What is a Concussion? A concussion occurs when a sudden force to the body interrupts brain function. Although it is commonly believed that a head injury is involved, this is not always the case. In addition, not every head injury results in a concussion—and other serious brain, head, and neck injuries could coincide with a concussion. Symptoms A concussion involves changes in the chemistry of the brain, although you do not need to lose consciousness to have a concussion. The chemical changes in the brain last longer than the symptoms, so your doctor will typically recommend that you rest and avoid contact sports for at least a week. The effects of concussions vary among individuals—and many mild concussions often go undiagnosed and unreported. Twenty percent of all concussions are sports-related. There are many symptoms athletes may report after a concussion. The most common are: Headache Dizziness Confusion Ringing in the ears Blurred vision Sensitivity to light or noise Upset stomach and/or vomiting Difficulty sleeping Cognitive disturbances such as memory lapses Difficulty retaining new information Some of the symptoms described above will only last an hour or two and others may last a week or more. If you have a suspected concussion, you should see your doctor or make an appointment with a physician in our Sports Concussion Program for further evaluation as soon as possible. Fast Fact: Sometimes, but not always, an athlete will be "knocked out" if he or she has suffered a concussion.