Preliminary evidence from a prospective DTI study suggests a posterior‐to‐anterior pattern of recovery in college athletes with sports‐related concussion

Abstract

ObjectivesWe compared the integrity of white matter (WM) microstructure to the course of recovery in athletes who sustained one sports‐related concussion (SRC), assessing individual longitudinal changes in WM fiber tracts following SRC using pre‐ and post‐injury measurements.Materials and MethodsBaseline diffusion tensor imaging (DTI) scans and neuropsychological tests were collected on 53 varsity contact‐sport college athletes. Participants (n = 13) who subsequently sustained an SRC underwent DTI scans and neuropsychological testing at 2 days, 2 weeks, and 2 months following injury.ResultsRelying on tract‐based spatial statistics (TBSS) analyses, we found that radial diffusivity (RD) and mean diffusivity (MD) were significantly increased at 2 days post‐injury compared to the same‐subject baseline (corrected p < 0.02). These alterations were visible in anterior/posterior WM regions spanning both hemispheres, demonstrating a diffuse pattern of injury after concussion. Implicated WM fiber tracts at 2 days include the following: right superior/inferior longitudinal fasciculus; right/left inferior fronto‐occipital fasciculus; right corticospinal tract; right acoustic radiation; right/left anterior thalamic radiations; right/left uncinate fasciculus; and forceps major/minor. At 2 weeks post‐injury, persistently elevated RD and MD were observed solely in prefrontal portions of WM fiber tracts (using same‐subject contrasts). No significant differences were found for FA in any of the post‐injury comparisons to baseline. Plots of individual subject RD and MD in prefrontal WM demonstrated homogenous increases from baseline to just after SRC; thereafter, trajectories became more variable. Most subjects’ diffusivity values remained elevated at 2 months post‐injury relative to their own baseline. Over the 2‐month period after SRC, recovery of WM fiber tracts appeared to follow a posterior‐to‐anterior trend, paralleling the posterior–anterior pattern of WM maturation previously identified in the normal population.ConclusionThese results suggest greater vulnerability of prefrontal regions to SRC, underline the importance of an individualized approach to concussion management, and show promise for using RD and MD for imaging‐based diagnosis of SRC.

Baseline vs. cross-sectional MRI of concussion: distinct brain patterns in white matter and cerebral blood flow

“…Substantial inter-individual differences have been seen in the patterns of concussion-related pathophysiology 23,24,27 potentially stemming from injury biomechanics 52 , but also likely confounded by variations in pre-injury brain physiology [17][18][19][20] . Although the present study was based on a limited sample size, the findings, in combination with emerging literature 26,27,57 , underscore the importance of research that includes baseline pre-injury data, to better characterize the neurobiology of concussion and validate existing group-level cross-sectional studies. The primary study finding, of distinct spatial patterns of concussion-related abnormalities for baseline and cross-sectional analyses, suggest that the use of pre-injury baseline data may be most critical in the identification of most sensitive brain regions for biomarkers and/or interventions 9 .…”

Concussion History and Heart Rate Variability During Bouts of Acute Stress

“…25 Furthermore, these brain regions and the interconnections among them are some of the most frequently impacted by concussions. 26 Accordingly, the differing HRV responses observed in athletes with a history of concussion during acute bouts of either mental or physical stressors, could be an indicator of improper or inefficient communication among physiological systems in response to the current situational demands.…”

Concussion in Sports

“…Neuroanatomical lesions are not present in this type of mTBI, meaning that concussed patients are negative on classical imaging techniques such as CT scan and MRI. However, advanced neuroimaging techniques, such as functional MRI (fMRI) and diffusion tensor imaging (DTI), are useful tools with which to evidence concussion-associated metabolic and ultrastructural brain alterations [ 33 , 34 ]. Additionally, 1 H-magnetic resonance spectroscopy ( 1 H-MRS) is a valid neuroradiological approach allowing to measure brain specific metabolites, such as N-acetylaspartate (NAA), strictly connected to cerebral energy metabolism and mitochondrial functions [ 6 , 15 , 24 , 27 ].…”

“…A series of studies have evidenced neurophysiologic changes, following a concussion, in the motor evoked potential waveform amplitude, in corticomotor conduction time, and in metabolic, ionic, and neurotransmitter (e.g., glutamate, GABA) processes [ 20 ]. This has sparked research incorporating advanced neuroimaging techniques, analysis of fluid biomarkers, and functional genomics and biomechanics, in addition to NP tests outcomes [ 23 , 24 , 33 , 34 , 44 , 45 , 46 ]. Furthermore, translational studies are constantly improving our understanding of optimal rehabilitation approaches, like subthreshold aerobic exercise [ 47 , 48 , 49 , 50 ], and have led to a shift from the earlier “complete rest” approach to the current gradual active management involvements after concussion [ 47 ].…”