Diminished white matter integrity four decades after traumatic brain injury in Vietnam War veterans

Abstract

Objective: Traumatic Brain Injury (TBI) and Post-Traumatic Stress Disorder (PTSD) are common in military veterans and have been associated with an increased risk of dementia. The mechanisms contributing to this relationship are poorly understood. Main aim: This study investigated the effect of TBI and PTSD on white matter (WM) integrity, hippocampal and cortical volume within a cohort of Vietnam veterans. Materials and methods: 87 male veterans in total. There were 31 with TBI (aged 69.0 ± 2.5 years), 35 with PTSD (aged 69.5 ± 2.6 years) and 21 controls (aged 70.1 ± 4.9 years) underwent 3Tesla Magnetic Resonance Imaging (MRI). The TBI cohort included 12 mild, 13 moderate and six severe injuries. WM integrity was assessed using tract-based spatial statistics and region- -specific analyses of fractional anisotropy (FA) images. Automated processing of T1-weighted magnetisation-prepared rapid gradient-echo (MPRAGE) images resulted in hippocampal volumes and whole-brain cortical thickness estimation. Analyses were adjusted for IQ, Body Mass Index (BMI) and psychiatric comorbidities. Results: The moderate-to-severe TBI group had significantly lower FA than controls in the genu (F(3,36)=8.81, p0.05, partial η2 = 0.17), and body (F(3,36)=4.39, p 0.05, partial η2=0.14) of the corpus callosum, as well as in global WM (F(3,36)=5.35, p 0.05, partial η2=0.13). The PTSD FA values did not differ from controls and neither the TBI nor PTSD group differed significantly from controls in hippocampal volume nor cortical thickness in Alzheimer’s disease vulnerable regions. Conclusion: These findings suggest that the widely reported loss of WM integrity observed after moderate to severe TBI persists throughout life but is not associated with hippocampal or grey matter atrophy after four decades. No PTSD-related structural or FA change was observed.