Diffuse Axonal Injury

Overview 

Diffuse axonal injury, DAI, is one of the most prominent factors of brain injury. It occurs when the brain rotates and shifts inside the skull violently and the brain tissue, especially axons are stretched and torn. (Axons are the branching structure of neurons, resembling the shape of tree roots. They serve to communicate with other neurons.) 

 

This could cause the neurons to lose elasticity and electrochemical transportation would be impaired. Axons are swelled and disconnected from other regions, which can account for most pathologies of traumatic brain injury. 

 

Although DAI is diffuse, which means that it has widespread effect all over the white matter of the brain (or as some believed, multifocal damages in the brain), it is very hard to detect because damages are microscopic. 

Causes and risk factors 

DAI usually occurs during sudden shake of the brain or quick hit to it. Some examples are car accidents, falls, sport games and violent attacks. 

 

Symptoms 

  • Loss of balance and orientation

  • Vomiting and nausea 

  • Headache 

  • Fatigue 

 

Coma and DAI

Coma is a frequent consequence of DAI. Particularly, DAI in brainstem, the most severe DAI, can account for most comas.  

 

Alzheimer’s Disease and DAI 

In one study, the research team examined the postmodern tissues of boxers with dementia pugilistica (“punch-drunk syndrome”). They found the accumulation of plaques like APP, which suggests DAI. At the same time, accumulation of Aβ peptides is a significant biomarker in patients with Alzheimer’s. Many evidence showed that APP in damaged brain tissue could increase the accumulation of Aβ peptides. They claimed that DAI has a potential link to Alzheimer’s Disease. 

 

Diagnosis 

DAI is usually diagnosed postmodern using immunohistochemical techniques. Since the axon swelling is not visible under neuroimaging methods like MRI and CT scans, DAI is believed to be under-diagnosed, even though 40% to 50% of traumatic brain injury cases that require hospitalization are DAI. However, weighted imaging and magnetization transfer imaging can detect the arrangement of molecules in the white matter and may provide some evidence for DAI. 

Treatment 

There are some effective treatments in rodent models. Unfortunately, all failed to pass human clinical trials. But inhibiting calcium-mediated proteolysis or modulating mitochondrial permeability showed some promising results in animal experiments, though it would not grant any success in human trials. Scientists are continuing to discover and test new methods to treat DAI. 

 

Reference 

An Overview of Diffuse Axonal Injury. (n.d.). Retrieved from https://www.biausa.org/professionals/research/tbi-model-systems/an-overview-of-diffuse-axonal-injury

Smith, D. H., Meaney, D. F., & Shull, W. H. (2003). Diffuse Axonal Injury in Head Trauma. Journal of Head Trauma Rehabilitation, 18(4), 307-316. doi:10.1097/00001199-200307000-00003

Traumatic Brain Injury. (n.d.). Retrieved from https://www.hopkinsmedicine.org/health/conditions-and-diseases/traumatic-brain-injury

Young, B. (2018, September 29). Diffuse Axonal Injury: Prognosis, Symptoms, and Treatment. Retrieved from https://www.healthline.com/health/diffuse-axonal-injury#symptoms

Resources by Cassie Wang