Advances in primary angiitis of the central nervous system.

Primary angiitis of the central nervous system (PACNS) is a rare idiopathic inflammatory syndrome targeting the vessels of the brain and spinal cord. Clinical presentation is variable, insidious, and non-specific; headache and encephalopathy are the most common symptoms. Multiple strokes affecting numerous vascular territories may be seen, and both focal and diffuse neurologic dysfunction may be present. Cerebrospinal fluid (CSF) analysis is crucial; a normal CSF along with normal brain parenchymal imaging carries a high negative predictive value in excluding PACNS. The role of imaging continues to evolve, and most patients have abnormal vascular imaging; however, the specificity of imaging for PACNS has historically been poor. Cerebral and meningeal biopsy is a valuable tool in confirming the diagnosis and excluding mimics. PACNS generally responds to immunosuppressive therapy. Failure to respond should prompt evaluation for an alternative diagnosis. Given the rarity of this disorder, exclusion of mimics such as the reversible cerebral vasoconstriction syndromes (RCVS) and infectious processes is essential.