| A type of developmental and epileptic encephalopathy that presents in individuals with a pre-existing neurodevelopmental disorder. It is characterized by plateauing or regression of various combinations of cognitive, language, behavioral, and motor functions that is concomitant with significant activation of spike-and-wave complexes during sleep. Onset of epileptic seizures is between 2 and 12 years of age (peak at 4 to 5 years). Epileptic seizures may or may not be clinically evident. There is no mandatory seizure type although focal seizures are common. Epileptic seizures typically worsen with the evolution of multiple seizure types including other focal seizure types, typical and atypical absence seizures, atonic seizures, and focal seizures with negative myoclonus. Neurological examination may be normal or reflect the underlying neurodevelopmental disorder. The EEG background during wakefulness may show focal or diffuse slowing and often contains focal or multifocal abnormalities but may be normal. Epileptiform abnormalities during wakefulness are not continuous. In drowsiness and sleep, there is marked activation of epileptiform activity, with slow (1.5 - 2Hz) spike-and-wave complexes in N-REM sleep. Spike-and-wave activation in sleep (SWAS) is usually diffuse but may occur more focally or multifocally. Normal sleep architecture is absent or difficult to distinguish. |
