Peri-orbital electrodes as a supplemental recording for detection of ictal discharges in medial temporal lobe epilepsy

Objective: The feasibility of peri-orbital electrodes, which are not invasive and do not induce pain, as a supplemental electrode for detection of ictal discharges in medial temporal lobe epilepsy (MTLE) was examined. Methods: Patients with MTLE, who underwent video-EEG monitoring with simultaneous peri-orbital and sphenoidal electrodes and obtained good outcome following standard anterior temporal lobectomy, were subjects in this study. Initial ictal discharge amplitudes were compared between sphenoidal (Sp1/ 2), standard anterior temporal in 10-20 system (F7/ 8), peri-orbital (superior orbital lateral: SOL, inferior orbital medial: IOM), frontopolar (Fp1/ 2), frontal (F3/4) and ear (A1/ 2) electrodes. Results: A total of 34 consecutive seizures from 20 patients were analyzed, with a maximum amplitude observed at Sp1/2 (57.57±5.59), followed by F7/8 (54.89±5.59), SOL (50.97±5.59), IOM (46.95±5.59), A1/2 (45.07±5.69), Fp1/2 (44.78±5.62), and F3/4 (37.75±5.66) (mean±standard error, μV). There was no statistical difference between Sp1/2, F7/8, SOL, and IOM values. When the sphenoidal electrode was omitted, 13 seizures (13/34, 38.2%) resulted in the highest amplitude at peri-orbital electrodes and 10 seizures (10/ 34, 29.4%) at F7/8. Conclusions: Peri-orbital electrodes could detect ictal discharges in MTLE as well as sphenoidal and standard anterior temporal electrodes in 10-20 system and are useful for supplemental recording for detecting ictal epileptiform discharges in MTLE.

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