Abstracts

Rationale: Patients with temporal lobe epilepsy (TLE) exhibit both volumetric and structural connectivity abnormalities relative to healthy controls (Hatton et al., 2020; Whelan et al., 2018). However, to our knowledge, no study has investigated how these abnormalities inter-relate within individual patients. To improve the treatment of patients, it is crucial that the mechanisms of TLE are understood at the individual-patient level. _x000D_
Methods: We computed volumetric changes and structural connectivity abnormalities of 82 regions of interest in 144 patients with unilateral TLE and 96 healthy controls. Grey matter regional volumes were calculated using T1-weighted MRI, while white matter structural connectivity was derived using white matter fibre tractography from diffusion-weighted MRI._x000D_ _x000D_ For each regional volume and each connection strength, we calculated the effect size between patient and control groups in a group-level analysis. We then applied hierarchical regression to investigate the relationship between volumetric and structural connectivity abnormalities in individual patients. Additionally, we quantified whether abnormalities co-localised within individual patients by computing Dice similarity scores._x000D_
Results: At a group level of patients with TLE, grey matter regions with the greatest atrophy and structural connectivity reductions (in white matter) were exclusively located in ipsilateral temporal and subcortical areas (Figure 1C)._x000D_ _x000D_ At an individual-patient level, connections between one normal and one atrophied region (p=0.003), and connections between two atrophied regions (p=0.018) had significantly reduced FA compared to connections between two normal regions (Figure 2C). Similarly, the volume of regions joined by abnormal connections were significantly reduced, as compared to regions joined by normal connections (p=0.021)._x000D_ _x000D_ The extent of volumetric and connectivity abnormalities related to epilepsy duration (r=0.17, p=0.05; r=0.23, p=0.01 respectively), but co-localisation did not (r=0.04, p=0.59). Co-localisation was primarily driven by neighbouring abnormalities in the ipsilateral hemisphere._x000D_
Conclusions: Overall, volumetric and structural connectivity abnormalities were related in TLE. Shared mechanisms may underlie changes in both volume and connectivity in patients with TLE._x000D_
Funding: G.P.W. was supported by the MRC (G0802012, MR/M00841X/1). P.N.T. is supported by a UKRI Future Leaders Fellowship (MR/T04294X/1). J.J.H. is supported by the Centre for Doctoral Training in Cloud_x000D_ Computing for Big Data (EP/L015358/1).