"Primary vasculitis of central nervous system.Primary vasculitis of central nervous system (PVCNS) is an uncommon condition and diagnosis with an acceptable degree of certainty remains a difficult challenge. Parietal inflammation of the cerebral vessels appears in the absence of systemic disease. Publication of large cohorts of well-explored patients in USA and France over the 2 past decades significantly increased the experience. Headache is the most frequent symptom, generally associated with stroke or encephalopathy. Brain imaging including MRI and vascular imaging (MRA/CT angiography + conventional angiography) is now the cornerstone of diagnosis and cerebral biopsy seldom performed. Favorable prognostic factors have been identified in PVCNS, i.e. distal vessel involvement, no/very few ischemic events and meningeal enhancements after gadolinium injection. When these are present, prednisone is usually the only treatment proposed. Otherwise, cyclophosphamide is added to prednisone for 4 to 6 months, and maintenance immunosuppressive therapy is prescribed. Mortality of PVCNS is now 5-10% at 5 years, thanks to modern and rational medical care."