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At least 19 recordsLinked to original sources

PubMed2026

Dose-dependent white matter changes associated with repetitive head impacts in former American football players.

Repetitive head impacts sustained during American football have been associated with neuropathological changes such as white matter shear injuries. However, the impact of specific factors, such as age of first exposure and cumulative head impact burden, on white matter integrity remains unclear. This study investigated in vivo white matter microstructural changes using diffusion tensor imaging and tract-based spatial statistics in 165 male former American football players (mean age 57.3 years, range 45-74) and 52 unexposed asymptomatic male controls (mean age 59.4 years, range 45-74) in the DIAGNOSE CTE Research Project. Compared to controls, former football players exhibited significantly higher fractional anisotropy (FA) in 1.97% of the white matter skeleton (1552 voxels; Cohen's d = 0.587) and higher tissue-corrected FA (FAt) in 1.48% of the white matter skeleton (1004 voxels; Cohen's d = 0.616). No significant differences were observed for mean diffusivity, axial diffusivity, radial diffusivity, or free water between football players and controls. Among football players, there were no significant differences in the white matter microstructure between players diagnosed with traumatic encephalopathy syndrome and those without the diagnosis. Lower FA was significantly associated with older age (P < 0.00001) and an earlier age of first exposure to tackle football (P < 0.01), while lower FAt was associated with greater cumulative head impact burden, specifically higher linear acceleration (P < 0.04) and rotational force (P < 0.02). This study highlights the influential role of exposure factors on white matter microstructure in former American football players, as well as the utility of diffusion tensor imaging to aid in characterizing the long-term effects of repetitive head impacts in contact sport athletes.

American football↗

PubMed2026

Regional ventricular enlargement as an in vivo biomarker of cumulative biomechanical neurodegeneration in former American football players.

INTRODUCTION: Repetitive head impacts (RHIs) have been linked to later life neurodegeneration, yet the in vivo structural correlates of cumulative biomechanical loading remain unclear. We examined whether regional ventricular morphology in former American football players reflects exposure burden and traumatic encephalopathy syndrome (TES) classification. METHODS: Participants included 170 male former football players and 54 age-matched asymptomatic male controls from the Diagnostics, Imaging, and Genetics Network for the Objective Study and Evaluation of Chronic Traumatic Encephalopathy Research Project. Subject-specific manual segmentation quantified lateral ventricle, inferior horn, third ventricle, and fourth ventricle volumes. Group and exposure associations were tested using generalized least squares models. RESULTS: Former players showed larger left inferior lateral ventricle volume than controls, with the largest effects among professional players. Greater cumulative linear and rotational acceleration exposure was associated with enlargement across lateral ventricular and inferior horn regions. DISCUSSION: Regional ventricular enlargement may represent an in vivo marker of cumulative biomechanical loading after RHI exposure.

Humans↗

PubMed2002

An evaluation of the cumulative concussive effect of soccer heading in the youth population.

Soccer is the most popular team sport in the world, with 120 million individuals participating and 16 million of these individuals being based in the United States. In addition, soccer has become the fastest growing team sport in the United States over the past 10 years. Head impact injuries have been cited as comprising 15% of all injuries related to soccer. Previous studies have identified the technique of heading as being a significant factor in head impact injuries. In fact, 85% of various subgroups of participants, 19 years of age and older, have had a diminution in cognitive function abilities on a permanent basis. It was the purpose of this study to evaluate the effect of repetitive head impacts due to heading in 57 youth soccer players with a mean age of 11.5 years. The data were collected over three seasons during the first year, which correlated to approximately 60 games and/or practices. One team of 18 boys was followed for an additional year. The data collected included a cognitive function test, as well as documentation of concussive symptoms. These cognitive evaluations, conducted at both periods of time, revealed that statistically significant differences were not evident when compared to standardized norms with the exception of verbal learning. There was an inverse relationship between the number of ball impacts and verbal learning. Of note, however, is that 49% of the year-one study group did complain of headaches after heading the ball.

Adolescent↗

PubMed2001

Mild head injury increasing the brain's vulnerability to a second concussive impact.

