Bilateral white matter diffusion changes persist after epilepsy surgery.
OBJECTIVE
Bilateral white matter diffusion tensor imaging (DTI) abnormalities have been reported in patients with temporal lobe epilepsy (TLE) and unilateral mesial temporal sclerosis (MTS), but it is unknown whether these are functional or structural changes. We performed a longitudinal study in patients with unilateral MTS who were seizure-free for 1 year after surgery to determine whether the observed presurgical white matter diffusion abnormalities were reversible.


METHODS
Eight TLE patients with unilateral MTS who were seizure-free after anterior temporal resection and 22 healthy subjects were recruited. DTI was performed before surgery and at 1-year follow-up. Tractography and region-of-interest (ROI) analyses were performed in the fornix, cingulum, genu, and splenium of the corpus callosum and external capsules. Diffusion tensor parameters were compared between groups and before and after surgery in the patient group.


RESULTS
The fornix, cingulum, and external capsules showed preoperative bilateral abnormal diffusion parameters (i.e., decreased diffusion anisotropy and increased mean and perpendicular diffusivities). The fornix and cingulum ipsilateral to the resected mesial temporal structures showed signs of wallerian degeneration at 1-year follow-up. The contralateral tracts of the fornix, cingulum, and external capsules, as well as the genu of the corpus callosum, failed to show a normalization of their diffusion parameters.


CONCLUSIONS
The irreversibility of the white matter DTI abnormalities on seizure freedom suggests underlying structural abnormalities (e.g., axonal/myelin degradation) as opposed to functional changes (e.g., fluid shifts due to seizures) in the white matter.
Concha
Luis
L
Department of Biomedical Engineering, University of Alberta, Edmonton, Alberta, Canada.
Beaulieu
Christian
C
Wheatley
B Matt
BM
Gross
Donald W
DW
D000328:Adult; D016880:Anisotropy; D038481:Anterior Temporal Lobectomy; D001921:Brain / Q000473:pathology* / Q000648:ultrastructure; D038524:Diffusion Magnetic Resonance Imaging / Q000706:statistics & numerical data*; D018572:Disease-Free Survival; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000601:surgery*; D005260:Female; D018495:Fluid Shifts / Q000502:physiology; D005500:Follow-Up Studies; D007839:Functional Laterality; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009434:Neural Pathways / Q000473:pathology / Q000601:surgery / Q000648:ultrastructure; D011184:Postoperative Period; D015203:Reproducibility of Results; D012598:Sclerosis; D013702:Temporal Lobe / Q000473:pathology / Q000601:surgery