F-FDG PET/MR in focal epilepsy: A new step for improving the detection of epileptogenic lesions.

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 F-FDG PET/MR images with those obtained by a previous F-FDG PET co-registered with MRI (PET+MR) in 25 consecutive patients (16 females, 13-60 years) 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), the confidence in results, the location of PET abnormalities and the presence of a structural lesion on MRI. Clinical impact on surgical strategy and outcome was assessed independently.

RESULTS

The location of epileptic focus was temporal in 9 patients and extra-temporal in 16 others. MRI was initially considered negative in 21 patients. PET stand-alone demonstrated metabolic abnormalities in 19 cases (76%), and the co-registration with MRI allowed the detection of 4 additional structural lesions. Compared to PET+MR, the PET/MR sensitivity was increased by 13% and new structural lesions (mainly focal cortical dysplasias) were detected in 6 patients (24%). Change of surgical decision-making was substantial for 10 patients (40%), consisting in avoiding invasive monitoring in 6 patients and modifying the planning in 4 others. Seizure-free outcome (follow-up>1 year) was obtained in 12/14 patients who underwent a cortical resection.

CONCLUSION

Hybrid PET/MR may improve 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.