Discriminating factors in access to video-EEG for epilepsy surgery in a French tertiary epilepsy center.

Equitable access to care and management is a priority for patients with epilepsy and may vary depending on each country's healthcare system. As this issue has not been specifically addressed in France, we conducted a retrospective study to identify discriminating factors in access to surgery at a French tertiary epilepsy center. Initially, we examined factors previously identified in other countries as influential in surgery access, including age at diagnosis, affected side, gender, years of education, socio-professional categories, and density of general practitioners in the residential area, in 293 consecutive French-native patients with refractory medial temporal lobe epilepsy and hippocampal sclerosis (MTLE-HS). Subsequently, we conducted a case-control study comparing patients born in France with 22 patients born abroad to specifically explore migratory status. The analysis revealed that the only three factors statistically influencing the delay between the onset of epilepsy and entry into video-EEG were early age at onset (associated with a longer delay), pensioner status (associated with a longer delay), and student status (associated with a shorter delay). Migratory status, gender, and socio-economic level (indirectly reflected by the level of education and socio-professional category) were not found to be discriminatory factors in access to video-EEG. Discrepancies between our study and foreign studies may be attributed to differences in healthcare systems and medical coverage among countries. Efforts in France to improve access to surgery should focus on enhancing communication among practitioners to promptly refer any MTLE-HS patient to an epilepsy surgery center, regardless of their age.

Cross-subject variability of the optic radiation anatomy in a cohort of 1065 healthy subjects.

INTRODUCTION: Optic radiations are tracts of particular interest for neurosurgery, especially for temporal lobe resection, because their lesion is responsible for visual field defects. However, histological and MRI studies found a high inter-subject variability of the optic radiation anatomy, especially for their most rostral extent inside the Meyer's temporal loop. We aimed to better assess inter-subject anatomical variability of the optic radiations, in order to help to reduce the risk of postoperative visual field deficiencies. METHODS: Using an advanced analysis pipeline relying on a whole-brain probabilistic tractography and fiber clustering, we processed the diffusion MRI data of the 1065 subjects of the HCP cohort. After registration in a common space, a cross-subject clustering on the whole cohort was performed to reconstruct the reference optic radiation bundle, from which all optic radiations were segmented on an individual scale. RESULTS: We found a median distance between the rostral tip of the temporal pole and the rostral tip of the optic radiation of 29.2 mm (standard deviation: 2.1 mm) for the right side and 28.8 mm (standard deviation: 2.3 mm) for the left side. The difference between both hemispheres was statistically significant (p = 1.10-8). CONCLUSION: We demonstrated inter-individual variability of the anatomy of the optic radiations on a large-scale study, especially their rostral extension. In order to better guide neurosurgical procedures, we built a MNI-based reference atlas of the optic radiations that can be used for fast optic radiation reconstruction from any individual diffusion MRI tractography.

Sex-related variability of white matter tracts in the whole HCP cohort.

Behavioral differences between men and women have been studied extensively, as have differences in brain anatomy. However, most studies have focused on differences in gray matter, while white matter has been much less studied. We conducted a comprehensive study of 77 deep white matter tracts to analyze their volumetric and microstructural variability between men and women in the full Human Connectome Project (HCP) cohort of 1065 healthy individuals aged 22-35 years. We found a significant difference in total brain volume between men and women (+ 12.6% in men), consistent with the literature. 16 tracts showed significant volumetric differences between men and women, one of which stood out due to a larger effect size: the corpus callosum genu, which was larger in women (+ 7.3% in women, p = 5.76 × 10-19). In addition, we found several differences in microstructural parameters between men and women, both using standard Diffusion Tensor Imaging (DTI) parameters and more complex microstructural parameters from the Neurite Orientation Dispersion and Density Imaging (NODDI) model, with the tracts showing the greatest differences belonging to motor (cortico-spinal tracts, cortico-cerebellar tracts) or limbic (cingulum, fornix, thalamo-temporal radiations) systems. These microstructural differences may be related to known behavioral differences between the sexes in timed motor performance, aggressiveness/impulsivity, and social cognition.