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PubMed2006

The "value added" of neurocognitive testing after sports-related concussion.

BACKGROUND: Neurocognitive testing has been endorsed as a "cornerstone" of concussion management by recent Vienna and Prague meetings of the Concussion in Sport Group. Neurocognitive testing is important given the potential unreliability of athlete self-report after injury. Relying only on athletes' reports of symptoms may result in premature return of athletes to contact sport, potentially exposing them to additional injury. HYPOTHESIS: Use of computer-based neurocognitive testing results in an increased capacity to detect postconcussive abnormalities after injury. STUDY DESIGN: Case control study; Level of evidence, 3. METHODS: High school and college athletes with a diagnosed concussion were tested 2 days after injury. Postinjury neurocognitive performance (Immediate Postconcussion Assessment and Cognitive Testing) and symptom (postconcussion symptom) scores were compared with preinjury (baseline) scores and with those of an age- and education-matched noninjured athlete control group. "Abnormal" test performance was determined statistically with Reliable Change Index scores. RESULTS: Sixty-four percent of concussed athletes reported a significant increase in symptoms, as judged by postconcussion symptom scores, compared with preinjury baseline at 2 days after injury. Eighty-three percent of the concussed sample demonstrated significantly poorer neurocognitive test results relative to their own baseline performance. The addition of neurocognitive testing resulted in a net increase in sensitivity of 19%. Ninety-three percent of the sample had either abnormal neurocognitive test results or a significant increase in symptoms, relative to their own baseline; 30% of a control group demonstrated either abnormalities in neurocognitive testing or elevated symptoms, as judged by postconcussion symptom scores. For the concussed group, use of symptom and neurocognitive test results resulted in an increased yield of 29% overreliance on symptoms alone. In contrast, 0% of the control group had both symptoms and abnormal neurocognitive testing. CONCLUSION: Reliance on patients' self-reported symptoms after concussion is likely to result in underdiagnosis of concussion and may result in premature return to play. Neurocognitive testing increases diagnostic accuracy when used in conjunction with self-reported symptoms.

Adolescent↗
PubMedDate not supplied

Concussions in college football. A multivariate analysis.

The purpose of this investigation was to examine risk patterns of concussion in college football. Multivariate models were used to interpret the data. Specifically, log-linear modeling and analysis techniques were incorporated into the investigation. An average of 49 college teams were studied over the 8 year period 1975 to 1982. This represented over 36,000 athlete-seasons and 395 team-seasons. The data selected were limited to 1,005 game-related concussions. The general hypotheses tested were the null hypothesis that the variables of team (offense and defense), player position, situation (rushing and passing), and activity (block and tackle) had no effect on the occurrence of these game-related concussions. It was found that concussions were a persistent and regular but relatively infrequent type of injury in college football. Concussions accounted for 75% of the total number of injuries on or about the head. The injuries were examined relative to player position, situation, and activity using a log-linear modeling technique, with interactions among the variables also established. The contribution of each variable was not always equal or completely interactive. Generally, the highest risk of concussion was associated with offensive and defensive players involved in a block on a rushing play. Specifically, running backs demonstrated the highest risk of concussion, regardless of activity. The lowest risk was for offensive linemen and quarterbacks while blocking on any type of play. On defense, the secondary exhibited the highest risk of concussion while being blocked on a running play. Similarly, linemen experienced their greatest risk while being blocked on plays run inside the tackle.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗
PubMed2004

Concussion in professional football: epidemiological features of game injuries and review of the literature--part 3.

OBJECTIVE: A 6-year study was performed to determine the circumstances, causes, and outcomes of concussions in the National Football League. METHODS: Between 1996 and 2001, the epidemiological features of concussions were recorded by National Football League teams with a standardized reporting form. Symptoms were reported and grouped as general symptoms, cranial nerve symptoms, memory or cognitive problems, somatic complaints, and loss of consciousness. The medical actions taken were recorded. In total, 787 game-related cases were reported, with information on the players involved, type of helmet impact, symptoms, medical actions, and days lost. Concussion risks were calculated according to player game positions. RESULTS: There were 0.41 concussions per National Football League game. The relative risk was highest for quarterbacks (1.62 concussions/100 game-positions), followed by wide receivers (1.23 concussions/100 game-positions), tight ends (0.94 concussion/100 game-positions), and defensive secondaries (0.93 concussion/100 game-positions). The majority of concussions (67.7%) involved impact by another player's helmet. The remainder involved impact by other body regions of the striking player (20.9%) or ground contact (11.4%). The three most common symptoms of mild traumatic brain injury were headaches (55.0%), dizziness (41.8%), and blurred vision (16.3%). The most common signs noted in physical examinations were problems with immediate recall (25.5%), retrograde amnesia (18.0%), and information-processing problems (17.5%). In 58 of the reported cases (9.3%), the players lost consciousness; 19 players (2.4%) were hospitalized. A total of 92% of concussed players returned to practice in less than 7 days, but that value decreased to 69% with unconsciousness. CONCLUSION: The professional football players most vulnerable to concussions are quarterbacks, wide receivers, and defensive secondaries. Concussions involved 2.74 symptoms/injury, and players were generally removed from the game. More than one-half of the players returned to play within 1 day, and symptoms resolved in a short time in the vast majority of cases.

