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Diffusion Tensor Imaging of Epilepsy Open Access


Other title
diffusion tensor imaging
Type of item
Degree grantor
University of Alberta
Author or creator
Liu, Min
Supervisor and department
Beaulieu, Christian (Biomedical Engineering)
Gross, Donald W (Medicine)
Examining committee member and department
Lin, Jack J (School of Medicine, University of California, Irvine)
Wilman, Alan (Biomedical Engineering)
Kalra, Sanjay (Medicine)
Malykhin, Nikolai (Biomedical Engineering)
Department of Biomedical Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
Temporal lobe epilepsy (TLE) and idiopathic generalized epilepsy (IGE) are two common epilepsy syndromes. TLE is a type of focal epilepsy. It is frequently associated with mesial temporal sclerosis (MTS), a condition that is also medically intractable. Although TLE is characterized by a focal lesion, widespread gray matter (GM) and white matter (WM) abnormalities have been observed in patients. These reports suggest that TLE is a network disorder. IGE is characterized by bilateral epileptic discharges prominently in the frontal lobe. Magnetic resonance images (MRI) of patients suffering from IGE appear normal. Diffusion tensor imaging (DTI) is sensitive to the WM microstructure in the brain. Tensor based tractography can reliably reconstruct large WM tracts in vivo. The integrity of WM tracts can be inferred through quantitative measurements performed on these reconstructed images. The research in this thesis attempts to track the acute stage of Wallerian degeneration after injury using DTI. The concomitant reduction of parallel and perpendicular diffusivities 1-2 days after injury may reflect beading and swelling of axolemma or other confounding physiological processes. DTI was used to probe WM abnormalities in subsyndromes of TLE. Patients with TLE and MTS were found to have more extensive WM abnormalities than TLE without MTS. The affected area extends beyond limbic WM to multiple extratemporal locations. Graph theoretical analysis provided further insight into the topological organization of the TLE brain network. Both global and local communication efficiency were impaired and the pivotal hubs were altered in TLE. It is unknown whether these white matter changes are progressive over time. A longitudinal study of TLE patients with and without surgery over a mean of six and a half years revealed Wallerian degeneration in the ipsilateral temporal WM but not in the contralateral side in the surgical patients. No progressive change was found in the non-surgical patients other than normal aging. Finally, two clinically similar subsyndromes of IGE, i.e. juvenile myoclonic epilepsy and IGE with generalized tonic-clonic seizures only, were demonstrated to have distinct patterns of GM and WM abnormalities, indicating that those subsyndromes of IGE are the result of different underlying disease mechanisms. Overall, quantitative DTI has revealed structural brain differences in epilepsy that are not visible on standard MRI.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
Liu, M., Gross, D.W., Wheatley, B.M., Concha, L., and Beaulieu, C. (2013). The acute phase of Wallerian degeneration: longitudinal diffusion tensor imaging of the fornix following temporal lobe surgery. Neuroimage 74, 128–139.Liu, M., Concha, L., Lebel, C., Beaulieu, C., and Gross, D.W. (2012). Mesial temporal sclerosis is linked with more widespread white matter changes in temporal lobe epilepsy. NeuroImage: Clinical 1, 99–105.Liu, M., Concha, L., Beaulieu, C., and Gross, D.W. (2011). Distinct white matter abnormalities in different idiopathic generalized epilepsy syndromes. Epilepsia 52, 2267–2275.Liu M, Chen Z, Concha L, Beaulieu C, Gross DW (2012). Disrupted anatomical white matter network in left mesial temporal lobe epilepsy. Poster presentation at American epilepsy society (AES) 66th annual meeting, Nov 30 - Dec 4, 2012, San Diego, CA, USA.

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