Tag Archives: brain

Attempting to “Knock Out” the Causes of Concussions

This image displays a human head experiencing impact to the forehead region.
This image is licensed under CC BY-SA 3.0 .

Approximately every 15 seconds, a traumatic brain injury occurs in the U.S. A concussion is a form of mild traumatic brain injury produced by a contact or inertial force to the head (or neck) area. A concussion causes the brain to rapidly move around inside the skull, harming natural brain function. According to the Brain Injury Research Institute, roughly 1.6 to 3.8 million concussions occur each year in the U.S., resulting from both recreation and sports related incidents. In fact, brain injuries cause more deaths than any other sports injury.

The high incidence of concussions has made the injury subject to several biomechanical studies in recent years. Kinematic, or motion-based, parameters of the head are used as common indicators to predict brain injury as they are suggestive of the brain’s response to force. Early efforts focused on the linear acceleration of the head during concussion as the primary prediction factor of the injury. The peak linear acceleration of the head is correlated to the peak pressure within the brain, and an increase in pressure within the brain can cause neurological damage. Modern sports protection equipment, including ice hockey helmets, maintain performance standards based on the peak linear acceleration experienced by the head during impact. However, linear acceleration does not entirely reflect the risk of concussion and rotational acceleration of the head must be considered. A shear force acts in a parallel direction to a surface or cross section. Shear forces and subsequent strains in the brain are correlated to peak rotational acceleration of the head. Brain tissue is one of the softest bodily materials and deforms quickly to shear forces. Therefore, rotational acceleration of the head is a common catalyst of severe concussion.

This image presents two human skull and brain combinations. The left skull has red horizontal arrows pointing to the brain to depict the linear acceleration of the head during a concussion. The right skull has red arrows acting in a circular manner around the head to represent rotational acceleration acting on the brain during concussion
This image is licensed under the Creative Commons Attribution 2.5 Generic License. Changes were made to the image in the form of text and red arrows.

A 2015 study introduces the addition of the brain deformation metric maximum principal stress (MPA) in order to aid in connecting kinematics and injury during concussion prediction.  The study used Hybrid III crash test dummy head forms to examine the result of varying forms and severities of impact. Each head form was equipped with nine single-axis accelerometers to study the acceleration of the head and hyperelastic models were used to study brain tissue deformation.

The results of the study revealed the existence of significant correlations between linear acceleration, rotational acceleration and maximum principal stress of brain matter, emphasizing the importance of considering several kinematic parameters in predictive concussion studies. Results of the study exemplified the magnitude of accelerations experienced by the head during concussion: the head forms experienced an average linear acceleration of approximately 40.62g and an average rotational acceleration of approximately 3388 rad/s2, which is equal to about  539 rev/s2. The extent of brain injury is revealed through the immensity of the accelerations experienced during impact.

This image presents a side view of the skull that presents all organs as semi-transparent, enabling viewers to effectively see the inner-workings of the head.
“Years in the making: How the risk for Alzheimer’s disease can be reduced.” (2018)

When determining the probability of concussion, it is limiting to utilize just one parameter. Instead, several parameters and the relationship between each must be considered. Additionally, factors like sex-specific characteristics and under-reporting of injury have been proven to affect the severity of brain injury through study.  While brain injury can never be fully avoided, these studies can help to make equipment more protective and reduce injury.

Interested in reading more?

Neuroscience, Biomechanics & the Risk of Concussion in Developing Brains

Additional Sources:

Biomechanics of Concussion

Brain Injury Prediction

Concussion in Female Collegiate Athletes

The Mystery Behind the ‘Folded’ Brain

 

Picture of a walnut which has a strong similarity to a human cerebral cortex
Image by Ulrike Leone from Pixabay

Have you ever wondered why one of the most mysterious organ in our body, the brain, has a distinctive shape which has a strong resemblance to a walnut? Or, what are the major factors that could play a significant role in developing its particular shape, with crests and valleys, that wires our motions, senses, feelings and thoughts, which makes each one of us a unique human being?

Brain cortex of 34 different species which indicates relative size and foldedness
From Heuer, K. et al., Cortex 2019 High-res version: https://doi.org/10.5281/zenodo.2538751

For almost a century, the researchers from various different disciplines such as, neurology, engineering, evolutionary biology and applied mathematics have tried to solve the enigma behind the convoluted nature of the cortex, i.e. the outermost layer of the brain. Although the degree of convolution has shown to vary proportionally with the size of the brain among different species, as was shown in a recent study, this (un-)foldedness trait can not be attributed to the size of brain only, while some of the human brain disorders, such as epilepsy, might include the smooth brain aspect,  i.e. lissencephaly.

