Clinical Pearls & Morning Reports

Posted by Carla Rothaus

Published February 22, 2023


What imaging findings are associated with primary angiitis of the central nervous system?

Brain biopsy is needed for the definitive diagnosis of primary angiitis of the central nervous system. Read the NEJM Case Records of the Massachusetts General Hospital here.

Clinical Pearls

Q: What is primary angiitis of the central nervous system (PACNS)?

A: PACNS is a rare vasculitis that is restricted to the small and medium arteries and veins of the brain, spinal cord, and leptomeninges. PACNS is most likely to occur in patients 40 to 60 years of age. It occurs twice as frequently in men as in women.

Q: What imaging findings are associated with PACNS?

A: Multifocal punctate infarcts on magnetic resonance imaging (MRI) are typical of PACNS. Other potential MRI findings include diffuse bihemispheric white-matter hyperintensities, leptomeningeal enhancement, and mass lesions that mimic tumors. Cerebrospinal fluid analysis reveals an elevated protein level and lymphocytic pleocytosis. Cerebral angiography, when positive, reveals multifocal nonconcentric arterial irregularities, usually in the distal branches. However, the sensitivity of cerebral angiography for the diagnosis of PACNS is only 10 to 20% because PACNS predominantly affects small-caliber arteries, which cannot be visualized.

Morning Report Questions 

Q: How is PACNS treated?

A: The clinical course of PACNS is typically progressive. Treatment strategies include induction therapy with glucocorticoids and intravenous cyclophosphamide, followed by maintenance therapy with immunomodulatory agents such as oral cyclophosphamide, azathioprine, mycophenolate mofetil, rituximab, and methotrexate.

Q: Describe the possible mechanisms by which a paraneoplastic vasculitis may mimic PACNS.

A: Lung, gastrointestinal, and other cancers are identified in up to 10% of patients with stroke, and stroke is the first manifestation of cancer in approximately 5% of cases. Common mechanisms of cancer-related stroke include hypercoagulability and nonbacterial (marantic) thrombotic endocarditis, which usually causes multifocal, widely distributed large and small infarcts. In rare cases, a paraneoplastic vasculitis that is similar to PACNS can result from one of the following processes: an immunologic reaction against vascular endothelium (molecular mimicry), endothelial injury due to the release of proinflammatory cytokines by tumor cells, or hypersensitivity to deposits of tumor protein or circulating immune complexes that contain tumor antigens on the vessel wall.

Browse more Clinical Pearls & Morning Reports »