Diffuse axonal injury (DAI) describes the stretching and shearing of white matter tracts in the brain. DAI not only impairs brain function immediately after the initial injury, but it is also thought to continue damaging the brain for months after, through secondary damage.
A recent study comparing DAI results from within 11 days after injury to DAI results from 6 months after injury found that, as expected, white matter tracts (as seen through diffusion tensor imaging) were damaged immediately after injury. In the 6 month follow-up scan, they found that further degeneration had occurred in the white matter tracts.
This provides evidence that initial evaluations of DAI will not capture the full extent of the injury. People who suffer a DAI may experience further damage that negatively affects outcome in the long-term.
Ljungqvist J, Nilsson D, Ljungberg M, et al. Longitudinal study of the diffusion tensor imaging properties of the corpus callosum in acute and chronic diffuse axonal injury. Brain Injury. (April 2011).