Identifying responders to vagus nerve stimulation based on microstructural features of thalamocortical tracts in drug-resistant epilepsy
(2024) Neurotherapeutics — Vol. 21, n° 5, p. e00422 [1-11] (2024)
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- Objective: The mechanisms of action of Vagus Nerve Stimulation (VNS) and the biological prerequisites to respond to the treatment are currently under investigation. It is hypothesized that thalamocortical tracts play a central role in the antiseizure effects of VNS, by disrupting the genesis of pathological activity in the brain. This pilot study aimed to explore whether in vivo microstructural features of thalamocortical tracts may differentiate Drug-Resistant Epilepsy (DRE) patients responding and not responding to VNS treatment. Methods: Eighteen patients with DRE (37.11 ± 10.13 years, 10 F), including 11 responders or partial responders and 7 non-responders to VNS were recruited for this high-gradient multi-shell diffusion Magnetic Resonance Imaging (MRI) study. Using Diffusion Tensor Imaging, and multi-compartment models - Neurite Orientation Dispersion and Density Imaging and Microstructure Fingerprinting, microstructural features were extracted from 12 subsegments of thalamocortical tracts. These characteristics were compared between responders/partial responders and non-responders. Subsequently, a Support Vector Machine (SVM) classifier was built incorporating microstructural features and 12 clinical covariates. Results: Multiple diffusion metrics consistently demonstrated significantly higher white matter fibers integrity in patients with a better response to VNS (pFDR < 0.05), mainly in subsegments of the inferior thalamocortical tracts - projecting to the insular cortex and the temporal lobe, and the posterior thalamocortical tracts - projecting to the occipital and parietal lobes. The SVM model achieved a classification accuracy of 94.12% with only 5 DTI metrics that were selected as the most discriminatory features. The inclusion of clinical covariates did not improve the classification performance. Significance: The results suggest that structural integrity of thalamocortical tracts may be reliably linked to the therapeutic effectiveness of VNS. We provide proof-of-concept that single- and multi-feature analyses can reveal the important potential of diffusion MRI for improving our understanding of the biological factors associated with the response to VNS therapy.
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Berger, A., Cerra, M., Joris, V., Danthine, V., Macq, B., Dricot, L., Vandewalle, G., Delinte, N., & El Tahry, R. (2024). Identifying responders to vagus nerve stimulation based on microstructural features of thalamocortical tracts in drug-resistant epilepsy. Neurotherapeutics, 21(5), e00422 [1-11]. https://doi.org/10.1016/j.neurot.2024.e00422 (Original work published 2024)