Increased Structural Connectivity between the Temporal Lobe and Insula in Patients with TLE
Poster No:
1771
Submission Type:
Abstract Submission
Authors:
Wen-Po Walden Chang1, Chih-Chin Heather Hsu1, Yi-Hsiu Chen1,2, Cheng-Chia Lee2, Ching-Po Lin1,3
Institutions:
1Institute of Neuroscience, National Yang Ming Chiao Tung University, Taipei, Taiwan, 2Taipei Veterans General Hospital, Taipei, Taiwan, 3Department of Education and Research, Taipei City Hospital, Taipei, Taiwan
First Author:
Wen-Po Walden Chang
Institute of Neuroscience, National Yang Ming Chiao Tung University
Taipei, Taiwan
Institute of Neuroscience, National Yang Ming Chiao Tung University
Taipei, Taiwan
Co-Author(s):
Chih-Chin Heather Hsu
Institute of Neuroscience, National Yang Ming Chiao Tung University
Taipei, Taiwan
Institute of Neuroscience, National Yang Ming Chiao Tung University
Taipei, Taiwan
Yi-Hsiu Chen
Institute of Neuroscience, National Yang Ming Chiao Tung University|Taipei Veterans General Hospital
Taipei, Taiwan|Taipei, Taiwan
Institute of Neuroscience, National Yang Ming Chiao Tung University|Taipei Veterans General Hospital
Taipei, Taiwan|Taipei, Taiwan
Ching-Po Lin
Institute of Neuroscience, National Yang Ming Chiao Tung University|Department of Education and Research, Taipei City Hospital
Taipei, Taiwan|Taipei, Taiwan
Institute of Neuroscience, National Yang Ming Chiao Tung University|Department of Education and Research, Taipei City Hospital
Taipei, Taiwan|Taipei, Taiwan
Introduction:
Recent invasive sEEG studies have demonstrated that electrical signals entering the insula during temporal lobe epilepsy (TLE) seizures, suggesting that the insula may be an epileptogenic or irritative zone (Zhang, 2022). Nevertheless, the role of the insula in TLE remains unclear, partly due to the overlap of symptoms with temporal lobe seizures and limited non-invasive methods for assessing the insula (Li, 2022). Therefore, our research aims to investigate the structural connections between the insula and temporal lobe in TLE patients. Given that seizure onset zones may exhibit high excitability and dense connectivity (Royer, 2022), our hypothesis is that there may be an increase in intra- and inter-connectivity between the insula and the temporal lobe in TLE patients.
Methods:
12 healthy participants (mean age [range] = 25±5.4 [14-30]) and 19 TLE patients (21±11.4 [5-52]) underwent T1w and DWI scans on a 3T GE Discovery MR 750 scanner. DWIs were acquired using 30 directions for b-value 1000s/mm2 with TR = 10.5s, TE = 80ms, flip angle = 90o, voxel size = 2-mm isotropic. DWIs were first preprocessed via iDIO (Hsu, 2023). Convex Optimization for Microstructure Informed Tractography 2 (COMMIT2, v.2.3.1) was used to calculate the connection weights. First, the connectome was constructed using the HCPex atlas with 426 regions (Huang, 2022). Second, the filtered tractogram was analyzed using the standard COMMIT model with group lasso regularization applied and the parameter lambda set to 5×10−4 to control for bundle size differences. Finally, COMMIT2 fit the streamlines with bundle regularization. A t-test was performed to compare the connection weights between TLE group and control group within the temporal and insular cortices.
Results:
The results showed enhanced connectivity between the insula and temporal lobe in the TLE group compared to control group. Figure 1 demonstrated the significantly different connections between the ipsilateral insula and temporal lobe. While some intra-connections exhibited decreased strength, the majority showed increased strength. Figure 2 showed significant differences in inter-region connections. In the left hemisphere, two connections displayed increased strength: from the anterior insula to the middle temporal lobe and from the posterior insula to the posterior temporal lobe. In the right hemisphere, increased strength was observed between the anterior insula and the middle temporal lobe.
·COMMIT2 Weight Between Insula and Temporal Lobe (Left/Right, Ipsilateral)
·COMMIT2 Weight of Insula and Temporal Lobe (Left/Right, Ipsilateral, Inter-region)
Conclusions:
This study revealed a decrease in connectivity strength, which was observed only within intra-region connections between the ipsilateral insula and temporal lobe. This finding may possibly reflect functional compensation within the regions (Royer, 2022). The differences and existence of tracts are similar to the short U-fibers between the insula and temporal lobe, which are called temporal-insular tracts (TIT), and TIT have not been fully elucidated in the previous literature (Catani, 2022). The inter-region connections could be classified into two categories based on their spatial distribution: the anterior TIT, connecting the anterior insula to the middle temporal lobe, and the posterior TIT, linking the posterior insula to the posterior temporal lobe (TITa/p). The increased connectivity suggested that the insula could be a seizure onset zone in TLE, thereby supporting our hypothesis that seizure onset zones in focal temporal epilepsy may have dense connectivity with the insular cortex.
This study supported the hypothesis that insula may play a role in TLE pathophysiology. Using an advanced tractography filtering procedure, we observed increased connectivity strength in TLE patients compared to controls. Specifically, the TITa/p demonstrated enhanced connectivity, supporting the hypothesis that the insula may act as a seizure onset zone. These findings underline the importance of exploring insular-temporal lobe connections in the context of epilepsy.
This study supported the hypothesis that insula may play a role in TLE pathophysiology. Using an advanced tractography filtering procedure, we observed increased connectivity strength in TLE patients compared to controls. Specifically, the TITa/p demonstrated enhanced connectivity, supporting the hypothesis that the insula may act as a seizure onset zone. These findings underline the importance of exploring insular-temporal lobe connections in the context of epilepsy.
Modeling and Analysis Methods:
Connectivity (eg. functional, effective, structural) 2
Diffusion MRI Modeling and Analysis
Neuroanatomy, Physiology, Metabolism and Neurotransmission:
White Matter Anatomy, Fiber Pathways and Connectivity 1
Keywords:
Epilepsy
MRI
Tractography
WHITE MATTER IMAGING - DTI, HARDI, DSI, ETC
1|2Indicates the priority used for review
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2. Hsu, C. H., Chong, S. T., Kung, Y. C., Kuo, K. T., Huang, C. C., & Lin, C. P. (2023). Integrated diffusion image operator (iDIO): A pipeline for automated configuration and processing of diffusion MRI data. Human brain mapping, 44(7), 2669–2683.
3. Huang, C. C., Rolls, E. T., Feng, J., & Lin, C. P. (2022). An extended Human Connectome Project multimodal parcellation atlas of the human cortex and subcortical areas. Brain structure & function, 227(3), 763–778.
4. Li, J., Reiter-Campeau, S., Namiranian, D., Toffa, D. H., Bouthillier, A., Dubeau, F., & Nguyen, D. K. (2022). Insular Involvement in Cases of Epilepsy Surgery Failure. Brain sciences, 12(2), 125.
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6. Zhang, X., Zhang, G., Yu, T., Xu, C., Zhu, J., Yan, X., Ma, K., & Gao, R. (2022). Temporal-insular spreading time in temporal lobe epilepsy as a predictor of seizure outcome after temporal lobectomy. Medicine, 101(33), e30114.