Abstract
ObjectiveTo characterise temporal lobe epilepsy (TLE) surgery-induced changes in brain network properties, as measured using diffusion weighted MRI, and investigate their association with postoperative seizure-freedom. MethodsFor 48 patients who underwent anterior temporal lobe resection, diffusion weighted MRI was acquired pre-operatively, 3–4 months post-operatively (N = 48), and again 12 months post-operatively (N = 13). Data for 17 controls were also acquired over the same period. After registering all subjects to a common space, we performed two complementary analyses of the subjects’ quantitative anisotropy (QA) maps. 1) A connectometry analysis which is sensitive to changes in subsections of fasciculi. 2) A graph theory approach which integrates connectivity information across the wider brain network. ResultsWe found significant postoperative alterations in QA in patients relative to controls measured over the same period. Reductions were primarily located in the uncinate fasciculus and inferior fronto-occipital fasciculus ipsilaterally for all patients. Larger reductions were associated with postoperative seizure-freedom in left TLE. Increased QA was mainly located in corona radiata and corticopontine tracts. Graph theoretic analysis revealed widespread increases in nodal betweenness centrality, which were not associated with patient outcomes. ConclusionSubstantial alterations in QA occur in the months after epilepsy surgery, suggesting Wallerian degeneration and strengthening of specific white matter tracts. Greater reductions in QA were related to postoperative seizure freedom in left TLE.
Highlights
Temporal lobe epilepsy (TLE) is the most common form of drugrefractory focal epilepsy
Greater reductions in QA were related to postoperative seizure freedom in left TLE
TLE patients showed a greater reduction in QA in the vicinity of the resected tissue, in ipsilateral inferior fronto-occipital fasciculus (IFOF) and uncinate fasciculus (UF)
Summary
Temporal lobe epilepsy (TLE) is the most common form of drugrefractory focal epilepsy. Many previous studies have investigated white matter properties in TLE patients and found differences relative to controls (Winston et al, 2014; Li et al, 2019; Keller et al, 2017; Schoene-Bake et al, 2009; Elliott et al, 2018; Gross et al, 2006; Riley et al, 2010; Taylor et al, 2015). Keller et al (2017) and Taylor et al (2018) demonstrated that preoperative white matter alterations that were later resected were associated with post-operative outcomes. Both studies investigated associations with postoperative seizure freedom, but did not use postoperative diffusion MRI
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