Miliary aneurysms and "fibrinoid" degeneration of cerebral blood vessels.

Three cases of intracerebral hemorrhage are described in which there was fibrinoid degeneration of cerebral arteries and arterioles or miliary aneurysms or both. Fibrous balls are shown to be sclerosed true aneurysms. These changes occurred in the absence of malignant hypertension and perhaps in the absence of any hypertension. A further point of interest was the finding of fibrinoid at the site of apparent aneurysm formation in a small artery on the cerebral surface, a location at which miliary aneurysms are not generally thought to form. The presence of intracerebral hemorrhage in all three cases, and the ready demonstration of similar changes in other cases of intracerebral hemorrhage, suggest but do not prove that the fibrinoid degeneration or aneurysm leads to vessel rupture and to hemorrhage itself. Also unsettled is the question of whether miliary aneurysms form only at sites already displaying fibrinoid change. Our data suggest that pre-existing fibrinoid may not be a prerequisite for miliary aneurysm formation.