Associations and implications of cerebral microbleeds.

Cerebral microbleeds (CMB) are small haemosiderin deposits, detected with varying sensitivity by specific MRI sequences. CMB prevalence increases most clearly and reliably with age, but CMB are also associated with various acquired and heritable cerebral vasculopathies (most commonly arteriolosclerosis and amyloid angiopathy). CMB often coincide with the other radiological features of small vessel disease, cortical microinfarction, lacunar infarction and periventricular white matter hyperintensity. CMB distribution may suggest an underlying cause; in particular, lobar-restricted or corticosubcortical CMB suggest amyloid angiopathy. In both ischaemic stroke and intracerebral haemorrhage, CMB appear to be a marker of underlying vasculopathy severity, and therefore a predictor of recurrence. Although CMB are also associated with several broad clinical neurological impairments (cognitive impairment, depression and gait instability), it is debatable whether CMB themselves are causative. The clinical implications of CMB detection remain unclear. Thrombolysis for ischaemic stroke is not contraindicated. It is uncertain whether more conservative antithrombotic strategies are warranted if CMB are detected in patients with symptomatic vascular disease or atrial fibrillation. Studies (observational and randomized) of various treatment strategies in patients with CMB and these concomitant conditions are required to resolve these treatment dilemmas.