Are lobar microbleeds of diagnostic value in the community?

Cerebral microbleeds (CMBs) mark underlying cerebral small vessel disease and an increased risk of future ischemic stroke, intracerebral hemorrhage, and dementia.(1) They have become the basis of a rapidly evolving body of literature investigating their clinical importance, and they are at the center of clinical dilemmas regarding risk-benefit analyses of antithrombotic therapy in patients with ischemic cardio/cerebrovascular disease.(2) The topographic distribution of CMBs can often aid in distinguishing the underlying microangiopathy in older individuals, with strictly deep and strictly lobar CMBs suggesting hypertensive arteriopathy and cerebral amyloid angiopathy (CAA), respectively.(3) Consistent associations between strictly lobar hemorrhages, including CMBs, and pathologically confirmed CAA have led to the Boston clinical-radiographic criteria, which allow clinicians to diagnose probable CAA during life in people aged 55 years and older in the absence of tissue biopsy.(4) These criteria have been validated in hospital cohorts, including the use of solely lobar CMBs to fulfill the criteria.(4,5) However, whether strictly lobar CMBs have the same diagnostic accuracy for CAA in the general population remains uncertain. Their value in this setting has come into question following disappointing positive (25%) and negative (50%) predictive values for probable CAA reported using strictly lobar CMB to fulfill Boston criteria in elderly Framingham Heart Study participants.(5) The use of -amyloid ligand neuroimaging may provide us with more insights in this regard.