EEG characteristics in Rett syndrome

Introduction: The clinical manifestations and the typical sequence of stages of Rett syndrome (RS) are well-known. 60–70% of the patients develop epilepsia. Electroencephalogram (EEG) pattern is invariably abnormal during the course of RS. Characteristic EEG patterns have been described and suggest a typical developmental pattern in this disorder. They have been correlated with the clinical staging. The aim of this study was to examine the correlation between clinical and EEG stages.

Methods: We compared clinical manifestations and EEG records from 9 classic cases. The age of these patients varied between 1¼ and 32 years, thus all four clinical stages were included.

Results: EEG patterns correlate only partially with the clinical stages. There is great variability in the course of EEG patterns in RS. Some typical manifestations in this disease (apneic pauses, episodic laughing, hand movements) can appear as fits without being of epileptic origin. Epileptogenic activity in the EEG is commonly present without clinical seizures. On the other hand there are patients with clinical seizures without epileptic discharges in their EEG.

Conclusion: There are characteristic EEG findings in RS without being diagnostic. EEG patterns correlate only partially with the clinical stages. To not overestimate or under-recognize seizures in patients with RS, the clinical history as well as the EEG pattern have to be followed carefully. Regarding the need for anticonvulsant therapy the clinical symptoms are most important.

Keywords: Rett syndrome, electroencephalography