Discriminating Mild Traumatic Brain Injury and Posttraumatic Stress Disorder Using Latent Neuroimaging and Neuropsychological Profiles in Active-Duty Military Service Members

OBJECTIVE

Mild traumatic brain injury (mTBI) and posttraumatic stress disorder (PTSD) commonly occur among military Service Members and Veterans and have heterogenous, but also overlapping symptom presentations, which often complicate the diagnoses of underlying impairments and development of effective treatment plans. Thus, we sought to examine whether the combination of whole brain gray matter (GM) and white matter (WM) structural measures with neuropsychological performance can aid in the classification of military personnel with mTBI and PTSD.

METHODS

Active-Duty US Service Members ( n = 156; 87.8% male) with a history of mTBI, PTSD, combined mTBI+PTSD, or orthopedic injury completed a neuropsychological battery and T1- and diffusion-weighted structural neuroimaging. Cortical, subcortical, ventricular, and WM volumes and whole brain fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD) were calculated. Latent profile analyses were performed to determine how the GM and WM indicators, together with neuropsychological indicators, classified individuals.

RESULTS

For both GM and WM, respectively, a 4-profile model was the best fit. The GM model identified greater ventricular volumes in Service Members with cognitive symptoms, including those with a diagnosis of mTBI, either alone or with PTSD. The WM model identified reduced FA and elevated RD in those with psychological symptoms, including those with PTSD or mTBI and comorbid PTSD. However, contrary to expectation, a global neural signature unique to those with comorbid mTBI and PTSD was not identified.

CONCLUSIONS

The findings demonstrate that neuropsychological performance alone is more robust in differentiating Active-Duty Service Members with mTBI and PTSD, whereas global neuroimaging measures do not reliably differentiate between these groups.

Naming and semantic processing of action-related stimuli following right versus left hemispherectomy

Previous neuroimaging research has shown left hemisphere dominance during the semantic processing of embodied action-related stimuli. The goal of our research was to examine how action-related stimuli are processed in individuals after right or left hemispherectomy. S.M. (right hemispherectomy), J.H. (left hemispherectomy), and healthy control participants completed naming and semantic generation tasks with picture and word stimuli with referents that are used by arms or legs. Our results showed evidence of a dissociation for pictures of objects used by legs. Specifically, the naming task showed that, relative to controls, S.M. is impaired on accuracy, whereas J.H. performs closer to normal levels. For the semantic generation task, the opposite result was obtained and is consistent with the response time data. Our results suggest that the right hemisphere is critical for normal picture naming, whereas the left hemisphere is critical for normal semantic generation of action-related knowledge.