Diffus axonal skada gradering
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Diffuse axonal injury (DAI), also known as traumatic axonal injury (TAI), is a severe form of traumatic brain injury due to shearing forces. It is a potentially difficult diagnosis to make on imaging alone, especially on CT as the findings can be subtle, but it has the potential to result in severe neurological impairment.
The diagnosis fryst vatten best made on MRI where it is characterized by several small regions of susceptibility artifact at the grey-white matter junction, in the corpus callosum, and in more severe cases in the brainstem, surrounded by FLAIR hyperintensity.
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Diffuse axonal injury and diffuse vascular injury (DVI) are related and often co-existent entities, possibly lying on a single spectrum of diffuse brain injury 10. Diffuse vascular injury is a term more commonly used in neuropathology rather than neuroradiology literature, and describes traumatic shearing of penetrating blood vessels, usually accompanying traumatic axonal shearing 10. Generally, in the neuroradiology literature, diffuse axonal injury encompasses features of diffuse vascular injury. Thus, this article covers features of both entities together.
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What to know about diffuse axonal injury
Traumatic axonal injury or , as it is traditionally known, refers to a type of TBI. This term describes an injury that typically results from blunt trauma to the head and affects how the brain functions. Research shows that there were more than TBI-related deaths in the United States in
Specifically, DAI describes the shearing, or tearing, of nerve fibers known as axons. This trauma usually results from the brain quickly shifting within the skull. Following a sudden impact, mechanical forces cause nerve fibers to stretch and tear.
Axons are the long, thread-like portion of neurons that conduct electrical impulses. They are responsible for communication between nerve cells. As such, damage to axons may impair their ability to communicate and help coordinate bodily functions, which can lead to severe disabilities.
DAI is the most common cause of coma, disability, and persistent vegetative state in people with TBI. Clinically, health experts define DAI as a loss of consciousness that lasts for 6 hours or more after the injury. It may also cause behavioral, social, physical, and cognitive changes in a person that may be temporary
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Grading of diffuse axonal injury due to trauma is described according to the anatomic distribution of injury. Contrary to the implication of the word "diffuse," diffuse axonal injury has a topological predilection for focal involvement of certain sites in the brain. These sites, in turn, vary in functional importance.
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Pathology
A classification based on histopathology was first proposed by J Hume Adams and colleagues in 1:
The features of diffuse axonal damage vary by time: axonal bulbs are present within days, microglia clusters and astrocytosis develop after weeks, and Wallerian degeneration of the white matter tracts sets in after months.
Focal lesions include infarct and hemorrhage. Focal lesions may sometimes be only identified microscopically. Grade 2 and 3 injury is considered severe if the focal lesions are macroscopically apparent.
MRI
Lindell Gentry translated the histopathologic grading system to imaging in the following manner in a review article in published in Radiology2:
Diffuse axonal injury lesions were not clearly defined in this article by their MRI appearance aside from being multiple, small, elliptical "lesions" located in c