Epilepsy and electroencephalographic features: comparative study of Down syndrome and non-syndromic mental retardation

Abstract

INTRODUCTION: Down syndrome (DS) is the most common chromosomal abnormality causing mental retardation and its association with epilepsy is highly variable in childhood. Although the first descriptions of the syndrome did not report seizures, their association with epilepsy is relatively common. METHODS: were evaluated 68 individuals with DS and 83 with non-syndromic mental retardation (N-SMR). All patients underwent digital EEG, lasting at least 30 minutes and electrodes positioned according to the International 10-20 System of Electrode Placement. Data were analyzed using descriptive statistics and proportions were compared with Student's t-test and test of Differences between Proportions with p<0.05 considered statistically significant. RESULTS: DS: 27.9% had epilepsy (first seizure with 2.2±3.7 years). Fifteen (22.1%) patients had epileptiform discharges, 5 (7.4%) hypsarrhythmia, 5 (7.4%) focal pattern, 3 (4.4%) generalized pattern and 2 (2.9%) multifocal pattern. N-SMR: 33.7% patients had epilepsy (first seizure with 1.2±4.5 years). Twenty-three (27.7%) patients had epileptiform discharges, 10 (12.0%) focal pattern, 5 (6.0%) generalized pattern and 8 (9.6%) multifocal pattern. CONCLUSION: The difference between the occurrence of epilepsy in DS and N-SMR was not statistically significant, as well as between normal EEG, EEGs with focal pattern, generalized pattern and multifocal pattern. In SD group 7.4% have shown hypsarrhythmia.The comparison with N-SMR was not possible because none of these has shown this EEG abnormality.