From the Guidelines
Diffuse axonal injury (DAI) is a severe form of traumatic brain injury characterized by widespread damage to the brain's white matter axons, primarily in the parasagittal white matter, corpus callosum, and dorsal upper brain stem, as evidenced by histological findings 1. The pathology of DAI is complex and involves shearing forces that stretch and tear axons throughout the brain, resulting in a range of severity from mild to severe.
Key Characteristics of DAI
- Widespread damage to white matter axons
- Involves multiple regions of the brain simultaneously
- Severity ranges from mild (temporary disruption of axonal function) to severe (complete axonal tearing with tissue destruction)
- Common causes include motor vehicle accidents, falls, sports injuries, and physical assaults
- Patients typically experience immediate loss of consciousness lasting 6 hours or more
- Outcomes range from complete recovery to persistent vegetative state or death depending on injury severity Some key points to consider in the diagnosis and management of DAI include:
- MRI is more sensitive than CT for detecting axonal damage, particularly in the acute phase 1
- T2* GRE imaging has been shown to be very sensitive to microhemorrhages within the brain, which are associated with acute, early subacute, and chronic stages of DAI 1
- The presence of traumatic microhemorrhages in DAI has been correlated with the presenting GCS, but the number of these micro-hemorrhages is not currently thought to be associated with injury severity or outcomes 1
- Rehabilitation is crucial for survivors to regain lost function, though complete recovery from severe DAI is uncommon due to the brain's limited ability to repair damaged axons The most recent and highest quality study recommends the use of MRI in the acute phase for patients with mild TBI and normal CTs, as it may provide valuable information for long-term prognostication 1.
From the Research
Definition of Diffuse Axonal Injury
Diffuse axonal injury (DAI) is a type of brain injury that occurs when the axons in the brain are damaged as a result of traumatic brain injury (TBI) 2, 3, 4, 5, 6.
Characteristics of Diffuse Axonal Injury
The characteristics of DAI include:
- Widespread damage to the axons of the brainstem, parasagittal white matter of the cerebral cortex, corpus callosum, and the gray-white matter junctions of the cerebral cortex 4
- Deformation of the brain due to plastic flow of the neural structures associated with DAI 4
- Micropathologic findings, radiologic findings, and medical and neuropsychologic complications from this type of injury mechanism 4
- Elevated rates of neurodegenerative diseases such as Alzheimer's disease and chronic traumatic encephalopathy 5
Causes and Risk Factors of Diffuse Axonal Injury
The causes and risk factors of DAI include:
- High-speed, long-duration deceleration injuries 4
- Transportation-related injuries and some sports injuries 4
- Traumatic brain injury (TBI) 2, 3, 4, 5, 6
- Severity of the lesion, classified on the ground of the cerebral anatomical structures involved after the trauma 3
Diagnosis and Prognosis of Diffuse Axonal Injury
The diagnosis and prognosis of DAI include:
- Advanced neuroimaging, electrophysiological, biomarker, and neurobehavioral evaluations 2
- Clinical prognostic factors such as glycemia, early GCS, the peripheral oxygen saturation, blood pressure, and time to recover consciousness 3
- Biomarkers such as GFAP, pNF-H, NF-L, microtubule associated protein tau, Aβ42, S-100β, NSE, AQP4, Drp-1, and NCX 3
- Diffusion MRI measures of diffuse axonal injury as a strong predictor of post-traumatic neurodegeneration 5