What MRI findings are contraindicated to anticoagulation (blood thinner) therapy in cerebral amyloid angiopathy (CAA)?

MRI Findings Contraindicated to Anticoagulation in Cerebral Amyloid Angiopathy

In cerebral amyloid angiopathy (CAA), specific MRI findings that contraindicate anticoagulation therapy include lobar hemorrhages >10 mm in diameter, presence of 4 or more microhemorrhages <10 mm in diameter, evidence of superficial siderosis, and significant white matter hyperintensities. 1

Key Contraindications on MRI

• Lobar macrohemorrhages >10 mm in diameter - These suggest underlying CAA and significantly increase the risk of recurrent hemorrhage with anticoagulation 1, 2
• Multiple microhemorrhages (≥4) <10 mm in diameter - These are highly predictive of future bleeding risk and contraindicate anticoagulation 1
• Superficial siderosis - Indicates previous hemorrhage into the subarachnoid space and is associated with high recurrence risk 1, 3
• Evidence of vasogenic edema - May indicate inflammatory CAA and increases bleeding risk 1, 2
• Significant white matter hyperintensities - Represent underlying small vessel disease that increases hemorrhage risk 1

Imaging Protocols for Detection

• MRI is mandatory for detecting these contraindications, as CT lacks sensitivity for microhemorrhages and superficial siderosis 1
• Required MRI sequences include:
  • T2* gradient-echo (GRE) or susceptibility-weighted imaging (SWI) - Most sensitive for detecting microhemorrhages and superficial siderosis 1, 3
  • T2 fluid-attenuated inversion recovery (FLAIR) - For white matter hyperintensities and edema 1
  • Diffusion-weighted imaging (DWI) - To assess for acute ischemia 1
• 3T MRI provides greater sensitivity for detection of microhemorrhages compared to 1.5T 1, 2

Risk Assessment and Decision-Making

• Lobar hemorrhages in CAA pose a greater risk of recurrence when anticoagulation is initiated compared to deep hemorrhages 1
• The risk of recurrent ICH is higher than that of ischemic stroke in the first year after initial hemorrhage (2.1% versus 1.3%) 1
• Decision analysis studies recommend against restarting anticoagulation in patients with lobar ICH and atrial fibrillation 1
• Additional risk factors that should be considered include:
  • Advanced age 1
  • Hypertension 1
  • Degree of anticoagulation 1
  • Presence of leukoaraiosis 1

Alternative Management Strategies

• For patients with CAA and atrial fibrillation requiring stroke prevention:
  • Left atrial appendage closure (LAAC) may be considered as an alternative to long-term anticoagulation 4
  • Short-term antiplatelet therapy (clopidogrel and/or aspirin for 6 weeks) may be used post-LAAC procedure 4
  • Aggressive blood pressure optimization is essential 4

Monitoring and Follow-up

• Regular MRI monitoring is essential for patients with CAA, especially if any antithrombotic therapy is considered 1
• Any new neurological symptoms should prompt immediate imaging to assess for new hemorrhages 2
• Blood pressure should be strictly controlled to reduce hemorrhage risk 4