***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
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    Input: CONTEXT The return-to-play decision after sport-related cerebral concussion depends in part on knowing when an athlete has fully recovered postural control after injury . OBJECTIVE To describe the postconcussion recovery of postural control using approximate entropy ( ApEn ) , a regularity statistic from nonlinear dynamics . DESIGN Retrospective case series analysis . SETTING Sports medicine research laboratory . PATIENTS OR OTHER PARTICIPANTS Collegiate athletes from whom center-of-pressure and symptom data were collected at preseason , less than 48 hours after injury , and 48 to 96 hours after injury . MAIN OUTCOME MEASURE(S ) Approximate entropy values reflecting the amount of r and omness contained in center-of-pressure oscillations were calculated for anterior-posterior ( AP ) and medial-lateral ( ML ) time series . Equilibrium scores reflecting the amplitude of center-of-pressure AP oscillations were used to indicate postural stability . The number and severity of symptoms were described . RESULTS Compared with the healthy preseason state , ApEn values for the AP and ML time series generally declined immediately after injury in both steady and unsteady injured athletes . At 48 to 96 hours after injury , ApEn values for the ML time series remained significantly depressed ( mean difference compared with preseason = -0.268 , st and ard error = 0.072 ) , even among athletes whose initial postural instability had resolved . We found few significant relationships between changes in ApEn values and changes in symptoms before and after injury . CONCLUSIONS The effects of cerebral concussion on postural control appear to persist for longer than 3 to 4 days , even among athletes with no signs of unsteadiness . Our results may reflect changes in neurophysiologic or mechanical constraints on postural control . Approximate entropy provides a theoretically distinct , valuable measurement alternative that may prove useful for reducing uncertainty in the return-to-play decision CONTEXT Approximately 300 000 sport-related concussions occur annually in the United States , and the likelihood of serious sequelae may increase with repeated head injury . OBJECTIVE To estimate the incidence of concussion and time to recovery after concussion in collegiate football players . DESIGN , SETTING , AND PARTICIPANTS Prospect i ve cohort study of 2905 football players from 25 US colleges were tested at preseason baseline in 1999 , 2000 , and 2001 on a variety of measures and followed up prospect ively to ascertain concussion occurrence . Players injured with a concussion were monitored until their concussion symptoms resolved and were followed up for repeat concussions until completion of their collegiate football career or until the end of the 2001 football season . MAIN OUTCOME MEASURES Incidence of concussion and repeat concussion ; type and duration of symptoms and course of recovery among players who were injured with a concussion during the seasons . RESULTS During follow-up of 4251 player-seasons , 184 players ( 6.3 % ) had a concussion , and 12 ( 6.5 % ) of these players had a repeat concussion within the same season . There was an association between reported number of previous concussions and likelihood of incident concussion .  Players reporting a history of 3 or more previous concussions were 3.0 ( 95 % confidence interval , 1.6 - 5.6 ) times more likely to have an incident concussion than players with no concussion history . Headache was the most commonly reported symptom at the time of injury ( 85.2 % ) , and mean overall symptom duration was 82 hours . Slowed recovery was associated with a history of multiple previous concussions ( 30.0 % of those with > or =3 previous concussions had symptoms lasting > 1 week compared with 14.6 % of those with 1 previous concussion ) . Of the 12 incident within-season repeat concussions , 11 ( 91.7 % ) occurred within 10 days of the first injury , and 9 ( 75.0 % ) occurred within 7 days of the first injury . CONCLUSIONS Our study suggests that players with a history of previous concussions are more likely to have future concussive injuries than those with no history ; 1 in 15 players with a concussion may have additional concussions in the same playing season ; and previous concussions may be associated with slower recovery of neurological function Diffuse axonal injury caused by mild closed head injury ( CHI ) is likely to affect the neural networks concerned with the planning and execution of sequences of memory-guided saccades . Thirty subjects with mild CHI and thirty controls  were tested on 2- and 3-step sequences of memory-guided saccades .  