Association of Cortical Superficial Siderosis with Post‐Stroke Epilepsy

OBJECTIVE: To assess whether post‐stroke epilepsy (PSE) is associated with neuroimaging findings of hemosiderin in a case–control study, and whether the addition of hemosiderin markers improves the risk stratification models of PSE. METHODS: We performed a post‐hoc analysis of the PROgnosis of POST‐Stroke Epilepsy study enrolling PSE patients at National Cerebral and Cardiovascular Center, Osaka, Japan, from November 2014 to September 2019. PSE was diagnosed when one unprovoked seizure was experienced >7 days after the index stroke, as proposed by the International League Against Epilepsy. As controls, consecutive acute stroke patients with no history or absence of any late seizure or continuing antiseizure medications at least 3 months after stroke were retrospectively enrolled during the same study period. We examined cortical microbleeds and cortical superficial siderosis (cSS) using gradient‐echo T2*‐weighted images. A logistic regression model with ridge penalties was tuned using 10‐fold cross‐validation. We added the item of cSS to the existing models (SeLECT and CAVE) for predicting PSE and evaluated performance of new models. RESULTS: The study included 180 patients with PSE (67 women; median age 74 years) and 1,183 controls (440 women; median age 74 years). The cSS frequency was higher in PSE than control groups (48.9% vs 5.7%, p < 0.0001). Compared with the existing models, the new models with cSS (SeLECT‐S and CAVE‐S) demonstrated significantly better predictive performance of PSE (net reclassification improvement 0.63 [p = 0.004] for SeLECT‐S and 0.88 [p = 0.001] for CAVE‐S at the testing data). INTERPRETATION: Cortical superficial siderosis was associated with PSE, stratifying stroke survivors at high risk of PSE. ANN NEUROL 2023;93:357–370