Brain injury in sports

Concussion Prone Scenarios: A Multi-Dimensional Exploration in Impact Directions, Brain Morphology, and Network Architectures Using Computational Models

While individual susceptibility to traumatic brain injury (TBI) has been speculated, past work does not provide an analysis considering how physical features of an individual's brain (e.g., brain size, shape), impact direction, and brain network features can holistically contribute to the risk of suffering a TBI from an impact. This work investigated each of these features simultaneously using computational modeling and analyses of simulated functional connectivity. Unlike the past studies that assess the severity of TBI based on the quantification of brain tissue damage (e.g., principal strain), we approached the brain as a complex network in which neuronal oscillations orchestrate to produce normal brain function (estimated by functional connectivity) and, to this end, both the anatomical damage location and its topological characteristics within the brain network contribute to the severity of brain function disruption and injury. To represent the variations in the population, we analyzed a publicly available database of brain imaging data and selected five distinct network architectures, seven different brain sizes, and three uniaxial head rotational conditions to study the consequences of 74 virtual impact scenarios. Results show impact direction produces the most significant change in connections across brain areas (structural connectome) and the functional coupling of activity across these brain areas (functional connectivity). Axial rotations were more injurious than those with sagittal and coronal rotations when the head kinematics were the same for each condition. When the impact direction was held constant, brain network architecture showed a significantly different vulnerability across axial and sagittal, but not coronal rotations. As expected, brain size significantly affected the expected change in structural and functional connectivity after impact. Together, these results provided groupings of predicted vulnerability to impact-a subgroup of male brain architectures exposed to axial impacts were most vulnerable, while a subgroup of female brain architectures was the most tolerant to the sagittal impacts studied. These findings lay essential groundwork for subject-specific analyses of concussion and provide invaluable guidance for designing personalized protection equipment.

Evaluation of Protective Properties of Commercially Available Medical Helmets: Are Medical Helmets Protective?

OBJECTIVES

The aims of the study were to evaluate and to compare protective properties of commercially available medical helmets for a set of standardized head injury risk measures.

METHODS

Eleven helmet types were evaluated to represent the variety of commercially available medical helmet designs and manufacturers. A test mannequin and sensor apparatus were used to simulate a backward-standing fall. The head/neck size, mass, and "standing" height of the mannequin (5'9″) were representative of a 50th percentile male. A triaxial array was placed at the head center of mass to position 3 linear accelerometers and 3 angular rate sensors. Data were collected for 5 single trials for each helmet, as well as 5 repeated trials. Five trials were also collected with no helmet scenarios. Three head injury risk measures were examined (linear acceleration, angular acceleration, and head injury criterion). Data were analyzed by clinical cutoff thresholds and continuous values.

RESULTS

Helmets varied in their performance across head injury risk measures. All helmets provided higher levels of protection compared with no helmet scenarios. No helmets were protective for subdural hematoma (measured by angular acceleration). All helmets lost protective properties with repeated falls. Results for skull fracture risk were inconsistent between linear acceleration and head injury criterion injury risk measures.

CONCLUSIONS

No helmets were protective across all head injury risk measures. Medical helmets may reduce some fall injury severity but may not prevent all types of head injury. All helmets exhibited worsening of protective properties with repeated falls. We recommend medical helmets be replaced after each fall incident where the helmet impacts another surface.

Describing headform pose and impact location for blunt impact testing

Reproduction of anthropomorphic test device (ATD) head impact test methods is a critical element needed to develop guidance and technologies that reduce the risk for brain injury in sport. However, there does not appear to be a consensus for reporting ATD pose and impact location for industry and researchers to follow. Thus, the purpose of this article is to explore the various methods used to report impact location and ATD head pose for sport-related head impact testing and provide recommendations for standardizing these descriptions. A database search and exclusion process identified 137 articles that met the review criteria. Only 4 of the 137 articles provided a description similar to the method we propose to describe ATD pose and impact location. We thus propose a method to unambiguously convey the impact location and pose of the ATD based on the sequence, quantifiable design, and articulation of ATD mount joints. This reporting method has been used to a limited extent in the literature, but we assert that adoption of this method will help to standardize the reporting of ATD headform pose and impact location as well as aid in the replication of impact test protocols across laboratories.

Analysis of head impact exposure and brain microstructure response in a season-long application of a jugular vein compression collar: a prospective, neuroimaging investigation in American football

Background

Historical approaches to protect the brain from outside the skull (eg, helmets and mouthpieces) have been ineffective in reducing internal injury to the brain that arises from energy absorption during sports-related collisions. We aimed to evaluate the effects of a neck collar, which applies gentle bilateral jugular vein compression, resulting in cerebral venous engorgement to reduce head impact energy absorption during collision. Specifically, we investigated the effect of collar wearing during head impact exposure on brain microstructure integrity following a competitive high school American football season.

Methods

A prospective longitudinal controlled trial was employed to evaluate the effects of collar wearing (n=32) relative to controls (CTRL; n=30) during one competitive football season (age: 17.04±0.67 years). Impact exposure was collected using helmet sensors and white matter (WM) integrity was quantified based on diffusion tensor imaging (DTI) serving as the primary outcome.

Results

With similar overall g-forces and total head impact exposure experienced in the two study groups during the season (p>0.05), significant preseason to postseason changes in mean diffusivity, axial diffusivity and radial diffusivity in the WM integrity were noted in the CTRL group (corrected p<0.05) but not in the collar group (p>0.05). The CTRL group demonstrated significantly larger preseason to postseason DTI change in multiple WM regions compared with the collar group (corrected p<0.05).

Discussion

Reduced WM diffusivity alteration was noted in participants wearing a neck collar after a season of competitive football. Collar wearing may have provided a protective effect against brain microstructural changes after repetitive head impacts.

Trial registration number

NCT02696200.