OBJECT: Mild, traumatic repetitive head injury (RHI) leads to neurobehavioral impairment and is associated with the early onset of neurodegenerative disease. The authors developed an animal model to investigate the behavioral and pathological changes associated with RHI. METHODS: Adult male C57BL/6 mice were subjected to a single injury (43 mice), repetitive injury (two injuries 24 hours apart; 49 mice), or no impact (36 mice). Cognitive function was assessed using the Morris water maze test, and neurological motor function was evaluated using a battery of neuroscore, rotarod, and rotating pole tests. The animals were also evaluated for cardiovascular changes, blood-brain barrier (BBB) breakdown, traumatic axonal injury, and neurodegenerative and histopathological changes between 1 day and 56 days after brain trauma. No cognitive dysfunction was detected in any group. The single-impact group showed mild impairment according to the neuroscore test at only 3 days postinjury, whereas RHI caused pronounced deficits at 3 days and 7 days following the second injury. Moreover, RHI led to functional impairment during the rotarod and rotating pole tests that was not observed in any animal after a single impact. Small areas of cortical BBB breakdown and axonal injury. observed after a single brain injury, were profoundly exacerbated after RHI. Immunohistochemical staining for microtubule-associated protein-2 revealed marked regional loss of immunoreactivity only in animals subjected to RHI. No deposits of beta-amyloid or tau were observed in any brain-injured animal. CONCLUSIONS: On the basis of their results, the authors suggest that the brain has an increased vulnerability to a second traumatic insult for at least 24 hours following an initial episode of mild brain trauma.

Animals↗

PubMed2003

Does soccer headgear attenuate the impact when heading a soccer ball?

UNLABELLED: There is increasing concern that repetitive blows to the head, such as those from heading a soccer ball, can cause measurable cognitive impairment. Reducing acceleration of impact could reduce neurologic sequelae. OBJECTIVE: To measure the effectiveness of four different types of soccer headgear in reducing the acceleration of impact. METHODS: A standard magnesium headform was instrumented with a triaxial accelerometer. A soccer ball was propelled at the headform at three different speeds known to occur in soccer play: 9, 12, and 15 m/sec (20, 26, and 34 mph). The main outcome was the peak acceleration of the headform associated with these impacts with and without protective headgear. RESULTS: Peak accelerations were found in a range from 144 m/s(2) to 289 m/s(2) (14.67-29.5 G, G = 9.81 m/s(2)). Using multivariate analysis of variance (MANOVA) methods to compare the headbands and controls, there was no significant difference in the measured accelerations at the center of gravity with or without headgear (p = 0.50). However, the interaction term of headbands, pressure, and speed was significant at F = 5.51 and p = 0.00001. Using contrasts within conditions, some headbands were found to cause a decrease in peak acceleration at the highest speed and pressure. CONCLUSIONS: Currently available headgear for soccer heading shows little ability to attenuate impact during simulated soccer heading. However, statistically significant decreases are present at the highest speeds and pressures tested, suggesting the headbands may play a role in decreasing impact for more forceful blows.

Acceleration↗

PubMed1997

Outcome after severe non-accidental head injury.

Over the past three years 15 children have been admitted to the paediatric intensive care unit (PICU) at Addenbrooke's hospital suspected of having non-accidental injuries; presentation was diverse and often mild and out of proportion to the degree of morbidity seen at discharge and follow up. When compared with a group of similar aged children admitted to the PICU with severe head injury caused by accidental impact trauma, the differences in morbidity were profound. It is suggested that these differences are explained in part by the predominant repetitive rotational forces experienced during severe shaking compared with the translocational forces that the head experiences during impact injuries. This anecdotal evidence supports the theory that shaking alone may cause severe intracranial injury. Thus campaigns should continue to increase public and doctors' awareness that shaking may be dangerous.

Accidents↗

PubMed2006

Acute hemispheric swelling associated with thin subdural hematomas: pathophysiology of repetitive head injury in sports.

INTRODUCTION: The most common head injury in sports is concussion, and repeated concussions occurring within a short period occasionally can be fatal. Acute subdural hematoma is the most common severe head injury and can be associated with severe neurologic disability and death in sports. We investigated severe brain damage resulting from repetitive head injury in sports, and evaluated the pathophysiology of sports-related repetitive injury. METHODS: We reviewed the literature containing detailed descriptions of repetitive severe sports-related head injury. In total, 18 cases were analyzed with regard to age, gender, type of sports, symptoms before second injury, and pathology of brain CT scans. RESULTS: The majority of cases involved young males aged 16 to 23 years old, who sustained a second head injury before symptoms from the first head injury had resolved. Ten of 15 cases did not suffer loss of consciousness at insult. Eight cases were confirmed on brain CT scans after the second injury, and all 8 cases revealed brain swelling associated with a thin subdural hematoma. CONCLUSIONS: Second impact syndrome is thought to occur because of loss of autoregulation of cerebral blood flow, leading to vascular engorgement, increased intracranial pressure, and eventual herniation. Our investigation suggests that the existence of subdural hematoma is a major cause of brain swelling following sports-related, repetitive head injury.

