What really happens inside the brain during a sports concussion

A concussion, according to the US Centers for Disease Control (CDC), is any kind of bump, blow or jolt to the head that causes the head and brain to move rapidly back and forth. This sudden movement causes the brain to bounce around in the skull, creating chemical changes in the brain and sometimes stretching and damaging brain cells. A concussion is a mild traumatic brain injury (mTBI). A sports concussion is any concussion that occurs while playing sports.

By some estimates, there are 3.8 million sports concussions per year

Concussions in sports have become a much-talked-about public health issue due to growing concern about long-term effects. You may have read in the news about a group of stakeholders who convened under the aegis of the CDC to systematically examine the issue. The group made a high-profile series of recommendations to address prevention and treatment of concussion in sports, including building a National Concussion Surveillance System.

According to the CDC, sports concussions occur in all sports with the highest incidence reported in football, hockey, rugby, soccer and basketball. The largest number of sports-related TBIs in men occurs in football, cycling and basketball; while for women, its cycling and horseback riding. Children and teens are more likely to get a concussion and can take longer to recover than adults.

But while we understand concussion at a broad level, there is still much to understand about the mechanics of concussion – exactly how the brain moves and vibrates inside the skull during impact – in order to better inform prevention, diagnosis and treatment efforts.

New research sheds light on what happens in the brain in a concussive impact

In March 2018, the Journal of APS Physics published Mechanistic Insights into Human Brain Impact Dynamics through Modal Analysis, which suggests that the biomechanics of sports concussion may be more complicated than we previously thought. The researchers behind this study felt that understanding the frequencies at which the brain slides back and forth inside the head when subjected to impact may enable medical professionals to provide better response to concussion in sports. For this study, they looked at the mechanics behind 537 real concussions experienced by male football players at Stanford.

For your convenience, we’ve summarized the background, methodology and findings of this latest research on sports concussions.

Research objective: better determine what happens in the deeper regions of the brain in a sports concussion

In the past, scientists investigated how the brain changes shape when pressure from impact is applied, assuming a rigid skull. Today, with more recent advances in imaging, research shows that axonal injury – the tearing or shearing of the brain’s long, connecting nerve fibers (axons) that happens when the brain is injured as it shifts and rotates inside the skull – has become the subject of the leading hypotheses behind the mechanics of concussion. 

Researchers in this study felt that axonal injury was a good starting point, but that there was still more to be studied. They felt a need to acquire “a greater understanding of the forceful motion of the brain during rapid head movements with various amplitudes, durations, and directions, as well as the reason for higher susceptibility of deep regions of the brain to strain.” [Fernandez, Wu, et al.].

Methodology: a unique dataset was developed using an innovative mouth guard that measures how fast the brain moves

Kaveh Laksari, the first scientist listed on this paper, a biomedical engineering professor at Stanford and now the University of Arizona, has been researching traumatic brain injury since 2007. 

At Stanford, Laksari and a team of scientists developed a unique athletic mouth guard, equipped with accelerometers and gyroscopes, that could measure and record kinematics – how fast the brain is moving in space. 

When an athlete’s head experiences a rapid movement, a microprocessor in the mouth guard triggers data-collecting sensors. This new method improved researchers’ ability to gather information about brain impact because it measured movement of the teeth, which are rigidly attached to the skull, rather than a helmet, which is designed to move independent of the skull.

To investigate the brain’s response in real-world head impact situations, Laksari, as well as Mehmet Kurt of the Stevens Institute of Technology in New Jersey, as well as additional researchers, simulated football head injuries using a finite element model (FEM). 

An FEM is a mathematical model – in this case, representing the mechanics of head injuries – that is used to perform a specific engineering analysis. Researchers entered the dataset of head collisions that Laksari had collected at Stanford – 537 football-related head injuries in all, including athletes who suffered loss of consciousness and other post-concussive symptoms – to run their mathematical model.

Findings: the difference in frequency of the brain movement in a concussion causes deep trauma patterns on brain tissue

What they found, in technical terms was, “each blow set the brain wobbling in a complicated way for a few tenths of a second. When broken down into dynamical modes – short-lived patterns of motion with distinct frequencies – the jolted brain oscillated most vigorously at about 30 cycles per second, roughly the same frequency as the second-lowest key on a piano.” Further, “different modes accentuated motion in different parts of the brain, potentially causing neighboring regions to oscillate at different frequencies,” this differential is what causes the most damage (Laksari, et al., 2018). 

To summarize the findings, when one part of the brain moves faster or slower than another part during impact, stretching or straining between the brain’s regions occurs. More instances of this phenomenon occur in the inner regions of the brain, especially in areas surrounding the brain’s ventricles where cerebrospinal (CSF) is produced, leading to deep trauma patterns occurring in the tissue well below the surface of the brain. In contrast, in the past, the superficial layer of the brain was the biggest area of focus in concussion research.

Significance of findings

Researchers agree the following three conclusions can be drawn from this study:

1. The hypothesis that concussions originate not so much from the collision of the brain with the skull, but in the stretching and shearing of tissue that head trauma causes deep within the brain, has been further validated.
2. The new methodology and tools used successfully in this study may significantly simplify the modeling of concussions in future research.
3. Better helmets could be designed to shield parts of the head in order to diminish the most damaging low-frequency vibrations.

When a sports concussion happens, what kind of treatment works best

The sooner a sports concussion is diagnosed, the sooner treatment can begin, which is important because symptoms can be lasting, particularly those affecting cognitive functions such as memory and attention. Those symptoms can be treated by a variety of professionals, ranging from speech-language pathologists to neurologists to educational specialists to occupational therapists. Programs like Constant Therapy can be helpful to work on these cognitive functions, particularly attention and memory. In fact, Constant Therapy has 8 Staying focused related tasks to choose from, in addition to 14 tasks designed to help address Remembering.

References:

• Laksari, K., and Kurt, M. (2018). Mechanistic Insights into Human Brain Impact Dynamics through Modal Analysis, Physical Review Letters,120, 138101.
• Fernandez, Wu (2015). Six Degree-of-Freedom Measurements of Human Mild Traumatic Brain Injury, Annals of Biomedical Engineering, Volume 43, Issue 8, pp 1918–1934.
• Meehan III, W.P., and Mannix, R. (2010). Pediatric Concussions in United States Emergency Departments in the Years 2002 to 2006, Journal Pediatrics, 157, 889.
• Centers for Disease Control (2017). Self-Reported Concussions from Playing a Sport or Being Physically Active Among High School Students — United States, 2017, Morbidity & Mortality Weekly Report.
• Centers for Disease Control (2017). What is a Concussion? Heads Up: Brain Injury Basics.