Primary angiitis of the central nervous system (PACNS) occurs when the disease process is confined to the brain, spinal cord, and overlying leptomeninges. Secondary CNS vasculitis can occur in any condition where there is vascular inflammation such as systemic vasculitis, infections, and lymphoproliferative disease.

There are no validated criteria for the diagnosis of PACNS. Classification is usually based on; (i) a history of acquired unexplained neurological deficit; (ii) high probability angiographic or histopathological evidence of angiitis in the CNS; (iii) no evidence of systemic vasculitis or other condition to which the angiographic appearance could be attributed [1]. PACNS once diagnosed is categorized into one of the recognized subsets or clinical variants such as granulomatous angiitis, benign angiopathy, and atypical. CNS angiitis may be associated with varicella zoster, sarcoid, or amyloidosis [2]. These subsets appear to have varyingly important prognostic and therapeutic implications.

There is a reported female predominance, and no age-group is known to be particularly prone to developing the condition. The annual incidence is 2.4/million in Olmsted County (USA).

The etiology of PACNS is unknown. Secondary forms are associated with herpes zoster infection, sarcoid, and amyloidosis.

Blood-based investigations are largely unhelpful in the diagnosis of primary CNS vasculitis. They are however important to exclude secondary CNS vasculitis; hence, autoantibody screening, clinical chemistry, and microbiological tests should be performed. Investigations are important to establish the extent of organ involvement.