Abstracts

Rationale: In patients with focal epilepsies considered for surgical treatment, the localizing results of EEG-video monitoring and MRI should be congruent. We investigated the occurrence and localization of interictal and ictal epileptiform EEG discharges in patients with lesional focal epilepsies. We also investigated whether the etiology of the lesions had an influence on the EEG results. Methods: We studied 467 patients with MRI documented lesions and focal epilepsies, who had been evaluated at our Epilepsy Monitoring Unit. We included patients with temporal (n=311; 66.6%), frontal (n=73; 15.6%), parieto-occipital (n=43; 9.2%) and central lesions (n=30; 6.4%). 2.1% of the patients had lesions involving 2 or more lobes or the hypothalamus. Results: Patients with central (46.7%) and frontal lesions (17.8%) showed more frequently lack of interictal spiking than patients with temporal (4.2%) or parieto-occipital lesions (7.0%) (p<0.01). Interictal epileptiform discharges (IED) were exclusively found in the lesional lobe in 45.6% of the temporal, 31.3% of the central, 25% of the frontal, and only 5% of the parieto-occipital lesions (p<0.01). Ictal EEG changes in the lesional lobe occurred more commonly in temporal (58%), frontal (43.8%) and central (42.1%) than in parieto-occipital lesions (28.9%) (p<0.05). Only in patients with a temporal lesion did the etiology of the lesion make a difference in the occurrence of IED and seizure patterns. Patients with a cavernoma had significantly more often IED exclusively in the lesional lobe than patients with hippocampal sclerosis (p=0.011), infectious etiology (p=0.006) or unspecific gliosis/defect (p=0.001).