A Case of Central Nervous System Vasculitis Mimicking Reversible Cerebral Vasoconstriction Syndrome in Young Stroke: A Diagnostic Conundrum

Central Nervous System Vasculitis (CNSV) is a rare cause of stroke in young adults and may closely mimic Reversible Cerebral Vasoconstriction Syndrome (RCVS), a more common non inflammatory vasculopathy. Distinguishing between these entities is crucial because their treatment and prognosis differ. The authors report a 40-year-old female who presented with one month of progressive right-sided hemicranial headache followed by onset of left hemiparesis. Initial non contrast Computed Tomography (CT) brain showed right parietal infarct with haemorrhagic transformation. Magnetic Resonance Imaging (MRI) with diffusion-weighted imaging revealed multiple watershed infarcts in the right fronto-parietal region, while gradient echo sequences demonstrated right parieto-occipital lobar haemorrhage with overlying convexity subarachnoid haemorrhage. Time-of-flight MR angiography showed multifocal segmental narrowing with irregular contour of the right M2 segment of the Middle Cerebral Artery (MCA), favouring a working diagnosis of RCVS, and she was started on nimodipine. However, Cerebrospinal Fluid (CSF) analysis showed mild pleocytosis with elevated protein, and inflammatory work-up revealed raised acute phase reactants with positive Antinuclear Antibody (ANA) and anti-U1 Ribonucleoprotein (RNP), suggestive of an underlying Mixed Connective Tissue Disease (MCTD)-associated CNSV. She was treated with highdose intravenous corticosteroids followed by monthly intravenous cyclophosphamide pulses, with good clinical and radiological improvement. The present case is unique because multifocal vasculitis involvement with combined ischaemic watershed infarcts and concomitant lobar and convexal haemorrhage simulated RCVS in a young woman without systemic autoimmune features. The report underscores the need to reconsider a vasculitis aetiology when atypical imaging, abnormal CSF and positive autoimmune markers coexist in a presumed case of RCVS, in order to avoid misdiagnosis and to initiate timely immunosuppression.