According to epilepsy syndromes, the diagnostic yield was the highest among patients with West syndrome (WS) with a history of neonatal seizures and mutations in KCNQ2 and STXBP1 were most frequently identified.
We conclude that KCNQ2R198Q is a model for a new subclass of KCNQ2 variants causing infantile spasms and encephalopathy, without preceding neonatal seizures.