Effects of seizure burden on structural global brain networks in patients with unilateral hippocampal sclerosis

Abstract

Abstract Background and purpose Temporal lobe epilepsy secondary to hippocampal sclerosis is related to epileptogenic networks rather than a focal epileptogenic source. Graph‐theoretical gray and white matter networks may help to identify alterations within these epileptogenic networks. Methods Twenty‐seven patients with hippocampal sclerosis and 14 controls underwent magnetic resonance imaging, including 3D‐T1, fluid‐attenuated inversion recovery, and diffusion tensor imaging. Subject‐specific structural gray and white matter network properties (normalized path length, clustering, and small‐worldness) were reconstructed. Group differences and differences between those with higher and lower seizure burden ( .05). Patients with lower seizure burden had significantly lower gray matter small‐worldness and normalized clustering compared to controls and those with higher seizure burden (all p < .04). A higher number of monthly seizures was significantly associated with increased gray and white matter small‐worldness, indicating a more rigid network. Conclusion Overall, there were no differences in network properties in this group of patients with hippocampal sclerosis. However, patients with lower seizure burden had significantly lower gray matter network indices, indicating a more random organization. The correlation between higher monthly seizures and a more rigid network is driven by those with higher seizure burden, who presented a more rigid network compared to those with a lower seizure burden.

Keywords

• graph theory
• gray matter network
• hippocampal sclerosis
• magnetic resonance imaging
• white matter network