J Korean Epilepsy Soc.  2001 Dec;5(2):137-141.

Usefulness of Sphenoidal Electrodes for Localization of Temporal Lobe Seizure Focus : Ictal EEG

  • 1Department of Neurology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea. salee@amc.seoul.kr
  • 2Department of Neurosurgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.


PURPOSE: Usefulness of sphenoidal electrodes for detecting mesial temporal seizure foci remains controversial. Our aim is to determine whether sphenoidal electrodes are superior to surface electrodes for EEG localization in patients with mesial temporal lobe epilepsy (TLE). METHODS: We retrospectively reviewed ictal EEGs recorded simultaneously with standard International 10-20 System, subtemporal and sphenoidal electrodes in 92 patients who underwent temporal lobectomy. Patients were divided into mesial (n=67) and neocortical (n=25) TLE. Ictal EEGs were reviewed in a blinded fashion in both longitudinal bipolar and Pz referential montages. RESULTS: Thirty four (13.1%) of 259 mesial temporal seizures were exclusively isolated to sphenoidal electrode at least 3 seconds before involvement of subtemporal electrodes or were localized to temporal lobe on sphenoidal electrode when scalp electrode failed to localize seizure onset, whereas only 2 (2.6%) of 75 neocortical temporal seizures were (p<0.05). The usefulness of sphenoidal electrode was related to the distribution but not the frequency of ictal onset on scalp EEG. CONCLUSIONS: Although isolated or localized sphenoidal seizure onset in patients with mesial TLE are not frequent, sphenoidal electrodes are superior to scalp electrodes for the localization of mesial temporal seizure foci.


Temporal lobe epilepsy; Ictal EEG; Sphenoidal electrodes; Scalp electrodes
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