The localizing yield of sphenoidal and anterior temporal electrodes in ictal recordings: a comparison study

PURPOSE: To compare the localizing yield of sphenoidal electrodes placed under fluoroscopic guidance (SEs) and anterior temporal electrodes (ATEs) in ictal recordings from a group of patients with seizure disorders of anterior temporal origin. METHODS: We compared ictal recordings of 156 seizures obtained with SEs and ATEs from 40 consecutive patients with seizures of anterior temporal origin. Four electroencephalographers reviewed ictal recordings independently and blind to the patients' identity, presurgical data, and inclusion of ATEs or SEs. Outcome variables included (a) number of correctly localized seizures with SE and ATE recordings by at least three raters; (b) number of ictal foci in which all seizures were localized only with SEs; and (c) number of seizures in which SEs identified the ictal onset > or =5 s earlier than ATEs. RESULTS: Interrater agreement among the four raters was significantly greater with SE than with ATE recordings (p < 0.0001). The number of seizures correctly localized was significantly greater with SEs (n = 144) than with ATEs (n = 99; p < 0.0001). All the seizures [n = 36 (23%)] originating from 14 ictal foci (29%) in 11 patients (27.5%) were localized only with SEs. Finally, the ictal onset was detected at SEs > or =5 s earlier than at ATEs in 67 (43%) seizures originating from 33 (69%) foci in 30 (75%) patients. CONCLUSIONS: SEs improve interrater agreement in the localization of seizures of anterior temporal origin, and in about one fourth of patients, SEs add ictal data not identified by ATEs.