Diffuse Axonal Injury
DAI

 

General Considerations

  • Result of deceleration injuries, especially in high-speed motor vehicle collisions
    • Also a major cause of morbidity in “Shaken Baby Syndrome”
  • Most frequent cause of persistent vegetative state following trauma
  • Result of rotational shear injuries that most often occur at the gray-white matter junction
    • Extent of injury is usually worse than that depicted by imaging
  • Shearing leads to edema, axoplasmic leakage, retraction ball formation and wallerian degeneration
  • Brainstem function is typically unaffected

Clinical Findings

  • Damage occurs at time of injury and then when secondary swelling occurs
  • Immediate loss of consciousness
    • Most, but not all, have no period of lucidity
  • Brainstem functions remain intact so it is rarely a cause of death

Imaging Findings

  • Diffuse
  • Bilateral
  • Majority of lesions (80%) are multiple
  • Occur at the gray-white matter junction
  • Lesions are most frequently ovoid, larger centrally than peripherally
  • Frequently involved are the
    • Frontal and temporal lobes
    • Posterior body and splenium of the corpus callosum
    • Caudate nuclei
    • Thalamus
    • Tegmentum
    • Internal capsule
      • More frequently associated with hemorrhage
    • MRI is the preferred method of study but CT is usually more available
  • On CT
    • 50-89 of patients with DAI may have a normal CT scan on presentation
    • Small petechial hemorrhages located at gray-white matter junction and  corpus callosum are characteristic but occur in only about 20%
    • There may also be small. Focal areas of decreased attenuation secondary to edema
  • On MRI
    • Gradient-echo sequences are very useful in demonstrating paramagnetic effects of petechial hemorrhages
    • Most common MRI finding
      • Presence of multiple focal areas of abnormally bright signal on T2-weighted images in the white matter of the temporal or parietal corticomedullary junction or in splenium of corpus callosum.
    • Hemorrhagic lesions appear hyperintense on T1-weighted images
    • Non-hemorrhagic lesions appear hyperintense on T2-weighted sequences
    • Gradient-echo sequences are very useful in demonstrating paramagnetic effects of petechial hemorrhages

Differential Diagnosis

  • Multiple sclerosis
  • Embolic or hemorrhagic stroke

Prognosis

  • Over 90% remain in persistent vegetative state
    • Chances of this occurring are greater with lesions that are supratentorial, involve the corpus callosum or corona radiata
  • Prognosis worsens with multiplicity of lesions

 


Diffuse Axonal Injury.
An axial, non-enhanced CT image of the brain demonstrates multiple small petechial hemorrhages at the gary-white matter junction, the caudate nucleus and the corpus callosum, characteristic of diffuse axonal injury in this male who was in a motor vehicle accident.
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Diffuse Axonal Injury  eMedicine  Wasserman, J; Koenigsberg, R