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PubMed2005

The effect of divided attention on gait stability following concussion.

BACKGROUND: The need to identify functional impairment following a brain injury is critical to prevent re-injury during the period of recovery. While many neuropsychological tests have been developed to assess cognitive performance, relatively little information on gait and dynamic stability is available on motor task performance for young adults following concussion. This study was performed to investigate the effect of divided attention following concussion on various gait variables. It was hypothesized that, when compared to uninjured controls, concussed subjects would demonstrate deficits in maintenance of dynamic stability. METHODS: Ten subjects with Grade 2 concussion completed testing within 48 h of injury as well as 10 age-, height-, weight-, and activity-matched controls. The gait protocol consisted of level walking under two conditions: (1) undivided attention (single-task) and (2) while simultaneously completing simple mental tasks (dual-task). Whole-body motion data were collected using a six-camera motion analysis system. A 13-segment biomechanical model was used to compute whole body center of mass motion and velocity. FINDINGS: Walking with a concurrent cognitive task resulted in significant changes in gait and center of mass measurements for both groups. Concussed subjects were found to be able to conservatively adjust their whole body center of mass motion to maintain dynamic stability while walking without divided attention. However, while walking with divided attention, subjects with concussion demonstrated a significantly greater medio-lateral center of mass sway. INTERPRETATION: These data suggest that the ability to control and maintain stability in the frontal plane during walking is diminished under divided attention in individuals following a concussion.

Adult↗
PubMed2006

Descriptive epidemiology of concussion.

To describe the epidemiology of reported concussion derived from a large, nationally representative health survey, the microdata files of the Canadian National Population Health Survey (1996-1997) were analyzed. Respondents reported whether they had "any injuries that were serious enough to limit their normal activities" in the preceding 12 months and the nature of the most serious injury. A total of 99.8% of 81,804 eligible respondents, representing 28,606,100 Canadians, reported their injury experience within the preceding year, with 89 reporting a concussion. The annual prevalence of Canadians reporting a concussion as their most serious injury was 110 per 100,000 population (95% confidence interval: 80, 140). Those reporting concussion were more likely to be younger (P < 0.001) and male (P = 0.02). Males were significantly overrepresented in the 16-34 year-old group (P = 0.004). More than 54% of all concussions were sport-related (95% confidence interval: 39%, 67%), occurring at a place for recreation or sport, with sport having a role in >85% of concussions in the 16-34 year-old group. This study presents annual prevalence estimates of reported concussion, derived from a sizeable, nationally representative population survey.

Adolescent↗
PubMed1983

[EEG and brain-stem evoked potentials in 125 recent concussions].

EEG and ipsi/contralateral BEPs have been recorded in 125 cases of concussion at most 48 h after the cerebral trauma. In 100 cases of minor concussion the temporary loss of consciousness lasted not more than 2 min. In 25 cases of mild concussion, the loss of consciousness lasted until their arrival at the hospital. In minor concussions an abnormal EEG was found in 17% of the cases and in mild concussions, in 56%. The abnormalities of the BEP, more often seen in mild concussions (60%) than in minor concussions (8%), are an increase of interpeak latencies or distorted responses with average to bad reproducibility. The results are discussed.

Adult↗
PubMed2005

The neuropsychological impact of sports-related concussion: a meta-analysis.

There is increasing interest in the potential neuropsychological impact of sports-related concussion. A meta-analysis of the relevant literature was conducted to determine the impact of sports-related concussion across six cognitive domains. The analysis was based on 21 studies involving 790 cases of concussion and 2014 control cases. The overall effect of concussion (d = 0.49) was comparable to the effect found in the non-sports-related mild traumatic brain injury population (d = 0.54; Belanger et al., 2005). Using sports-concussed participants with a history of prior head injury appears to inflate the effect sizes associated with the current sports-related concussion. Acute effects (within 24 hr of injury) of concussion were greatest for delayed memory, memory acquisition, and global cognitive functioning (d = 1.00, 1.03, and 1.42, respectively). However, no residual neuropsychological impairments were found when testing was completed beyond 7 days postinjury. These findings were moderated by cognitive domain and comparison group (control group versus preconcussion self-control). Specifically, delayed memory in studies utilizing a control group remained problematic at 7 days. The implications and limitations of these findings are discussed.