Brain Concussion↗
PubMed2005

Concussion in professional football: biomechanics of the striking player--part 8.

OBJECTIVE: Concussive impacts in professional football were simulated in laboratory tests to determine the collision mechanics resulting in injury to the struck player and the biomechanics of the striking players, who were not concussed or neck-injured in the tackle. METHODS: Twenty-seven helmet-to-helmet collisions were reconstructed in laboratory tests using Hybrid III dummies. The head impact velocity, direction, and kinematics matched game video. Translational and rotational head accelerations and six-axis upper neck loads and moments were used to evaluate how the striking player delivered the concussive blow. The neck injury criterion, Nij, was calculated to assess neck injury risks in the striking player. RESULTS: The time-averaged impact force reached 6372 +/- 2486 N at 7.2 milliseconds because of 46.8 +/- 21.7 g head acceleration and 3624 +/- 1729 N neck compression force in the striking player. Fifty-seven percent of the load was contributed by neck compression. The striking players had their heads down and lined up the impact axis through their necks and torsos. This allowed momentum transfer with minimal neck bending and increased the effective mass of the striking player to 1.67 times that of the struck player at peak load. The impact caused 94.3 +/- 27.5 g head acceleration in the concussed players and 67.9 +/- 14.5 g without concussion (t = 2.06, df = 25, P = 0.025). The striking player's Nij was greater than tolerance in 9 of 27 cases by exceeding the 4000 N neck compression limit. For these cases, the average neck compression force was 6631 +/- 977 N (range, 5210-8194 N). Nij was 1.25 +/- 0.16 for eight cases above the tolerance Nij = 1.0. CONCLUSION: In the NFL, striking players line up their heads, necks, and torsos to deliver maximum force to the other player in helmet-to-helmet impacts. The concussive force is from acceleration of the striking player's head and torso load through the neck. Even though neck responses exceeded tolerances, no striking player experienced neck injury or concussion. A head-up stance at impact would reduce the torso inertial load in the collision and the risk of concussion in the struck player.

Biomechanical Phenomena↗
PubMed2001

Recommendations for grading of concussion in athletes.

Mild sports-related concussions, in which there is no loss of consciousness, account for >75% of all sports-related brain injury. Universal agreement on concussion definition and severity grading does not exist. Grading systems represent expertise of clinicians and researchers yet scientific evidence is lacking. Most used loss of consciousness and post-traumatic amnesia as markers for grading concussion. Although in severe head injury these parameters may have been proven important for prognosis, no study has done the same for sport-related concussion. Post-concussion symptoms are often the main features to help in the diagnosis of concussion in sport. Neuropsychological testing is meant to help physicians and health professionals to have objective indices of some of the neurocognitive symptoms. It is the challenge of physicians, therapists and coaches involved in the care of athletes to know the symptoms of concussion, recognise them when they occur and apply basic neuropsychological testing to help detect this injury. It is, therefore, recommended to be familiar with one grading system and use it consistently, even though it may not be scientifically validated. Then good clinical judgement and the ability to recognise post-concussion signs and symptoms will assure that an athlete never returns to play while symptomatic.

Athletic Injuries↗
PubMed2003

[A study on the expression of C-FOS protein after experimental rat brain concussion].

OBJECTIVE: To study the relationship between expression of C-FOS protein and brain concussion and find a sensitive marker of diagnosis of the brain concussion. METHODS: Fifty-five rats were randomly divided into brain concussion groups and control group. The expression of C-FOS protein was microscopically observed by immunohistochemical method. RESULTS: There were negative expression of C-FOS protein in control group. In brain concussion group, however, positive expression of C-FOS protein in some neurons was seen at 15 min after brain concussion, and reach to the peak at 6 h after brain concussion, then decreased gradually. CONCLUSION: These findings suggest that detection of C-FOS protein could be an index of diagnosis of brain concussion and a sensitive marker of timing of injury after brain concussion.

