Diffuse axonal injury in head injury: Definition, diagnosis and grading

TLDR

Diffuse axonal injury is a major form of brain damage from non‑missile head injury that is hard to diagnose post‑mortem unless the pathologist is familiar with its features, and experience has led to a three‑grade classification. Grade 1 involves axonal injury in white matter of the cerebral hemispheres, corpus callosum, brain stem and occasionally cerebellum, while grade 2 adds a focal lesion in the corpus callosum and grade 3 further includes a focal lesion in the dorsolateral rostral brain stem. Among 434 fatal non‑missile head injuries, diffuse axonal injury was found in 122 cases (10 grade 1, 29 grade 2, 83 grade 3), with 24 requiring microscopy for diagnosis and 31 needing it to assess severity.

Abstract

Diffuse axonal injury is one of the most important types of brain damage that can occur as a result of non‐missile head injury, and it may be very difficult to diagnose post mortem unless the pathologist knows precisely what he is looking for. Increasing experience with fatal non‐missile head injury in man has allowed the identification of three grades of diffuse axonal injury. In grade 1 there is histological evidence of axonal injury in the white matter of the cerebral hemispheres, the corpus callosum, the brain stem and, less commonly, the cerebellum; in grade 2 there is also a focal lesion in the corpus callosum; and in grade 3 there is in addition a focal lesion in the dorsolateral quadrant or quadrants of the rostral brain stem. The focal lesions can often only be identified microscopically. Diffuse axonal injury was identified in 122 of a series of 434 fatal non‐missile head injuries–‐10 grade 1, 29 grade 2 and 83 grade 3. In 24 of these cases the diagnosis could not have been made without microscopical examination, while in a further 31 microscopical examination was required to establish its severity.