Cerebral microbleeds: from depiction to interpretation

Abstract

Cerebral microbleeds (CMBs) are defined as hypointense foci visible on T2*-weighted and susceptible-weighted MRI sequences. CMBs are increasingly recognised with the widespread use of MRI in healthy individuals as well as in the context of cerebrovascular disease or dementia. They can also be encountered in major critical medical conditions such as in patients requiring extracorporeal mechanical oxygenation. The advent of MRI-guided postmortem neuropathological examinations confirmed that, in the context of cerebrovascular disease, the vast majority of CMBs correspond to recent or old microhaemorrhages. Detection of CMBs is highly influenced by MRI parameters, in particular field strength, postprocessing methods used to enhance T2* contrast and three dimensional sequences. Despite recent progress, harmonising imaging parameters across research studies remains necessary to improve cross-study comparisons. CMBs are helpful markers to identify the nature and the severity of the underlying chronic small vessel disease. In daily clinical practice, presence and numbers of CMBs often trigger uncertainty for clinicians especially when antithrombotic treatments and acute reperfusion therapies are discussed. In the present review, we discuss those clinical dilemmas and address the value of CMBs as diagnostic and prognostic markers for future vascular events.

Cerebral Small Vessel Disease Phenotype and 5-year Mortality in Asymptomatic Middle-to-old Aged Individuals

“…17,18 They showed that mixed CMBs were associated with cardiovascular mortality, while lobar CMBs were associated with stroke-speci c mortality compared to patients without CMBs; 17,18 these results correspond with the notion that mixed CMBs are considered to re ect hypertensive arteriopathy and, therefore, systemic vascular disease, while lobar CMBs are indicative of CAA and primarily restricted to the brain. 14 Although not provided in the literature, the strokes related to lobar CMB-associated mortality were probably intracerebral hemorrhage, a major clinical consequence of CAA. 19 Therefore, we postulated that causes of mortality in the CSVD type 4 in this study were primarily hemorrhagic strokes.…”

“…Bleeding CSVDs were further strati ed into different subtypes with CMBs of speci c topographic features that have distinct underlying microvasculopathy: strictly lobar CMBs considering as CAA and mixed CMBs as arteriosclerosis/lipohyalinosis microvasculopathy. 14,15 Regarding nonbleeding CSVDs, individuals with severe WMHs were further divided depending on whether a lacune was present. This phenotyping method overcomes the limitations of other classi cation methods in that it only counts the number of CSVD markers but does not consider their nature.…”

Cerebral small vessel disease phenotype and 5-year mortality in asymptomatic middle-to-old aged individuals

“…The first step of the stratification scheme differentiated CSVD into bleeding and nonbleeding subtypes. Bleeding CSVDs were further stratified into different subtypes with CMBs of specific topographic features that have distinct underlying microvasculopathy: strictly lobar CMBs considering as CAA and mixed CMBs as arteriosclerosis/lipohyalinosis microvasculopathy 14 , 15 . Regarding nonbleeding CSVDs, individuals with severe WMHs were further divided depending on whether a lacune was present.…”

Imaging Markers of Subcortical Vascular Dementia in Patients With Multiple-Lobar Cerebral Microbleeds

“…Cerebral microbleeds increase the risk of spontaneous intracerebral hemorrhage (ICH), ischemic stroke, cognitive impairment, and gait disturbance ( 9 , 10 ). Two main sporadic forms of SVD present with CMBs: hypertensive arteriopathy (HA) and cerebral amyloid angiopathy (CAA).…”

“…Multiple lobar CMBs, like strictly lobar CMBs, could suggest CAA pathology ( 12 ). A mix of lobar with nonlobar CMBs can occur in HA, but a HA-CAA synergism could also be responsible for CMB pathogenesis, which implies an SVD spectrum ( 10 , 11 , 13 ).…”