Diffuse axonal injury DAI is a type of traumatic brain injury (TBI) that can occur without a blow to the head. It is the most common type of severe TBI, and it can be very difficult to detect with standard medical imaging. DAI is the result of the brain moving violently inside the skull, in a back and forth or rotating motion. The injury itself is tearing of the axons which are nerve fibers in the brain. 90% of survivors of severe DAI will remain in a persistent vegetative state. Those who wake up typically experience long-term impairment. Cognitive impairment is the most prominent impairment in DAI survivors.
Diffuse Axonal Injury vs. Focal Brain Injury
Focal brain injury is confined to one area of the brain. The effects of focal brain injury can be predicted based on the area of the brain that is damaged. Focal injuries are easier to see on standard imaging, and therefore, more easily diagnosed.
In diffuse brain injury there is microscopic damage throughout many areas of the brain. The axons are nerve fibers that nerve cells rely on to communicate with each other. DAI can progress over a period of days as toxic chemicals are released in the brain causing brain cell death. DAI can also involve torn blood vessels with continued bleeding and increasing swelling and pressure inside the skull, causing more brain cell death.
Causes of Diffuse Axonal Injury
Common causes of DAI include:
- Auto accidents
- Falls
- Shaken baby, and other physical child abuse
- Sports accidents
- Violent acts
- Explosions
For more on head and brain injuries, review our Head Injury Guidebook.
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