Abstract
PurposePsychosis is one of the most important psychiatric comorbidities in temporal lobe epilepsy (TLE), and its pathophysiology still remains unsolved. We aimed to explore the connectivity differences of structural neuroimaging between TLE with and without psychosis using a graph theoretical analysis, which is an emerging mathematical method to investigate network connections in the brain as a small-world system.Materials and MethodsWe recruited 11 TLE patients with unilateral hippocampal sclerosis (HS) presenting psychosis or having a history of psychosis (TLE-P group). As controls, 15 TLE patients with unilateral HS without any history of psychotic episodes were also recruited (TLE-N group). For graph theoretical analysis, the normalized gray matter images of both groups were subjected to Graph Analysis Toolbox (GAT). As secondary analyses, each group was compared to 14 age- and gender-matched healthy subjects.ResultsThe hub node locations were found predominantly in the ipsilateral hemisphere in the TLE-N group, and mainly on the contralateral side in the TLE-P group. The TLE-P group showed significantly higher characteristic path length, transitivity, lower global efficiency, and resilience to random or targeted attack than those of the TLE-N group. The regional comparison in betweenness centrality revealed significantly decreased connectivity in the contralateral temporal lobe, ipsilateral middle frontal gyrus, and bilateral postcentral gyri in the TLE-P group. The healthy subjects showed well-balanced nodes/edges distributions, similar metrics to TLE-N group except for higher small-worldness/modularity/assortativity, and various differences of regional betweenness/clustering.ConclusionIn TLE with psychosis, graph theoretical analysis of structural imaging revealed disrupted connectivity in the contralateral hemisphere. The network metrics suggested that the existence of psychosis can bring vulnerability and decreased efficiency of the whole-brain network. The sharp differences in structural networks between morphologically homogeneous groups are remarkable and may contribute to a better understanding of psychosis in TLE.
Highlights
Temporal lobe epilepsy (TLE) is the most common focal epilepsy among adults [1], and psychosis is one of the most important psychiatric comorbidities [2]
The network metrics suggested that the existence of psychosis can bring vulnerability and decreased efficiency of the whole-brain network
As for structural neuroimaging, a previous study has reported no significant difference in gray matter between TLE with and without psychosis using voxel-based morphometry [3]
Summary
Temporal lobe epilepsy (TLE) is the most common focal epilepsy among adults [1], and psychosis is one of the most important psychiatric comorbidities [2]. As for structural neuroimaging, a previous study has reported no significant difference in gray matter between TLE with and without psychosis using voxel-based morphometry [3]. Graph theoretical analysis can be applied to structural MR imaging for evaluation of networks, and recently anatomical covariance methods using regional gray matter volumes have increasingly been reported [8, 9]. We hypothesized that the existence of psychosis in TLE could affect neuronal networks on structural MRI, and that relatively homogeneous patient groups would be desirable for comparison because the influence of local atrophy on graph theoretical analysis has not yet been thoroughly investigated [12]. The aim of this study was use a graph theory technique to investigate connectivity differences in structural imaging of TLE and HS patients with and without psychosis
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