Evaluation of Focal Cortical Dysplasia and Mixed Neuronal and Glial Tumors in Pediatric Epilepsy Patients Using 18F-FDG and 11C-Methionine PET

Focal cortical dysplasia (FCD) and mixed neuronal and glial tumors share many clinical characteristics; therefore, the presurgicaldifferentialdiagnosisofthesediseasesusingMRIisdifficultin somecases.Theaimofthisstudywastodeterminewhether 11Cmethionine PET, compared with 18 F-FDG PET, was useful for the evaluation of these diseases. Methods: The clinical and imaging data of 30 pediatric lesional epilepsy patients pathologically diagnosed with FCD, dysembryoplastic neuroepithelial tumor (DNT), or ganglioglioma were reviewed. Eleven patients had FCD, 8 patients had a DNT, and 11 patients had a ganglioglioma. 18 F-FDG and 11 C-methinine PET scans were obtained from 25 patients and 15 patients, respectively. Visual grading analysis and quantitative assessment of 18 F-FDG and 11 C-methionine PET, represented as a lesion‐to‐gray matter ratio (LGR), were performed. Results: In the visual grading analysis, both 18 F-FDG PET and 11 C-methionine PET detected a significant difference among the 3 disease groups (P 5 0.033 and P 5 0.016, respectively),butdiscrimination ofFCD frommixedneuronaland glial tumors was possible only with 11C-methionine PET. The mean LGR of 18 F-FDG PET was 0.502 6 0.119 for FCD, 0.631 6 0.107 for DNTs, and 0.620 6 0.196 for gangliogliomas; there was no significant difference in LGR among the groups (P 5 0.111). However, the mean LGR of 11 C-methionine PET was 1.078 6 0.182 for FCD, 1.564 6 0.368 for DNT, and 2.114 6 0.723 for gangliogliomas; there was a significant difference in LGR among the groups (P 5 0.014). Post hoc analysis revealed that the LGR of FCD was significantly different from that of DNTs and gangliogliomas. The mean LGR value of DNTs fell between those of FCD and gangliogliomas. Conclusion: Although 18 FFDG plays a major role in the preoperative work-up of epilepsy surgery patients, it appears from this study that 18 F-FDG does not contribute to the differential diagnosis and that another tracer such as 11C-methinine is required. 11C-methinine PET results cor