One of the most common and severe types of brain injury is known as diffuse axonal injury, or DAI. With DAI, the damage to the brain occurs over a large area, and is one of the major causes of unconsciousness and long-term coma after traumatic brain injury.
Unlike brain trauma that occurs due to a direct blow, DAI is the result of the twisting and tearing of the connections between the cells of the brain. This is called a shearing injury and is caused when the head violently starts or stops a movement, such as in auto collisions, falls, and assaults. This type of injury usually results from rotational forces or violent stopping.
Vehicle collisions are the most frequent causes of DAI. Other common causes include child abuse, for example shaken baby syndrome. Though diffuse axonal injury seldom kills, the outcome is often not predictable. In severe DAI, patients are frequently in a coma, and many will never regain consciousness.