Comparison of high gamma electrocorticography and fMRI with electrocortical stimulation for localization of somatosensory and language cortex.
OBJECTIVE
We investigated the contribution of electrocortical stimulation (ECS), induced high gamma electrocorticography (hgECoG) and functional magnetic resonance imaging (fMRI) for the localization of somatosensory and language cortex.


METHODS
23 Epileptic patients with subdural electrodes underwent a protocol of somatosensory stimulation and/or an auditory semantic decision task. 14 Patients did the same protocol with fMRI prior to implantation.


RESULTS
ECS resulted in the identification of thumb somatosensory cortex in 12/16 patients. Taking ECS as a gold standard, hgECoG and fMRI identified 53.6/33% of true positive and 4/12% of false positive contacts, respectively. The hgECoG false positive sites were all found in the hand area of the post-central gyrus. ECS localized language-related sites in 7/12 patients with hgECoG and fMRI showing 50/64% of true positive and 8/23% of false positive contacts, respectively. All but one of the hgECoG/fMRI false positive contacts were located in plausible language areas. Four patients showed post-surgical impairments: the resection included the sites positively indicated by ECS, hgECoG and fMRI in 3 patients and a positive hgECoG site in one patient.


CONCLUSIONS
HgECoG and fMRI provide additional localization information in patients who cannot sufficiently collaborate during ECS.


CONCLUSIONS
HgECoG and fMRI make the cortical mapping procedure more flexible not only by identifying priority cortical sites for ECS or when ECS is not feasible, but also when ECS does not provide any result.
Department of Neurology and Fundamental Neurosciences, Geneva University Hospitals, Switzerland.
M
M
Genetti
Department of Neurology and Fundamental Neurosciences, Geneva University Hospitals, Switzerland.
R
R
Tyrand
Department of Radiology and Medical Informatics, Geneva University Hospitals, Switzerland.
F
F
Grouiller
Department of Neurology, Geneva University Hospitals, Switzerland.
A M
AM
Lascano
Department of Neurology, Geneva University Hospitals, Switzerland.
S
S
Vulliemoz
Department of Neurology, Geneva University Hospitals, Switzerland.
L
L
Spinelli
Department of Neurology, Geneva University Hospitals, Switzerland.
M
M
Seeck
Department of Neurosurgery, Geneva University Hospitals, Switzerland.
K
K
Schaller
Department of Neurology and Fundamental Neurosciences, Geneva University Hospitals, Switzerland. Electronic address: christoph.michel@unige.ch.
C M
CM
Michel
D000161:Acoustic Stimulation / Q000379:methods; D000293:Adolescent; D000328:Adult; D001931:Brain Mapping / Q000379:methods*; D002648:Child; D002675:Child, Preschool; D004558:Electric Stimulation / Q000379:methods; D004567:Electrodes, Implanted; D004569:Electroencephalography / Q000379:methods; D004827:Epilepsy / Q000175:diagnosis / Q000503:physiopathology; D005260:Female; D065818:Gamma Rhythm / Q000502:physiology*; D006801:Humans; D007802:Language; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D013003:Somatosensory Cortex / Q000502:physiology*; D055815:Young Adult
ECS; ECoG; Language; Presurgical mapping; Somatosensory; fMRI