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Aim

The aim of the study was to characterize epilepsy, febrile seizures, electrographic features, and brain abnormalities in a large, national cohort of individuals with Prader–Willi syndrome (PWS).

Method

This was an observational cohort study. Clinic charts of 126 individuals (63 males, 63 females) with genetically confirmed PWS (due to a deletion in 72 cases, to uniparental disomy [UPD] in 51 cases, and to an imprinting centre defect in two cases), aged from 1 month to 48 years (mean age 13y), were reviewed and 119 interviews conducted. Information regarding seizures, medication, imaging studies, and family history of seizures was collected. Ninety-five individuals (aged 1mo–48y) underwent electroencephalography (EEG).

Results

Five individuals had epilepsy (4.0%), three of whom had major cerebral findings on imaging, and eight others had febrile seizures (6.4%). Of the three genetic abnormalities, deletion was associated with seizures. Focal epileptiform abnormalities were found in 12 out of 94 individuals, and five out of these 12 had a frank electrographic seizure pattern. Epileptogenic EEG abnormalities were associated with young age.

Interpretation

The risk of epilepsy and febrile seizures in PWS is significantly lower than in Angelman syndrome and is associated with brain abnormalities. Electrographic seizures and focal epileptiform activity were present in 5% of individuals and were associated with young age. The underpinnings of epileptiform abnormalities in PWS and how they differ from those of the Angelman syndrome should be studied further.