Primary angiitis of the central nervous system.

Primary central nervous system vasculitis, also known as primary angiitis of CNS (PACNS), is a rare and heterogeneous inflammatory disorder of blood vessels restricted to the central nervous system. The most common presenting symptoms are headache, focal neurological deficits, and altered cognition. Subtypes of PACNS can have different presentations. Diagnosis is challenging due to clinical, imaging, and histopathological heterogeneity, as well as numerous mimics. The goal of diagnostic work-up is to establish that the neurological presentation is due to an underlying vasculitis based on angiographic or histopathologic features and to exclude infection, systemic vasculitis, or other mimics. Treatment is based on anecdotal evidence and consensus, and includes glucocorticoids and cyclophosphamide for induction of remission, as well as mycophenolate mofetil, rituximab, azathioprine, and methotrexate for maintenance therapy. Only two-thirds of the patients achieve a good neurological outcome. A detailed understanding of the etiopathogenesis and heterogeneity will be necessary for developing more effective biomarkers, precision therapies, and improved outcomes.