Primary angiitis of the central nervous system: differential diagnosis and treatment.

While primary angiitis of the central system (PACNS) remains a rare entity, the poor specificity of the available diagnostic tests and its multiple mimics create a major diagnostic challenge. Recently, there have been advances in understanding PACNS and differentiating it from its mimics. A recent breakthrough is the proposal of reversible cerebral vasoconstriction syndromes (RCVS) as a unifying concept for a group of disorders that highly mimics PACNS. RCVS are characterised by acute-onset, recurrent headaches, with or without additional neurologic events, with reversible vasoconstriction of the central nervous system (CNS) vasculatures, mimicking CNS vasculitis. RCVS are considered the most common mimics of PACNS. Advances in our understanding of RCVS have allowed for identification of patients previously confused with PACNS. The scope of this article focusses on the work-up, differential diagnosis and evaluation of PACNS, as well as a discussion of the secondary CNS vasculitides with emphasis on their clinical findings, diagnoses and treatment.