Adolescent↗

PubMedDate not supplied

Freiberg's infraction in identical twins: a case report.

Freiberg's infraction is an ostechondrosis of a lesser metatarsal head resulting in degeneration of the metatarsophalangeal joint. Several mechanisms have been suggested in its pathenogenesis. Freiberg first described the entity and believed single impact trauma was the underlying cause. Repetitive biomechanical microtrauma is the most widely accepted etiologic theory. Other factors contributing to its development include aseptic necrosis, ischemia, and a congenital predisposition. We present a case report of Freiberg's infraction occurring in identical twins involving multiple metatarsals in various stages of degeneration. One of the twins was affected unilaterally whereas the other twin was affected bilaterally. Both twins had involvement of the second metatarsal on the same side extremity. The occurrence of Freiberg's infraction in identical twins suggests that an underlying congenital predisposition to the condition may play more of a role than previously considered.

Adult↗

PubMed2000

[Effect of repetitive prenatal corticosteroid medication on intrauterine growth and growth in early childhood].

OBJECTIVE: The evaluation of the effects of repeated antenatal corticosteriod (CS) medication on birth size and size at the age of 4 years. METHODS: 82 children exposed to CS initially between 26 and 28 weeks of gestation were matched with 82 controls of the same gestational age and sex. RESULTS: No differences were observed between the CS and control groups with regard to weight, head circumference, and length at birth and at the age of 4 years. CONCLUSIONS: Our study failed to demonstrate that repetitive antenatal medication with CS in order to induce lung maturation has a negative impact on intrauterine growth and growth in early childhood.

Betamethasone↗

PubMed2004

Traumatic axonal injury is exacerbated following repetitive closed head injury in the neonatal pig.

Inflicted brain injury is associated with widespread traumatic axonal injury (TAI) and subdural hematoma and is the leading cause of death in infants and children. Anesthetized 3-5-day-old piglets were subjected to either a single (n = 5) or double (n = 6, 15 min apart) rapid (<15 msec), non-impact, axial rotations of the head. Peak rotational velocities (averaging 172 rad/sec for single and 138 rad/sec for double loads) were lower than those utilized to induce severe injuries (240-260 rad/sec; Raghupathi and Margulies, 2002). At 6 h post-injury, brains were evaluated for the presence TAI using immunohistochemistry for the 200-kDa neurofilament protein (NF200). Accumulation of NF200 was observed in both contiguous (swellings) and in disconnected axons (axon bulbs) predominantly in central deep and peripheral subcortical white matter regions in the frontal, temporal, and parietal lobes of all injured piglets. Although the density of injured axons did not significantly increase after two rotational loads, the distribution of injured axons shifted from a few foci (2.2 +/- 2.3 per animal) with 1-2 swellings/bulbs following a single rotation to significantly more foci (14.7 +/- 11.9), and additional foci (2.5 +/- 1.9) containing 3 or more axon swellings/bulbs following two rotational loads. The density and distribution of injured axons following a single mild rotation were significantly reduced compared with those obtained previously following a single more severe rotational load. Collectively, these data are indicative of the graded response of the immature brain to rotational load magnitude, and importantly, the vulnerability to repeated, mild, non-impact loading conditions.

Animals↗

PubMed2005

The effect of postural correction on muscle activation amplitudes recorded from the cervicobrachial region.

In clinical practice, postural correction is a common treatment approach for individuals with neck and shoulder pain. As chronic static muscle use is thought to be associated with the onset of some neck and shoulder pain syndromes, it is important to understand the impact a postural correction program might have on muscle activation amplitudes in the neck and shoulder regions. Normalized surface electromyographic data were recorded from the levator scapulae, upper trapezius, supraspinatus, posterior deltoid, masseter, rhomboid major, cervical erector spinae, and sternocleidomastoid muscles of the dominant side of each of eighteen healthy subjects. Subjects performed five repetitions of each of four seated typing postures (habitual, corrected, head-forward and slouched) and four standing postures (habitual, corrected, and head-forward and slouched). Repeated-measures analysis of variance models (alpha=0.05) revealed that in sitting postural correction tended to decreased the level of muscle activation required in all muscles studied during seated computer work, however this finding was not statistically significant. Corrected posture in sitting did, however produce a statistically significant reduction in muscle activity compared to forward head posture. Corrected posture in standing required more muscle activity than habitual or forward head posture in the majority of cervicobrachial and jaw muscles, suggesting that a graduated approach to postural correction exercises might be required in order to train the muscles to appropriately withstand the requirements of the task. A surprising finding was that muscle activity levels and postural changes had the largest impact on the masseter muscle, which demonstrated activation levels in the order of 20% maximum voluntary electrical activation.

