Traumatic brain injury (TBI) happens when a bump, blow, jolt, or other head injury causes damage to the brain. Every year, millions of people in the U.S. suffer brain injuries. More than half are bad enough that people must go to the hospital. The worst injuries can lead to permanent brain damage or death. Half of all TBIs are from motor vehicle accidents. Military personnel in combat zones are also at risk.

Symptoms of a TBI may not appear until days or weeks following the injury. A concussion is the mildest type. It can cause a headache or neck pain, nausea, ringing in the ears, dizziness, and tiredness. People with a moderate or severe TBI may have those, plus other symptoms:

• A headache that gets worse or does not go away
• Repeated vomiting or nausea
• Convulsions or seizures
• Inability to awaken from sleep
• Slurred speech
• Weakness or numbness in the arms and legs
• Dilated eye pupils

Health care professionals use a neurological exam and imaging tests to assess TBI. Serious traumatic brain injuries need emergency treatment. Treatment and outcome depend on how severe the injury is. TBI can cause a wide range of changes affecting thinking, sensation, language, or emotions. TBI can be associated with post-traumatic stress disorder. People with severe injuries usually need rehabilitation.

NIH: National Institute of Neurological Disorders and Stroke