URL of this page: //medlineplus.gov/ency/article/000799.htm. A concussion may occur when the head hits an object, or a moving object strikes the head. A concussion is a minor or less severe type of brain injury, which may also be called a traumatic brain injury. A concussion can affect how the brain works for a awhile. It may lead to headaches, changes in alertness, or loss of consciousness. A concussion can result from a fall, sports activities, or car accidents. A big movement of the brain (called jarring) in any direction can cause a person to lose alertness (become unconscious).