A concussion is a type of head injury caused by a heavy blow to or violent shake of the head. It occurs when the brain is shifted from its usual position and comes into contact with the hard bones of the skull. Concussions are often mild, although they can sometimes cause more severe brain damage.

Concussions are a common injury among children and adolescents, especially those who participate in contact sports. Concussion is also a common injury sustained during accidents involving vehicles. Although it may not always be possible to avoid concussion, the risk of sustaining a concussion can be reduced by wearing protective head gear while playing sports and taking necessary safety precautions while on the road, as a driver, passenger or pedestrian.

The most common symptoms of concussion include:

• Headache
• Short-term confusion
• Dizziness or lightheadedness
• Nausea
• Feelings of irritability or lethargy
• Blurred vision
• Ringing in the ears (tinnitus)
• Memory loss

These symptoms usually go away after a short period of time. However, in some cases, the symptoms of concussion become more severe. This may be an indication of a more serious brain injury. People who have a head injury and experience any of the following symptoms should call emergency medical services as soon as possible:

• Increasing sleepiness or confusion
• Persistent vomiting
• Paralysis of one or more limbs
• Inability to speak coherently
• Lack of coordination
• Clear fluid (cerebrospinal fluid) draining from nose or mouth

In diagnosing a concussion, physicians will conduct a medical history and a physical examination. A physician may ask about the circumstances of the injury and questions designed to assess the patient’s level of consciousness. Physicians may also use imaging tests to assess the extent of a head injury. Imaging tests, such as x-rays, computed axial tomography (CAT) scans and magnetic resonance imaging (MRI), can help physicians to identify any damage that may have been sustained to the skull or brain.

The most effective treatment for a concussion is rest because the brain needs time to recover after an injury. Some people may experience the mild symptoms of concussion for several months. This is called postconcussive syndrome. Postconcussive syndrome is not usually an indication of severe brain injury, although it can be distressing and disruptive for the patient.