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Dipole Localization for Identification of Neuronal Generators in Independent Neighboring Interictal EEG Spike Foci
Author(s) -
Ochi Ayako,
Otsubo Hiroshi,
Chitoku Shiro,
Hunjan Amrita,
Sharma Rohit,
Rutka James T.,
Chuang Sylvester H.,
Kamijo Kenichi,
Yamazaki Toshimasa,
Snead O. Carter
Publication year - 2001
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1046/j.1528-1157.2001.27000.x
Subject(s) - ictal , dipole , electroencephalography , scalp , electrocorticography , epilepsy , epilepsy surgery , magnetic resonance imaging , nuclear magnetic resonance , neuroscience , physics , psychology , medicine , anatomy , radiology , quantum mechanics
Summary: Purpose: We evaluated dipole localizations of independent neighboring interictal spike foci using scalp electroencephalogram (EEG) to identify neuronal generators of epileptic discharges. Methods: Three pediatric patients with extratemporal lobe epilepsy who had two independent neighboring interictal spike foci on scalp EEG were studied. Prolonged video EEG was digitally recorded from 19 scalp electrodes, whose positions were registered using a three‐dimensional digitizer. Interictal spikes were visually selected based on negative phase reversals on bipolar montages. We analyzed the dipole position and moment of each spike using a single moving dipole and three‐shell spherical head model. The dipoles were overlaid onto magnetic resonance (MR) images and divided into two groups based on two spike foci. Results: The dipoles of the two groups were oriented either tangentially or radially to the scalp in close proximity to each other. The dipoles oriented radially were located underneath the electrode with a negative peak; those oriented tangentially were between electrodes with a negative and positive peak. The positions of tangential dipoles were more concentrated than those of radial dipoles. The epileptogenic regions corresponded to the dipole localizations. Surgical excisions were performed based on the results of electrocorticography. After surgery, two patients were seizure free, and one had rare seizures (follow‐up period, 13–31 months). Conclusions: We showed that dipoles in close proximity but with different orientations projected two negative maxima on scalp EEG in three patients with extratemporal localization‐related epilepsy. Equivalent current dipole analysis of individual interictal spikes can provide useful information about the epileptogenic zone in these patients.