Wallerian degeneration (WD) in the central nervous system produces a contiguous tract of gliosis, starting at a damaged region of cerebral cortex and running through the deeper brain structures according to the topography of the involved white-matter tracts. The process starts immediately after injury but evolves to complete after months-to-years. On Magnetic Resonance Imaging (MRI), chronic WD of the corticospinal tract can be observed as shrinkage of the ipsilateral cerebral peduncle . We herein illustrated WD via selection of a range of MRI’s with atrophied cerebral peduncles secondary to various causes.
MRI of an 83-year-old man with aphasia and right hemiplegia caused by intracerebral hemorrhage. Compare computed tomography (CT) and MRI during the hemorrhage (Figure 3) are compared to MRI three years later (Figure 4).
MRI of a 61-year-old woman with glioblastoma multiforme in the left cerebrum. Figure 5 shows the lesions on preoperative and postoperative MRI’s and Figure 6 displays the evolution of WD with prolonged time after surgery (Figure 6).
MRI of a 53-year-old woman with brain trauma due to a fall. Eventually she developed spastic paresis, especially on the left side. Figure 7 shown the CT and MRI at time of trauma, and Figure 8 shows the respective size and T2-WI signal intensity of the cerebral peduncles over time (Figure 8).
MRI of a 42-year-old woman with a large arachnoid cyst (Figure 9).
MRI of a 2-year-old girl with hypoplastic left cerebrum (Figure 10).
The degree of poststroke and posthemorragic peduncular atrophy is correlated with size of cerebral injury [2, 3]. Deduced from our cases, it seems likely that this also applies for other mechanisms of injury.
In addition to the chronic atrophy of the cerebral peduncle on the long term, the acute signs of WD are also visible on MRI by Diffusion-Weighted-Imaging. It is important to recognize these diffusion-restricted areas as acute WD from damage higher in the ipsilateral corticospinal tract, and not to mistake these with secondary zones of infarction .
More recent investigation with Diffusion-Tensor-Imaging brought more insight on the progress of WD by the measurements of fractional anisotropy: the process of WD in the subacute phase of ischemia proved to be a predictor for later functional recovery .
Cerebral injury frequently leads to Wallerian degeneration of the cerebral peduncle. It reflects degree of cerebral damage and predicts functional recovery, making it worth mentioning in the radiologic report.
The authors have no competing interests to declare.
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