Structural brain network analysis in occipital lobe epilepsy

Abstract

Background: This study aimed to analyze the structural brain network in patients with occipital lobe epilepsy (OLE) and investigate the differences in structural brain networks between patients with OLE and healthy controls.

Methods: Patients with OLE and healthy controls with normal brain MRI findings were enrolled. They underwent diffusion tensor imaging using a 3.0T MRI scanner, and we computed the network measures of global and local structural networks in patients with OLE and healthy controls using the DSI studio program. We compared network measures between the groups.

Results: We enrolled 23 patients with OLE and 42 healthy controls. There were significant differences in the global structural network between patients with OLE and healthy controls. The assortativity coefficient (-0.0864 vs. -0.0814, p = 0.0214), mean clustering coefficient (0.0061 vs. 0.0064, p = 0.0203), global efficiency (0.0315 vs. 0.0353, p = 0.0086), and small-worldness index (0.0001 vs. 0.0001, p = 0.0175) were lower, whereas the characteristic path length (59.2724 vs. 53.4684, p = 0.0120) was higher in patients with OLE than those in the healthy controls. There were several nodes beyond the occipital lobe that showed significant differences in the local structural network between the groups. In addition, the assortativity coefficient was negatively correlated with the duration of epilepsy (r=-0.676, p = 0.001).

Keywords: Diffusion tensor imaging; Epilepsy; Occipital lobe.

Fig. 1

The process for structural network analysis in this study. DTI, diffusion tensor imaging

Fig. 2

The regions showing significant differences in the local structural networks between the patients with occipital lobe epilepsy and healthy controls The betweenness centrality of the red circles is decreased in patients with occipital lobe epilepsy compared to healthy controls PCG.L: left posterior cingulate, FFG.L: left fusiform gyrus, STG.L: left superior temporal gyrus, MTG.L: left middle temporal gyrus, IOG.L: left inferior occipital gyrus, LING.L: left lingual gyrus, SPG.L: left superior parietal gyrus, PCG.R: right posterior cingulate gyrus, IFO.R: right inferior frontal gyrus opercular part, PHG.R: right parahippocampal gyrus, PCG.R: right postcentral gyrus, TPO.R: right temporal pole middle temporal gyrus, CAL.R: right calcarine fissure and surrounding cortex, PCG.R: right precentral gyrus, INS.R: right insula, LING.R: right lingual gyrus, SOG.R: right superior occipital gyrus, STG.R: right superior temporal gyrus

Fig. 3

Correlation analysis between clinical characteristics and structural network in patients with occipital lobe epilepsy The assortative coefficient is positively correlated with age at seizure onset (r = 0.531, p = 0.019) (A), whereas it is negatively correlated with the duration of epilepsy (r=-0.676, p = 0.001) (B)