A rare form of epileptic encephalopathy with spike-wave activation in sleep (EE-SWAS) characterized by various combinations of acquired cognitive, language, behavioral, and motor deficits associated with marked spike- and- wave activation in sleep. In Landau-Kleffner syndrome, receptive language is mainly affected, with an acquired auditory verbal agnosia. The disease is MONDO_0009509 (Landau-Kleffner syndrome). Also known as: LKS, acquired epileptic aphasia.