Prevalence of small cerebral bleeds in patients with a neurodegenerative dementia: a neuropathological study.

BACKGROUND: Small cerebral bleeds are frequently observed on magnetic resonance imaging in patients with Alzheimer dementia (AD). Histological confirmations in post-mortem brains are scarce. This study describes the prevalence of cerebrovascular lesions and the quantification of the "bleeding load" in post-mortem brains of patients with neurodegenerative dementias. PATIENTS AND METHODS: Forty-five brains of AD patients, 8 of dementia with Lewy bodies (DLB) and 12 of fronto-temporal dementia (FTD) were compared to 10 controls. Histological examination was performed for the evaluation of cerebral amyloid angiopathy (CAA), white matter changes (WMCs), micro-infarcts, and cerebral micro- and mini-bleeds (MnBs). The latter were evaluated semi-quantitatively on a coronal section of a whole cerebral hemisphere and on a horizontal section through the pons and cerebellum.
RESULTS: Arterial hypertension (AH) was the main vascular risk factor in the patients with AD and DLB (P<0.05). MnBs, consisting of small perivascular bleeds, were significantly more frequent (P<0.001) in AD brains. They were mainly and equally present in the cerebral cortex of AD and DLB brains (P=0.04). Combined AD and DLB pathologies were present in 15%. CAA and WMCs occurred more frequently in AD brains (P<0.001). Occasional MnBs were observed in 60% of the controls.
CONCLUSIONS: This neuropathological study confirms the frequent presence of MnBs and WMCs in AD brains. The relative high incidence of cortical MnBs in DLB brains is probably due to the high incidence of AH and the frequent association with AD and CAA.