IV. Spontaneous Intracerebral Hemorrhage
A. General Comments
Intracerebral (intraparenchymal) hemorrhage accounts for about 15% of "strokes". It is much less common than infarction but more lethal - hemorrhage is the most common cause of death among cerebrovascular disorders and about 35-40% of patients survive the first year. Hypertension is the most important risk factor for spontaneous intracerebral hemorrhage. Other etiologies include AV malformation, ruptured aneurysm, amyloid angiopathy, leukemia and associated blood dyscrasias. Hemorrhage most often results from spontaneous rupture of small vessels damaged by chronic hypertension or amyloid angiopathy. In this module, only hypertensive hemorrhage will be discussed.
B. Pathogenesis of Hypertensive Hemorrhage
Hypertension is associated with arteriolosclerosis - a disorder of small arteries and arterioles (arteriolosclerosis is one type of arteriosclerosis; atherosclerosis of large arteries is also a type of arteriosclerosis). Hypertension-associated pathological changes in small vessels include thickening of the vessel walls with increased cellularity, hyalinization of the media, and the formation of small (micro-) aneurysms known as Charcot-Bouchard aneurysms. Autoregulation is impaired and vascular permeability increases. Rupture of blood vessels results in hemorrhage into the substance of the brain, but the cause of rupture is not clear. There is spontaneous rupture of small penetrating vessels damaged by chronic hypertension.