The electroencephalographic (EEG) characteristics of Rett’s syndrome were studied in 17 girls between the ages of 1 and 16 yrs at the Sections of Neurophysiology and Pediatric Neurology, Baylor College of Medicine and The Methodist Hospital, Houston, TX. The criteria for the diagnosis of Rett’s syndrome included: (1) normal prenatal and perinatal development (2) normal neurological development for the first 7 to 18 mths; (3) cessation of development between 1 and 4 yrs of age and subsequent regression; (4) dementia and autistic features, (5) loss of purposeful use of the hands and development of stereotypical movements; (6) ataxia; (7) acquired microcephaly (8) seizures.
A specific diagnostic EEG pattern was not seen but serial records were characterized by a progressive deterioration: (1) slowing; (2) loss of vertex transients and spindles in sleep; (3) multifocal epileptiform abnormalities; and (4) almost continuous generalized slow spike-and-wave activity. These EEG patterns appeared to correlate with the clinical stages: (1) early onset stagnation; (2) rapid destructive; (3) pseudo-stationary; and (4) late motor deterioration (see Am J Med Genet 1986 (suppl). The EEG of 3 patients was not typical and the average age at onset of their symptoms was later than usual. The authors suggest that the EEG may help to identify variants or atypical cases of Rett’s syndrome. 
COMMENT. Others have described similar age-related changes in the EEG’s of patients with Rett’s syndrome. This EEG classification correlated with clinical stages may be useful in diagnosis and prognosis. The imprecise nature of the clinical-EEG correlation, admitted by the authors, may be explained by the nonspecific character and frequency of atypical cases of Rett’s syndrome of undetermined etiology.