Adult↗

PubMed2005

[Deformation of the fist due to Taekwondo training].

Over a period of 25 years a 40-year-old taekwondo world champion had conditioned his hand for so-called "breaking championships", by repeatedly striking progressively harder materials (sand, dried peas, a mixture of dried peas and small stones, and such like). An MRI investigation revealed an augmentation of tissue between the heads of the metacarpals. The biomechanical effect resulting from this "smoothing" of the striking area of the fist is to reduce the peak load acting on the prominent bony elements on impact, and thus reduce the risk of injury. The build-up of tissue represents a response of connective tissue to repetitive microtrauma.

Adult↗

PubMed2002

Lacrosse Helmet Designs and the Effects of Impact Forces.

OBJECTIVE: To examine the effects of repetitive impact forces on lacrosse helmets and increase awareness of helmet safety standards about reconditioning and recertification practices. DESIGN AND SETTING: The independent variables for this study consisted of 4 lacrosse helmets of various design: 2 contemporary helmets (Sport Helmets Cascade and Cascade Air) and 2 traditional helmets (Sport Helmets Ultralite and Bacharach Ultralite). The dependent variable was attenuation of impact forces as measured by the Gadd Severity Index (GSI). Helmets were tested at an independent testing facility certified by the National Athletic Equipment Reconditioners Association. MEASUREMENTS: Helmets were raised to 152 cm and released onto an anvil padded with a 1.27-cm rubber modular elastomer programmer. Ten treatments to a front (FD) and right rear boss drop site (RD) were performed. A triaxial accelerometer within the head form measured impact force. Peak acceleration data were integrated into the GSI. We performed a 1-way analysis of variance and calculated descriptive statistics and the Tukey post hoc test. RESULTS: A statistically significant difference was seen in FD GSI score (F(3,36) = 9.680, P <.05) and in the RD GSI score (F(3,36) = 28.140, P <.05) between helmet types. Mean GSI scores were 1166.1, 1117.6, 857, and 1222.8 for the FD and 974.5, 1022.1, 1376.3, and 1496.5 for the RD for Sport Helmets Cascade, Cascade Air, Ultralite, and Bacharach Ultralite, respectively. With repetitive drops, GSI scores increased, indicating a greater chance for cerebral injury. Percentage increases in GSI scores from drops 1 to 10 were 48.8, 54.3, 45.6, and 18.8 on the FD and 22.6, 35.9, 71.7, and 57.4 on the RD for the Sport Helmets Cascade, Cascade Air, Ultralite, and Bacharach Ultralite, respectively. CONCLUSIONS: Our findings indicate differences between helmets at the 2 drop sites and decreasing capacity of the helmets to dissipate forces with repetitive impacts.

Journal Article↗

PubMedDate not supplied

Dissociation of modular humeral head components: a biomechanical and implant retrieval study.

In vivo dissociation of the Morse-taper of shoulder arthroplasty modular humeral components has been reported. The incidence of this complication appears to be approximately 1:1000. The objective of this study was to identify conditions that might affect the Morse-taper interface strength in humeral components. Mechanical tests were performed to load and dissociate humeral heads from the humeral stems (titanium). The effect of loading rate, load amplitude, and number of impactions was investigated. Dissociation force was measured after the taper was contaminated with water, oil, blood, and bone cement particles. The mean dissociation force after two impactions with a mallet was 2926 +/- 955 N. Dissociation force was linearly proportional to impaction force. Repetitive loading beyond two impactions did not significantly increase taper strength. Contamination of the taper with as little as 0.4 ml of fluid could prevent fixation of the taper.

Biomechanical Phenomena↗

PubMed1998

Autocorrelation of acoustic signals from the temporomandibular joint.

Although there have been many investigations of TMJ sounds in the time and frequency domains, no previous reports have been found of investigations of the autocorrelation spectra of these sounds. In the present study, TMJ sounds were digitized at 1.7 kHz and 300 ms samples containing either clicks (single short duration sounds), crepitus (long duration continuous sounds) or creaks (a series of two or more clicks) were selected. These samples were compared with sounds of known origin: tooth impact sounds, frictional sounds elicited by scratching the head, and bruxing sounds resulting from stick-slip friction as teeth were slid against one another under high pressure. There were clear qualitative and quantitative differences between the autocorrelation spectra of the three types of TMJ sounds. Clicks were similar to tooth impact contact sounds, creaks were similar to the bruxing sounds, and crepitus was similar to the scratching sounds. The repetition rate of creaks was 16 Hz (s.d. 9 Hz), this being similar to the resonance of the mandible about the condylar axis. It is suggested that the creaks are due to stick-slip friction in the lower joint compartment of the TMJ.

