Correlation of survival time with size of axonal swellings in diffuse axonal injury

Widespread damage to axons in the white matter of the brain is a well-recog nised consequence of nonmissile head injury. This diffuse axonal injury is characterised by a gradual swelling of the axon associated with an accumula tion of cellular organelles and proteins. We have investigated the relation ship between the size of the swellings of the damaged axon with survival ti me in postmortem brain tissue. Sixty-six cases of head injury with known le ngth of post-traumatic survival were selected for study, and immunohistoche mistry for beta-amyloid precursor protein (beta APP) was carried out. The m inimum diameter of the beta APP-immunolabelled damaged axons was measured i n micrometers using the IBAS image analysis system. There was a strong, pos itive and significant relationship between the mean size of axonal swelling and survival time which plateaued at around 85 h post injury. With longer survival times the situation becomes more complex. beta APP immunolabelling of damaged axons can contribute evidence about trauma and post-injury surv ival time in the forensic setting but should always be assessed with other evidence.