Axonal Injury in Children after Motor Vehicle Crashes: Extent,Distribution,and Size of Axonal Swellings Using β -APP Immunohistochemistry

The brains of 32 children (3 months to 16 years) who died as a result of motor vehicle collisions were examined for axonal injury using β-APP immunohistochemistry. The extent and distribution of axonal injury was assessed and quantified throughout the forebrain, brainstem and cerebellum. The mean diameter of immunoreactive axons in the corpus callosum was measured for this pediatric group and, for comparison, a small adult sample. β-APP immunoreactivity was seen in 14 pediatric cases (survival 35 mins to 87 h), most frequently in the parasagittal white matter (12/14), the corpus callosum(11/14), the brainstem (10/14) and cerebellum (9/14). In 2 cases, axon swelling was visualized in the internal capsule after only 35-45-min survival, earlier than has previously been reported. No immunoreactivity was seen in the remaining 18 cases who died within 1 h. The extent and distribution of axonal injury throughout the brain showed a rapid early increase with increasing survival time and then a slower progression. The diameter of individual callosal axons increased with increasing survival times, rapidly over the first 24 h and then more slowly. There was no statistical difference (p < 0.05) for callosal axon diameters at different survival times between the children and the adults sampled here. The extent and distribution of axonal injury throughout the brain appears to be similar in children to that previously reported in adults. The spatial and temporal spread of axonal damage suggests there may be therapeutic potential for the process to be arrested or slowed in its early stages.