A concussion, also known as a mild traumatic brain injury (mTBI), is a head injury that temporarily affects brain functioning. Symptoms may include headache, dizziness, difficulty with thinking and concentration, sleep disturbances, a brief period of memory loss, brief loss of consciousness, problems with balance, nausea, blurred vision, and mood changes. Concussion should be suspected if a person indirectly or directly hits their head and experiences any of the symptoms of concussion. Signs and symptoms of a concussion usually occur within minutes to hours of the injury, usually within 72 hours. However, symptoms may be delayed by 1–2 days after the accident. It is not unusual for symptoms to last 2 weeks in adults and 4 weeks in children. Symptoms of a concussion may make it difficult to return to work, school, sports (in cases of sports related concussions) or prior level of functioning, with disability usually lasting days to weeks. Fewer than 10% of sports-related concussions among children are associated with loss of consciousness.
Common causes include motor vehicle collisions, falls, sports injuries, and bicycle accidents. Risk factors include physical violence, drinking alcohol and a prior history of concussion. The mechanism of injury involves either a direct blow to the head or forces elsewhere on the body that are transmitted to the head. This is believed to result in neuron dysfunction, as there are increased glucose requirements, but not enough blood supply. A thorough evaluation by a qualified medical provider working in their scope of practice (such as a physician or nurse practitioner) is required to rule out life-threatening head injuries, injuries to the cervical spine, and neurological conditions and to use information obtained from the medical evaluation to diagnose a concussion. Glasgow coma scale score 13 to 15, loss of consciousness for less than 30 minutes, and memory loss for less than 24 hours may be used to rule out moderate or severe traumatic brain injuries. Diagnostic imaging such as a CT scan or an MRI may be required to rule out severe head injuries. Routine imaging is not required to diagnose concussion and is, by definition, normal after concussions.