Athletic Injuries↗
PubMed2006

Is there a relationship between whiplash-associated disorders and concussion in hockey? A preliminary study.

PRIMARY OBJECTIVE: To examine the relationship between the occurrence of whiplash-associated disorders and concussion symptoms in hockey players. RESEARCH DESIGN: Prospective cohort observational study to examine the relationship between whiplash associated disorders and concussion in actual hockey play. METHODS AND PROCEDURES: Twenty hockey teams were followed prospectively for one season. Team therapists completed acute and 7-10 day follow-up evaluation questionnaires for all of the players who received either a whiplash mechanism or a concussion. MAIN OUTCOMES AND RESULTS: 183 players were registered for this study; 13 received either a whiplash mechanistic injury or a concussion injury. Initial injuries ranged from WAD I to WAD III and all subjects reported concussion symptoms. Only three subjects reported full resolution of both WAD and concussion symptoms at the 7-10 day follow-up evaluation. CONCLUSIONS: There is a strong association between whiplash induced neck injuries and the symptoms of concussion in hockey injuries. Both should be evaluated when dealing with athletes/patients suffering from either injury.

Adolescent↗
PubMed1996

Neuropsychological deficits following concussion.

The term 'concussion' has been applied to head injuries of varying severity. Most studies have examined subjects suffering concussion of a severity requiring hospital observation, usually as a consequence of motor vehicle accidents. Milder concussive injuries such as those resulting from contact sport are often not reported in hospital-based studies. In this study, subjects with mild concussive injuries were studied with the aim of determining if neuropsychological sequelae are detectable. The subjects received their injuries while playing Australian Rules Football. Baseline (pre-injury) measures on the Paced Auditory Serial Addition Test (PASAT), Digit Symbol Substitution Test (DSST) and Four-Choice Reaction time, involving measures of decision time (DT) and movement time (MT), were obtained in a sample of 130 players. Ten players subsequently concussed were re-tested at 5 days post-injury. A control group of age-matched umpires were assessed on two corresponding occasions. Analyses of covariance showed poorer performances following concussion on the DSST and DT measures. The results suggested that neuropsychological deficits are detectable after resolution of neurological symptoms in the early stages following mild concussive injury.

Brain Concussion↗
PubMed2001

Concussive convulsions: emergency department assessment and management of a frequently misunderstood entity.

Immediate concussive convulsions are an unusual but dramatic sequela to head injuries. Previously believed to be an epileptic phenomenon, they are now thought to be a brief traumatic functional decerebration that results from loss of cortical inhibition. With concussive convulsions generally occurring within seconds of head impact and lasting up to several minutes, patients are initially in a tonic phase, followed by a clonic convulsion. A postictal phase is generally brief if it occurs at all with these episodes. Patients with isolated concussive convulsions have no evidence of structural brain injury as assessed with neuroimaging studies or physical examination. Neuropsychological testing often demonstrates transient cortical dysfunction consistent with the concussive episode. The long-term outcome for patients with isolated concussive convulsion is universally good, with no long-term neurologic sequelae and no increased incidence of early or late posttraumatic epilepsy. Emergency department management should focus on evaluation of the associated concussive injury. The concussive convulsion requires no specific therapy, and antiepileptic medication is not indicated.

Adult↗
PubMed2004

Incidence of cerebral concussions associated with type of mouthguard used in college football.