Animals↗
PubMed2005

Concussion in professional football: players returning to the same game--part 7.

OBJECTIVE: A 6-year study was conducted to determine the signs, symptoms, and outcome of players who were concussed and either returned immediately or were rested and returned to the same game in the National Football League (NFL). METHODS: From 1996 to 2001, concussions were recorded by NFL teams by use of a special standardized reporting form filled out by team physicians. Signs and symptoms were grouped by general symptoms, somatic complaints, cranial nerve effects, cognition problems, memory problems, and unconsciousness. Action taken after concussion was recorded for 887 patients. RESULTS: There were 135 players (15.2%) who returned immediately and 304 (34.3%) who rested and returned to the same game after concussion. There were few differences by player position or team activity about the injury or action taken. However, the mean number of signs and symptoms progressively increased from those who returned immediately (1.52), rested and returned to play (2.07), were removed from play (3.51), or were hospitalized (6.55). Immediate recall problems (odds ratio [OR], 1.93; confidence interval [CI], 1.26-2.94), memory problems (OR, 1.52; CI, 1.06-2.19), and the number of signs and symptoms (OR, 1.39; CI, 1.25-1.55) were predictive of removal from play or hospitalization. There was no statistical association between return to play in the same game and a subsequent concussion or a more serious concussion involving 7+ days out. CONCLUSION: Players who are concussed and return to the same game have fewer initial signs and symptoms than those removed from play. Return to play does not involve a significant risk of a second injury either in the same game or during the season. The current decision-making of NFL team physicians seems appropriate for return to the game after a concussion, when the player has become asymptomatic and does not have memory or cognitive problems.

Brain Concussion↗
PubMed2006

[The expression of GFAP after brain concussion in rats].

OBJECTIVE: To study the expression of GFAP and pathologic changes after rats brain concussion, so that to provide evidence on brain concussion for forensic identification. METHODS: Forty-five SD rats were divided into 3, 6, 12, 24 h and 2, 4, 7, 10 d and normal control groups in terms of different wounding time after brain concussion model established, and the expression of GFAP after rats brain concussion were then observed by using SP immunohistochemical method. RESULTS: In normal control brain, low-level GFAP expressions could be observed. After six hours' brain concussion, GFAP positive cells increased obviously. The trend reached to the peak at 7d, partly declined at 10d, then decreased gradually. CONCLUSION: Brain concussion induced the expression of GFAP. The detection of GFAP could be useful for diagnosis of brain concussion on forensic pathology, and could be a reference index for timing of injury after brain concussion.

Animals↗
PubMed2006

Concussions in adolescent athletes.

A concussion is defined as a complex pathophysiologic process affecting the brain that is induced by traumatic biomechanical forces. Concussions are caused by a direct or indirect blow that leads to a graded set of syndromes characterized by functional rather than structural disturbances to the brain. Concussions are characterized by a wide variety of presenting symptoms, including loss of consciousness, amnesia, confusion, headache, and nausea. Concussions occur in patients participating in all levels of athletic activities, with most occurring in younger athletes. The evaluation of a patient with a concussion should include assessment of the airway, breathing, circulation, level of consciousness, orientation, memory, concentration, and neurologic function. Multiple grading scales and return to play guidelines have been published to assist the clinician in the treatment of patients with concussions. Diagnostic and treatment concerns include spinal cord injury, intracranial pathology, second impact syndrome, and long-term impairment of cognitive function. Computerized neuropsychologic testing is a new tool in the treatment of concussions. These tests measure memory, new learning, attention, and reaction time and should be used as an adjunct to other tools for clinical decision making. Published guidelines will assist in treatment decisions; however, it should be kept in mind that all concussions are unique injuries.

Adolescent↗
PubMed2001

A Survey of Practice Patterns in Concussion Assessment and Management.

