Add‐on cannabidiol significantly decreases seizures in 3 patients with SYNGAP1 developmental and epileptic encephalopathy

Abstract Mutations in SYNGAP1 are associated with developmental delay, epilepsy, and autism spectrum disorder (ASD). Epilepsy is often drug‐resistant in this syndrome with frequent drop attacks. In a prospective study of add‐on cannabidiol (CBD), we identified three patients with SYNGAP1 mutations: two boys and one girl. Seizure onset was at 3.5, 8, and 18 months (M), respectively, with numerous atypical absences per day associated with eyelid myoclonia (2/3 patients), upper limb myoclonic jerks (2/3 patients), and drop attacks (all patients).