Decreased Structural Connectivity Between Thalamic Nuclei and Hippocampus in Temporal Lobe Epilepsy-A Diffusion Tensor Imaging-Based Study

Mehmet S Yildirim; Radheshyam Stepponat; Florian Ph S Fischmeister; Matthias Tomschik; Victor Schmidbauer; Farjad Khalaveh; Johannes Koren; Christoph Baumgartner; Ekaterina Pataraia; Silvia Bonelli; Karl Rössler; Gregor Kasprian; Christian Dorfer

doi:10.1111/ene.70040

Decreased Structural Connectivity Between Thalamic Nuclei and Hippocampus in Temporal Lobe Epilepsy-A Diffusion Tensor Imaging-Based Study

Eur J Neurol. 2025 Jan;32(1):e70040. doi: 10.1111/ene.70040.

Authors

Mehmet S Yildirim^{1

2}, Radheshyam Stepponat², Florian Ph S Fischmeister^{2

3}, Matthias Tomschik¹, Victor Schmidbauer³, Farjad Khalaveh¹, Johannes Koren^{4

5}, Christoph Baumgartner^{4

5}, Ekaterina Pataraia⁶, Silvia Bonelli⁶, Karl Rössler¹, Gregor Kasprian^{2

3}, Christian Dorfer¹

Affiliations

¹ Department of Neurosurgery, Medical University of Vienna, Vienna, Austria.
² Developmental and Interventional Neuroimaging Lab (DINLAB), Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria.
³ Division of Neuroradiology and Musculoskeletal Radiology, Medical University of Vienna, Vienna, Austria.
⁴ Department of Neurology, Clinic Hietzing, Vienna, Austria.
⁵ Karl Landsteiner Institute for Clinical Epilepsy Research and Cognitive Neurology, Vienna, Austria.
⁶ Department of Neurology, Medical University of Vienna, Vienna, Austria.

Abstract

Background: Temporal lobe epilepsy (TLE) can lead to structural brain abnormalities, with thalamus atrophy being the most common extratemporal alteration. This study used probabilistic tractography to investigate the structural connectivity between individual thalamic nuclei and the hippocampus in TLE.

Methods: Thirty-six TLE patients who underwent pre-surgical 3 Tesla magnetic resonance imaging (MRI) and 18 healthy controls were enrolled in this study. Patients were subdivided into TLE with HS (TLE-HS) and MRI-negative TLE (TLE-MRneg). Tractography and whole brain segmentation, including thalamus parcellation, were performed to determine the number of streamlines per mm³ between the thalamic nuclei and hippocampus. Connectivity strength and volume of regions were correlated with clinical data.

Results: The volume of the entire thalamus ipsilateral to seizure onset was significantly decreased in TLE-HS compared to controls (Mann-Whitney-U test: p_FDR < 0.01) with the anterior thalamic nuclei (ANT) as important contributor. Furthermore, decreased ipsilateral connectivity strength between the hippocampus and ANT was detected in TLE-HS (p_FDR < 0.01) compared to TLE-MRneg and controls which correlated negatively with the duration of epilepsy (ρ = -0.512, p = 0.025) and positively with seizure frequency (ρ = 0.603, p = 0.006). Moreover, ANT volume correlated negatively with epilepsy duration in TLE-HS (ρ = -0.471, p = 0.042).

Conclusions: ANT showed atrophy and decreased connectivity in TLE-HS, which correlated with epilepsy duration and seizure frequency. Understanding the dynamics of epileptogenic networks has the potential to shed light on surgery-resistant epilepsy and refine the selection process for ideal neurosurgical candidates, consequently enhancing post-surgical outcomes.

Keywords: anterior thalamic nuclei; diffusion tensor imaging; hippocampal sclerosis; structural brain network; temporal lobe epilepsy.

MeSH terms

Adult
Diffusion Tensor Imaging* / methods
Epilepsy, Temporal Lobe* / diagnostic imaging
Epilepsy, Temporal Lobe* / pathology
Female
Hippocampus* / diagnostic imaging
Hippocampus* / pathology
Humans
Male
Middle Aged
Neural Pathways / diagnostic imaging
Neural Pathways / pathology
Thalamic Nuclei* / diagnostic imaging
Thalamic Nuclei* / pathology
Young Adult