A new ‘spin’ on concussions

The crunch of a tackle may indicate more than just the end of a football play. It could trigger a concussion. That’s a potentially serious brain injury that can lead to headaches, dizziness or forgetfulness. Scientists have long known that rapid forward, backwards or side-to-side movements could damage the brain. A new study finds signs that the worst damage may stem from rotational forces deep within the brain.

Those rotational forces may lead to mild brain injuries like concussion, explains Fidel Hernandez. A mechanical engineer at Stanford University in Palo Alto, Calif., he led the new study. (A mechanical engineer uses physics and materials science to design, build and test mechanical devices.) His team published its findings December 23 in the Annals of Biomedical Engineering.

Water in and around the brain helps the organ maintain its shape as we move. Because water resists compression, it cannot be pushed into a smaller volume. So that layer of fluid helps protect the brain. But the water changes shape easily. And when the head rotates, the fluid can rotate too — like a whirlpool.

Rotation can twist and even break delicate cells. This increases the risk of brain injury, including concussion. But actually observing such brain twisting during an athletic event has proven challenging. Hernandez and his team devised a way to measure rotational forces and then visualize their impacts.

The researchers outfitted a special athletic mouthguard with an electronic sensor. Like most mouthguards, it has a piece of plastic that fits around an athlete’s upper teeth. The sensor recorded front-to-back, side-to-side and up-and-down movements.

The sensor also contained a gyroscope. A gyroscope rotates. That allowed the sensor to detect rotational acceleration, or turning movements. One of the rotational forces Hernandez measured was associated with a forward or backward tilt of the head. Another was a turn to the left or right. A third occurred when the athlete’s ear rolled down near his or her shoulder.

Hernandez and his team recruited football players, boxers and a mixed-martial-arts fighter for their study. Each athlete was fitted with a mouthguard. He or she wore it to practices and in competitions. The researchers also recorded video during those times. This allowed the scientists to view head movement when sensors recorded strong acceleration events. More than 500 head impacts occurred. Each athlete was evaluated for evidence of a concussion caused by those head impacts. Only two concussions emerged.

The scientists then fed their data into a computer program that modeled the head and brain. It showed what brain areas were most likely to twist or suffer some other type of strain. The two collisions that led to concussion both caused strain in the corpus callosum. This bundle of fibers connects the two sides of the brain. It allows them to communicate.

This brain region also manages depth perception and visual judgment. It does this by allowing information from each eye to move between the left and right sides of the brain, observes Hernandez. “If your eyes can’t communicate, your ability to perceive objects in three dimensions may be impaired and you may feel out of balance.” And that, he notes, “is a classic concussion symptom.”

There isn’t enough information yet to know for certain whether that strain caused the concussions, Hernandez says. But rotational forces are the best explanation. The direction of rotation also may determine which area of the brain gets damaged, he adds. That’s because fibers crisscross the brain, connecting different areas. Depending on the direction of rotation, one brain structure may be more susceptible to damage than another.

Outfitting all athletes with specialized mouthguards may not be possible. That’s why Hernandez is looking for the link between the mouthguard data and videos of sports action. If he and his team can identify head movements that frequently result in injury, video alone may one day prove a useful tool in diagnosing concussion.

The new paper raises awareness of the need to measure damage caused by rotational forces, says Adam Bartsch. This engineer at the Cleveland Clinic Head, Neck and Spine Research Laboratory in Ohio was not involved with the study. He cautions, however, that the study’s impressive-looking head impact data must be rigorously verified. Keep in mind, he adds, methods used to measure head impact forces are not yet reliable enough for doctors to use to diagnose a likely head injury.

Power Words

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acceleration  The rate at which the speed or direction of something changes over time.

compression  Pressing on one or more sides of something in order to reduce its volume.

computer program  A set of instructions that a computer uses to perform some analysis or computation. The writing of these instructions is known as computer programming.

concussion  Temporary unconsciousness, or headache, dizziness or forgetfulness due to a severe blow to the head.

corpus callosum  A bundle of nerve fibers that connects the right and left sides of the brain. This structure allows the two sides of the brain to communicate.

engineering   The field of research that uses math and science to solve practical problems.

force  Some outside influence that can change the motion of a body, hold bodies close to one another, or produce motion or stress in a stationary body.

gyroscope  A device to measure the 3-dimensional orientation of something in space. Mechanical forms of the device tend to use a spinning wheel or disc that allows one axle inside it to take on any orientation.

materials science  The study of how the atomic and molecular structure of  a material is related to its overall properties. Materials scientists can design new materials or analyze existing ones. Their analyses of a material’s overall properties (such as density, strength and melting point) can help engineers and other researchers select materials that best suited to a new application.

mechanical engineer  Someone who uses physics and materials science to design, develop, build and test mechanical devices, including tools, engines and machines.

physics  The scientific study of the nature and properties of matter and energy. Classical physics An explanation of the nature and properties of matter and energy that relies on descriptions such as Newton’s laws of motion.

sensor  A device that picks up information on physical or chemical conditions — such as temperature, barometric pressure, salinity, humidity, pH, light intensity or radiation — and stores or broadcasts that information. Scientists and engineers often rely on sensors to inform them of conditions that may change over time or that exist far from where a researcher can measure them directly.

strain  (in physics) The forces or stresses that seek to twist or otherwise deform a rigid or semi-rigid object.