Localization of epileptic auras induced on stimulation by subdural electrodes.
OBJECTIVE
This study evaluates the localization of stimulation-induced auras (SIA) and tries to determine whether the SIA can help to define the boundaries of resection in epilepsy surgery.


METHODS
Using subdural grid electrodes, 31 patients with drug resistant focal epilepsy were examined in a retrospective and prospective study lasting 2 years.


RESULTS
On stimulation by subdural electrodes, we elicited habitual auras in 16 patients (52%). The zone of SIA overlapped the epileptogenic lesion in 12 patients (75%), the EEG seizure onset zone in 12 patients (75%), and the irritative zone of interictal spikes in eight patients (50%). Postoperative results showed a significant correlation with the complete removal of the epileptogenic lesion (p < 0.001). Because the number of patients in the study was small, we could not find a significant correlation with the complete removal of the SIA zone, EEG seizure onset zone, and irritative zone.


CONCLUSIONS
Our study confirms previous analyses which indicate that complete resection of the epileptogenic lesion is essential to achieve a good outcome. Frequent overlap of the SIA zone with the epileptogenic lesion and the EEG seizure onset zone indicates proximity of the SIA with the epileptogenic zone. Nevertheless, this study does not support the concept that the SIA zone and the EEG seizure onset zone have additional value in defining the boundaries of resection in epilepsy surgery. Three case presentations suggest that SIA result from facilitated pathways between the stimulated cortex, the epileptogenic zone around the lesion, and the symptomatogenic zone. Functional reorganization in the vicinity of the cortical lesion cannot be ruled out but was not seen in our patients. Thus, SIA often do not reflect the normal function of the stimulated underlying cortex.
Schulz
R
R
Mara gGmbH, Epilepsiezentrum Bethel, Klinikum Grosshadern, München, Germany.
Lüders
H O
HO
Tuxhorn
I
I
Ebner
A
A
Holthausen
H
H
Hoppe
M
M
Noachtar
S
S
Pannek
H
H
May
T
T
Wolf
P
P
D000293:Adolescent; D000328:Adult; D002540:Cerebral Cortex / Q000503:physiopathology* / Q000601:surgery; D002648:Child; D004558:Electric Stimulation; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods / Q000706:statistics & numerical data*; D004828:Epilepsies, Partial / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012189:Retrospective Studies; D013355:Subdural Space; D016896:Treatment Outcome