Even Tiny Bumps To Your Brain Can Cause Trauma Over Time

And football helmets only protect against the big ones

Head To Head

From the Centers of Disease Control and Prevention

Your brain is an extremely sensitive organ—little bumps that may cause temporary injuries elsewhere on the body can have lasting damage in the brain. Researchers have been investigating the effects of head trauma caused by contact sports like football, but they've really only been looking into big hits that cause concussions. In a new study, researchers from Stanford University look into the effects of smaller hits of the brain against the inside of the skull, concluding that even tiny injuries can have a huge effect when they build up over time.

Every year, 1.7 million people are diagnosed with traumatic brain injury in the U.S. Eighty percent of those cases are mild, resulting in headache and dizziness but no concussion. Severe trauma from an external force isn’t the primary cause of these mild injuries—it’s the inertia of the brain itself that causes it to bash into the inside of the skull when the head stops quickly. But researchers didn’t know how fast the brain could move inside the skull, or how much force would cause damage.

In the study, researchers used MRI data from the brains of three patients to determine how much the brain was able to move inside the skull, and in which directions. They were looking for information about the frequency at which the brain rattles around inside the head, measured at cycles per second, or hertz. Using a statistical model along with the physical data, the researchers concluded that the brain could be damaged when the brain oscillates at a rate of 15 hertz. The typical rate is 5 hertz for things like turning your head when someone comes in the room or to look down at your phone, but contact sports can push it to 20 hertz. And unlike concussive injuries that can happen in less than a second, these results suggest that little bumps over the duration of a football game, for example, can cause just as much damage, whether a player is wearing a helmet or not.

The researchers suggest that their findings could influence a new way to design helmets for contact sports that would decrease the amount of movement of the brain inside the skull.