Dear Editor,

Treatment of Primary Angiitis of the CNS (PACNS) is a challenge aiming at minimizing the risk of treatment failure and recurrent vasculitis while avoiding adverse effects of immunosuppressive agents. Identification of markers of outcome may help tailor immunosuppressive therapy. We designed an observational, prospective, multicenter, cohort study, the INTERnational Study of Primary Angiitis of the CEntral nervous system (INTERSPACE), whose primary objective is to identify predictors of death and dependence (modified Rankin Scale: 3–6) at the end of clinical follow-up (≥one-year following recruitment). Patients aged ≥16 with PACNS confirmed by central nervous system biopsy or autopsy or with a presumptive diagnosis (biopsy not performed or results inconclusive) are eligible. Patients in whom immunosuppressive therapy was initiated before obtaining brain magnetic resonance imaging (MRI) (and spinal cord MRI if relevant) or >180 days prior to study enrolment are excluded. Study patients should be managed according to the site investigator's usual approach to PACNS. Electronic case report forms are used to collect patient data at baseline, upon neurological deterioration, and at prespecified follow-up visits. Blind analysis of all neuroimaging and histopathology specimens is centralized in study core labs. PACNS diagnosis and reports of neurological decline due to treatment failure or recurrent vasculitis are adjudicated. Assuming death or dependence in 30% of 200 PACNS adjudicated patients, six predictors may be integrated in a multivariate model. INTERSPACE offers the opportunity to improve our understanding of PACNS, its management, and its prognosis. Because PACNS is rare, the collective effort of many centers is required. The prospect of recruiting only one or a few patients to INTERSPACE must not hinder participation of potential study centers. Each patient recruited is a major contribution. To this end, an invitation is sent to the world: to join INTERSPACE, study investigators are invited to contact the Coordination Centre at


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  2. Acknowledgements

The authors thank ‘La Fondation des Gouverneurs de l'Espoir’, which generously provided unrestricted funding of INTERSPACE. Thanks are extended also to Drs Ruth Geraldes, Jessika Kovitch-Lensch, and Paolo Vitali for their translation of the consent form.