CHI subjects showed more directional errors , larger position errors , and hypermetria of primary saccades and final eye position . No deficits were seen in temporal accuracy ( timing and rhythm ) . These results suggest that computerized tests of saccade sequences can provide sensitive markers of cerebral dysfunction after mild CHI Following on from our earlier findings of a close relationship between motor function and outcome after mild traumatic brain injury ( mTBI ) , this study examined whether it might be possible to predict poor recovery in the form of postconcussion syndrome ( PCS ) based upon early eye and arm motor function . Within 1 week post-injury , we assessed 37 mTBI patients on measures of saccades , oculomotor smooth pursuit , upper-limb visuomotor function , neuropsychological status , and self-reported health condition .  At 3 months , 8 patients met the criteria for PCS . Using discriminant function analyses , we examined whether this future PCS-group could be identified prospect ively based on motor function , neuropsychological status , and self-reported health condition at 1 week post-injury . Early eye movement function was the most effective in distinguishing between PCS and non-PCS patients , achieving a sensitivity and specificity of 100 % in the present sample . This was followed by self-reported early health condition ( sensitivity : 87 % , specificity : 97 % ) , early upper-limb motor performance ( 87 % , 97 % ) , neuropsychological function ( 62 % , 100 % ) , and age , gender , education and clinical measures of trauma severity ( 37 % , 87 % ) . Leave-one-out validation analyses confirmed eye movements as the most robust discriminator ( sensitivity : 62 % , specificity : 97 % ) . Assessment of eye movement function after mTBI may contribute to a prospect i ve identification of patients who develop PCS , supporting the targeting of early health-care intervention Background : Sports-related concussion commonly affects the visual pathways . Current sideline protocol s test cognition and balance but do not include assessment s of visual performance . We investigated how adding a vision-based test of rapid number naming could increase our ability to identify concussed athletes on the sideline at youth and collegiate levels . Methods : Participants in this prospect i ve study included members of a youth ice hockey and lacrosse league and collegiate athletes from New York University and Long Isl and University . Athletes underwent preseason baseline assessment s using : 1 ) the King – Devick ( K-D ) test , a < 2-minute visual performance measure of rapid number naming , 2 ) the St and ardized Assessment of Concussion ( SAC ) , a test of cognition , and 3 ) a timed t and em gait test of balance .  The SAC and timed t and em gait are components of the currently used Sport Concussion Assessment Tool , 3rd Edition ( SCAT3 and Child-SCAT3 ) . In the event of a concussion during the athletic season , injured athletes were retested on the sideline/rink-side . Nonconcussed athletes were also assessed as control participants under the same testing conditions . Results : Among 243 youth ( mean age 11 ± 3 years , range 5–17 ) and 89 collegiate athletes ( age 20 ± 1 years , range 18–23 )  , baseline time scores for the K-D test were lower ( better ) with increasing participant age ( P < 0.001 , linear regression models ) . Among 12 athletes who sustained concussions during their athletic season , K-D scores worsened from baseline by an average of 5.2 seconds ; improvement by 6.4 seconds was noted for the nonconcussed controls ( n = 14 ) . The  vision-based K-D test  showed the greatest capacity to distinguish concussed vs control athletes based on changes from preseason baseline to postinjury ( receiver operating characteristic [ ROC ] curve areas from logistic regression models , accounting for age = 0.92 for K-D , 0.87 for timed t and em gait , and 0.68 for SAC ; P = 0.0004 for comparison of ROC curve areas ) . Conclusions : Adding a vision-based performance measure to cognitive and balance testing enhances the detection capabilities of current sideline concussion assessment . This observation in patients with mild traumatic brain injury reflects the common involvement and widespread distribution of brain pathways dedicated to vision Behavioral studies in monkeys and humans suggest that systematic and variable errors of memory-guided saccades reflect distinct neuronal computations in primate spatial memory . We recorded memory-guided saccades  with a 2-s delay in three patients with unilateral ischemic lesions of the frontal eye field and in three