Primary angiitis of the central nervous system: diagnostic criteria.

Primary angiitis of the central nervous system (PACNS) is a vasculitis of small arteries and veins of unknown cause restricted to the central nervous system (CNS), and controversy and disagreement exist over the means to establish the diagnosis. Cerebral arteriography, cerebrospinal fluid examination, and MRI singly or in combination do not have sufficiently demonstrated positive predictive value to establish the diagnosis. An alternative diagnosis is established at biopsy in 35% of cases. Histologic confirmation is required for the diagnosis of PACNS. Patients without histologic confirmation should not be included in case reports, case series, or reviews.