a positive declaration intended to give confidence: He received assurances of support for the project. 2. promise or pledge; guaranty; surety: He gave his assurance that the job would be done. 3. full confidence; freedom from doubt; certainty: to act in the assurance of success.
Summary. 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.
How Your Brain Can Get Hurt. A hard blow to the head can shake the brain inside the skull, resulting in bruising, broken blood vessels, or nerve damage to the brain. When you take a hard hit to the head but there's no outward bleeding or opening in the skull, it could result in a closed brain injury.