Microstructural integrity of early- versus late-myelinating white matter tracts in medial temporal lobe epilepsy

Authors

  • Chu-Yu Lee,

    1. Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, South Carolina, U.S.A
    2. Center for Biomedical Imaging, Medical University of South Carolina, Charleston, South Carolina, U.S.A
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  • Ali Tabesh,

    1. Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, South Carolina, U.S.A
    2. Center for Biomedical Imaging, Medical University of South Carolina, Charleston, South Carolina, U.S.A
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  • Andreana Benitez,

    1. Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, South Carolina, U.S.A
    2. Center for Biomedical Imaging, Medical University of South Carolina, Charleston, South Carolina, U.S.A
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  • Joseph A. Helpern,

    1. Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, South Carolina, U.S.A
    2. Center for Biomedical Imaging, Medical University of South Carolina, Charleston, South Carolina, U.S.A
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  • Jens H. Jensen,

    1. Department of Radiology and Radiological Science, Medical University of South Carolina, Charleston, South Carolina, U.S.A
    2. Center for Biomedical Imaging, Medical University of South Carolina, Charleston, South Carolina, U.S.A
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  • Leonardo Bonilha

    Corresponding author
    1. Center for Biomedical Imaging, Medical University of South Carolina, Charleston, South Carolina, U.S.A
    2. Division of Neurology, Department of Neurosciences, Comprehensive Epilepsy Center, Medical University of South Carolina, Charleston, South Carolina, U.S.A
    • Address correspondence to Leonardo Bonilha, Division of Neurology, Department of Neurosciences, Medical University of South Carolina, 96 Jonathan Lucas St, 3rd floor CSB, Charleston, SC 29425, U.S.A. E-mail: bonilha@musc.edu

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Summary

Purpose

Patients with medial temporal lobe epilepsy (MTLE) exhibit structural brain damage involving gray matter (GM) and white matter (WM). The mechanisms underlying tissue loss in MTLE are unclear and may be associated with a combination of seizure excitotoxicity and WM vulnerability. The goal of this study was to investigate whether late-myelinating WM tracts are more vulnerable to injury in MTLE compared with early myelinating tracts.

Methods

Diffusional kurtosis imaging scans were obtained from 25 patients with MTLE and from 36 matched healthy controls. Diffusion measures from regions of interest (ROIs) for both late- and early myelinating WM tracts were analyzed. Regional Z-scores were computed with respect to normal controls to compare WM in early myelinating tracts versus late-myelinating tracts.

Key Findings

We observed that late-myelinating tracts exhibited a larger decrease in mean, axial, and radial kurtosis compared with early myelinating tracts. We also observed that the change in radial kurtosis was more pronounced in late-myelinating tracts ipsilateral to the side of seizure onset.

Significance

These results suggest a developmentally based preferential susceptibility of late-myelinating WM tracts to damage in MTLE. Brain injury in epilepsy may be due to the pathologic effects of seizures in combination with regional WM vulnerability.

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