Vasculitis is an inflammation of the vessel wall. It may be either primary or secondary. Primary vasculitis includes systemic vasculitis (large, medium, and small-vessel vasculitis) and localized vasculitis (isolated angiitis of the central nervous system and non-systemic vasculitic neuropathy). Secondary vasculitis may be present in connective tissue disorders or may be caused by infections, neoplasms, and substance abuse. Patients presenting with symptoms suggestive of vasculitis require brain neuroimaging, lumbar puncture, and angiography, but only biopsy allows a definite diagnosis.