Interestingly, the human brain is not always folded throughout its stay in the womb. The gyrification (development of gyri and sulci, the two characteristics of the cerebral folding) begins only after the mid-gestation (sixth month of fetal life) and further continues to develop postnatally until adulthood. This remarkable phenomena of the brain has lead the researchers from the University of Jyvaskyla, Harvard and Aix-Marseille to collaborate and startlingly they had been able to replicate this unique behavior of the brain on 3D-printed soft composite layered gel samples using smooth fetal brain morphology obtained from magnetic resonance images (MRI) as a starting point. According to the first co-author Dr. Tallinen from their original research paper which is published in Nature Physics in 2016, when this composite layered gel is submerged in a jar of solvent called Hexanes at room temperature for 20-30 minutes,  the differential swelling of the outer layer of the gel is observed, and this leads to the formation of sulci and gyri which is similar in morphology to the cortex of the brain and occurs in a similar relative time frame that is observed in real fetal brain development. Another great article written on this study is also published in TheHarvardGazette!

The theory behind this naturally and experimentally observed cortical patterning can be explained by mechanical principles, and is a result of the mechanical instability generated by constrained cortical expansion due to growth. The computer simulations of gyri and sulci formation which was performed by researchers from Stanford University on 2015 further support this mechanistic perspective such that the mechanical environment and neuronal growth rate on preferred orientations plays a crucial role in controlling the gyral and sulcal pattern formation. Axons or the nerve fibers, which are the transmission cables of our nervous system, tend to respond to mechanical stretch during growth by dynamically adjusting their length, which ultimately serves as a regulator for cortical folding.

Interested in reading more on why our brains are folded? Check out these impressive articles from LiveScience and McGovernMIT!

Also check out this cool TED video from Prof. Suzana Herculano-Houzel here!

Will Removing Headgear Make Boxing Safer?

Our brains are made of a very soft material but luckily our skulls provide the brain protection from the outside world. However, during violent movements the brain is free to move inside the skull and collide with the skull. This impact can cause injury to the brain, known as a concussion, that can lead to various symptoms depending on severity. A 2014 paper by McIntosh et al. researched the biomechanics of concussions for Australian football players. Their research showed that a linear acceleration of 88.5 g to the head results in a 75% likelihood of a concussion. A g is the unit of acceleration and a single g is equivalent to the force of gravity at the Earth’s surface.

A very serious long-term effect of brain injury is Chronic Traumatic Encephalopathy known as CTE. Additional reading on CTE can be found here. Proper care must be taken to ensure the long-term health of contact sport athletes. Some contact sports utilize protective equipment such as helmets or mouth guards. However, the world of amateur boxing went a very different route to prevent brain injuries. An article by the New York Times reviews the International Boxing Association’s (A.I.B.A.) decision to remove headgear from international, male boxing competitions. In 2016, Olympic boxers entered the ring without headgear for the first time since 1984 according to the article. Apparently, this seemingly counterintuitive decision makes boxing safer. A cross-sectional study by the A.I.B.A. Medical Commission found there were more stoppages, caused by hard hits to the head, in fights with headgear. In fact, the data suggests that boxing without headgear lowers the chance of a stopped fight by 43%.

The A.I.B.A. claims that headgear did little to prevent brain injuries, however, there is counter research that refutes the A.I.B.A.’s claim. For example, a study by McIntosh and Patton researched the capability of A.I.B.A.-approved headgear to protect against injury. A glove was mounted to a driver and a Hybrid III head was used to record the head accelerations at different contact points and speeds. According to this study, head accelerations were significantly reduced by the headgear.

Boxing glove on piston delivering punch to a crash test dummy head
Modified from McIntosh & Patton, British Journal of Sports Medicine 2015

Headgear by no means prevents all concussions, for example, when the glove speed reached 8.34 m/s in the previously mentioned McIntosh and Patton study. Without headgear, the head experienced 133 g from a punch to the side of the head and 131 g from a punch to the front center of the head. With headgear, the head experienced 86 g from the lateral punch and 88 g from a punch to the front center of the head. The results showed there is a chance those with headgear could develop a concussion. However, without headgear, a concussion is guaranteed.

Headgear will not prevent all concussions but it can significantly decrease the chances of getting one. At some point, the force will surpass the protective capability of the headgear. Both sides of the argument present interesting and compelling data. In short, boxing is a contact sport. There will most likely always be a chance the athletes could develop brain injury.  In order to ensure the safety of the athletes, it is important to make decisions based on their health with definitive proof it protects them. The video below shows different sides to the debate.