OBJECTIVES: To identify methods used by athletic trainers to assess concussions and the use of that information to assist in return-to-play decisions and to determine athletic trainers' familiarity with new standardized methods of concussion assessment. DESIGN AND SETTING: A 21-item questionnaire was distributed to attendees of a minicourse at the 1999 National Athletic Trainers' Association Annual Meeting and Clinical Symposia entitled "Use of Standardized Assessment of Concussion (SAC) in the Immediate Sideline Evaluation of Injured Athletes." SUBJECTS: A total of 339 valid surveys were returned by the attendees of the minicourse. MEASUREMENTS: We used frequency analysis and descriptive statistics. RESULTS: Clinical examination (33%) and a symptom checklist (15.3%) were the most common evaluative tools used to assess concussions. The Colorado Guidelines (28%) were used more than other concussion management guidelines. Athletic trainers (34%) and team physicians (40%) were primarily responsible for making decisions regarding return to play. A large number of respondents (83.5%) believed that the use of a standardized method of concussion assessment provided more information than routine clinical and physical examination alone. CONCLUSIONS: Athletic trainers are using a variety of clinical tools to evaluate concussions in athletes. Clinical evaluation and collaboration with physicians still appear to be the primary methods used for return-to-play decisions. However, athletic trainers are beginning to use standardized methods of concussion to evaluate these injuries and to assist them in assessing the severity of injury and deciding when it is safe to return to play.

Journal Article↗
PubMed2001

Management of Cerebral Concussion in Sports: The Athletic Trainer's Perspective.

OBJECTIVE: To present a new approach in the evaluation and management of concussion from the athletic trainer's perspective. BACKGROUND: The evaluation and management of concussion continues to be a controversial topic among sports medicine professionals. Inconsistent management, lack of objective data, and confusion concerning assessment techniques may lead to inappropriate decisions regarding when to return an athlete to competition after concussion. In this article, we provide recommendations and considerations for the certified athletic trainer in the management of concussion. We also present a quantifiable assessment technique that provides more information on which return-to-play decisions can be made; this technique can be used during the initial sideline examination as well as during subsequent follow-up examinations. RECOMMENDATIONS: Certified athletic trainers and team physicians should consistently use appropriate grading scales. Assessment of concussion should include a symptom checklist, the Balance Error Scoring System, and the Standardized Assessment of Concussion, and the results should be compared with the athlete's normal baseline scores. Follow-up neuropsychological and postural stability testing is recommended. Return-to-play decisions should be based on the grade of concussion, scores on objective tests, and presence of concussive symptoms during exertional activities.

Journal Article↗
PubMed2001

Standardized Mental Status Testing on the Sideline After Sport-Related Concussion.

OBJECTIVE: The effects of concussion on mental status are often difficult to assess on routine clinical examination. I investigated the efficacy of standardized mental status testing on the sport sideline to detect abnormalities that result from concussion and provide an objective measure of postinjury cognitive recovery. DESIGN AND SETTING: All subjects underwent a standardized preseason baseline mental status evaluation. Standardized testing of injured and uninjured control subjects was repeated on the sideline immediately after concussion and 48 hours after injury. SUBJECTS: Sixty-three high school and collegiate football players with concussion and 55 uninjured control subjects were studied. MEASUREMENTS: The Standardized Assessment of Concussion (SAC) was administered to evaluate neurocognitive functioning and neurologic status. RESULTS: Immediately after concussion, injured subjects performed significantly below preinjury baseline and below uninjured controls on the SAC. Measurable deficits in orientation, concentration, and memory were evident immediately after concussion. A decline in SAC score at time of injury was 95% sensitive and 76% specific in accurately classifying injured and uninjured subjects on the sideline. Injured subjects demonstrated significant improvements in SAC score 48 hours after injury. CONCLUSIONS: Standardized mental status testing can be a valuable tool to assist the sports medicine clinician in detecting the immediate effects of concussion on mental status, tracking resolution of immediate postconcussive mental status abnormalities, and making more informed decisions on return to play after injury.

Journal Article↗
PubMed2003

Sex Differences and the Incidence of Concussions Among Collegiate Athletes.

OBJECTIVE: To compare sex differences regarding the incidence of concussions among collegiate athletes during the 1997-1998, 1998-1999, and 1999-2000 seasons. DESIGN AND SETTING: A cohort study of collegiate athletes using the National Collegiate Athletic Association (NCAA) Injury Surveillance System; certified athletic trainers recorded data during the 1997-2000 academic years. SUBJECTS: Collegiate athletes participating in men's and women's soccer, lacrosse, basketball, softball, baseball, and gymnastics. MEASUREMENTS: Certified athletic trainers from participating NCAA institutions recorded weekly injury and athlete-exposure data from the first day of preseason practice to the final postseason game. Injury rates and incidence density ratios were computed. Incidence density ratio is an estimate of the relative risk based on injury rates per 1000 athlete-exposures. RESULTS: Of 14 591 reported injuries, 5.9% were classified as concussions. During the 3-year study, female athletes sustained 167 (3.6%) concussions during practices and 304 (9.5%) concussions during games, compared with male athletes, who sustained 148 (5.2%) concussions during practices and 254 (6.4%) concussions during games. Chi-square analysis revealed significant differences between male and female soccer players (chi(2)(1) = 12.99, P =.05) and basketball players (chi(2)(1) = 5.14, P =.05). CONCLUSIONS: Female athletes sustained a higher percentage of concussions during games than male athletes. Of all the sports, women's soccer and men's lacrosse were found to have the highest injury rate of concussions. Incidence density ratio was greatest for male and female soccer players.

