Analysis of the characteristics of epilepsy in 37 patients with the molecular diagnosis of Angelman syndrome

Abstract

Angelman syndrome is a genetic disorder caused by defects in the maternally inherited imprinted domain located on chromosome 15q11-q13. Most patients with Angelman syndrome present with severe mental retardation, characteristic physical appearance, behavioral traits, and severe, early-onset epilepsy. We retrospectively reviewed the medical histories of 37 patients, all with the molecular diagnosis of Angelman syndrome and at least three years of follow-up in our neurology department, for further information about their epilepsy: age of onset, type of seizures initially and during follow-up, EEG recordings, treatments and response. The molecular studies showed 87% deletions de novo, 8% uniparental, paternal disomy, and 5% imprinting defects. The median age at diagnosis was 6.5 years, with 20% having begun to manifest febrile seizures at an average age of 1.9 years. Nearly all (95%) presented with epilepsy, the majority under the age of three (76%). The most frequent seizure types were myoclonic, atonic, generalized tonic-clonic and atypical absences. At onset, two patients exhibited West syndrome. EEG recordings typical of Angelman syndrome were found in 68%. Normalization of EEG appeared in 12 patients after nine years. Control of epileptic seizures improved after the age of 8.5 years. The most effective treatments were valproic acid and clonazepam. We conclude that epilepsy was present in nearly all of our cases with Angelman syndrome, and that the EEG can be a useful diagnostic tool. On comparing the severity of epilepsy with the type of genetic alteration, we did not find any statistically significant correlations.