Angiitis of the CNS remains a poorly understood form of vascular inflammatory disease. Primary angiitis of the CNS or PACNS, a disease once considered extremely rare, recently has been reported more frequently. Traditional views of PACNS held it to be a relentless and uniformly fatal disease if untreated, but it is now viewed as more heterogeneous, with some relatively benign subsets. Its pathophysiology is poorly understood. Secondary vasculitis of the CNS can occur with a variety of other conditions and diseases; each requires a different diagnostic and therapeutic approach. Regardless of whether primary or secondary CNS vasculitis is considered, an understanding of the limitations of currently available neurodiagnostic investigations is essential.