Journal Article↗
PubMed2006

Emergency department assessment of mild traumatic brain injury and prediction of post-concussion symptoms at one month post injury.

Mild traumatic brain injury (mTBI) is a common injury and a significant proportion of those affected report chronic symptoms. This study investigated prediction of post-concussion symptoms using an Emergency Department (ED) assessment that examined neuropsychological and balance deficits and pain severity of 29 concussed individuals. Thirty participants with minor orthopedic injuries and 30 ED visitors were recruited as control subjects. Concussed and orthopedically injured participants were followed up by telephone at one month to assess symptom severity. In the ED, concussed subjects performed worse on some neuropsychological tests and had impaired balance compared to controls. They also reported significantly more post-concussive symptoms at follow-up. Neurocognitive impairment, pain and balance deficits were all significantly correlated with severity of post-concussion symptoms. The findings suggest that a combination of variables assessable in the ED may be useful in predicting which individuals will suffer persistent post-concussion problems.

Adult↗
PubMed2003

On-field predictors of neuropsychological and symptom deficit following sports-related concussion.

OBJECTIVE: Investigate the relationship between on-field markers of concussion severity and postinjury neuropsychological and symptom presentation in an athlete-specific population. DESIGN: Case control study. SETTING: Multicenter analysis of high school and college athletes. PARTICIPANTS: A total of 78 athletes sustaining sports-related concussion were selected from a larger sample of 139 concussed athletes. ASSESSMENT OF PREDICTOR VARIABLES: On-field presence of disorientation, posttraumatic amnesia, retrograde amnesia, and loss of consciousness. MAIN OUTCOME MEASURES: ImPACT, a computerized neuropsychological test battery, was administered pre-season and, on average, 2 days postinjury. Good postinjury presentation (n = 44) was defined as no measurable change, relative to baseline, in terms of both ImPACT memory and symptom composite scores. Poor presentation (n = 34) was defined as a 10-point increase in symptom reporting and 10-point decrease in memory functioning (exceeding the 80% confidence interval for measurement error on ImPACT). Athletes failing to meet good or poor selection criteria (n = 61) were not included in the analysis. RESULTS: Odds ratios revealed that athletes demonstrating poor presentation at 2 days postinjury were over 10 times more likely (P < 0.001) to have exhibited retrograde amnesia following concussive injury when compared with athletes exhibiting good presentation. Similarly, athletes with poor presentation were over 4 times more likely (P < 0.013) to have exhibited posttraumatic amnesia and at least 5 minutes of mental status change. There were no differences between good and poor presentation groups in terms of on-field loss of consciousness. CONCLUSIONS: The presence of amnesia, not loss of consciousness, appears predictive of symptom and neurocognitive deficits following concussion in athletes. Athletes presenting with on-field amnesia should undergo comprehensive and individualized assessment prior to returning to sport participation. Continued refinement of sports concussion grading scales is warranted in lieu of consistent findings that brief loss of consciousness is not predictive of concussion injury severity.

Adolescent↗
PubMed2006

Cognition in the days following concussion: comparison of symptomatic versus asymptomatic athletes.

BACKGROUND: Concussion is a common neurological injury occurring during contact sport. Current guidelines recommend that no athlete should return to play while symptomatic or displaying cognitive dysfunction. This study compared post-concussion cognitive function in recently concussed athletes who were symptomatic/asymptomatic at the time of assessment with that of non-injured (control) athletes. METHODS: Prospective study of 615 male Australian Rules footballers. Before the season, all participants (while healthy) completed a battery of baseline computerised (CogSport) and paper and pencil cognitive tasks. Sixty one injured athletes (symptomatic = 25 and asymptomatic = 36) were reassessed within 11 days of being concussed; 84 controls were also reassessed. The serial cognitive function of the three groups was compared using analysis of variance. RESULTS: The performance of the symptomatic group declined at the post-concussion assessment on computerised tests of simple, choice, and complex reaction times compared with the asymptomatic and control groups. The magnitude of changes was large according to conventional statistical criteria. On paper and pencil tests, the symptomatic group displayed no change at reassessment, whereas large improvements were seen in the other two groups. CONCLUSION: Injured athletes experiencing symptoms of concussion displayed impaired motor function and attention, although their learning and memory were preserved. These athletes displayed no change in performance on paper and pencil tests in contrast with the improvement observed in asymptomatic and non-injured athletes. Athletes experiencing symptoms of concussion should be withheld from training and competition until both symptoms and cognitive dysfunction have resolved.