Controversy exists among sports dentists as to whether or not a 'custom made' mouthguard is more effective in reducing the incidence of cerebral concussion than the boil-and-bite 'non-custom made' mouthguard. While members on each side remain steadfast in their opinion, not a single epidemiological study has been conducted to investigate the effect of type of mouthguard worn on the incidence of cerebral concussion. The aim of this study was to determine if there was a difference between the type of mouthguard worn and the incidence of cerebral concussions among National Collegiate Athletic Association (NCAA) Division I-A football players. During the 15-week 2001 college football season, trainers entered, via an interactive web site, weekly data for each game and practice sessions for the preceding week. Eighty-seven (76%) out of a possible 114 Division I teams participated. A total of 506 297 athletic exposures were recorded; 369 brain concussions were reported. The incidence of cerebral concussions per 1000 exposures was 0.73. Utilizing a risk ratio with a 95% confidence interval, no statistical difference occurred in the incidence of cerebral concussions between football players wearing custom made versus non-custom made mouthguards (0.990,1.750). In this study, there was no advantage of wearing a custom made mouthguard over a boil-and-bite mouthguard to reduce the risk of cerebral concussion in football players.

Brain Concussion↗
PubMedDate not supplied

Epidemiology of concussion in collegiate and high school football players.

Despite evolutionary changes in protective equipment, head injury remains common in football. We investigated concussion in football and associated epidemiologic issues such as 1) incidence of injury, 2) common signs and symptoms, and 3) patterns in making return-to-play decisions. We received 242 of 392 surveys (62%) that were sent to high school and collegiate certified athletic trainers at the beginning of three football seasons. Of the 17,549 football players represented, 888 (5.1%) sustained at least one concussion, and 131 (14.7% of the 888) sustained a second injury during the same season. The greatest incidence of concussion was found at the high school (5.6%) and collegiate division III (5.5%) levels, suggesting that there is an association between level of play and the proportion of players injured. Players who sustained one concussion in a season were three times more likely to sustain a second concussion in the same season compared with uninjured players. Contact with artificial turf appears to be associated with a more serious concussion than contact with natural grass. Only 8.9% of all injuries involved loss of consciousness, while 86% involved a headache. Overall, 30.8% of all players sustaining a concussion returned to participation on the same day of injury.

Adolescent↗
PubMed2003

Computer-based assessment of sports-related concussion.

Sports-related concussion has received considerable attention from neuropsychologists, athletic trainers, team coaches, physicians, families, and athletes. In this context, researchers have recently developed computer programs for the assessment of sports-related concussion. Computer-based assessment of sports-related concussion saves time, allows for team baseline testing, and can be easily incorporated into the sports medicine environment. This article reviews the advantages and limitations of computer-based assessment of sports-related concussion. Within a well-coordinated concussion management program that includes input from a neuropsychologist, computer-based assessment of sports-related concussion will soon be the most common approach for assessing concussion in athletes.

Athletic Injuries↗
PubMed2001

Concussion: the history of clinical and pathophysiological concepts and misconceptions.

Concussion is a well-recognized clinical entity; however, its pathophysiologic basis remains a mystery. One unresolved issue is whether concussion is associated with lesser degrees of diffuse structural change seen in severe traumatic brain injury, or is the mechanism entirely caused by reversible functional changes. This issue is clouded not only by the lack of critical data, but also by confusion in terminology, even in contemporary literature. This confusion began in ancient times when no distinction was made between the transient effects of concussion and severe traumatic brain injury. The first clear separate recognition of concussion was made by the Persian physician, Rhazes, in the 10th century. Lanfrancus subsequently expanded this concept as brain "commotion" in the 13th century, although other Renaissance physicians continued to obscure this concept. By the 18th century, a variety of hypotheses for concussion had emerged. The 19th century discovery of petechial hemorrhagic lesions in severe traumatic brain injury led to these being posited as the basis of concussion, and a similar logic was used later to suggest diffuse axonal injury was responsible. The neuropathology and pathophysiology of concussion has important implications in neurology, sports medicine, medicolegal medicine, and in the understanding of consciousness. Fresh approaches to these questions are needed and modern research tools, including functional imaging and experimental studies of ion-channel function, could help elucidate this puzzle that has evolved over the past 3,000 years.

Brain Concussion↗
PubMed2003

Concussion in professional football: location and direction of helmet impacts-Part 2.

