Nontraumatic parenchymal brain hemorrhages.

Before the availability of computerized tomography (CT), it was estimated that 25% of parenchymal brain hemorrhages (PBH) was diagnosed as ischemic stroke. Clinical studies were biased toward large hemorrhages with high mortality rates. More recently, the full clinical spectrum of PBH has been appreciated only with studies correlating clinical findings and CT results. In the pre-CT era, hypertension was thought to be the major risk factor for PBH. Chronic hypertensive vascular changes were believed to cause arteriolar wall damage, and rupture of weakened dilated vessels thought to result in PBH. The occurrence of PBH in previously normotensive patients was underrepresented in pre-CT era studies. Current CT findings in PBH patients have shown that normotensive patients and hypertensive patients with chronic vascular changes have smaller hemorrhages resulting in lower mortality than hypertensive patients without chronic vascular changes. Because chronic hypertensive vascular changes are believed to be common in patients with PBH, this finding is unexpected and previously unreported. Chronic vascular changes may therefore offer some unexplained "protection" for brain blood vessels. Alternatively the mechanism of hypertensive PBH may be somewhat different than previously postulated.