patients with unilateral ischemic lesions of the frontal eye field and the dorsolateral prefrontal cortex . Results suggest that systematic errors of memory-guided saccades originate in the frontal eye field and variable errors in the dorsolateral prefrontal cortex . These data are the first human lesion data to support the hypothesis that these regions provide functionally distinct contributions to spatial short-term memory AIM To use the King-Devick ( KD ) test and Sports Concussion Assessment Tool 2 ( SCAT2 ) in amateur rugby union players to identify witnessed and unrecognised episodes of concussion that occurred from match participation . METHODS A prospect i ve observational cohort study was conducted on a premier club level amateur rugby union team during the 2012 competition in New Zeal and . Every player completed a pre-competition question naire on concussion history , a baseline PCSS and two trials of the KD before they participated in any match activities . RESULTS For players reporting a concussion in the previous three years there was an average of 4.0±2.8 concussions per player . There were 22 concussive incidents recorded over the duration of the competition ( 46 per 1000 match hours ) . Five concussive incidents were witnessed ( 11 per 1000 match hours ) and 17 unrecognised concussive incidents were identified with the KD ( 37 per 1000 match hours ) . Witnessed concussions recorded , on average , a longer KD on the day of injury ( 5.5±2.4s ) than unrecognised concussions ( 4.4±0.9s ) when compared with their baseline KD . DISCUSSION The KD was able to identify players that had not shown , or reported , any signs or symptoms of a concussion but who had meaningful head injury . The current rate of concussion reported was a ten-fold increase in previously reported concussion injury rates . This makes the KD suitable for rapid assessment in a limited time frame on the sideline such as a five-minute window to assess and review suspected concussed players in rugby union AIM To use the King-Devick ( K-D ) test in senior amateur rugby union and rugby league players over a domestic competition season to see if it could identify witnessed and unwitnessed episodes of concussion that occurred from participation in competition matches over three years . METHODS A prospect i ve observational cohort study was conducted on a club level senior amateur rugby union team ( n=36 players in 2012 and 35 players in 2013 ) and a rugby league team ( n=33 players in 2014 ) during competition seasons in New Zeal and . All 104 players completed two trials 10min apart of the K-D at the beginning of their competition season . Concussions ( witnessed or unwitnessed ) were only recorded if they were formally diagnosed by a health practitioner . RESULTS A total of 52 ( 8 witnessed ; 44 unwitnessed ) concussive events were identified over the duration of the study result ing in a concussion injury incidence of 44 ( 95 % CI : 32 to 56 ) per 1000 match participation hours . There was a six-fold difference between witnessed and unwitnessed concussions recorded . There were observable learning effects observed between the first and the second K-D test baseline testing ( 50 vs. 45s ; z=-8.81 ; p<0.001 ) . For every 1 point reduction in each of the post-injury SAC components there was a corresponding increase ( worsening ) of  K-D test times post-match for changes in orientation ( 2.9s ) , immediate memory ( 1.8s ) concentration ( 2.8s ) , delayed recall ( 2.0s ) and SAC total score ( 1.7s ) . DISCUSSION The rate of undetected concussion was higher than detected concussions by using the K-D test routinely following matches . Worsening of the K-D test post-match was associated with reduction in components of the SAC . The appeal of the K-D test is in the rapid , easy manner of its administration and the reliable , objective results it provides to the administrator . The K-D test helped identify cognitive impairment in players without clinical ly observable symptoms Eye movements were recorded electro-oculographically in three patients with a small ischemic lesion affecting the left frontal eye field ( FEF ) and in 12 control subjects .  Reflexive visually guided saccades ( gap and overlap tasks ) , antisaccades , predictive saccades , memory-guided saccades , smooth pursuit and optokinetic nystagmus ( OKN ) were studied in the three patients .  Staircase saccades and double step saccades were also studied in one of the three patients . For both leftward and rightward saccades , latency in the  
    Output:
    
Conclusion Rapid number naming adds to sideline assessment and contributes a critical dimension of vision to sports-related concussion testing