Head trauma from a violent impact, fall or an accident can precipitate personality, cognitive or behavior changes. The brain, or the covering of the brain and its blood vessels and nerves, is damaged. Usually there is haemorrhage and sometime seizures. Brain function is affected, resulting in a variety of behavioural and cognitive difficulties resulting from impairment of attention, learning and motor speed. If brain injury is mild, previous functioning may be restored over time. In cases of moderate to severe head trauma, brain impairment may be lasting. Survivors of TBI have difficulties with recall and daily routines (such as parenting), with job-related tasks and with academic tasks. They usually have specific learning difficulties. TBI sufferers also often have difficulty with regulating mood and managing social interactions; many are lonely. Motor vehicle accidents are the primary cause of TBI.
Secondary or delayed injury can occur hours after the impact, and is due to a lack of oxygen or blood flow to the brain.
A survey in the USA found that TBI sufferers tend to be male (78%), and that 39% were between the ages of 16-25 (the mean age was 34 years). More specifically age appears to be related to aetiology of injury. In other words, in those below the age of 25, motor vehicle crashes were the primary cause of injury; violence related injuries were most frequently found in the 36-45 age group; pedestrian accidents most frequently occurred in those above 65 and 76% of the falls happened to those above 56. 76% of those wearing seat belts and 84% of those in motorcycle crashes were not wearing helmets at the time of injury. 51% of those included in the database had elevated blood alcohol levels at the time of injury.