Wallerian Degeneration

Clinical:

  • A 52 years old lady
  • Underlying multiple medical problems
  • Presented with sudden onset right sided body weakness
  • CT brain done showed MCA-territorial infarction
  • MRI done 4 weeks after the CT scan
MRI brain in axial planes
MRI brain in axial plane T2-weighted images at different level

MRI findings:

  • Abnormal signal intensity¬† seen in the left temporoparietal lobe sparing the parasagittal region (yellow arrows)
  • It is heterogenously hypointense on T1/T2/FLAIR with gyriform hyperintense region seen
  • Blooming artifact seen on SWI sequence
  • Associated volume loss is seen
  • These changes correspond to subacute MCA territorial infarction with hemorrhagic transformation
  • Another abnormality seen as hyperintensity inferior to left lentiform nucleus to the left cerebral peduncle (red arrows) corresponding to changes along the corticospinal tract.

Radiological diagnosis: Wallerian degeneration due to massive infarction.

Discussion:

  • Wallerian degeneration is disruption of the myelin and axons along the entire length of the nerve below the site of the lesion.
  • It may result following neuronal loss due to cerebral infarction, trauma, necrosis, focal demyelination or hemorrhage.
  • In post infarction, WD appears in the chronic phase (>30 days)
  • CT is less sensitive than MRI the evaluation of this changes
  • It is seen as contiguous tract of gliosis from a region of cortical or subcortical neuronal injury towards deep cerebral structures along the expected topographical course of the involved white matter tract
  • The tract descend through subcortical white matter and form the anterior two-thirds of the posterior limb of the internal capsule. Then it pass through the ventral midbrain and continue through the pons. In the medulla oblongata corticospinal fibres collect into a discrete bundle forming the pyramid.
  • The pyramid is a discrete triangular column on the ventral medulla oblongata next to the midline. This is why the corticospinal tract is also called the pyramidal tract.

 

Author: radhianahassan