[18F]FDG PET/MRI in Pediatric Focal Epilepsies

: We hypothesized that [18F]FDG PET/MRI would improve presurgical lesion detection compared with MRI alone in pediatric patients with focal epilepsy. We analyzed surgical outcomes and the presurgical evaluation pipeline. Methods: We included pediatric patients undergoing [18F]FDG PET/MRI between January 2017 and October 2021. Eligible patients were 18 y or younger, had a diagnosis of focal epilepsy under surgical evaluation, and had a negative or inconclusive MRI result. Data analysis phases included evaluation of prior MRI data (phase 0), masked review of PET/MRI-acquired MR sequences (phase 1), joint (nuclear medicine/neuroradiology) PET/MRI assessment (phase 2), and verification of PET/MRI findings against the hypothesized epileptogenic zone (EZ) (through electroencephalography in all cases; through stereoelectroencephalography outcomes and histology when relevant) (phase 3). Results: Seventy-nine patients were included in the study (49 male; mean age, 9.5 y). Patients' mean duration of epilepsy was 4.4 y, and 65 (83%) had drug-resistant seizures. Initial MRI results were inconclusive in 26 (33%) patients and negative in 53 (67%) patients. Blinded 3-T MRI identified suspect lesions in 36 (46%) patients, identifying additional lesions in 10 patients. Joint PET/MRI reading revealed that 46 (58%) patients had concordant PET-positive/MRI-positive results, 24 (30%) had PET-positive/MRI-negative results, and 8(10%) had PET-negative/MRI-negative results. Concordant PET-positive/MRI-positive findings demonstrated high accuracy in identifying epileptogenic lesions, particularly focal cortical dysplasia. PET/MRI showed metabolic alterations in 70 (89%) patients: 67 of 70 (96%) with hypometabolism and 6 of 70 (9%) with mixed areas of hypometabolism and hypermetabolism. The results were concordant with the electroclinical hypothesis in 45 (98%) of 46 patients with PET-positive/MRI-positive results and in 15 (63%) of 24 patients with PET-positive/MRI-negative results. Twenty-four patients underwent resection or disconnection, and 5 underwent thermocoagulation. Of these, 22 (76%) achieved Engel Class IA outcomes (average follow-up, 2.1 y). Conclusion: [18F]FDG PET/MRI offered significant diagnostic and prognostic value, especially in MRI-negative or inconclusive cases, enhancing presurgical evaluation precision and guiding clinical decision-making in pediatric epilepsy surgery.