Relationship between 18F-FDG PET hypometabolism and EEG findings in pediatric focal epilepsy: Visual assessment versus statistical parametric mapping (SPM) and surgical implication

Abstract

Objective: 18 F-FDG PET hypometabolism localizing value in drug resistant pediatric focal epilepsy evaluated by both visual assessment and statistical parametric mapping (SPM). Methods: Interictal 18F-FDG PET scans was performed for 33 pediatric patients with drug resistant focal epilepsy. Brain MRI and interictal epileptiform discharges (IEDs) were analyzed. When the MRI was positive, we only included patients with high concordance between IEDs and MRI findings. To assess the 18F-FDG PET hypometabolic image, an SPM analysis as well as visual interpretation were applied. Results: MRI showed structural lesions in 10 patients and normal findings in 23 subjects. 18F-FDG PET showed a strong correlation with IEDs in 23 patients (69.7%) by visual assessment, especially in MRI positive subjects (100%). The SPM analysis demonstrated a worse correlation with IEDs (39.3%) and it often showed more than one epileptic focus (46.1%). When the visual interpretation was negative even the SPM analysis was negative in both MRI positive and MRI negative patients. 2 patients with MRI positive were undergone to the surgery; both showed a favorable surgical outcome at 1 year of follow up. In these two subjects the visual interpretation showed an excellent correlation with the surgical resection cavity (100%), while the SPM analysis was not concordant in 1 patient and it showed more than one epileptic focus in the other subject. Conclusion: Our results suggested that the analysis of 18F-FDG PET hypometabolism by using visual assessment showed superior localization compared to SPM analysis in pediatric patients with drug resistant focal epilepsy, especially in MRI positive cases. Furthermore, our results suggested the limited usefulness of SPM analysis when the visual assessment showed negative findings.