DAI usually occurs in older children. DAI is related to excitotoxic mechanisms, particularly glutamate and NMDA receptors ⁽¹⁵⁾. Axonal damage often occur at the node of Ranvier (a short interval between processes of oligodendrocytes), resulting in a traumatic defect in the axonal membrane. That causes leakage of glutamate in the extracellular space ⁽¹⁶⁾. The excessive glutamate by leakage leads to glial cell and axonal swelling, resulting in necrosis or axonal degeneration. DWI shows diffuse axonal injury as hyperintense lesions associated with decreased ADC often seen in the corpus callosum, white matter and brain stem ⁽¹⁷⁾ (Figure 5). Hemorrhagic components often accompany these brain injuries.

Figure 5. An 11-year-old girl with diffuse axonal injury due to a motor vehicle accident

A. T2WI shows a round hyperintense lesion in the body of corpus callosum.

B,C. DWI shows this lesion as very hyperintense with decreased ADC representing cytotoxic edema due to excitotoxic injury related to the leakage of glutamate via the axonal membrane.