Wallerian Degeneration of Pyramidal Tract after Paramedian Pons Infarct

Abstract

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.

Diffusion Tensor Imaging Predicts Long-Term Motor Functional Outcome in Patients with Acute Supratentorial Intracranial Hemorrhage

“…However, edematous volume growth in patients with ICH was shown to be most rapid during the first 2 days after onset but to continue until day 12 postonset [26]; therefore, WD in the cerebral peduncle at 2 weeks following ICH onset may differ from CST damage at the level of the PLIC at the same stage in patients with an infarct. Moreover, Grassel et al [14] found that it was not possible to predict functional outcome according to initial DTI parameters, as the changes observed in DTI following WD are time dependent and only become apparent after several days. Therefore, predicting the potential for motor rehabilitation based on DTI parameters demands both an initial and a follow-up MRI to evaluate the individual time course of WD.…”

“…Fractional anisotropy (FA), the most widely used parameter of DTI, represents the degree of directionality of microstructures and has been used to evaluate the extent of fiber damage or changes in subcortical neural structures [11]. A decrease in the FA measurement of the involved pyramidal tract (PT) typically signifies alterations of both the CST and corticobulbar tract, which become progressively reduced during the acute-to-chronic stage of an ischemic stroke and have been shown to correlate with motor deficits [12,13,14]. In a recent study, Kusano et al [6] concluded that DTI can be used to evaluate motor deficits quantitatively and may predict the functional outcome at 28 days for patients with ICH who were scanned within 2 days of onset.…”

Microstructural analysis of human white matter architecture using polarized light imaging: views from neuroanatomy

“…However, the low magnification of DTI (see also Figures 4A,B) in this region only allows evaluation of large fiber tracts, such as the pyramidal tract (Grässel et al, 2010). …”

“…PLI is applied for detection and segmentation as well as for morphometric analysis of these fiber tracts. Although, the analysis of the pyramidal tract is also undertaken with diffusion MRI such as for Wallerian degeneration after stroke (Grässel et al, 2010), smaller fiber tracts such as the lemniscus medialis and many others are difficult to be reliably imaged using MRI.…”

Progressive Multifocal Leukoencephalopathy with Wallerian Degeneration

“…Wallerian degeneration results from axonal disintegration following a stereotypical time course and is due to various pathologies including stroke [1,2] and progressive multifocal leukoencephalopathy. …”