Longitudinal observation of electroencephalograms in the Rett syndrome

The long-term electroencephalographical observations were documented during the course of the Rett syndrome in 8 patients. The abnormal EEG findings changed with age and the clinical stage. In the premonitory stage (birth-1.5 years of age), EEG seemed to be normal. In the acute exacerbation stage (1.5-5 years old), occipital dominant alpha wave-like activity was characteristic and persisted for a few years, but it disappeared afterwards along with the seizure activity. At around 4 years of age, when the whole spectrum of symptoms manifested, the EEG background activity in the waking stage showed higher amplitude, lower frequency and more irregular than normal. Sleep spindles were hardly observed, while frequent seizure activity was found on sleep EEG. Before the onset of epileptic attacks, paroxysmal discharges, such as diffuse spike-and-wave complexes, were noted during sleep recordings. In the chronic stage (after age 6), a monotonous theta rhythm (MTR), which was not influenced by either opening or closing of the eyes but attenuated only by a big noise or strong pain stimuli, characteristically dominated the waking tracing. The MTR was generalized over both hemispheres. After age 20, the MTR tended to be more localized to the centro-parietal area. This suggests that a reduction in responsiveness to visual and other stimuli occurs in this disease, which may be attributable to a dysfunction of the reticular activating system in the brainstem.