Interictal spike dipole estimation by MEG: Comparison with direct cortical recording by implanted grid electrodes

Interictal MEG dipoles associated with temporal lobe epilepsy (TLE) can be classified according to localization and orientation into anterior temporal horizontal (ATH), anterior temporal vertical and posterior temporal vertical (PTV) dipoles [1, 2, 3]. The MEG dipole pattern may be related to the seizure onset zone [2, 3] or symptomatology [4]. These dipoles are considered to originate from the temporal tip, superior temporal plane and basal temporal cortex [1]. The scalp EEG/MEG dipole is the summation of cortical activity over a wide area because extensive epileptic activity is required to produce adequate electrical potentials/magnetic fields detectable through the skull and scalp [1, 5]. Little is known about the relationship between actual cortical activities and MEG findings [6]. This study estimated interictal spike dipoles by MEG for comparison with electrocorticography (ECoG) findings.