The sensitivity of (18)F-FDG PET to localize epileptogenic zones in frontal lobe epilepsy was evaluated by both visual assessment and statistical parametric mapping (SPM).
Methods: Twenty-nine patients with frontal lobe epilepsy were examined. All patients showed good outcome after surgical resection (Engel class I or II). On pathologic examination, 22 patients had cortical dysplasia, 4 had tumors, 1 had cortical scars, and 2 had an old infarct. Hypometabolic lesions were found on (18)F-FDG PET images by both visual assessment and SPM analysis. On SPM analysis, the cutoff threshold was varied and sensitivity to find epileptogenic zones was compared.
Results: MRI showed structural lesions in 15 patients and normal findings in 14. (18)F-FDG PET correctly localized the epileptogenic zones in 16 patients (55%) by visual assessment. The sensitivity of (18)F-FDG PET was 36% in patients without structural lesions on MRI and 73% in patients with structural lesions. On SPM analysis, using an uncorrected probability value of 0.005 as the threshold, the sensitivity of SPM analysis was 66%, which was not statistically different from the sensitivity of visual assessment. The sensitivity decreased according to the decrease in probability value.
Conclusion: (18)F-FDG PET was sensitive in localizing epileptogenic zones by revealing hypometabolic areas in nonlesional patients with frontal lobe epilepsy as well as in lesional patients. SPM analysis showed a comparable sensitivity to visual assessment and could be used as an aid in diagnosing epileptogenic zones in frontal lobe epilepsy.