Interictal electroencephalogram: sensibility in the diagnosis of epileptic seizures in childhood

Abstract

INTRODUCTION: It is currently estimated that more than 10 million children all over the world have epilepsy and the EEG is the most commonly used diagnostic test in the investigation of these patients. The aim of this study was to analyze the sensibility of the EEG in revealing abnormalities in children with the clinical hypothesis of an epileptic seizure. METHODS: Out of 970 EEGs obtained between April 2005 and August 2006 at Pequeno Príncipe Children's Hospital, Curitiba, PR, Brazil, 692 fit the criteria proposed (clinical hypothesis of an epileptic seizure after the evaluation of a pediatric neurologist). All EEGs were recorded digitally, with minimal duration of 20 minutes and electrodes positioned according to the International System 10-20. Neonates were excluded. RESULTS: Age ranged from 30 days to 16.5 years (mean of 6.4 years and median of 4.1 years), 403 were female (58.2%). Out of the 692 EEG included in the study, 281 (40.6%) yielded abnormal results, 96 (34.2%) with abnormalities of the background activity (disorganization and/or asymmetry) and 185 (65.8%) with epileptiform paroxysms. The sensibility of the EEG was 40.6%. Sharpe wave occurred in 77 cases (41.6%), spike in 21 (11.4%), polispike in 14 (7.6%), spike-wave in 17 (9.2%), polispike-wave in 24 (13.0%) and exams with discharges of more than one morphology in 32 (17.3%). CONCLUSION: Our data strengthen the concept that even though the diagnosis of epilepsy is clinical and based on the semiological description of the epileptic crisis, the EEG has a good sensibility when properly indicated.