Abstracts

Rationale: Frontal lobe epilepsies are often difficult to treat and many patients are candidates for epilepsy surgery. The absence of a structurally visible MRI lesion can challenge the presurgical evaluation, especially if other diagnostic methods also fail to clearly localize a seizure focus. We investigate the value of cognitive fMRI to identify dysfunctional cortex in these patients. Methods: In an ongoing study we examined nine patients with non-lesional frontal lobe epilepsy and 15 healthy controls. Subjects had to perform a set of frontal lobe fMRI tasks, including verbal fluency, verb generation, spatial and verbal working memory. fMRI images were acquired on a 3T Scanner, using a whole brain acquisition of 50 slices, 2.5 mm slice thickness and a TR of 2.5 sec. fMRI analysis was carried out using SPM 5 software. Results: Four patients showed normal cortical activation patterns in all cognitive tasks. Three patients showed reduced activation in both working memory paradigms, four patients had a atypical language dominance. In two patients one frontal lobe (one left, one right) failed to activate in any of the four cognitive tasks, whilst other areas activated normally. In both patients seizure semiology was not lateralizing and EEG showed bilateral findings, whereas fMRI was clearly lateralising and indicated dysfunction of structurally normal frontal lobes. Conclusions: In patients with non-lesional focal epilepsy, fMRI with a comprehensive set of cognitive tasks can help to localize cortical dysfunction. This can therefore guide further presurgical evaluation, including the Implantation of invasive electrodes.