A concussion is a type of traumatic brain injury, or TBI, caused by a bump, blow or jolt to the head or by a hit to the body that causes the head and brain to move rapidly back and forth.

Concussions can stretch and bruise nerves and blood vessels and cause chemical changes in your brain that result in a temporary loss of normal brain function.

They often result in symptoms of headaches, blurred vision, sensitivity to light or sound. A single concussion usually doesn’t cause permanent damage to your brain. However, multiple concussions over a lifetime may result in structural changes in your brain.