A 72-year-old woman on warfarin for atrial fibrillation presents with sudden onset weakness and speech difficulty. MRI shows a lobar hemorrhage in the parietal region with microhemorrhages scattered throughout the cerebral cortex on susceptibility-weighted imaging (SWI). Which imaging pattern best distinguishes cerebral amyloid angiopathy (CAA) from anticoagulant-related hemorrhage?

Explanation

## Distinguishing Cerebral Amyloid Angiopathy (CAA) from Anticoagulant-Related Hemorrhage **Key Point:** Multiple microhemorrhages (microbleeds) on susceptibility-weighted imaging (SWI) predominantly in cortical and subcortical (lobar) regions is the hallmark of CAA and distinguishes it from anticoagulant-related hemorrhage, which typically presents as a single acute hemorrhage without multiple microbleeds. ### Comparison Table: CAA vs. Anticoagulant-Related ICH | Feature | Cerebral Amyloid Angiopathy (CAA) | Anticoagulant-Related ICH | | --- | --- | --- | | **Acute hemorrhage location** | Lobar (cortical/subcortical) | Lobar or deep (variable) | | **Microhemorrhages (microbleeds)** | **Multiple, scattered** | Absent or very few | | **Distribution of microbleeds** | **Cortical and subcortical** | N/A | | **Number of acute bleeds** | Often recurrent (multiple over time) | Usually single acute event | | **Age of presentation** | Typically >60 years | Any age (on anticoagulation) | | **Risk factors** | Amyloid deposition, hypertension | INR elevation, warfarin/DOACs | | **SWI/GRE findings** | Multiple hypointense foci (microbleeds) | Single or few hypointense foci | **High-Yield:** The presence of **multiple microhemorrhages on SWI** in a cortical/subcortical distribution is virtually pathognomonic for CAA. Anticoagulant-related hemorrhage typically shows a single acute bleed without the chronic microbleed burden. ### Clinical Pearl **Microhemorrhages (microbleeds)** represent chronic amyloid deposition in small cortical and subcortical vessels. They appear as small hypointense dots on SWI/GRE sequences and accumulate over years in CAA. Their presence in a lobar hemorrhage patient is a strong indicator of underlying CAA. **Mnemonic: MICROBLEEDS in CAA** — **M**ultiple, **I**n cortical/subcortical distribution, **C**hronic (accumulated), **R**ecurrent (over time), **O**ld and new bleeds, **B**rain amyloid, **L**obar location, **E**vidence on SWI/GRE, **E**xcluding anticoagulation as sole cause, **D**ifferentiates from single anticoagulant bleed, **S**usceptibility imaging shows them. ### Why Lobar Location Alone Is Not Sufficient While both CAA and anticoagulant-related hemorrhage can present with lobar bleeds, anticoagulant-related ICH can also occur in deep locations. The **pattern of microbleeds** is the discriminating feature. **Warning:** Do not assume all lobar hemorrhages are due to CAA. Look for the burden of microhemorrhages on SWI to confirm CAA.