Prolonged video/EEG/polygraphic monitoring was conducted in 82 Rett syndrome females, ages 2 to 30 years, at Baylor College of Medicine, Houston, TX. Clinical manifestations of reported seizures in 55 (67%) patients included motor symptoms, generalized jerking, stiffening, behavioral changes, and staring. All had abnormal EEGs, epileptiform in 67 (81%). During monitoring, electrographic seizures were recorded in only 13 (16%) patients, and parents identified the clinical events confirmed as seizures in only 5. Symptoms considered by parents as typical of ’seizures’ were not associated with EEG discharges during monitoring in 23 (42%) of the 55 patients considered initially to have seizures. These ’non-seizures’ consisted of twitching, jerking, head turning, falling, trembling, staring, laughing, pupil dilatation, breath holding, and hyperventilation. The occurrence of epileptic seizures in RS is overestimated while true seizures may be under-recognized. 
COMMENT. Clinical seizures confirmed by electrographic video monitoring are frequently not recognized as seizures by parents of patients with Rett syndrome, whereas non-seizures are often considered to represent epileptic events. The authors have previously reported correlation of EEG abnormalities in Rett syndrome with the age-related changes in clinical stages. Serial records are characterized by a progressive deterioration, which further confuses the differentiation of seizures and non-seizures. Robb, Harden, and Boyd, at Great Ormond Street Hospital, London, found that EEG seizure discharges in 43 of 52 girls with Rett syndrome were not related to the onset of clinical seizures. These and other articles on Rett syndrome are reviewed in Progress in Pediatric Neurology I 1991;pp513-528.
Growth failure in Rett syndrome was not explained by increased energy expenditure associated with repetitive involuntary movement, in a study of 14 girls at Baylor College of Medicine, Houston. 
Head circumference at birth in Rett syndrome patients was lower than that for a reference population in a study at the University of Western Australia, Perth. Birth weights were also lower, and 40% had reported perinatal difficulties and abnormalities in development in the first 6 months. Contrary to the criteria for diagnosis of Rett syndrome, head circumference at birth, perinatal period, and the first 6 months development may not be normal.