New onset epilepsy in Prader-Willi syndrome: semiology and literature review.

Prader-Willi syndrome is a chromosomal disorder caused by absence of expression of the paternal active genes in the 15q11∼q13 chromosome region; it is associated with an increased incidence of epilepsy and narcolepsy. Presented here is the case of a 2.5-year-old boy with Prader-Willi syndrome and a history of neonatal superior sagittal sinus thrombosis with new onset of atonic seizures with electrographic onset from the parasagittal region. It is postulated that microscarring from neonatal venous sinus thrombosis, history of febrile seizures, and Prader-Willi syndrome are factors predisposing him to epilepsy. The importance of video electroencephalography with electromyography electrodes is emphasized for Prader-Willi syndrome patients with drop episodes, to differentiate cataplexy from seizures. This being a novel report of a Prader-Willi syndrome patient with atonic seizures, the literature on seizure semiology among patients with Prader-Willi syndrome is reviewed.