Concussions are a mild traumatic brain injury common in sports, though they can also be caused by falls and accidents. About 1.5 to 3.8 million sports-related concussions occur annually in the U.S., according to the American Academy of Neurology. Concussions affect millions of kids and teens a year.

The search for a new quarterback began late last night for the Miami Dolphins, hours after quarterback Tua Tagovailoa went down with a concussion in a loss against the Buffalo Bills.

The Miami Dolphins will bring in another quarterback while starter Tua Tagovailoa deals with his latest concussion, coach Mike McDaniel said Friday. For now, Skylar Thompson will be considered the Dolphins' starter while Tagovailoa is sidelined.