The Presence or Absence of Hippocampal Atrophy Differently Disrupts Graph Theory Properties of Cerebral Functional Connectivity in Temporal Lobe Epilepsy.
Lucas Silva1, Italo Karmann Aventurato1, Raphael Casseb1, Brunno de Campos1, Fernando Cendes1, Clarissa Yasuda1
1University of Campinas
Objective:
To investigate brain connectivity and network properties with graph theory methods in TLE patients according to the presence or absence of HA.
Background:

Although temporal lobe epilepsy (TLE) with unilateral hippocampal atrophy (HA) has been extensively investigated, the impact of bilateral HA and the absence of HA on brain connectivity and networks' efficiency remains unknown.

Design/Methods:

We analyzed 216 3T-MRI resting-state images of TLE patients (median age: 48years; 122 women): 92 LEFT-HA, 70 RIGHT-HA, 25 BILATERAL-HA, 29 NEGATIVE-TLE, and 216 healthy controls. We used the CONN connectivity_toolbox/MATLAB2019 to extract graph theory measures (global efficiency (Global-eff), average path length (PATH), degree/cost (DEGREE), betweenness centrality (BC), local efficiency (Local-eff), and clustering coefficient (CC). We considered a cost of 0.15 (including only the 15% more statistically significant results) and reported p-values<0.05. 

Results:

The LEFT-HA and RIGHT-HA presented a trend to higher measures of global connectivity (Global-Con), local connectivity (Local-Con), and centrality in the brain (higher Global-eff, DEGREE, BC, Local-eff, CC, and lower PATH) and a trend to lower Global-Con, Local-Con, and centrality in the cerebellum. The LEFT-HA and RIGHT-HA presented higher DEGREE in the ipsilateral hippocampus and higher Local-eff /CC in the contralateral hippocampus. The NEGATIVE-TLE group showed a trend to lower Global-eff and higher average PATH, DEGREE and CC in the brain. The BILATERAL-HA presented a trend to higher Local-eff /CC in the brain.

Conclusions:

Overall, there was a trend for higher local connectivity to the detriment of the Global-eff. Our data indicate more severe alterations in the unilateral groups, as the presence of unilateral HA disturbs hemispheric connectivity, which may disrupt global connections. While the unilateral groups showed higher connectivity levels in the brain (with higher ipsilateral hippocampal Global-Con and probable compensatory higher contralateral hippocampal Local-Con), the NEGATIVE-TLE presented concordantly higher Local-Con and lower Global-Con in the brain.

10.1212/WNL.0000000000202796