Purpose:  Angelman syndrome (AS) commonly presents with epilepsy (>80%). The goal of this study was to examine the natural history and various treatments of epilepsy in AS in a large population.

Methods:  A detailed electronic survey containing comprehensive questions regarding epilepsy in AS was conducted through the Angelman Syndrome Foundation.

Results:  There were responses from 461 family members of individuals with AS, of whom 86% had epilepsy (60% with multiple seizure types), the most common being atonic, generalized tonic–clonic, absence, and complex partial. Partial‐onset seizures only were reported in 11% of those with epilepsy. Epilepsy was most common among those with maternal deletions and unknown subtypes, with catastrophic epilepsies present in only these two subtypes. These epilepsies were refractory to medication, with only 15% responding to the first antiepileptic drug (AED). The most commonly prescribed AED were valproic acid and clonazepam, but lamotrigine and levetiracetam appeared to have similar efficacy and tolerability.

Discussion:  This is the largest study to date assessing epilepsy in AS. Although epilepsy in AS is considered a generalized epilepsy, there was a high prevalence of partial seizures. There are few previous data regarding the use of newer AED in AS, and the results of this study suggest that these newer agents, specifically levetiracetam and lamotrigine, may have efficacy similar to that of valproic acid and clonazepam, and that they appear to have similar or better side‐effect profiles. Nonpharmacologic therapies such as dietary therapy and vagus nerve stimulation (VNS) also suggest favorable efficacy and tolerability, although further studies are needed.