Interictal EEG coherence in patients with partial temporal lobe epilepsy

Aims. The purpose of this research was to study the spatio-temporal characteristics of the correlation that exists between two simultaneous EEG signals (coherence) in the interictal period inpatients with partial epilepsy that is presumably symptomatic of the temporal lobe (ILAE). Patients and methods. A study of 13 patients, aged between 17-60 years, was conducted (53% females). A digital EEG was performed on each patient using the 10120 system of electrode location. 24 artifact-free segments were selected from the recording made in a rest-waking state with the patient's eyes closed. Fourier's transformation was employed to obtain cross spectrum matrices, which were then used to calculate the intrahemispheric(Cohintra) and interhemispheric (Cohinter) coherences expressed by the Z transformation. These values were ordered by regions considering the known anatomical connections. Results. In both the overall and the individual analyses, we found greater alterations of the Cohintra and the Cohinter in the temporal regions, and there was a predominance of the left hemisphere. The individual analysis of coherence, unlike the visual interpretation of the EEG recording, showed significant alterations in all the patients in the sample. Conclusions. Incorporating this type of tool would enable us to reach a more accurate topographic diagnosis in cases of epilepsy of unknown aetiology. At the same time the possible means of medical and surgical treatment available would be widened.