OBJECTIVE: National Football League game video was analyzed for the typical locations of severe helmet impacts in professional football. By use of selected cases that were reconstructed in laboratory tests and reported previously, the magnitude and direction of force causing concussion was determined for these locations. METHODS: Multiple video views were obtained for 182 severe helmet impacts that occurred between 1996 and 2001. From a top view, the helmet was divided into 45-degree quadrants with 0 degrees eyes forward. From a side view, it was divided into seven equal levels, four (+Q1 to +Q4) above the head center of gravity and three below (-Q1 to -Q3). The initial helmet contact was located in these regions. Thirty-one impacts were reconstructed with helmeted Hybrid III dummies involving 25 concussions. Measurement of head translational and rotational acceleration was used to determine the average and +/-1 standard deviation in responses, with impacts reflected to the right side. RESULTS: From video, the majority (71%) of impact is to the helmet shell primarily from a striking player's helmet, arm, or shoulder pad to the side (45-135 degrees) or from ground contact to the back (135-180 degrees). Most impacts were high on the helmet at +Q2 to +Q4. The remainder (29%) were primarily from helmet contact on the facemask at an oblique frontal angle (0-45 degrees) and -Q3 to +Q1 height. From reconstructions, concussion occurred with the lowest peak head acceleration in facemask impacts at 78 +/- 18 g versus an average 107 to 117 g for impacts on other quadrants (t = 2.90, P < 0.005). There was a significantly higher head acceleration for concussed versus nonconcussed players (t = 2.85, P < 0.05). The vector of peak force was essentially horizontal for facemask impacts and downward at 12 to 27 degrees for impacts to the helmet side and back. Concussion in professional football involves four typical conditions, as follows: A, 0- to 45-degree quadrant, -Q3 to +Q3 level, peak force 49 +/- 18 degrees from front and horizontal; B, 45- to 90-degree quadrant, -Q2 to +Q3 level, peak force 73 +/- 12 degrees and horizontal; C, 90- to 135-degree quadrant, +Q1 to +Q4 level, peak force 97 +/- 9 degrees and 12 degrees downward; and D, 135- to 180-degree quadrant, +Q1 to +Q4 level, peak force 157 +/- 1 degrees and 27 degrees downward. Concussed players averaged 3.6 +/- 2.7 initial signs and symptoms. The most common were headaches, dizziness, immediate recall problems, and difficulty with information processing. CONCLUSION: The location, direction, and severity of helmet impacts causing concussion in the National Football League have been defined from analysis of game video and laboratory reconstruction. These conditions define the circumstances in which helmets need to reduce head injury risks in professional football.

Acceleration↗
PubMed2005

Concussion in professional football: brain responses by finite element analysis: part 9.

OBJECTIVE: Brain responses from concussive impacts in National Football League football games were simulated by finite element analysis using a detailed anatomic model of the brain and head accelerations from laboratory reconstructions of game impacts. This study compares brain responses with physician determined signs and symptoms of concussion to investigate tissue-level injury mechanisms. METHODS: The Wayne State University Head Injury Model (Version 2001) was used because it has fine anatomic detail of the cranium and brain with more than 300,000 elements. It has 15 different material properties for brain and surrounding tissues. The model includes viscoelastic gray and white brain matter, membranes, ventricles, cranium and facial bones, soft tissues, and slip interface conditions between the brain and dura. The cranium of the finite element model was loaded by translational and rotational accelerations measured in Hybrid III dummies from 28 laboratory reconstructions of NFL impacts involving 22 concussions. Brain responses were determined using a nonlinear, finite element code to simulate the large deformation response of white and gray matter. Strain responses occurring early (during impact) and mid-late (after impact) were compared with the signs and symptoms of concussion. RESULTS: Strain concentration "hot spots" migrate through the brain with time. In 9 of 22 concussions, the early strain "hot spots" occur in the temporal lobe adjacent to the impact and migrate to the far temporal lobe after head acceleration. In all cases, the largest strains occur later in the fornix, midbrain, and corpus callosum. They significantly correlated with removal from play, cognitive and memory problems, and loss of consciousness. Dizziness correlated with early strain in the orbital-frontal cortex and temporal lobe. The strain migration helps explain coup-contrecoup injuries. CONCLUSION: Finite element modeling showed the largest brain deformations occurred after the primary head acceleration. Midbrain strain correlated with memory and cognitive problems and removal from play after concussion. Concussion injuries happen during the rapid displacement and rotation of the cranium, after peak head acceleration and momentum transfer in helmet impacts.

