Primary angiitis of the central nervous system.

Primary angiitis of the central nervous system (PACNS) was first identified half a century ago, but it remains a rare and challenging disease. However, important advances have been made in the field of PACNS, mainly through recently published retrospective analyses of large groups of PACNS patients, and the consideration of reversible cerebral vasoconstriction syndrome as a distinct entity. Clinical manifestations of PACNS are variable and non-specific. Even though neuroimaging can be suggestive of vasculitis, only a leptomeningeal biopsy can definitively confirm vasculitis. However, a brain sample is taken in less than half the patients and cannot further help to distinguish between PACNS and secondary vasculitis of the central nervous system. Hence, physicians should be aware of all alternative diagnoses and PACNS mimickers, which are now well-known. Whereas prognosis now appears to be much better than for the first reported cases, probably attributable to the use of corticosteroids and immunosuppressants, mainly cyclophosphamide, the optimal therapeutic regimen, potentially based on each patient's characteristics, and its duration remain to be determined. Only multicenter studies and prospective therapeutic trials will be able to clarify these issues on therapy and eventually provide some data on PACNS physiopathogenesis, which remains a poorly explored domain.