Abstracts

A bilateral representation of the epileptic disturbance, a widespread unilateral distribution of the interictal spiking, or its absence, represent significant limiting factors of EEG localization in extratemporal epilepsy (ETE). We studied the localizing effectiveness of MEG in ETE and compared it with the EEG and MRI results.
22 patients (9 females, mean age: 24 years) with ETE underwent EEG, MEG (148 channels) and 3D-MRI (1,5 and 3 Tesla). The anatomical distribution of the epileptogenic area/lesion was: Frontal (F): 14, Central (C): 3, Parietal (P): 4 and Insular (I): 1 patients. Ten patients had MRI lesions (7F, 2C and 1P).
7/22 (32%) patients presented with bilateral epileptiform EEG discharges (6F and 1 P). In 5 of them (71.4%), MEG provided a correct lateralization.
4/22 (18%) patients (3F and 1P), showed widespread unilateral EEG spiking. MEG accuratly localized the epileptic activity in all of them.
5/22 patients (23%) presented with normal EEGs. MEG demonstrated localized/lateralized epileptiform activity in all of them.
In 3/22 patients (13.5%), MEG improved the EEG localization or corrected the EEG lateralization in regards to the MRI lesion.
In the remaining 3/22 patients (13,5%) the MEG and EEG findings colocalized in the same brain region.
MEG and neuroimaging findings were concordant in all 10 patients with MRI lesions.
While EEG achieved proper localization of the epileptogenic area in 7/22 patients with ETE (31,8%), MEG reliably localized the epileptogenic area in 20/22 of them (90%). Concordance of MEG-MRI findings was seen in all patients with structural lesions.
Our results show that MEG provides a better localization of the epileptic abnormality in ETE as compared to EEG.