Brain Concussion↗
PubMed2006

Concussion in professional football: helmet testing to assess impact performance--part 11.

OBJECTIVE: National Football League (NFL) concussions occur at an impact velocity of 9.3 +/- 1.9 m/s (20.8 +/- 4.2 mph) oblique on the facemask, side, and back of the helmet. There is a need for new testing to evaluate helmet performance for impacts causing concussion. This study provides background on new testing methods that form a basis for supplemental National Operating Committee on Standards for Athletic Equipment (NOCSAE) helmet standards. METHODS: First, pendulum impacts were used to simulate 7.4 and 9.3 m/s impacts causing concussion in NFL players. An instrumented Hybrid III head was helmeted and supported on the neck, which was fixed to a sliding table for frontal and lateral impacts. Second, a linear pneumatic impactor was used to evaluate helmets at 9.3 m/s and an elite impact condition at 11.2 m/s. The upper torso of the Hybrid III dummy was used. It allowed interactions with shoulder pads and other equipment. The severity of the head responses was measured by a severity index, translational and rotational acceleration, and other biomechanical responses. High-speed videos of the helmet kinematics were also recorded. The tests were evaluated for their similarity to conditions causing NFL concussions. Finally, a new linear impactor was developed for use by NOCSAE. RESULTS: The pendulum test closely simulated the conditions causing concussion in NFL players. Newer helmet designs and padding reduced the risk of concussion in 7.4 and 9.3 m/s impacts oblique on the facemask and lateral on the helmet shell. The linear impactor provided a broader speed range for helmet testing and more interactions with safety equipment. NOCSAE has prepared a draft supplemental standard for the 7.4 and 9.3 m/s impacts using a newly designed pneumatic impactor. No helmet designs currently address the elite impact condition at 11.2 m/s, as padding bottoms out and head responses dramatically increase. CONCLUSIONS: The proposed NOCSAE standard is the first to address helmet performance in reducing concussion risks in football. Helmet performance has improved with thicker padding and fuller coverage by the shell. However, there remains a challenge for innovative designs that reduce risks in the 11.2 m/s elite impact condition.

Biomechanical Phenomena↗
PubMed2006

Examining concussion rates and return to play in high school football players wearing newer helmet technology: a three-year prospective cohort study.

OBJECTIVE: The purpose of this study was to compare concussion rates and recovery times for athletes wearing newer helmet technology compared to traditional helmet design. METHODS: This was a three-year, prospective, naturalistic, cohort study. Participants were 2,141 high school athletes from Western Pennsylvania. Approximately half of the sample wore the Revolution helmet manufactured by Riddell, Inc. (n = 1,173) and the remainder of the sample used standard helmets (n = 968). Athletes underwent computerized neurocognitive testing through the use of ImPACT at the beginning of the study. Following a concussion, players were reevaluated at various time intervals until recovery was complete. RESULTS: In the total sample, the concussion rate in athletes wearing the Revolution was 5.3% and in athletes wearing standard helmets was 7.6% [chi (1, 2, 141) = 4.96, P < 0.027]. The relative risk estimate was 0.69 (95% confidence interval = 0.499- 0.958). Wearing the Revolution helmet was associated with approximately a 31% decreased relative risk and 2.3% decreased absolute risk for sustaining a concussion in this cohort study. The athletes wearing the Revolution did not differ from athletes wearing standard helmets on the mechanism of injury (e.g., head-to-head strike), on-field concussion markers (e.g., amnesia or loss of consciousness), or on-field presentation of symptoms (e.g., headaches, dizziness, or balance problems). CONCLUSION: Recent sophisticated laboratory research has better elucidated injury biomechanics associated with concussion in professional football players. This data has led to changes in helmet design and new helmet technology, which appears to have beneficial effects in reducing the incidence of cerebral concussion in high school football players.

