Source localization of scalp-EEG interictal spikes in posterior cortex epilepsies investigated by HR-EEG and SEEG.
OBJECTIVE
To determine the validity of scalp-electroencephalography (EEG)-interictal spike (IIS) source localization in posterior cortex epilepsies (PCE).


METHODS
Eleven patients with drug-resistant PCE were studied with high-resolution EEG (HR-EEG) and stereoelectroencephalography (SEEG). Sixty-four scalp channels, a realistic head model, and different algorithms [multiple signal classification (MUSIC) and equivalent current dipoles] were used. Results were compared to intracerebral SEEG recordings. For SEEG, a semiautomatic detection of intracerebral IIS was used, allowing a classification of intracerebral IIS into one of three groups: Medial, lateral, and mediolateral.


RESULTS
In the medial group (two patients), scalp-EEG IIS were usually absent for one patient whereas for the other, scalp-EEG was misleading. Indeed, scalp-EEG IIS had a posterior projection, predominantly contralateral to the source. In the lateral group (two patients), scalp-EEG IIS were subcontinuous and accurately localized. In the mediolateral group (seven patients), intracerebral interictal distribution was complex and bilateral for four of seven patients. Source localizations were able to determine only a part, whether lateral or medial, of the intracerebral interictal distribution.


CONCLUSIONS
The accuracy of scalp-EEG IIS source localization is dependant on the type of intracerebral interictal distribution. In the most frequent type of PCE, patients proved to have a complex interictal distribution between both medial and lateral cortices, and source localizations always underestimated intracerebral IIS. In cases where intracranial sources were quite focal, surface EEG sources were localized with accuracy, even in medial occipital lobe structures.
Gavaret
Martine
M
INSERM UMR 751, Laboratoire de Neurophysiologie et Neuropsychologie, Marseille, France. martine.gavaret@ap-hm.fr
Trébuchon
Agnès
A
Bartolomei
Fabrice
F
Marquis
Patrick
P
McGonigal
Aileen
A
Wendling
Fabrice
F
Regis
Jean
J
Badier
Jean-Michel
JM
Chauvel
Patrick
P
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D004292:Dominance, Cerebral / Q000502:physiology; D004569:Electroencephalography / Q000379:methods*; D004828:Epilepsies, Partial / Q000503:physiopathology* / Q000601:surgery; D005260:Female; D005911:Gliosis / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D054220:Malformations of Cortical Development / Q000175:diagnosis / Q000503:physiopathology / Q000601:surgery; D008875:Middle Aged; D009778:Occipital Lobe / Q000503:physiopathology* / Q000601:surgery; D010296:Parietal Lobe / Q000503:physiopathology* / Q000601:surgery; D012815:Signal Processing, Computer-Assisted; D055815:Young Adult