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Published on: December 15, 2014
Wallerian degeneration of pyramidal tract after paramedian pons infarct
David Grässel1, Thomas M Ringer, Clemens Fitzek
1Hans Berger Clinic for Neurology, Jena University Hospital, Friedrich-Schiller-University Jena, Erlanger Allee 101, Jena, Germany.
Background:
The intention of this study was the prospective analysis of Wallerian degeneration of the pyramidal tract after paramedian pons infarction.
Methods:
Patients with paramedian pons infarct underwent MR imaging including diffusion tensor imaging at admission and got 1-3 MR scans up to 6 months of follow-up. Clinical scores and transcranial magnetic stimulation were acquired in the acute phase and 3-6 months later. The pyramidal tracts were manually segmented in fractional anisotropy (FA) color maps after coregistration of all MR datasets of each patient. FA as well as axial and radial diffusivity were measured in the volume of lesioned and contralateral pyramidal tracts distally to the ischemic lesion.
Results:
From 11 patients studied, 7 developed Wallerian degeneration detected as statistically significant decrease in FA over time in the distal pyramidal tract. Wallerian degeneration could be detected at the earliest between the first and the third days after the onset of symptoms. A continuous decrease in FA and an increase in axial and radial diffusivity in degenerating pyramidal tracts over time were demonstrated. A significant correlation between NIHSS score on admission and the slope of relative axial diffusivity and a significant correlation between motor-evoked potential amplitudes of the arm on admission and the outcome relative FA was found.
Conclusions:
The initial MR image cannot predict the following Wallerian degeneration. However, the severity of motor disturbance and the motor-evoked potential of the arm on admission could be possible parameters to predict Wallerian degeneration. For estimation of Wallerian degeneration over time, at least 2 diffusion tensor imaging measurements have to be done at different time points.
Insights
Wallerian degeneration in the pyramidal tract after stroke can be detected early using diffusion tensor imaging. Motor deficits and evoked potentials may predict its severity over time.
Area of Science:
- Neuroimaging
- Neurology
- Radiology
Background:
- Investigating Wallerian degeneration in the pyramidal tract following paramedian pons infarction.
- Understanding the progression of neurodegeneration after ischemic stroke.
Purpose of the Study:
- To prospectively analyze Wallerian degeneration of the pyramidal tract after paramedian pons infarction.
- To identify predictors of Wallerian degeneration and its progression.
Main Methods:
- Prospective analysis of 11 patients with paramedian pons infarct.
- MR imaging including diffusion tensor imaging (DTI) at admission and follow-up (up to 6 months).
- Manual segmentation of pyramidal tracts and measurement of fractional anisotropy (FA), axial diffusivity, and radial diffusivity.
Main Results:
- Seven out of 11 patients showed Wallerian degeneration, indicated by decreased FA over time.
- Degeneration was detectable as early as 1-3 days post-symptom onset.
- Significant correlations found between NIHSS scores, motor-evoked potentials, and DTI-derived measures of degeneration.
Conclusions:
- Initial MR imaging cannot predict subsequent Wallerian degeneration.
- Motor disturbance severity and arm motor-evoked potentials may predict Wallerian degeneration.
- At least two DTI measurements are necessary to estimate Wallerian degeneration over time.
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