Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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July 7, 2022
Amyloid-Beta–related Angiitis (ABRA)
- Background:
- ABRA is a rare clinic-pathologic entity where amyloid-β (Aβ) deposits within the cerebral blood vessels lead to a transmural angiodestructive inflammatory response, often granulomatous, in the cortical and leptomeningeal vessel walls.
- It is a type of inflammatory cerebral amyloid angiopathy but is distinct from cerebral amyloid angiopathy–related inflammation, which is limited to the perivascular region without destructive vasculitis.
- Clinical Presentation:
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ABRA mostly presents in the seventh decade of life, with a mean age of 67 years. It has no gender predilection.
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The most common symptoms include focal neurologic deficits, seizures, acute to subacute cognitive dysfunction, and headaches.
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Mental status changes, including hallucinations and cerebellar features, are also seen.
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It can progress to dementia.
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- Key Diagnostic Features:
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Blood tests have little diagnostic value.
- Vasogenic edema in the subcortical white matter associated with numerous microbleeds, the latter best seen on the susceptibility-weighted sequence
- Larger hematomas or superficial cortical siderosis may also be seen. Mass effect can be seen with resemblance to a neoplastic disease process. Leptomeningeal enhancement may be seen.
- CSF shows elevated protein (60–90%) and lymphocytic pleocytosis in 50% of cases.
- Cerebral angiography is mostly normal but can rarely show narrowing of medium-sized vessels.
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Brain biopsy is the gold standard, which shows perivascular and intramural inflammatory infiltrates with fibrinoid deposits and granulomatous features involving the leptomeninges and cortical blood vessels.
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Congo red and beta amyloid immunostaining are positive.
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- Differential Diagnoses:
- Cerebral amyloid angiopathy–related inflammation (CAA-RI): Imaging features overlap with ABRA and often are difficult to differentiate without a biopsy. On histopathology, CAA-RI lacks the angiodestructive process.
- Amyloid-related imaging abnormalities (ARIA): Seen in the context of amyloid-lowering monoclonal antibodies
- Primary CNS angiitis: Mostly presents as multiple cerebral infarcts of variable ages in different vascular territories. T2 or FLAIR hyperintensities are common but nonspecific. Cerebral angiogram may show multifocal vascular narrowing involving small- and medium-sized vessels.
- Primary CNS lymphoma: It has a predilection for periventricular white matter and is mostly supratentorial (75–85%). MRI typically shows a T1-hypointense, T2-hypo- or isointense lesion with homogeneous contrast enhancement and diffusion restriction. Ring enhancement can be seen in immunocompromised patients. MR spectroscopy shows a large choline peak and decreased NAA.
- Gliomatosis cerebri: It is a growth pattern of diffuse gliomas involving at least 3 lobes, frequently bilateral and extending infratentorially. MRI shows loss of gray-white matter differentiation, iso- to hypointense gray matter on T1, hyperintense on T2 with minimal or no contrast enhancement, and minimal mass effect. PET scan demonstrates marked hypometabolism.
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Treatment:
- Corticosteroids can lead to dramatic clinical and radiologic improvement.
- To prevent relapse, most patients need long-term immunosuppressant therapy. Cyclophosphamide is the most commonly used immunosuppressant.
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