Development and Retrospective Application of Novel Outcome Measure: Sturge-Weber Syndrome Acute Crisis (SWAC) Index.

Objective: Sturge-Weber syndrome (SWS) symptoms frequently overlap in neurological acute crises (ACs) presenting with seizures, stroke-like episodes (SLE), and headaches. Recent efforts to develop a prospective drug trial highlighted the need for a new outcome measure capable of quantifying these symptoms during an SWS AC. We aimed to develop such a measure and evaluate its practical application. Methods: The Sturge Weber Acute Crisis (SWAC) index was developed based on clinical care guidelines and experience. We retrospectively applied the SWAC to an open-label prospective drug trial published in 2020; SWAC scores were assigned for every AC during 6-month baseline and treatment phase periods. Results: Six of 10 subjects experienced 670 ACs; only 78/670 ACs were included in the primary quantitative analyses (one subject was an extreme outlier) and 71/78 events were single-symptom while 7/78 included multiple symptoms. Three of six subjects experienced improved median seizure total score; all three improved their median SLE total score. Three of five subjects with headache improved their median headache total score. Poisson-log GLMM models demonstrated significant improvements in composite severity and total, SLE duration and total, and headache severity and total index scores. Interpretation: The newly developed SWAC index, applied retrospectively, reflected site-PI clinical experience, quantified the severity and duration of SWS ACs ranging from mild to severe, and better enabled comparison of treatment versus baseline responses. These results support additional studies with the SWAC index to further assess clinical utility and use in future treatment trials in SWS.