RT Journal Article SR Electronic T1 The diagnosis of primary central nervous system vasculitis JF Practical Neurology JO Pract Neurol FD BMJ Publishing Group Ltd SP 109 OP 114 DO 10.1136/practneurol-2018-002002 VO 20 IS 2 A1 Claire M Rice A1 Neil J Scolding YR 2020 UL http://pn.bmj.com/content/20/2/109.abstract AB The diagnosis of primary central nervous system (CNS) vasculitis is often difficult. There are neither specific clinical features nor a classical clinical course, and no blood or imaging investigations that can confirm the diagnosis. Contrast catheter cerebral angiography is neither specific nor sensitive, yet still underpins the diagnosis in many published studies. Here we describe an approach to its diagnosis, emphasising the importance of obtaining tissue, and present for discussion a new, binary set of diagnostic criteria, dividing cases into only ‘definite’ primary CNS vasculitis, where tissue proof is available, and ‘possible,’ where it is not. We hope that these criteria will be modified and improved by discussion among experts, and that these (improved) criteria may then be adopted and used as the basis for future prospective studies of the clinical features and diagnosis of this difficult and dangerous disorder, particularly for coordinated multicentre therapeutic trials.