Patients with Temporal Lobe Epilepsy (TLE) suffer from
widespread subtle white matter abnormalities and abnormal
functional connectivity extending beyond the affected
lobe, as revealed by Diffusion Tensor MR Imaging,
volumetric and functional MRI studies. Diffusion Spectrum
Imaging (DSI) is a diffusion imaging technique with high
angular resolution for improving the mapping of white
matter pathways. In this study, we used DSI, connectivity
matrices and topological measures to investigate how the
alteration in structural connectivity influences whole
brain structural networks. Eleven patients with
right-sided TLE and hippocampal sclerosis and 18 controls
underwent our DSI protocol at 3T. The cortical and
subcortical grey matters were parcellated into 86 regions
of interest and the connectivity between every region
pair was estimated using global tractography and a
connectivity matrix (the adjacency matrix of the
structural network). We then compared the networks of
patients and controls using topological measures. In
patients, we found a higher characteristic path length
and a lower clustering coefficient compared to controls.
Local measures at node level of the clustering and
efficiency showed a significant difference after a
multiple comparison correction (Bonferroni). These
significant nodes were located within as well outside the
temporal lobe, and the localisation of most of them was
consistent with regions known to be part of epileptic
networks in TLE. Our results show altered connectivity
patterns that are concordant with the mapping of
functional epileptic networks in patients with TLE.
Further studies are needed to establish the relevance of
these findings for the propagation of epileptic activity,
cognitive deficits in medial TLE and outcome of epilepsy
surgery in individual patients.