The unknown face of Sturge-Weber Syndrome type 3 - a hybrid scoping review of the literature.

Sturge-Weber syndrome (SWS) type 3 is a rare neurocutaneous disorder characterised by isolated leptomeningeal angiomatosis without facial capillary malformation or ocular involvement. Existing literature is limited to case reports and small series, resulting in incomplete characterisation of its clinical and radiological phenotype and frequent diagnostic delay. The increased prevalence of contrast-enhanced MRI has improved detection of pial angiomatosis and associated parenchymal abnormalities. This scoping review aimed to map the available evidence and define current knowledge gaps. Our aim is to synthesise published data on SWS type 3, describe demographic, clinical, and imaging features, and contribute a 15-patient institutional cohort.PubMed and EMBASE were systematically searched (31 March-4 April 2025), with additional studies identified through reference screening. Eligible studies reported isolated leptomeningeal angiomatosis without port-wine birthmark and included contrast-enhanced MRI. Seventy-five published cases were identified. Heterogeneity in study design and reporting precluded quantitative pooling; data were synthesised descriptively. SWS type 3 demonstrates a consistent pattern of unilateral, predominantly occipitoparietal leptomeningeal angiomatosis, most commonly presenting with focal-onset seizures. Despite improved MRI-based recognition, substantial gaps remain regarding natural history, pathophysiology, and optimal management. Prospective, standardised studies are required to refine diagnostic criteria and guide evidence-based care.