Severe Diffuse Axonal Injury – Life Threatening Trauma

Severe Diffuse Axonal Injury Causes Most Severe Coma

By Gordon S. Johnson, Jr.

Severe Diffuse Axonal Injury is among the most serious of brain injuries, even though it may not show up on CT scans. Axonal tracts are torn, causing coma.

There is increasing recognition of the role of diffuse axonal injury after brain injury but that attention is usually focused on explaining the injury in context of milder brain injuries. In the context of severe brain injury, Severe Diffuse Axonal Injury (DAI) is brain injury which may involve immediate coma and catastrophic injury. The type of Severe Diffuse Axonal Injury (DAI) which causes immediate coma is classified as Type Three Diffuse Axonal Injury. In Severe Diffuse Axonal Injury, shear forces actually sever large portions of the brain’s axonal tracts.

Shear damage occurs when brain layers of different weight and density slide across each other when the brain is rotated in a traumatic event.  Much of the injury after concussion occurs as a result of this rotational acceleration/deceleration phenomenon. In a severe DAI, the force literally tears the brain apart at its roots, the axonal tracts.

The axonal tracts are the gatherings of axons which cross from the gray matter into the white matter. The axons of myelinated neurons make up the brain’s white matter. The myelin sheath, an insulation around the axon, is white. One of the most important axonal tract is the corpus callosum. The corpus callosum is the white matter tract which connects the brain’s two hemispheres together. The corpus callosum is where the white matter crisscrosses between the two sides of the brain.

Diffuse axonal injury is classified as Type One thru Type Three. Type Three is the most severe. Even though Type Three likely results in immediate unconsciousness and often death, it does not necessarily show up on CT scans done upon admission to the hospital. The majority of brain injury which involve immediate coma, involve severe diffuse axonal injury.