The significance of small cerebral bleeds in neurodegenerative dementia syndromes.

Small cerebral bleeds are frequently observed in brains of patients with Alzheimer disease (AD) and cerebral amyloid angiopathy (CAA). However, they are also observed in patients with other neurodegenerative dementias and in persons without cognitive impairment. The aim of this survey is to compare the bleeding load in brains with different dementia syndromes and in age-matched controls. Hundred sixty-five brains were examined. The prevalence and the severity of the different cerebrovascular lesions were examined. Quantification of the number of mini-bleeds allowed to determinate the bleeding load in different cerebral regions. Micro-bleeds were considered as small macroscopically visible lesions while mini-bleeds were defined as small perivascular accumulations of red blood cells or siderophages only visible on microscopic examination. Several types of cerebrovascular lesions prevailed in AD brains with CAA, compared to the controls. White matter changes prevailed in frontotemporal lobar degeneration. Mini-bleeds were significantly more frequent in the cerebral cortex of AD and Lewy body dementia brains. They also prevailed around the dentate nucleus of the cerebellum and in the tegmentum pontis of patients with progressive supranuclear palsy. On the other hand the bleeding load in frontotemporal lobar degeneration and in corticobasal degeneration was similar to that in age-matched control brains. Cerebrovascular lesions, including micro-bleeds, predominated in AD brains with CAA. Mini-bleeds, on the other hand, were more related to the neurodegenerative process itself and reflected associated disruption of the blood-brain barrier.