Central Nervous System Vasculitis and Related Diseases

Central nervous system (CNS) vasculitis can be classified into (1) primary vasculitis limited to the CNS and (2) secondary CNS vasculitis, which is either a manifestation of systemic vasculitis or a complication associated with certain specific pathologies, such as infections (viral, bacterial, or fungal), neoplasia, drugs, connective tissue diseases (e.g., systemic lupus erythematous, rheumatoid arthritis, and Sjögren syndrome), and sarcoidosis. Isolated vasculitis limited to the CNS is known as primary angiitis of the CNS (PACNS). PACNS is associated with various clinical and neurological features. There is no specific test for PACNS at present, rendering the diagnosis difficult. The diagnosis is currently based on the following features: (1) exclusion of other pathologies associated with CNS vasculitis, such as infection, neoplasm, drug, and systemic disease-mediated vasculitis; (2) radiologic identification of segmental arterial wall narrowing “vessel beading,” followed by poststenotic dilatation; and (3) the pathological findings of granulomatosis, lymphocytic, or acute necrotizing patterns. The first line of induction therapy is the combination of corticosteroids and cyclophosphamide, followed by maintenance therapy using mycophenolate mofetil, azathioprine, and methotrexate. Involvement of larger or proximal cerebral vessels requires aggressive treatment. The diagnosis of secondary vasculitis in the CNS requires the identification of exogenous agents or conditions. Withdrawal/Removal of the causal agents or treatment of the underlying conditions often leads to improvement of vasculitis. Due to phenotypic overlap between the various forms of CNS vasculitis, a comprehensive workup is often required.