Adolescent↗
PubMed2006

Concussion in professional football: performance of newer helmets in reconstructed game impacts--Part 13.

OBJECTIVE: The performance of five newer helmets was compared with the baseline VSR-4 helmet in 10 reconstructed cases of National Football League (NFL) collisions causing concussion. The laboratory reconstructions were conducted to determine changes in concussion risk with newer football helmets. METHODS: In 60 laboratory tests, translational and rotational head accelerations were measured in the striking and struck players represented by Hybrid III dummies. Six-axis upper neck loads and moments were measured in five cases with the struck player and five with the striking player. Biomechanical responses and concussion risks were evaluated for each collision to determine changes with newer helmet designs. RESULTS: Thirty-two out of 50 reconstructed cases showed greater than 10% reduction in severity index with newer helmets compared with the VSR-4; four cases increased. The average reduction in concussion risk with newer helmets was 10.8% (range, 6.9-16.7%) based on severity index. The reduction was 9.7% (range, 6.5-13.9%) based on translational acceleration and 18.9% (range, 10.6-23.4%) with rotational acceleration. Neck responses in the struck player showed a general reduction in moment and force with newer helmets. CONCLUSION: With newer football helmets, there was a trend toward 10 to 20% lower risks of concussion in reconstructed National Football League game collisions. However, a few designs and cases showed increased responses. The evaluation of football helmets to the proposed National Operating Committee on Standards for Athletic Equipment concussion standard should lead to more uniform reductions in concussion risk with future football helmets.

Athletic Injuries↗
PubMedDate not supplied

Post-concussion syndrome and the coping hypothesis.

Neuropsychological functioning and level of subjective symptomatology was assessed in 15 adults at 2 weeks, 1 month, and 3 months post-concussion. Performance by the concussion subjects was compared to the results obtained by a matched group of normal controls. At 2 weeks post-injury the concussion subjects had deficits in intellectual, attentional, memory, and language abilities. Visuospatial constructional abilities were relatively preserved. Concussed subjects also reported high levels of disturbance in affective, cognitive, and social functioning. By 3 months post-injury the concussed subjects were still displaying deficits in attentional and language functioning. The level of subjective symptoms reported by the concussed subjects was not significantly different from that reported by controls. Results provide some support for the 'coping hypothesis' explanation of post-concussion syndrome.

Adaptation, Psychological↗
PubMed2003

Recovery from mild concussion in high school athletes.

OBJECT: A computerized neuropsychological test battery was conducted to evaluate memory dysfunction and self-reporting of symptoms in a group of high school athletes who had suffered concussion. METHODS: Neuropsychological performance prior to and following concussion was compared with the test performance of an age-matched control group. Potentially important diagnostic markers of concussion severity are discussed and linked to recovery within the 1st week of injury. CONCLUSIONS: High school athletes who had suffered mild concussion demonstrated significant declines in memory processes relative to a noninjured control group. Statistically significant differences between preseason and postinjury memory test results were still evident in the concussion group at 4 and 7 days postinjury. Self-reported neurological symptoms such as headache, dizziness, and nausea resolved by Day 4. Duration of on-field mental status changes such as retrograde amnesia and posttraumatic confusion was related to the presence of memory impairment at 36 hours and 4 and 7 days postinjury and was also related to slower resolution of self-reported symptoms. The results of this study suggest that caution should be exercised in returning high school athletes to the playing field following concussion. On-field mental status changes appear to have prognostic utility and should be taken into account when making return-to-play decisions following concussion. Athletes who exhibit on-field mental status changes for more than 5 minutes have longer-lasting postconcussion symptoms and memory decline.

Adolescent↗