Electroencephalographic findings in Rett syndrome.

Rett syndrome is a progressive neurologic condition, affecting only girls and characterized by acquired microcephaly, dementia, seizures, autistic behavior, spontaneous hyperventilation, spasticity, hyperreflexia and a peculiar characteristic stereotypic movement disorder. A review of 35 EEGs (obtained over 0-8.5 years of follow-up) in 9 such patients revealed a striking age-related change in the electroencephalographic pattern. Often initially normal, the EEG shows a variety of epileptiform abnormalities but intact background activity between 3 and 5 years. Between 5 and 10 years of age, the background activity exhibits some slowing, epileptiform abnormalities persist and paroxysmal high-amplitude theta activity occurs over extended periods, related to spontaneous hyperventilation. After 10 years, there is a general reduction in the epileptiform activity but further slowing of the background rhythms is usually observed. As all other laboratory tests are mostly normal in Rett syndrome, EEG promises to be a powerful tool in confirming the diagnosis in a compatible setting, in follow-up of these patients, and in objective evaluation of any future therapeutic interventional modalities in this serious and common condition.