OBJECTIVES: I. Evaluate electrocardiographic parameters, including QT and PR intervals and QRS morphology/duration, across clinical stages in patients with Rett syndrome.

II. Characterize abnormalities of cardiac conduction and repolarization. III. Assess arrhythmias, heart rate variability, and autonomic nervous system function in these patients using 24-hour Holter monitoring.

IV. Record events believed to represent seizures with video, electroencephalogram (EEG), and polygraph monitoring in patients who have more than 1 clinical seizure every 5 days.

V. Characterize these events with respect to clinical manifestations, EEG correlates, and other physiologic data.

VI. Determine the frequency of seizures vs. events without electrographic correlates in these patients.

VII. Determine whether Rett syndrome patients have characteristic or unique types of seizures and/or an epileptic syndrome.

PROTOCOL OUTLINE: Patients receive an electrocardiogram at baseline and every 6 months for 3 years. Clinical stage II patients undergo 24-hour Holter monitoring on the same schedule; age-matched controls are tested once.

A group of patients with more than 1 seizure or possible seizure every 5 days undergo 5-day continuous electroencephalogram/polygraphic/video monitoring, with respiratory effort assessment, end tidal carbon dioxide and oxygen saturation levels, and a seizure log.

• Classical Rett syndrome meeting Rett Syndrome Diagnostic Work Group criteria
• Age-matched girls without neurologic or cardiac problems entered as controls