You’re playing a pick-up game of basketball and get hit in the head with the ball. The jolt leaves you feeling slightly dizzy and queasy but you are able to continue playing. The question is, should you?

Dizziness and nausea are two signs of concussion - one of the least understood sports injuries, says Ned Shannon, head athletic trainer and instructor at the University of Indianapolis. “People assume a concussion means you’re unconscious but that isn’t always the case. A concussion simply signifies injury to the brain has occurred.”

A Grade One, or mild, concussion never results in loss of consciousness but should not be ignored, Shannon says, as it can lead to serious consequences if you’re reinjured. Possible symptoms are mild headache, ringing in the ears, blurred vision, dizziness, impairment of thought processes or memory, or sensitivity to light.

“Don’t underestimate the injury that may have happened to you,” Shannon advises. “Stop the activity and contact your physician for possible evaluation. Once your symptoms have completely gone (usually several days), try an activity that increases your heart rate and blood pressure, such as walking or running, to see if the symptoms return.”

Failure to allow the brain to heal from a mild concussion can result in serious bleeding if a second injury is sustained, Shannon cautions. “When you see an athlete collapse during a game, that’s often the result of a second concussion, and the first was never reported. Athletes underreport concussions because they don’t want to be removed from their sport. What they don’t realize is that a serious concussion could sideline them permanently.”