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.