Diffusion tensor tractography detection of functional pathway for the spread of epileptiform activity between temporal lobe and Rolandic region.
OBJECTIVE
The aim of the study was to assess the connectivity between magnetoencephalographic (MEG) dipoles in the temporal lobe and Rolandic region in children with temporal lobe epilepsy using diffusion tensor imaging (DTI) tractography.


METHODS
Six pediatric patients with intractable focal epilepsy had MEG performed, which showed MEG dipoles over both temporal and Rolandic regions in a unilateral hemisphere. DTI tractography was performed on each patient. Six control subjects were studied for comparison. Two volumes of interest (VOIs) that encompassed the MEG dipoles were drawn, one placed in temporal lobe and the other in Rolandic region. Similar VOIs were placed in the contralateral side in the patients and on both sides in controls. Fractional anisotropy (FA) and trace of the external capsules were compared between patients and controls.


RESULTS
In all patients, a tractography pathway traversing through the external capsule, connecting the temporal and Rolandic MEG dipoles, was visualized. However, on the contralateral hemisphere in each patient, there was no evidence of a similar fiber tract. There was no corresponding tractography pathway identified in either hemisphere within the controls. There were no significant differences in FA and trace between the seizure focus side and contralateral side in the patients. There was no significant difference in FA, but a difference in trace between patients and controls.


CONCLUSIONS
We have found aberrant tractography pathway traversing through the external capsule, connecting two distant foci of epileptiform activity. Chronic interictal epileptogenic discharge could play a causal role in the de novo organization of these tracts.
Bhardwaj
Ratan D
RD
Division of Neurosurgery, Department of Surgery, The Hospital for Sick Children, Suite 2608-12 Yonge Street, Toronto, ON, Canada. ratan.bhardwaj@gmail.com
Mahmoodabadi
Sina Zarei
SZ
Otsubo
Hiroshi
H
Snead
O Carter
OC
Rutka
James T
JT
Widjaja
Elysa
E
D016880:Anisotropy; D001921:Brain / Q000473:pathology* / Q000503:physiopathology*; D002648:Child; D056324:Diffusion Tensor Imaging / Q000379:methods; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000503:physiopathology*; D005260:Female; D007839:Functional Laterality; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000473:pathology / Q000502:physiology; D009434:Neural Pathways / Q000473:pathology / Q000503:physiopathology; D013702:Temporal Lobe / Q000473:pathology* / Q000503:physiopathology*