Imaging spectrum of CNS vasculitis.

Cerebral vasculitis is characterized by inflammation of the walls of blood vessels and may affect vessels of any size. The pathogenesis of vasculitis remains poorly understood. Vasculitis may affect large vessels (Takayasu arteritis, giant cell arteritis), medium-sized vessels (Kawasaki disease, polyarteritis nodosa), small vessels (immunoglobulin A vasculitis, microscopic polyangiitis, granulomatosis with polyangiitis, eosinophilic granulomatosis with polyangiitis), or variable-sized vessels (Behçet disease, Cogan syndrome). Primary angiitis of the central nervous system (CNS) is an idiopathic disorder with no evidence of generalized inflammation that may simulate reversible cerebral vasoconstriction syndromes. Vasculitis may be secondary to systemic disease, infection, malignancy, drug use, or radiation therapy. Imaging findings vary from small ischemic changes to frank infarction, hemorrhage, and white matter edema and may show contrast material enhancement. The cerebral arteries may demonstrate a beaded appearance with variable degrees of stenosis, occlusion, and contrast enhancement of the vessel wall. Correlation of imaging findings with clinical presentation and laboratory test results helps establish the diagnosis of CNS vasculitis.