Whole-head MEG in presurgical epilepsy evaluation

We report combined scalp-EEG and MEG recordings using a 143 channel whole-head MEG system during the presurgical evaluation of patients suffering from medically refractory mesial temporal lobe epilepsy (MTLE). We applied dipole modeling techniques to calculate the three-dimensional intracerebral location and orientation of the neuronal sources underlying the interictal epileptic spike complexes. The dipoles could be localized to the temporal lobes in all patients with both techniques. On EEG, dipoles were oriented oblique with their positive poles pointing in the superior, posterior and medial direction in all patients. On MEG horizontal dipoles with their positive poles pointing posterior and vertical dipoles with their positive poles oriented superior were observed. We conclude that EEG/MEG dipole modeling is useful to study the functional organization of the irritative zone in MTLE non-invasively.