Diffuse axonal brain injury: macro- and microscopic signs Diffuse axonal injury is one of the most common and important pathologic features of traumatic brain injury. The susceptibility of axons to mechanical injury appears to be due to both their viscoelastic properties and their high organization in white matter tracts. Although axons are supple under normal conditions, they become brittle when exposed to rapid deformations associated with brain trauma. Accordingly, rapid stretch of axons can damage the axonal cytoskeleton resulting in a loss of elasticity and impairment of axoplasmic transport. Subsequent swelling of the axon occurs in discrete bulb formations or in elongated varicosities that accumulate transported proteins. Ultimately, swollen axons may become disconnected and contribute to additional neuropathologic changes in brain tissue. Diffuse axonal injury may largely account for the clinical manifestations of brain trauma. However, diffuse axonal injury is extremely difficult to detect noninvasively and is poorly defined as clinical syndrome.