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A Wallerian degeneration pattern in patients at risk for MS
J H Simon1, R P Kinkel, L Jacobs
1Neuroradiology/MRI Department, University of Colorado Health Sciences Center, Denver 80262, USA. jack.simon@uchsc.edu
Background:
Demyelination alone may not explain the progressive disability that frequently develops in MS. An alternative explanation for irreversible disability assumes a contribution from axonal injury or loss. In theory, axonal injury may occur in the focal areas characterized by early inflammation, or can be more distant, as in Wallerian degeneration. However, Wallerian degeneration is thought of as a rare or a late finding in MS.
Methods:
Studies showing a classic Wallerian degeneration pattern in the corticospinal tract were selected from a review of MR studies from patients enrolled in a longitudinal treatment trial. Entry was based on first occurrence of an isolated neurologic syndrome consistent with MS and a positive MRI.
Results:
This report is based on five cases followed longitudinally who showed development of a classic T2-hyperintense lesion along the ipsilateral corticospinal tract, subsequent to an initial inciting event located in the white matter located in the superior aspect of the corona radiata. Lesions were evident as T2-hyperintensity persisting throughout the 12 to 18 months of observation.
Conclusions:
This series suggests that Wallerian degeneration, implying axonal injury, may occur as a sequela of acute demyelinating lesions in patients presenting with their first symptoms suggestive of MS. This can produce a component of the increasing burden of T2-hyperintense lesions temporally and spatially dissociated from inflammatory or demyelinating activity. Further studies are required to determine if Wallerian degeneration is an important factor contributing to disability progression in MS.
Insights
Wallerian degeneration, indicating axonal injury, may follow acute demyelinating lesions in early multiple sclerosis (MS). This process contributes to lesion burden independently of inflammation, potentially impacting disability progression.
Area of Science:
- Neuroimaging
- Neurology
- Pathology
Background:
- Progressive disability in multiple sclerosis (MS) may involve more than demyelination.
- Axonal injury or loss is a potential contributor to irreversible disability in MS.
- Wallerian degeneration, a form of axonal degeneration, is typically considered rare or late-onset in MS.
Purpose of the Study:
- To investigate the occurrence and pattern of Wallerian degeneration in the corticospinal tract in early MS.
- To determine if Wallerian degeneration can be identified following acute demyelinating events in MS.
Main Methods:
- Review of MRI studies from patients with a first isolated neurologic syndrome consistent with MS.
- Selection criteria included a positive MRI and longitudinal follow-up.
- Focus on cases demonstrating a classic Wallerian degeneration pattern in the corticospinal tract.
Main Results:
- Five longitudinally followed cases showed T2-hyperintense lesions in the corticospinal tract.
- These lesions appeared after an initial inciting event in the corona radiata.
- Lesions persisted for 12-18 months, consistent with Wallerian degeneration.
Conclusions:
- Wallerian degeneration may occur as a consequence of acute demyelinating lesions in early MS.
- This process can contribute to the lesion burden independently of active inflammation.
- Further research is needed to establish the role of Wallerian degeneration in MS disability progression.