Cerebral Microbleeds: Detection, Associations and Clinical Implications.

Vigorous investigations for cerebral microbleeds (CMBs) have been made since the late 1990s. CMBs on paramagnetic-sensitive magnetic resonance sequences correspond pathologically to clusters of hemosiderin-laden macrophages and have emerged as an important new imaging marker of cerebral small vessel disease, including intracerebral hemorrhage (ICH). The prevalence of CMBs varies according to the specific disease settings (stroke subtypes and dementing disorders) and is highest (60%) in ICH patients. The associations of CMBs with aging, hypertension and apolipoprotein E genotype are consistent with the two major underlying pathogeneses of CMBs: hypertensive arteriopathy and cerebral amyloid angiopathy (CAA). The distributional patterns of CMBs might help us to understand the predominant small vessel disease pathogenesis in the brain; the strictly lobar type of CMBs often reflects the presence of advanced CAA, while the other types of CMBs, such as 'deep or infratentorial CMBs', including the mixed type, are strongly associated with hypertension. CMBs might be associated with cognitive function (especially executive function), gait performance, and cerebrovascular events (spontaneous, antithrombotic drug-related or post-thrombolysis ICH). In the field of CAA, an understanding of CAA-related CMBs might help to guide decision making with regard to new therapeutic approaches, including the use of monoclonal antibodies against vascular amyloid. These concepts of CMBs might allow us to advance research on ICH as well as for dementia.