Which mechanism best explains diffuse axonal injury?

Which mechanism best explains diffuse axonal injury?

• A. Compression from skull fracture.
• B. Rapid acceleration-deceleration with shearing forces causing widespread axonal disruption.
• C. Direct contusion from focal impact.
• D. Hypoxic-ischemic injury from systemic hypotension.

Answer: (B)

Diffuse axonal injury happens when the head undergoes rapid acceleration and deceleration, so the brain shifts inside the skull and the long axons are stretched and torn by shear forces. This mechanical tearing tends to affect axons across many areas, especially at the gray–white matter junctions like the corpus callosum and brainstem, leading to widespread disconnection rather than a single focal injury. That’s why DAI often presents with immediate unconsciousness and can show multiple tiny hemorrhages on MRI in these regions. Other mechanisms, such as a focal skull fracture with compression, a direct focal contusion from a single impact, or hypoxic-ischemic injury from systemic hypotension, produce localized damage or energy failure rather than the diffuse axonal disruption seen in DAI.

Diffuse axonal injury happens when the head undergoes rapid acceleration and deceleration, so the brain shifts inside the skull and the long axons are stretched and torn by shear forces. This mechanical tearing tends to affect axons across many areas, especially at the gray–white matter junctions like the corpus callosum and brainstem, leading to widespread disconnection rather than a single focal injury. That’s why DAI often presents with immediate unconsciousness and can show multiple tiny hemorrhages on MRI in these regions. Other mechanisms, such as a focal skull fracture with compression, a direct focal contusion from a single impact, or hypoxic-ischemic injury from systemic hypotension, produce localized damage or energy failure rather than the diffuse axonal disruption seen in DAI.