032-22 – An investigation of MRI morphometric endophenotypes in patients with idiopathic generalised epilepsy and their first-degree relatives

Idiopathic generalised epilepsy (IGE) is a collection of genetically based, non-lesional, epileptic syndromes, characterized by widespread alterations of brain networks. Previous studies have discovered cognitive and network topology endophenotypes in IGE, however, studies of morphological endophenotypes have not been conducted before. Extensive morphological alterations are commonly found in cortical and subcortical structures in IGE thus to determine how structural changes are related to underlaying genetics in the disorder, we investigated cortical network organisation and thalamic morphology in patients with IGE and their first-degree relatives.

Thirty patients with IGE, thirty-six asymptomatic first-degree relatives and forty age and sex matched healthy controls were recruited for this study. Morphometric similarity networks (MSNs) were constructed from combined morphometric features inferred from T1W images using FreeSurfer. Network based statistics and a Mahalanobis distance (similarity) measure (M) was used to compare MSNs between patients with IGE, asymptomatic first-degree relatives, and healthy controls. Thalamic nuclei volumetry was conducted using THalamus Optimized Multi Atlas Segmentation software. Spearman’s correlations were calculated between thalamic nuclei volumes and participants similarity score M, and patient clinical features.

Cortical morphometric profiles of patients and their first-degree relatives were significantly different than controls. Patients displayed thalamic nuclei atrophy compared to controls and relatives. Weak to moderate associations were found between thalamic nuclei volumes and M, and epilepsy onset and duration.

The use of MSNs is a novel method which has the potential to increase the understanding of cortical organisation and morphometric endophenotypes in IGE. Thalamic structural integrity is disrupted in IGE regardless of subsyndrome with alterations becoming more extensive potentially due to seizure insult.