Cerebral microbleeds (CMBs) on gradient-echo T2* weighted MRI, which are characterized histologically by the presence of hemosiderin around small vessels, are now accepted as a manifestation of cerebral small vessel disease (SVD) pathologies, including hypertensive small vessel disease and cerebral amyloid angiopathy (CAA). CMBs are often detected in patients with stroke, Alzheimer's disease, and mild cognitive impairment. The pathological differences in MBs according to distribution is now well known, with MBs in deep regions considered to be associated with hypertensive arteriopathy, whereas strictly lobar MBs share risk factors with CAA.
Evidence suggests that CMBs should not be considered to be clinically "silent". When CMBs are detected in healthy adults, physicians should recognize that subclinical SVD might have begun in their brain. Chronic hypertension can affect HA-related CMBs, as well as CAA-related CMBs. Furthermore, both types of CMBs are risk factor for intracranial hemorrhage under the antithrombotic drug use. Thus, CMBs should be considered as "warning sign" for inappropriate blood pressure control and antithrombotic drug use.
It seems clear that CMBs should be an important component of future studies to investigate how SVD influence neurodegeneration via neurovascular units in elderly populations.
