Temporal and extratemporal BOLD responses to temporal lobe interictal spikes.
OBJECTIVE
Simultaneous EEG and functional MRI (fMRI) allows measuring metabolic changes related to interictal spikes. Our objective was to investigate blood oxygenation level-dependent (BOLD) responses to temporal lobe (TL) spikes by using EEG-fMRI recording.


METHODS
We studied 35 patients who had a diagnosis of temporal lobe epilepsy (TLE) and active TL spiking on routine scalp EEG recording. Two-hour sessions of continuous EEG-fMRI were recorded, and spikes were identified after offline artifact removal and used as events in the fMRI analysis. Each type of spike was analyzed separately, as one EEG-fMRI study. We determined significant (p < 0.05) positive (activation) and negative (deactivation) BOLD responses for each study.


RESULTS
Twenty-seven patients had spikes during scanning (19 unilateral and eight bilateral). From a total of 35 fMRI studies, 29 (83%) showed BOLD responses: 14 had both activations and deactivations; 12, activations only; and three, deactivations only. Six (17%) showed no responses. Nineteen studies had mainly neocortical TL activation: Sixteen (84%) of 19 concordant with spikes, 12 of 16 with concomitant activation of the contralateral TL, and 16 of 19 with additional extratemporal activation; few showed exclusively mesial TL activation. Seventeen studies showed deactivation, either extratemporal plus temporal (n = 8) or exclusively extratemporal (n = 9).


CONCLUSIONS
BOLD responses to TL spikes occurred in 83% of studies, predominated in the spiking temporal lobe, and manifested as activation or deactivation. Responses often involved the contralateral homologous cortex at the time of unilateral spikes and were frequently observed in extratemporal regions, suggesting that TL epileptic spikes can affect neuronal activity at a distance through synaptic connections.
Kobayashi
Eliane
E
Montreal Neurological Institute and Hospital, McGill University, 3801 University Street, Montreal, Quebec, Canada H3A 2B4. eliane.kobayashi@mail.mcgill.ca
Bagshaw
Andrew P
AP
Bénar
Christian-George
CG
Aghakhani
Yahya
Y
Andermann
Frederick
F
Dubeau
François
F
Gotman
Jean
J
D000328:Adult; D001931:Brain Mapping; D004569:Electroencephalography / Q000706:statistics & numerical data; D004833:Epilepsy, Temporal Lobe / Q000097:blood / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D007839:Functional Laterality / Q000502:physiology; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D008297:Male; D019579:Neocortex / Q000503:physiopathology*; D009434:Neural Pathways / Q000502:physiology / Q000503:physiopathology; D010100:Oxygen / Q000097:blood; D011446:Prospective Studies; D013702:Temporal Lobe / Q000503:physiopathology*
D010100:Oxygen