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MR imaging of Wallerian degeneration in the brainstem: temporal relationships
Y Inoue1, Y Matsumura, T Fukuda
1Department of Radiology, Osaka City University Medical School, Japan.
Abstract:
Degeneration of the myelin sheath and axon distal to the most proximal site of axonal interruption secondary to axonal disease has been called wallerian degeneration. On MR imaging, wallerian degeneration of the pyramidal tract can be observed as an abnormal signal intensity, showing prolonged T1 and T2 relaxation times that correspond to the corticospinal tract, with or without shrinkage of the ipsilateral cerebral peduncle and pons. Review of MR studies in 150 cases of supratentorial cerebrovascular accidents showed abnormal signal alterations in the ipsilateral brainstem in 33 of the cases. Abnormal intensity in the ipsilateral brainstem was seen as early as 5 weeks after the supratentorial ictus and was fully evident after 10 weeks in all 33 cases. Signal alterations were strongest at about 3-6 months when compared with alterations seen at 10 weeks or even 10 months after the ictus. Shrinkage of the ipsilateral brainstem appeared as early as 8 months and was demonstrated in all cases 13 months after the ictus. MR seems to be the most effective technique for early detection of wallerian degeneration and may provide insight into its pathophysiological and chemical changes.
Insights
Magnetic resonance imaging (MRI) can detect wallerian degeneration, a nerve damage process, in the brainstem early after stroke. This imaging technique reveals characteristic signal changes and shrinkage, aiding in understanding nerve degeneration.
Area of Science:
- Neurology
- Radiology
- Neuroscience
Background:
- Wallerian degeneration is the process of myelin and axon breakdown distal to axonal injury.
- It is a common consequence of various neurological diseases and injuries.
- Understanding its progression is crucial for diagnosing and managing neurological conditions.
Purpose of the Study:
- To evaluate the utility of Magnetic Resonance (MR) imaging in detecting and characterizing wallerian degeneration of the pyramidal tract.
- To determine the timeline of MR signal alterations and anatomical changes associated with wallerian degeneration after supratentorial cerebrovascular accidents.
Main Methods:
- Review of MR imaging studies in 150 patients with supratentorial cerebrovascular accidents.
- Analysis of signal intensity changes (T1 and T2 relaxation times) in the corticospinal tract and brainstem.
- Assessment of brainstem shrinkage over time.
Main Results:
- Abnormal MR signal intensity indicative of wallerian degeneration was observed in the ipsilateral brainstem in 33% of cases.
- These signal alterations appeared as early as 5 weeks post-stroke, becoming fully evident by 10 weeks.
- Brainstem shrinkage was detectable by 8 months and present in all affected cases by 13 months.
- Signal alterations peaked in intensity around 3-6 months post-ictus.
Conclusions:
- MR imaging is highly effective for the early detection of wallerian degeneration.
- The characteristic signal changes and shrinkage patterns observed on MRI provide insights into the pathophysiology of axonal degeneration.
- MRI can serve as a valuable tool for monitoring the progression of wallerian degeneration following brain injury.