• cerebral microbleeds (CMBs) – hemosiderin deposits caused by small hemorrhages, may serve as a radiologic biomarker of small vessel disease (SVD)
    • black, round, or oval lesions on blood-sensitive MRI sequences – (T2*/GRE or SWI)
    • 2-5 mm in diameter
  • often found incidentally on MRI scans; incidence increases with age
    • incidence in the general population is approx. 10-15%   (Sveinbjornsdottir, 2008)
    • 6.5% in the individuals aged 45-50 years
    • up to 40% in the population > 80 years    [Poels, 2009]
    • incidence of CMBs in AD is 20-43%; in vascular dementia up to 85%!  [Seo, 2007]
  • microhemorrhages are associated with:
    • older age
    • hypertension
    • smoking
    • white matter disease and lacunar stroke
    • previous ischemic stroke or ICH
    • COVID-19 leukoencephalopathy (mostly in critically ill patients) (Agarwal, 2020)
  • a high number of microbleeds is associated with an increased risk of:

  • higher risk of progression with:
    • severe SVD (Subcortical Vascular Disease or Small Vessel Disease)
    • CAA with APOE ε2 and ε4  [McCarron, 2000]


  • subcortical (mainly caused by arteriolopathy)  → Binswanger´s disease
  • cortical (mostly caused by CAA – with a higher risk of lobar hemorrhage)
  • combined (combination of CAA and arteriolosclerosis or rather arteriolosclerosis alone) [Jung, 2020]

Cerebral amyloid angiopathy (CAA) on GRE

Cortical cerebral microbleeds and lobar hematomas in patient with cerebral amyloid angiopathy
Cortical cerebral microbleeds (CMBs)
Cortical cerebral microbleeds (CMBs) on SWI sequence

Differential diagnosis

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  • no specific therapy
  • strict treatment of hypertension
  • careful indication and monitoring of anticoagulant (preferably use DOACs) and antiplatelet therapy (avoid DAPT if possible)

CMBs and the risk of a hemorrhage

  • the risk of ICH increases with the number of CMBs
    • ≥ 5 CMBs – OR for ICH is 2.8
    • ≥ 10 CMBs – OR for ICH is 5.5!
  • according to the CROMIS-2 trial, the risk of bleeding in patients with CMBs is 9.8/1000 vs. 2.6/1000 patient-years (adjusted hazard ratio 3·67, 95% CI 1·27–10·60) [Wilson, 2018]
  • the incidence of ICH is up to 5%/year in multiple lobar CMBs [Van Etten, 2014]
  • the risk of symptomatic intracranial hemorrhage (sICH) may be increased after thrombolytic therapy in patients with cerebral microbleeds (CMBs)
  • CMBs < 10  ⇒  IVT seems safe (ESO 2021) (AHA/ASA 2019 IIa/B-NR)
  • CMBs > 10 ⇒ IVT has a higher risk of ICH; the expected benefit of treatment must outweigh the risk – consider IVT in patients with a severe stroke (AHA/ASA 2019 IIb/B-NR)
    • the smaller study retrospectively found a slightly increased risk (3%) of bleeding in patients with microbleeds on GRE [Fiehler, 2007]
    • increased risk is associated with CAA as a cause of microbleeds
  • no MRI screening is recommended to assess CMB burden before making a treatment decision regarding IVT (ESO 2021)
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  • single antiplatelet therapy is a safe and beneficial approach, even in the presence of cerebral microbleeds (RESTART trial subanalysis) [Salman, 2019]

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Cerebral Microbleeds (CMB)