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Cerebral Amyloid Angiopathy (CAA)


KEY FACTS

Terminology

  • Cerebral amyloid deposition occurs in 3 morphologic varieties

    • Common: Cerebral amyloid angiopathy (CAA)

    • Uncommon: Mass-like lesion (amyloidoma)

    • Rare: Inflammatory; diffuse (encephalopathic) white matter involvement

Imaging

  • General findings

    • Normotensive demented patient

    • Lobar hemorrhage(s) of different ages

    • Multifocal “black dots” on T2* or SWI MR

  • Protocol advice

    • Best initial screening (for acute hemorrhage) = CT

    • MR with T2* &/or SWI

Top Differential Diagnoses

  • Multifocal “black dots” on T2/T2* MR

    • Hypertensive microhemorrhages

    • Multiple cavernous malformations (type 4)

    • Ischemic stroke with microhemorrhage

    • Diffuse axonal injury

    • Hemorrhagic metastases

    • Posterior reversible encephalopathy syndrome

Clinical Issues

  • CAA: Common cause of “spontaneous” lobar hemorrhage in elderly patients

    • Causes up to 15-20% of primary intracranial hemorrhage (ICH) in patients > 60 years old

    • Stroke-like clinical presentation with “spontaneous” lobar ICH

    • Chronic: Can cause vascular dementia

  • CAA common in elderly patients with dementia

    • 2/3 normotensive, 1/3 hypertensive

    • 40% with subacute dementia/overt Alzheimer (overlap common)

Axial graphic shows an acute hematoma
with a blood-fluid level
. Multiple microbleeds
and old lobar hemorrhages
are also typical findings in cerebral amyloid disease.

Axial SWI MR in a 70-year-old man with cognitive impairment and acute visual changes shows multiple lobar hemorrhages
and microhemorrhages
related to cerebral amyloid angiopathy (CAA). SWI and T2* sequences are the most sensitive sequences for identifying microhemorrhages characteristic of CAA.

Axial CT in a 72-year-old woman with no history of hypertension shows an acute right occipital lobe hemorrhage
.

Axial GRE MR in the same patient shows multiple foci of susceptibility artifact
“blooming” related to microhemorrhages in a typical location for CAA. CAA patients most often present with acute focal neurologic deficits related to the lobar hemorrhage. Patients also present with cognitive impairment related to the microhemorrhages.

TERMINOLOGY

Abbreviations

  • Cerebral amyloid angiopathy (CAA)

Synonyms

  • Congophilic angiopathy, cerebral amyloidosis

Definitions

  • CAA is common cause of “spontaneous” lobar hemorrhage in elderly patients

  • Cerebral amyloid deposition occurs in 3 morphologic varieties

    • CAA (common)

    • Amyloidoma (uncommon)

    • Inflammatory CAA: Amyloid β-related angiitis (ABRA) with diffuse white matter (WM) inflammatory involvement (rare)

IMAGING

General Features

  • Best diagnostic clue

    • Normotensive demented patient with

      • –

        Lobar hemorrhage(s) of different ages

      • –

        Multifocal cortical/subcortical microhemorrhages (“black dots”) on T2*

  • Location

    • Cortical/subcortical WM (gray-white junction)

    • Parietal + occipital lobes most common at autopsy; also frontal + temporal on imaging

    • Less common in brainstem, deep gray nuclei, cerebellum, hippocampus

  • Size

    • Acute lobar hemorrhage tends to be large

    • Hypointense foci on dark T2*/susceptibility sequences (“blooming”) seen with chronic microbleeds, but not specific for CAA

      • –

        Microbleeds and macrobleeds may represent distinct entities in CAA

      • –

        Increased vessel wall thickness may predispose to microbleed > macrobleed formation

  • Morphology

    • Acute hematomas are large, often irregular, with dependent blood sedimentation

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