Adult↗
PubMed2004

Concussion in professional football: injuries involving 7 or more days out--Part 5.

OBJECTIVE: A 6-year study was conducted to determine the signs, symptoms, and outcome of concussions with 7 or more (7+) days out from play or extended postconcussion recovery in the National Football League (NFL). METHODS: From 1996 to 2001, reporting of concussion was performed by NFL teams using a special standardized reporting form filled out by team physicians. Signs and symptoms were grouped by general symptoms, somatic complaints, cranial nerve effects, cognition problems, memory problems, and unconsciousness. Medical action taken and management were recorded. In all, 887 concussions were reported in practices and games. RESULTS: There were 72 concussions (8.1%) involving 7+ days out from play. The highest frequency occurred in quarterbacks (14.8%), the return unit on special teams (11.8%), and secondary (10.8%). Quarterbacks had the highest odds ratio (OR) of 7+ days out with concussion (OR = 2.10, P = 0.049), whereas running backs had the lowest relative risk (OR = 0.13, P = 0.021). The greatest fraction of 7+ days out occurred in passing plays (36.1%) and kickoffs (22.2%). Many signs and symptoms occurred at a greater frequency on initial examination in players 7+ days out; the average number per player was 4.64 with 7+ days out versus 2.58 with fewer days out (t = 6.02, df = 77.1). The signs and symptoms with the highest incidence for 7+ days out were disorientation to time (chi(2) = 51.2, P = 001), retrograde amnesia (chi(2) = 33.2, P = 0.001), fatigue (chi(2) = 28.1, P = 0.001), and the general category of cognition problems (chi(2) = 21.7, P = 0.001). Loss of consciousness for more than 1 minute was a predictor of 7+ days out (chi(2) = 33.5, P = 0.001), although it occurred in only 7.9% of cases. Of players with 7+ days out, 72.2% were removed from the game and 12.5% were hospitalized. These frequencies were significantly greater than for players with fewer than 7 days out (chi(2) = 68.03, df = 3, P < 0.0001). Approximately 90% of players were managed by rest, irrespective of days out, but a greater fraction were given drug or medical therapies with prolonged days out. CONCLUSION: The most vulnerable players for 7+ days out with concussion were quarterbacks and the secondary in professional football. Although 8.1% of concussions involved 7+ days out, only 1.6% involved a prolonged postconcussion syndrome. They recovered from symptoms and had a consistent return to play in the NFL.

Adult↗
PubMed1982

Spectral analysis of the electroencephalographic response in experimental concussion in the rat.

The phenomenon of concussion was studied in 32 non-anesthetized Sprague-Dawley male rats, previously implanted with chronic epidural electrodes for bipolar recording of the electroencephalogram (EEG). EEG records were taken continuously preceding during and following concussion, which was produced by a lead-tipped dart, shot from a spring-loaded pistol. The mass and velocity of the striking instrument were measured, so that its momentum and kinetic energy could be calculated. Spectral analysis of the EEG was performed by means of computer, using Fast Fourier Transform. In stage 1-2 of concussion, the power spectra of alpha, beta, and theta frequency bands were decreased by 25%, 37% and 10%, respectively. The delta spectrum alone was increased by 15%. Stage 3-4 of concussion was characterized by more profound depression of the power spectra of alpha, beta, theta and delta frequency bands (56%, 49%, 34% and 31%, respectively). EEG depression occurred immediately, reached a peak at 5 min and recovered at an average of 2 h in the concussed rats. In 5 rats, which did not recover completely, post-mortem examination revealed cerebral contusion or intracranial hematomas. These rats were not included in the analysis of 'concussion'. The EEG changes suggest the involvement of the cerebral cortex in the traumatic unconsciousness of concussion and are similar to those of spreading depression, as noted by previous investigators.

Animals↗