Abstracts

Rationale: Executive dysfunction is commonly seen in patients with mesial temporal lobe epilepsy (mTLE). However, the mechanism underlying executive dysfunction in mTLE remains unknown. The anterior insula has been demonstrated as a brain ‘hub’ where plays a key role in executive function. This study aimed to investigate structural and functional alterations of the anterior insula in mTLE with executive dysfunction. Methods: In the present study, we consecutively recruited 21 left mTLE patients with hippocampal sclerosis and 22 age-matched healthy controls. A series of neuropsychological examinations (such as Wisconsin Card Sorting Test, Trail Making Test, Digit Span and Self-Ordered Pointing Test) were performed to assess executive function including attention, working memory, abstraction, mental flexibility and strategy. According to the executive function performance, patients with left mTLE were further divided into two subgroups: mild and severe executive dysfunction groups. An established manual segmentation of the anterior insula was adopted to build region of interest. Functional connectivity (FC) and probabilistic diffusion tractography of the bilateral hippocampal-anterior insular pathway were assessed, respectively. Comparisons were initially made between left mTLE patients and healthy controls, and subsequently made between patients with mild and severe executive dysfunction. Results: Patients with left mTLE exhibited significant and generalized executive dysfunction including attention, working memory, abstraction, mental flexibility and strategy (p<0.05 for all parameters). And eight of them showed mild executive dysfunction, while the other thirteen showed severe executive dysfunction. Compared with healthy controls, left mTLE patients showed decreased volume of the left anterior insular cortex (p<0.05), decreased FC (p<0.05) and fractional anisotropy (FA, p<0.05) of the left hippocampal-anterior insular pathway, as well as increased mean diffusivity of the left hippocampal-anterior insular pathway (MD, p<0.05). Compared to mild executive dysfunction group, severe executive dysfunction group showed decreased volume of the left anterior insular cortex (p<0.05) and FC of the left hippocampal-anterior insular pathway (p<0.05). Moreover, there was a positive correlation between FC value of the left hippocampal-anterior insular pathway and executive function performance (p<0.0001 and r>0.8 for parameters reflecting abstraction, mental flexibility and strategy). Conclusions: These findings indicate a central role of the ipsilateral anterior insular cortex in the pathophysiology of executive dysfunction in mTLE. Funding: No funding