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MR imaging of wallerian degeneration in the human brain stem after ictus
Abstract:
Magnetic resonance (MR) imaging of wallerian degeneration in the brain stem was studied in 30 hemiplegic patients within 12 months of ictus. As early as 25 days after the ictus, decreased signal intensities on proton-density(PD)-weighted images were observed in the brain stem ipsilaterally. This hypointensity gradually approached an isointense stage during 70-80 days after the ictus, abnormal intensities were not detected in any pulse sequence. We termed this phenomenon "Fogging effect of wallerian degeneration". In later stages, at least 81 days after the ictus, increased signal intensities on T2-weighted images, with or without decreased signal intensities on T1-weighted images, were observed in the brain stem, ipsilaterally. Finally, at least six months after the ictus, mild shrinkage of the ipsilateral brain stem was newly detected on the T1-weighted images. MR imaging has proven to be a sensitive diagnostic modality for evaluating wallerian degeneration in the brain stem.
Insights
Magnetic resonance imaging reveals early changes in brain stem wallerian degeneration following ictus. A unique "fogging effect" is observed, followed by later signal changes and shrinkage, highlighting MR imaging
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Wallerian degeneration is a process that occurs after nerve injury.
- It affects the white matter tracts of the central nervous system.
- Early detection of brain stem wallerian degeneration is crucial for patient management.
Purpose of the Study:
- To investigate the temporal changes of wallerian degeneration in the brain stem using Magnetic Resonance (MR) imaging.
- To characterize the MR imaging findings in hemiplegic patients within 12 months post-ictus.
- To identify a potential diagnostic imaging phenomenon in early-stage wallerian degeneration.
Main Methods:
- Prospective study of 30 hemiplegic patients.
- Serial MR imaging of the brain stem within 12 months of ictus.
- Evaluation of signal intensities on proton-density (PD)-weighted and T2-weighted images.
- Assessment of T1-weighted images for signal changes and brain stem morphology.
Main Results:
- Decreased signal intensities (hypointensity) on PD-weighted images observed as early as 25 days post-ictus.
- A transient isointense stage occurred between 70-80 days, termed the "Fogging effect of wallerian degeneration".
- Later stages (≥81 days) showed increased T2-weighted signal intensities and decreased T1-weighted signal intensities.
- Mild ipsilateral brain stem shrinkage detected on T1-weighted images at least six months post-ictus.
Conclusions:
- MR imaging is a sensitive tool for diagnosing brain stem wallerian degeneration.
- The "Fogging effect" represents a distinct early MR imaging finding.
- MR imaging can track the progression of wallerian degeneration from acute to chronic stages.