Effective connectivity alteration according to recurrence in transient global amnesia

Abstract

Purpose: This study aimed to evaluate alterations in structural covariance network and effective connectivity of the intrahippocampal circuit in patients with transient global amnesia (TGA). We also investigated whether there were differences of them according to recurrence.

Methods: We enrolled 88 patients with TGA and 50 healthy controls. We classified patients with TGA into two groups: the single event group (N = 77) and recurrent events group (N = 11). We performed volumetric analysis using the FreeSurfer program and structural covariance network analysis based on the structural volumes using a graph theoretical analysis in patients with TGA and healthy controls. The effective connectivity of the intrahippocampal circuit was also evaluated using structural equation modeling.

Results: There were no significant differences between patients with all TGA events/a single TGA event and healthy controls with regard to global structural covariance network. However, patients with recurrent events had significant alterations in global structural covariance network with a decrease in the small-worldness index (0.907 vs. 0.970, p = 0.032). In patients with all events/a single, there were alterations in effective connectivity from the entorhinal cortex to CA4, only. However, in patients with recurrent events, there were alterations in effective connectivity from the subiculum to the fimbria as well as from the entorhinal cortex to CA4 in bilateral hemispheres.

Conclusion: Our study revealed significant alterations in structural covariance network and disruption of the intrahippocampal circuit in patients with TGA compared to healthy controls, which is more prominent when amnestic events recurred. It could be related to the pathogenesis of TGA.

Keywords: Effective connectivity; Structural network; Transient global amnesia.