EEG abnormalities aid diagnosis of Rett syndrome.

Nine girls with Rett syndrome had 22 electroencephalographic studies performed over 5 years. Nineteen walking tracings demonstrated moderate background slowing. Focal epileptiform activity was observed in 13 studies, 10 of which had bilateral independent foci. Spikes were invariably maximal in central regions, diphasic or triphasic, and of very short duration. In 3 patients, epileptiform activity preceded clinical seizures by up to 2 years. Two children had spontaneous hyperpnea preceding apnea during wakefulness with further background slowing. Video monitoring of 2 children revealed that episodic behavioral changes were not seizures. Ten of 12 sleep recordings had abnormal background activity with absent or rudimentary spindles. Normal activity occurred only in girls younger than 2 1/2 years of age. Epileptiform activity was markedly increased during sleep in 8 tracings in which both wakefulness and sleep were obtained. It was characterized by bilaterally independent and bisynchronous spike-and-wave activity, maximal in parasagittal areas. One patient had bursts of high-voltage slow-wave activity followed by attenuation. No apneic episodes were recorded during sleep. In Rett syndrome, electroencephalographic abnormalities include background slowing, centrally located short-duration spikes, and increased epileptiform activity during sleep. This activity commonly preceded clinical seizures in patients studied at initial presentation.