Abstracts

Rationale:
Using functional magnetic resonance imaging (fMRI) we have previously found an enhanced level of synchrony over a brain network covering the frontal lobes, sensorimotor areas, and precuneus, or generalized spike-wave discharge (GSW) network, in patients with genetic-generalised-epilepsy (GGE) and unaffected first-degree relatives, compared to healthy controls [1]. In this study, we aimed to investigate if there was a structural connectivity correlate of these functional connectivity abnormalities derived from diffusion tensor imaging (DTI).
Method:
We recruited 16 patients, 17 first-degree unaffected relatives and 28 healthy controls. Each participant underwent two 10-minute resting state fMRI sessions (with 285 timepoints) and a DTI scan (b-value = 1500 s/mm2, 32 directions). The fMRI data were bandpass filtered (0.04-0.07Hz). Following brain parcellation using the automated anatomical labelling (AAL) atlas, the first principal component of each brain region was taken, and a Hilbert transform was applied. We then generated a series of 90x90x285 adjacency binary matrices of value equal to 1, if phase difference was < π/6. Afterwards we applied tensor decomposition techniques to minimise the effect of noise. Finally, we took the average across 285 time-points to calculate the temporal averaged brain synchrony [1,2]. DTI data were pre-processed and parcellated into the standard 90 AAL regions using MRtrix [3]. We then estimated a 90x90 structural connectivity matrix as the number of fibres connecting each pair of regions normalised by their combined volumes. Finally, we estimated the averaged mean degree centrality over the GSW network from both fMRI and DTI matrices, and compared them between groups with a one-way analysis of variance (ANOVA) with age as a covariate.