Due to differences in modalities , time course , study design and outcomes , it is not possible to define a single ‘ physiological time window ’ for SRC recovery .
Multiple studies suggest physiological dysfunction may outlast current clinical measures of recovery , supporting a buffer zone of gradually increasing activity before full contact risk .
Aim or objective The aim of this study is to consoli date studies of physiological measures following sport-related concussion ( SRC ) to determine if a time course of postinjury altered neurobiology can be outlined .
This biological time course was considered with respect to clinical ly relevant outcomes such as vulnerability to repeat injury and safe timing of return to physical contact risk .
Temporal Profile of Cerebrovascular Reactivity Impairment, Gray Matter Volumes, and Persistent Symptoms after Mild Traumatic Head Injury
Objective Increased awareness around neurocognitive deficits after mild traumatic brain injury ( mTBI ) has progressed the search for objective , diagnostic , and monitoring tools , yet imaging biomarkers for mTBI and recovery are not established in clinical use . It has been suggested that mTBI impairs cerebrovascular reactivity ( CVR ) to CO2 , which could be related to post-concussive syndrome ( PCS ) . We investigate CVR evolution after mTBI using blood-oxygen-level dependent ( BOLD ) magnetic resonance imaging ( MRI ) and possible correlation with PCS . Methods A prospect i ve cohort of 25 mTBI patients and 18 matched controls underwent BOLD MRI CVR measurements . A subset of 19 mTBI patients underwent follow-up testing . Visits took place at a mean of 63 and 180 days after injury . Symptoms were assessed with the  Sport Concussion Assessment Tool 2 ( SCAT2 ) . Symptoms , CVR and brain volume [ gray matter ( GM ) , white matter ( WM ) , and whole brain ( WB ) ] , age , and sex , were examined between groups and longitudinally within traumatic brain injury ( TBI ) patients . Results Traumatic brain injury participants were 72 % males , mean age being 42.7 years . Control participants were 61 % with mean age of 38.7 years .  SCAT2 scores tended to improve among those mTBI patients with follow-up visits ( p = 0.07 ) ; however , they did not tend to recover to scores of the healthy controls . Brain volumes were not statistically different between groups at the first visit ( WM p = 0.71 ; GM p = 0.36 ) . In mTBI patients , there was a reduction in GM volume between visits 1 and 2 ( p = 0.0046 ) . Although mean CVR indexes were similar ( WM p = 0.27 ; GM p = 0.36 ; and WB p = 0.35 ) , the correlation between SCAT2 and CVR was negative in controls ( WM-r = −0.59 ; p = 0.010 ; GM-r = −0.56 ; p = 0.016 ; brain-r = −0.58 ; p = 0.012 ) and weaker and positive in mTBI ( brain-r = 0.4 ; p = 0.046 ; GM-r = 0.4 ; p = 0.048 ) . SCAT2 correlated with GM volume ( r = 0.5215 , p = 0.0075 ) in mTBI but not in controls ( r = 0.2945 , p = 0.2355 ) . Conclusion There is a correlation between lower GM CVR indexes and lower performance on SCAT2 in patients with mTBI , which seems to be associated with more symptoms . This correlation seems to persist well beyond 120 days . mTBI may lead to a decrease in GM volume in these patients
Due to differences in modalities , time course , study design and outcomes , it is not possible to define a single ‘ physiological time window ’ for SRC recovery .
Multiple studies suggest physiological dysfunction may outlast current clinical measures of recovery , supporting a buffer zone of gradually increasing activity before full contact risk .
Aim or objective The aim of this study is to consoli date studies of physiological measures following sport-related concussion ( SRC ) to determine if a time course of postinjury altered neurobiology can be outlined .
This biological time course was considered with respect to clinical ly relevant outcomes such as vulnerability to repeat injury and safe timing of return to physical contact risk .