from Electroencephalographic (EEG) and

Long-term scalp video-electroencephalographic (EEG) studies of patients with medically refractory localization-related epilepsy demonstrate that lateralized interictal discharges correlate with good surgical outcomes.1–3 Even patients with bilateral or multilobar interictal discharges might be candidates for surgical seizure con-trol when they have a single ictal onset zone in a primary epilep-togenic hemisphere,4 that is, a hemisphere that includes an epilep-togenic zone. In localization-related epilepsy, seizures originate from a focal area in an epileptic network and propagate secondarily through anatomic and functional networks.5 Interictal epileptiform dis-charges that vary in location and appearance on scalp EEG and mag-netoencephalography reflect these propagations.4 EEG and magnetoencephalographic dipole analyses reveal the variability by quantifying the interictal epileptiform discharges and by localizing their sources in the brain. Equivalent current dipole analyses suc-cessfully delineate epileptogenic regions for surgical excision in pediatric patients with localization-related epilepsy.6–11 Since EEG and magnetoencephalographic dipole analyses visualize the ori-entations, phases, and extents of epileptic discharges differently, the data from these two diagnostic modalities can be used com-plementarily.10 Combining information from the two methods might further clarify the propagation of interictal epileptiform discharges within abnormal neural networks