Do clinical variables predict an abnormal EEG in patients with complex febrile seizures?

PURPOSE Febrile seizures are the commonest convulsive event in children younger than 5 years of age (incidence of 2-5%). Electroencephalography (EEG) is not indicated in the work up of simple febrile seizures. Information about its role in the assessment of complex febrile seizures (CFSs) is unclear and EEGs are frequently ordered. This study was designed to assess utility of clinical variables at presentation in predicting the likelihood of an abnormal EEG. METHODS EEG requisitions, EEG reports, clinic charts and medical records over an 11-year period (1990--2001) were retrospectively reviewed. The relationship between clinical variables like age, timing of the EEG since CFS, family history of seizures, neurological assessment and EEG abnormalities was statistically analyzed. RESULTS One hundred and seventy-five children were included in the study. Of these 39.43% had EEG abnormalities. Children with a normal EEG were younger than those with an abnormal EEG (mean age 15.72 months versus 19.75 months, p<0.05). Using multivariate analysis, factors predictive of abnormal EEGs in children with CFS were; age >3 years (p=0.010; 95% CI: 1.5--18.8), EEGs performed within 7 days (p=0.00; 95% CI: 1.78--7.12) and an abnormal neurological exam (p=0.053; 95% CI: 0.98--16.9). A family history of febrile seizures was more likely to be associated with a normal EEG (p=0.01; 95% CI: 0.04--0.60). CONCLUSIONS Clinical variables at presentation can be used to screen children with CFS for whom an EEG is considered. This may lead to better use of resources. Whether abnormal EEG translates to future recurrences or epilepsy needs a prospective study.