Application of PET/MRI in localization of refractory epilepsy in children

Objective To compare MRI versus PET/MRI in the localization of epileptic foci in children with intractable epilepsy, and further improve the detection of MRI negative cases through PET/MRI. Methods Clinical data about 61 children with intractable epilepsy in Chinese PLA General Hospital from September 2015 to April 2018, including gender, age, age of onset, EEG, MRI, PET/MRI and postoperative pathological results were retrospectively analyzed. According to the localization of EEG, symptoms of clinical seizures, seizure video, MRI and PET/MRI, the possible lesions were judged, and the presence of the epileptic foci was further confirmed by the surgical and pathological results. Results There were 61 children with intractable epilepsy, including 32 males and 29 females, with male to female ratio of 1.1∶ 1. The average age of onset was (6.45±3.04) months in male, and(7.21±3.44) months in female, with no significant difference. Abnormal discharges of EEG in 61 children were found. In MR imaging of brain, 28 lesions were found with the positive rate of 45.9%. All cases had ¹⁸F-FDG PET/MRI imaging in the interictal period of epileptic seizures and the lesions were all with low metabolism, including 17 cases of single focus and 44 cases of multiple foci. Among the 33 cases with negative MRI, single hypermetabolic focus was found in 10 cases and multiple hypermetabolic foci in 23 cases (69.7%); of the 28 children with positive MRI, PET/MRI imaging showed that 7 cases had single hypermetabolic focus, 21 cases (75.0%) had multiple hypermetabolic foci. Multifocal abnormalities were much more detected by PET/MRI imaging than MRI (χ²=7.50, P=0.006). Of the 61 children, 19 (31.1%) cases underwent surgery, including 7 cases undergoing dissection, 10 cases undergoing epileptogenic resection, and 2 cases undergoing thermal coagulation. Of the 10 cases with surgical excision, 1 case (10.0%) was diagnosed as centralneurocytoma by pathological result, 1 (10.0%) case was left temporal cysts and 8 (80.0%)cases were reported to be focal cortical dysplasia. Of the 19 cases, surgical location in 16 (84.2%) children were consistent with the preoperative localization results. The follow-up lasted for 6 to 24 months, 2 (10.5%) cases recurred at 6 months after operation, including 1 case undergoing hemispherical dissection and 1 case with anterior resection of corpus callosum and left frontal cortex thermocautery, but the seizure frequency decreased by 50%. The other 17 cases had no recurrence. Conclusion The detection rate of intractable epilepsy by MRI brain imaging is 45.9% in children. For MRI-negative cases, PET/MRI can significantly improve the detection of the focus, by showing metabolism decrease in multiple foci, with high safety and small radiation, which is especially suitable for children. If there exists any surgical indications, surgical resection is a favorable option for children with intractable epilepsy.