Electrical source imaging for presurgical focus localization in epilepsy patients with normal MRI.
OBJECTIVE
Patients with magnetic resonance (MR)-negative focal epilepsy (MRN-E) have less favorable surgical outcomes (between 40% and 70%) compared to those in whom an MRI lesion guides the site of surgical intervention (60-90%). Patients with extratemporal MRN-E have the worst outcome (around 50% chance of seizure freedom). We studied whether electroencephalography (EEG) source imaging (ESI) of interictal epileptic activity can contribute to the identification of the epileptic focus in patients with normal MRI.


METHODS
We carried out ESI in 10 operated patients with nonlesional MRI and a postsurgical follow-up of at least 1 year. Five of the 10 patients had extratemporal lobe epilepsy. Evaluation comprised surface and intracranial EEG monitoring of ictal and interictal events, structural MRI, [(18)F]fluorodeoxyglucose positron emission tomography (FDG-PET), ictal and interictal perfusion single photon emission computed tomography (SPECT) scans. Eight of the 10 patients also underwent intracranial monitoring.


RESULTS
ESI correctly localized the epileptic focus within the resection margins in 8 of 10 patients, 9 of whom experienced favorable postsurgical outcomes.


CONCLUSIONS
The results highlight the diagnostic value of ESI and encourage broadening its application to patients with MRN-E. If the surface EEG contains fairly localized spikes, ESI contributes to the presurgical decision process.
Brodbeck
Verena
V
Functional Brain Mapping Laboratory, 4 Rue Gabrielle-Perret-Gentil, Geneva, Switzerland. verena.brodbeck@unige.ch
Spinelli
Laurent
L
Lascano
Agustina M
AM
Pollo
Claudio
C
Schaller
Karl
K
Vargas
Maria I
MI
Wissmeyer
Michael
M
Michel
Christoph M
CM
Seeck
Margitta
M
D000293:Adolescent; D000328:Adult; D038481:Anterior Temporal Lobectomy; D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000503:physiopathology / Q000601:surgery; D002648:Child; D002675:Child, Preschool; D004292:Dominance, Cerebral / Q000502:physiology; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery*; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D005625:Frontal Lobe / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D049268:Positron-Emission Tomography; D015899:Tomography, Emission-Computed, Single-Photon; D014057:Tomography, X-Ray Computed; D055815:Young Adult