Pseudocataplexy: gelastic-atonic seizures.

Gelastic-atonic seizures are characterized by laughing and then loss of muscle tone. They are difficult to differentiate from laughter-induced cataplexy and may be indicative of Niemann-Pick disease Type C or variants. We studied an 11-year-old girl who had gelastic-atonic seizures that were triggered by laughing. The nature of her attacks was established by ictal EEG ambulatory recordings at home. There was no evidence of Niemann-Pick disease.