18f-fdg Pet/mr in Focal Epilepsy: a New Step for Improving the Detection of Epileptogenic Lesions

Abstract Purpose: Hybrid PET/MR is a promising tool in focal drug-resistant epilepsy, however the additional value for the detection of epileptogenic lesions and surgical decision-making remains to be established.Methods: We retrospectively compared 18F-FDG PET/MR images with those obtained by a previous 18F-FDG PET co-registered with MRI (PET+MR) in 25 consecutive patients (16 females, 13-60 year-old) investigated for focal drug-resistant epilepsy. Visual analysis was performed by two readers blinded from imaging modalities, asked to assess the technical characteristics (co-registration, quality of images), confidence in results, location of PET abnormalities and presence of a structural lesion on MRI. The clinical impact on surgical strategy and outcome was assessed independently.Results: The location of epilepsy was temporal in 9 patients and extra-temporal in 16 others. MRI was initially considered negative in 21 of them. PET alone demonstrated metabolic abnormalities in 19 cases (76%), and the co-registration with MRI allowed the detection of 4 additional structural lesions. PET/MR was considered better performing than PET+MR in 56% of patients. The increase in sensitivity was 13% and new structural lesions (mainly focal cortical dysplasias) were detected in 6 patients (24%). Change of surgical decision-making was substantial for 40% of patients, consisting in avoiding invasive monitoring in 6 patients and modifying the planning in 4 others. Seizure-free outcome was obtained in 13/14 patients who underwent a cortical resection.Conclusion: Hybrid PET/MR improves the detection of epileptogenic lesions, allowing to optimize the presurgical work-up and to increase the proportion of successful surgery even in the more complex cases.