Teasing apart trauma: neural oscillations differentiate individual cases of mild traumatic brain injury from post-traumatic stress disorder even when symptoms overlap

Abstract

Post-traumatic stress disorder (PTSD) and mild traumatic brain injury (mTBI) are highly prevalent and closely related disorders. Affected individuals often exhibit substantially overlapping symptomatology – a major challenge for differential diagnosis in both military and civilian contexts. According to our symptom assessment, the PTSD group exhibited comparable levels of concussion symptoms and severity to the mTBI group. An objective and reliable system to uncover the key neural signatures differentiating these disorders would be an important step towards translational and applied clinical use. Here we explore use of MEG (magnetoencephalography)-multivariate statistical learning analysis in identifying the neural features for differential PTSD/mTBI characterisation. Resting state MEG-derived regional neural activity and coherence (or functional connectivity) across seven canonical neural oscillation frequencies (delta to high gamma) were used. The selected features were consistent and largely confirmatory with previously established neurophysiological markers for the two disorders. For regional power from theta, alpha and high gamma bands, the amygdala, hippocampus and temporal areas were identified. In line with regional activity, additional connections within the occipital, parietal and temporal regions were selected across a number of frequency bands. This study is the first to employ MEG-derived neural features to reliably and differentially stratify the two disorders in a multi-group context. The features from alpha and beta bands exhibited the best classification performance, even in cases where distinction by concussion symptom profiles alone were extremely difficult. We demonstrate the potential of using ‘invisible’ neural indices of brain functioning to understand and differentiate these debilitating conditions.

Blast effects on post-concussive and mental health outcomes: Data from Canadian Armed Forces breachers and snipers

“…Nevertheless, it has been unclear whether psychiatric illnesses are caused by mTBI, or whether the two con ditions emerge in parallel in relation to the high-level blast event. 2,21,22 Now emerging evidence suggests repeated occu pational exposure to low-level blast -overpressure resulting from outgoing munitions, such as firing heavy weapons systems (e.g., artillery) and/or rifl es (e.g., .50 caliber guns) -can also result in impairments in health and performance. 4 Recently, Belding et al made an important contribution to this literature by conduct ing a population-based epidemiological investigation to examine the association between occupational risk of low-level blast exposure, clinically diagnosed TBI, and conditions comorbid with concussion (e.g., mental health outcomes).…”

Repetitive subconcussion results in disrupted neural activity independent of concussion history

“…Pathological rhythmic neuronal activity -or 'oscillopathies' -and functional connectivity are important pathogenic markers of psychiatric and neurological disorders, including concussion, [21][22][23][24][25][26] post-traumatic stress disorder (PTSD), 21 Parkinson's disease (PD), 27 and Alzheimer's disease (AD). 28 "Pathological slowing" of rhythmic activity and changes in functional connectivity are common features of brain injury and neurodegeneration in military personnel and Veterans with concussion.…”

Earliest Marker of Brain Injury in Repetitive Sports-Related Concussion

“…Improved understanding will also likely occur in future studies with expanded multimodal imaging methods such as magnetoencephalography, which may provide another sensitive neurophysiologic marker of underlying mTBI neuropathology. 10 All of these findings add to the importance of further mTBI research to better understand and detect the neuropathologic consequences of concussion, which begs the question of how benign an SRC really may be. If additional studies can replicate the Churchill et al findings, then objectively assessing CC and CG integrity as early as possible with advanced neuroimaging methods may lead to clinical utility for neurology.…”