Acoustics↗

PubMedDate not supplied

Maternal employment and preventive child health practices.

BACKGROUND: The impact of maternal employment on preventive child health practices has not been studied empirically. Using a household production model, we investigated the relationship between level of maternal employment and child immunization status, use of automobile seat belts, and use of bicycle helmets. METHODS: Data from a longitudinal study of public school children in Pinellas County, Florida, were used to draw an analytic sample of 4,153 African American and white non-Hispanic children whose mothers responded to school surveys in 1989, 1991, and 1993. Analyses of the relationship between maternal hours worked per week and preventive child health practices were performed using multiple logistic regression procedures, controlling for maternal age and education, household income, ethnicity and gender of child, and number of siblings living at home. RESULTS: No significant statistical relationships were found between maternal employment and child immunization status or use of automobile seat belts. However, maternal employment was significantly associated with bicycle helmet use, after controlling for confounders. Children of mothers who worked less than 21 h per week were 37% more likely to wear helmets compared with children of mothers who worked 21 h or more per week. CONCLUSIONS: Findings suggest that children of full-time working mothers are not at greater risk for under-immunization or failure to use seat belts regularly, but they may be less likely to use bicycle helmets. These results support the hypothesis that employment does not affect episodic child health practices but may have some negative impact on preventive practices involving daily, repetitive activities. It also suggests that the effects of maternal employment may be greater on preventive practices that are nonnormative and occur in the absence of adult supervision.

Adult↗

PubMed2004

Vitamin E reduces amyloidosis and improves cognitive function in Tg2576 mice following repetitive concussive brain injury.

Traumatic brain injury is a well-recognized environmental risk factor for developing Alzheimer's disease. Repetitive concussive brain injury (RCBI) exacerbates brain lipid peroxidation, accelerates amyloid (Abeta) formation and deposition, as well as cognitive impairments in Tg2576 mice. This study evaluated the effects of vitamin E on these four parameters in Tg2576 mice following RCBI. Eleven-month-old mice were randomized to receive either regular chow or chow-supplemented with vitamin E for 4 weeks, and subjected to RCBI (two injuries, 24 h apart) using a modified controlled cortical impact model of closed head injury. The same dietary regimens were maintained up to 8 weeks post-injury, when the animals were killed for biochemical and immunohistochemical analyses after behavioral evaluation. Vitamin E-treated animals showed a significant increase in brain vitamin E levels and a significant decrease in brain lipid peroxidation levels. After RBCI, compared with the group on regular chow, animals receiving vitamin E did not show the increase in Abeta peptides, and had a significant attenuation of learning deficits. This study suggests that the exacerbation of brain oxidative stress following RCBI plays a mechanistic role in accelerating Alphabeta accumulation and behavioral impairments in the Tg2576 mice.

Amyloid↗

PubMed2004

Impact of conventional anesthesia on auditory brainstem responses in mice.

Anesthesia is known to affect the auditory brainstem response (ABR) in animals often used in hearing research. This study describes the differences in ABRs between awake and anesthetized FVB/N mice. Intracranial electrodes connected to a head fixation pedestal were used for click-evoked ABR recordings. This pedestal served to immobilize mice, either awake or under anesthesia, in a 'free' sound field. The presence of myogenic noise in the awake condition obviously increases recording time. However it is demonstrated that recording times can be significantly reduced by increasing the stimulus repetition rate from 23 up to 80 impulses per second. This causes only a small but significant increase in absolute peak latencies in the awake condition, but has no significant effect on the overall ABR-waveform, nor on the ABR-threshold, nor on the ABR interpeak latencies, nor on the absolute peak latencies in the anesthetized condition. Anesthesia with ketamine/xylazine caused a significant prolongation of ABR-peak latencies and interpeak latencies as well as a significant upward shift (8.0+/-1.8 dB) of ABR-thresholds as compared to the awake condition. Under anesthesia the measurement accuracy of peak latencies, interpeak latencies and thresholds decreases. In conclusion, the awake condition is preferable for more accurate measurements of ABR characteristics, in spite of the myogenic noise concomitant with this condition.

Acoustic Stimulation↗