Robust RT deficits were observed acutely following concussion .
Minimal magnitude differences were noted when comparing between- and within-subject effects , suggesting that pre-injury baselines may not add clinical value in determining post-injury RT impairment .
RT deficits persisted up till the intermediate-term ( 21–59 days post-injury ) timeframe and indicate lingering deficits exist .
Mean effect size differences were observed between RT measure types and computerized neurocognitive testing platforms ; however , all categories displayed negative effects consistent with impaired RT following concussion .
Reaction time ( RT ) deficits are reported following concussion , but it is unknown when these deficits normalize to pre-injury status .
It is also unclear how factors such as RT measurement technique and participant characteristics influence post-concussion RT .
The purpose of this systematic review and meta- analysis was to ( 1 ) characterize acute post-concussion ( 0–3 days ) RT impairments , ( 2 ) examine RT recovery over time , and ( 3 ) explore moderating factors related to acute RT impairment following concussion .
Recovery of cerebral blood flow following sports-related concussion.
IMPORTANCE Animal models suggest that reduced cerebral blood flow ( CBF ) is one of the most enduring physiological deficits following concussion . Despite this , longitudinal studies documenting serial changes in regional CBF following human concussion have yet to be performed . OBJECTIVE To longitudinally assess the recovery of CBF in a carefully selected sample of collegiate athletes and compare time course of CBF recovery with that of cognitive and behavioral symptoms . DESIGN , SETTING , AND PARTICIPANTS A cohort of collegiate football athletes ( N = 44 ) participated in this mixed longitudinal and cross-sectional study at a private research institute specializing in neuroimaging between March 2012 and December 2013 .  Serial imaging occurred approximately 1 day , 1 week , and 1 month postconcussion for a subset of participants ( n = 17 ) . All athletes reported no premorbid mood disorders , anxiety disorders , substance abuse , or alcohol abuse . MAIN OUTCOMES AND MEASURES  Arterial spin labeling magnetic resonance imaging  was used to collect voxelwise relative CBF at each visit . Neuropsychiatric evaluations and a brief cognitive screen  were also performed at all 3 points . Clinicians trained in sports medicine provided an independent measure of real-world concussion outcome ( ie , number of days withheld from competition ) . RESULTS The results indicated both cognitive ( simple reaction time ) and neuropsychiatric symptoms at 1 day postinjury that resolved at either 1 week ( cognitive ; P < .005 ) or 1 month ( neuropsychiatric ; P < .005 ) postinjury . Imaging data suggested both cross-sectional ( ie , healthy vs concussed athletes ; P < .05 ) and longitudinal ( 1 day and 1 week vs 1 month postinjury ; P < .001 ) evidence of CBF recovery in the right insular and superior temporal cortex . Importantly , CBF in the dorsal midinsular cortex was both decreased at 1 month postconcussion in slower-to-recover athletes ( t11 = 3.45 ; P = .005 ) and was inversely related to the magnitude of initial psychiatric symptoms ( Hamilton Depression Scale : r = -0.64 , P = .02 ; Hamilton Anxiety Scale : r = -0.56 , P = .046 ) , suggesting a potential prognostic indication for CBF as a biomarker . CONCLUSIONS AND RELEVANCE To our knowledge , these results provide the first prospect i ve evidence of reduced CBF in human concussion and subsequent recovery . The resolution of CBF abnormalities closely mirrors previous reports from the animal literature and show real-world validity for predicting outcome following concussion
Robust RT deficits were observed acutely following concussion .
Minimal magnitude differences were noted when comparing between- and within-subject effects , suggesting that pre-injury baselines may not add clinical value in determining post-injury RT impairment .
RT deficits persisted up till the intermediate-term ( 21–59 days post-injury ) timeframe and indicate lingering deficits exist .
Mean effect size differences were observed between RT measure types and computerized neurocognitive testing platforms ; however , all categories displayed negative effects consistent with impaired RT following concussion .
Reaction time ( RT ) deficits are reported following concussion , but it is unknown when these deficits normalize to pre-injury status .
It is also unclear how factors such as RT measurement technique and participant characteristics influence post-concussion RT .
The purpose of this systematic review and meta- analysis was to ( 1 ) characterize acute post-concussion ( 0–3 days ) RT impairments , ( 2 ) examine RT recovery over time , and ( 3 ) explore moderating factors related to acute RT impairment following concussion .