Notched delta, phenotype, and Angelman syndrome.

The notched delta pattern is one of the characteristic EEG features found in Angelman syndrome patients. The purpose of this study was to evaluate the possibility of using the notched delta pattern as a detection tool for Angelman syndrome patients by analyzing its frequency in a tertiary care pediatric center, its specificity for Angelman syndrome, and the age at which it was observed. The authors performed a retrospective review of the video-EEG recordings of all the patients who had either the notched delta pattern or a phenotype consistent with Angelman syndrome. The notched delta was observed in 1.1% of all the EEGs performed. Its specificity for Angelman syndrome was evaluated at 38%. The youngest age at which it was noted was 14 months. The results indicate that the notched delta pattern is relatively rare, but more frequent than expected, and is easily recognizable. The pattern was observed not only in Angelman syndrome patients, but also in children with a spectrum of conditions wider than reported. It is a powerful detection tool for Angelman syndrome when correlated to a suggestive phenotype, and the association of these features should raise suspicion for Angelman syndrome in both infants and adults.