Diffuse Axonal Injury (DAI) is one of the most common types of severe trauma to the brain, occurring in about half of all head traumas. DAI occurs as a result of traumatic acceleration and deceleration combined or rotational forces on the head.
Axons exist mostly in the white matter of the brain, the inner portion, while nerves generally line the outermost layer of the brain called grey matter. The axons work like telephone wires, sending messages between nerve cells.
When the head moves quickly and violently, the outer portion, grey matter, moves faster than the inner portion, white matter, tearing the axons. This is known as shearing.
Shearing cuts the axon, stopping blood flow and signals between nerve cells, effectively killing those nerves in the affected areas of the brain. The axon need not be completely torn apart to kill the cell. A partially torn, stretched or twisted axon can result in a slow swelling of the axon as blood builds up until it eventually bursts, killing the nerve cell more gradually. Because of the effect on the nerves, DAI is commonly referred to as nerve damage.
In the mildest cases, DAI can go unnoticed and not have any impactful effect on one’s life. More serious symptoms of DAI include unconsciousness, problems with cognition and motor function and death.
If you or someone you love has suffered a violent acceleration and deceleration or rotational injury to the head, such as in a motor vehicle accident, it is crucial to see a medical professional about the appropriate testing for DAI.