Long-term EEG monitoring in epilepsy diagnosis

Abstract

EEG long-term monitorings were carried out in 149 patients using a portable 4-channel miniature recorder system. In most cases EEG was recorded for 48 hours. In addition to preceding routine EEG controls, long-term EEG monitoring disclosed epileptic phenomena in 32.7% of patients suspected for epileptic seizures from their history. This gain of information was based mainly on the detection of abnormal potentials or epileptic seizures appearing during sleep. Using EEG long-term recording numerous EEG routine controls could be replaced which otherwise are often necessary for ensuring the diagnosis of epilepsy. If the patient's history, however, gives only poor reason to believe epileptic seizures, positive findings in EEG long-term monitorings are unlikely. Consequently, careful evaluation of the patient's history is crucial for the indication of this laborious examination. As the limited number of recorder channels may cause false negative results, normal findings should be utilized with caution. Only the sum of all clinical and neurophysiological data should be used for exclusion of suspected epilepsy. The second, even more important application of EEG long-term recordings is the special examination of patients with known epilepsy, such as studies of the circadian profiles of epileptic excitability, documentation of seizure frequency, and electrographic analysis of the course of seizure. Therapy control of epileptic patients can be improved by such informations. In view of the large amount of data which results from long-term recordings, computer assisted methods supporting the visual analysis are necessary. In this regard the continuous spectral analysis of the EEG long-term recordings proved to be highly useful.