0014 Reduced Cortical Thickness as a Biomarker of Daytime Sleepiness in Mild Traumatic Brain Injury

Abstract

Abstract Introduction Sleep disruptions, including the increase of daytime sleepiness, are reported in roughly 70% of all individuals who have suffered a mild traumatic brain injury (mTBI). Prior research using magnetic resonance imaging (MRI) has identified associations between functional brain changes and daytime sleepiness following mTBI. In the present study, we aimed to identify whether structural differences in cortical thickness are associated with increased daytime sleepiness in adults with mTBI. Methods A total of 58 adults between 18 and 45 years of age (M=23.58±5.31) participated in the study, including 19 healthy controls and 39 individuals with a documented mTBI. Individuals with mTBI were further divided based on time-since-injury into a sub-acute (n=22) or chronic (n=17) group. Daytime sleepiness was assessed using the Epworth Sleepiness Scale (ESS) and cortical thickness was measured using high-resolution T1-weighted structural MRI. Whole-brain vertex-wise estimations of cortical thickness were calculated using FreeSurfer (v.6.0) and entered into a GLM to identify between-group differences in cortical thickness and the association with ESS. Results Significant differences in cortical thickness were found between the two mTBI groups (cluster-forming threshold p<.01; cluster-wise threshold p<.05; two-tailed; FWE-corrected). Specifically, lower cortical thickness in the left hemisphere was found in the inferior parietal lobule (p=.01), precuneus (p=.03), and pars triangularis (p=.04) for the sub-acute, compared to chronic group. Furthermore, a significant negative correlation was found between ESS and cortical thickness in the inferior parietal lobule (r=-.55, p=.009) for the sub-acute mTBI group. Conclusion More daytime sleepiness was associated with reduced inferior parietal cortical thickness in those 2 to 12-weeks post-injury, an association not observed in those 6 to 12-months post-injury or healthy controls. The inferior parietal lobule is part of the frontoparietal attention network and has been associated with vulnerability to sleep loss. Our findings suggest structural damage to the attention network following mTBI may be one factor affecting daytime sleepiness in mTBI. These findings may reflect a potential biomarker of sleep disturbances in mTBI. Support USAMRMC grant (W81XWH-12–0386).