But concussions can also result from car accidents, work, or even playground activity.
[Ads /]
Dr. Nina Gentile sees hundreds of potential brain injuries every year in the emergency department at Temple University Hospital.
Severe injuries will show on CT scans or MRIs, but not milder ones.
"Right now, I'm very frustrated by the lack of testing," says Dr. Gentile.
"There are people that don't even realize they've had a traumatic brain injury," she added.
Doctors have to rely on symptoms, which may not show for weeks.
They can be as serious as depression, or as subtle as trouble balancing a checkbook.
[Ads /]
"They may have headaches, they may be confused, they may have memory loss," she says.
So Servio Ramirez, Ph.D., and his team are developing a test to measure small bits of material called vesicles, which are released by blood vessels during head trauma.
"There's a direct association, or perhaps correlation, with the degree of injury and the amount of these vesicles that are present in the bloodstream," says Dr. Ramirez.
The work is being supported with a QED 'proof of concept' grant from the Philadelphia Science Center.
The goal is a test that's sensitive, accurate, and works quickly, for use in the emergency room.
Dr. Ramirez says an incident with his son adds to his motivation.
[Ads /]
"He fell from a swing and hit the back of his head, and 'Mommy, Daddy, I'm seeing purple,'" he notes.
The doctor's son recovered quickly.
When a test is developed, Dr. Gentile believes it will change treatment.
"We'd be able to approach those patients, be able to target therapy for those patients," says Dr. Gentile.
Right now, potential brain injury patients are being asked for blood samples when they come in, and during follow-ups, so researchers can track blood vessel changes.