Rett syndrome: an EEG study in 52 girls.

EEG studies have been carried out on 52 girls with Rett syndrome, the majority of records being taken between two and 7 years of age. Discharges were a common feature, occurring in 43 patients, and did not appear to be related to the onset of seizures. The discharges, consisting of sharp waves or spikes, were characteristically most prominent around the middle third of the head, often occurring asymmetrically and could be infrequent or almost continuous. They were usually enhanced by light sleep and were seen only during sleep in 15 EEGs taken in 13 patients, most of whom were under four years of age. These EEG features when present may help confirm the diagnosis of Rett syndrome in the appropriate clinical setting and in particular are quite distinct from the usual EEG patterns seen in Angelman (Happy Puppet) syndrome.