Advancing Knowledge in CNS Vasculitis

Only a few well-described cohorts of patients with primary CNS vasculitis (PCNSV; sometimes called primary angiitis of the CNS [PACNS]) have been published with enough follow-up to be able to really assess global and neurologic outcomes.1,2 There is still no definitive clinical tool or biomarker to confirm the diagnosis of PCNSV.The commonly used 1988 diagnostic criteria from Calabrese and Malek, slightly modified in 2009 by Birnbaum and Hellmann, have not been thoroughly validated, but made sense and matched clinical practice and diagnostic reasoning.3 A brain and/or leptomeningeal biopsy is the only way to definitively confirm CNS vasculitis, but a plethora of more frequent mimickers and causes for secondary CNS vasculitis have still to be ruled out, especially in patients with a diagnosis based on angiographic abnormalities and/or without obvious inflammatory CNS features on CSF analysis, gadolinium-enhancing lesions, or vessel wall enhancement on MRI. 3 A follow-up helps support the diagnosis, but possibly in the future, a minority of patients in these cohorts will be found to have a new genetic or infectioustriggered CNS condition.The list of PCNSV mimickers and secondary CNS vasculitis has been increasing steadily, with the identification of new genetically determined vasculopathies, such as deficiency in adenosine deaminase 2, and more sensitive tools, such as metagenomic nextgeneration sequencing, to detect rare CNS infections. 4 Hence, in real-world practice, as in the main published cohorts of PCNSV, only 30%-50% of reported patients had a brain biopsy, and only 50%-65% of the latter had biopsy-proven CNS vasculitis.1,2 Additional information on the main subsets of PCNSV that have been described is also needed to better determine their respective outcomes and, in clinical practice, how best to treat them.In this issue of Neurology ® Neuroimmunology & Neuroinflammation, Paramasivan et al. 5 report an update of one of the few large and well-described cohorts of PCNSV, which now includes 72 adults with PCNSV confirmed either on biopsy (30.5% of the patients; 44 had a biopsy, half of them showing vasculitis) or on angiography and in whom mimicking or secondary processes of CNS vasculitis were excluded as thoroughly as possible.As in most previous cohorts, patients were divided into 2 subgroups: those with medium/large vessel or with small vessel PCNSV.Major findings were younger age at onset, delay in diagnosis and therapy, greater relapse risk, and poorer outcomes at 1 year in the small vessel PCNSV group vs more strokes and more frequent wall imaging abnormalities (as per the definition of this subgroup, somehow) in the medium/large vessel group.Eventually, 69.8% of the patients had a good outcome at 1 year, and relapse occurred in 49% with a median follow-up of approximately 2 years (68% of the patients had at least 1 year of follow-up).Intriguingly, the choice of treatments was not associated with outcomes or relapses.This latter finding seems difficult to reconcile with the overall principles that patients with PCNSV should receive aggressive treatment, as was in fact done in this cohort and, ultimately, recommended by the authors.The authors indeed acknowledge a possible indication bias, not specific or unique to this cohort: "the small vessel vasculitis group… received maintenance therapies which, if not given, could have resulted in further relapses and increased disability."Their standard treatment policies for patients with aggressive presentation have been established and rely on induction with glucocorticoids and cyclophosphamide, then maintenance with glucocorticoids, and a corticosteroid-sparing agent, at least to minimize the adverse effects of long-term glucocorticoid exposure.Whether the strongest maintenance From the Vasculitis Clinic (C.P.)

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