Abstracts

To assess the localization value of interictal F-18-FDG PET and Subtraction Ictal SPECT Coregistered with MRI (SISCOM, 99 Tc-ECD) in correctly determining the ictal EEG onset zone and the epileptogenic focus in patients with complicated intractable partial epilepsy. The study consists of consecutive patients who had both PET and SISCOM because their seizures were not localized sufficiently with MRI and noninvasive video-EEG recording. Localization of PET and SISCOM was determined by two nuclear medicine specialists who were blind to other data. The locations of PET and SISCOM foci were compared with that of intracranial ictal EEG focus. We also determined the association between resection of the foci and post-surgical seizure improvement (excellent or favorable outcome; mean follow up of 17.4 months). Thirty-four patients (17 male, 17 female, mean age 26.8, range 0-50 years) were identified. Twenty-one (62%) had concordant PET and SISCOM localization (PET/SISCOM focus). Sixteen of these 21 patients (76%) had intracranial EEG recordings. Eleven out of these 16 patients (69%) had concordant intracranial ictal EEG onset. Surgical resection of the PET/SISCOM/EEG site in 9 of the 11 patients resulted in seizure improvement in 8 (89%). On the other hand, the two patients whose surgical resection did not involve the PET/SISCOM/EEG site had no improvement (P=0.05).
Thirteen of 34 patients (38%) had SISCOM and PET localizations that were discordant with each other. Although 12 had intracranial EEG recordings, only 5 (42%) had intracranial seizures with localized onset. Co-localization of PET and SISCOM highly predicts the location of ictal EEG onset zone. The probability of seizure improvement is very high when the region localized by PET, SISCOM and intracranial EEG is resected in patients with complicated intractable epilepsy. (Supported by Mayo Fundation for Research and Education.)