Brain microbleeds: more evidence, but still a clinical dilemma

Purpose of review Brain microbleeds (BMBs) are a radiological construct that is meant to represent a specific underlying microscopic pathology: perivascular collections of hemosiderin deposits. BMBs may represent two different types of underlying vasculopathies: hypertensive vasculopathy and cerebral amyloid angiopathy. This brief review highlights some recent works discussing their nature, and both their diagnostic and prognostic values. Recent findings The improvement of detection techniques has modified our perception of BMBs prevalence, which can reach 35% among healthy people compared with 5% when conventional techniques are used. Our knowledge on BMBs is evolving very quickly. The careful study of their anatomical distribution sheds light on their histological significance: deep BMBs may represent hypertensive vasculopathies and lobar ones cerebral amyloid angiopathy. Summary Despite an explosion of publications on BMBs, their diagnostic and prognostic values have only received indirect support and remain to be explored. To date, BMBs should not contraindicate antithrombotic treatment in settings wherein benefits have clearly been demonstrated in clinical trials and meta-analyses. One intriguing field is Alzheimer's disease, in which BMBs may be a missing link between two important theories on the neuropathogenesis of Alzheimer's disease: the amyloid cascade hypothesis and the vascular hypothesis.