EEG spectral analysis in children with febrile delirium

Febrile delirium is defined as an acute and transient confusional state with high fever. There are very few reports on febrile delirium, although fever is one of the commonest symptoms in children. We previously found a posterior slowing in the electroencephalogram (EEG) of delirious patients with fever. The purpose of this study is to evaluate the features of occipital slow waves by spectral analysis and to find a parameter associated with clinical improvement. Methods: Digital EEG tracings were investigated by Fourier analysis in 20 patients aged from 2 to 13 years. The fast Fourier transform (FFT) was computed for 20 s tracing from the P3-A1 and P4-A2 derivations. The spectral analysis of EEG was repeated in 7 patients. The tracings of 34 control subjects were also analyzed by FFT. EEG of a febrile, nine-year-old girl without delirium was also studied. Results: Febrile delirium was seen during the first three days of fever. The episodes lasted up to 10 min. Four patients showed febrile delirium again after admission but they became conscious a few minutes later. The relative power in the delta frequency band was increased in 65% of patients with preservation of the occipital alpha rhythm. In addition, repeated febrile delirium did not cause worsening of the posterior slowing. The duration of abnormal EEG was only a few days and the decrease of relative power in the delta frequency band was the best parameter of clinical improvement. Posterior slowing was also found in a febrile patient without delirium. Conclusion: Febrile delirious children showed the characteristic clinical and spectral analytical features and the numerical data of EEG facilitate the comparison of the serial findings.