Extratemporal white matter abnormalities in mesial temporal lobe epilepsy demonstrated with diffusion tensor imaging.
OBJECTIVE
Recent studies have demonstrated bilateral white matter abnormalities in temporal lobe epilepsy (TLE) patients with unilateral mesial temporal sclerosis (MTS). The purpose of this project was to determine whether abnormalities of water diffusion are seen in extratemporal white matter of patients with TLE and pathologically confirmed MTS and to determine whether these findings are associated with worse surgical outcome.


METHODS
Eleven patients with TLE and unilateral MTS confirmed in surgical specimens and 14 controls were studied by using cerebrospinal fluid-suppressed diffusion tensor imaging (DTI) and T2 relaxometry.


RESULTS
Hippocampal T2 signal for patients was significantly elevated both ipsilateral (p<0.001) and contralateral (p=0.006) to MTS. DTI demonstrated reduced fractional anisotropy of the genu of the corpus callosum (p=0.003) and external capsule (p=0.02) and elevated mean diffusivity of the genu (p=0.005), splenium (p=0.03), and external capsule (p<0.001). For both the genu and external capsule, parallel diffusion of patients was not different from that of controls (genu, p=0.81; external capsule, p=0.45), whereas perpendicular diffusion was elevated (genu, p=0.001; external capsule, p<0.001). With mean postsurgical follow-up of 18.5 months, eight of 11 patients were entirely seizure free and the remaining three had all experienced a worthwhile reduction in seizure frequency.


CONCLUSIONS
Our findings suggest that although patients with TLE and MTS have extensive bilateral and extratemporal pathology, these findings may not be associated with a worse postsurgical outcome.
Gross
Donald W
DW
Division of Neurology, Department of Medicine, University of Alberta, Edmonton, Alberta, Canada. donald.gross@ualberta.ca
Concha
Luis
L
Beaulieu
Christian
C
D000328:Adult; D016880:Anisotropy; D001921:Brain / Q000473:pathology* / Q000601:surgery; D001931:Brain Mapping; D002540:Cerebral Cortex / Q000473:pathology / Q000601:surgery; D003337:Corpus Callosum / Q000473:pathology; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods / Q000706:statistics & numerical data*; D018572:Disease-Free Survival; D004833:Epilepsy, Temporal Lobe / Q000473:pathology* / Q000601:surgery; D005260:Female; D005500:Follow-Up Studies; D007839:Functional Laterality; D006624:Hippocampus / Q000473:pathology; D006801:Humans; D020772:Internal Capsule / Q000473:pathology; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care; D012598:Sclerosis / Q000473:pathology; D013702:Temporal Lobe / Q000473:pathology / Q000601:surgery; D016896:Treatment Outcome