriate artery, 150-660 microns in diameter. Fibrinoid necrosis and microaneurysm occur in more peripheral arterioles, 70-200 microns. Thus, hypertensive medial damage with significant reduction of the smooth muscle area to less than 50% of the total media is viewed as an additional important factor which predisposes to sudden arterial rupture and massive cerebral hemorrhage.