Correlation Analysis of Quantitative Diffusion Parameters in Ipsilateral Cerebral Peduncle during Wallerian Degeneration with Motor Function Outcome after Cerebral Ischemic Stroke
To evaluate the time periods of Wallerian degeneration (WD) in which the diffusion parameters of ipsilateral corticalspinal tract (CST) can be used to predict the motor function outcome after brain infarction.
This retrospective study classified 48 diffusion tensor imaging patients with WD along CST into four groups based on the following time points after stroke onset, Group 1: within the first 2 weeks; Group 2: from 3 to 4 weeks; Group 3: from 5 to 14 weeks; Group 4: after 14 weeks. The apparent diffusion coefficient (ADC), fractional anisotropy (FA), and their ratios (=ipsilateral diffusion value/contralateral value) of cerebral peduncle were evaluated. The correlation between imaging parameters in each group and the motor function scores appraised at 8 months after stroke onset were assessed.
There was no evident correlation of FA ratio (rFA) in Group 1 with motor function score (P = .05). The rFA and FA correlated with motor function score in other groups (P < .001 in each group). The ADC ratio and ipsilateral ADC value only showed significant correlation of with motor function score in Group 4 (P= .016 and .029, respectively).
The rFA and ipsilateral FA values after 2 weeks of stroke onset correlate with the motor function outcome.
Available from: Chang-Hyun Park
- "c o m / l o c a t e / y n i c l 2011). Alternatively, anatomical landmark-based ROIs refer to regions manually delineated on the brain, relying on anatomical landmarks, without reconstruction of the CST by tractography (Jayaram et al., 2012; Lindberg et al., 2007; Liu et al., 2012; Madhavan et al., 2011; Qiu et al., 2011; Stinear et al., 2007; Yeo et al., 2011). Once the ROI has been defined, the FA can be reported as an absolute measure from the ipsilesional side (FA ipsi ) (Jang et al., 2006; Lindenberg et al., 2012; Møller et al., 2007; Nelles et al., 2008; Pierpaoli et al., 2001; Puig et al., 2010) or contralesional side (FA contra ) (Jang et al., 2006; Lindenberg et al., 2012; Pierpaoli et al., 2001; Puig et al., 2010). "
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ABSTRACT: The structural integrity of the corticospinal tract (CST) after stroke is closely linked to the degree of motor impairment. Simple and reliable methods of assessing white matter integrity within the CST would facilitate the use of this measure in routine clinical practice. Commonly, diffusion tensor imaging is used to measure voxel-wise fractional anisotropy (FA) in a variety of regions of interest (ROIs) representing the CST. Several methods are currently in use with no consensus about which approach is best. ROIs are usually either the whole CST or the posterior limb of the internal capsule (PLIC). These are created manually on brain images or with reference to an individual's CST determined by tractography. Once the ROI has been defined, the FA can be reported as an absolute measure from the ipsilesional side or as a ratio in comparison to the contralesional side. Both corticospinal tracking and manual ROI definition in individual stroke patients are time consuming and subject to bias. Here, we investigated whether using a CST template derived from healthy volunteers was a feasible method for defining the appropriate ROI within which to measure changes in FA. We reconstructed the CST connecting the primary motor cortex to the ipsilateral pons in 23 age-matched control subjects and 21 stroke patients. An average healthy CST template was created from the 23 control subjects. For each patient, FA values were then calculated for both the template CST and for their own CST. We compared patients' FA metrics between the two tracts by considering four measures (FA in the ipsilesional side, FA in the contralesional side, FA ratio of the ipsilesional side to the contralesional side and FA asymmetry between the two sides) and in two tract-based ROIs (whole tract and tract section traversing the PLIC). There were no significant differences in FA metrics for either method, except for contralesional FA. Furthermore, we found that FA metrics relating to CST damage all correlated with motor ability post-stroke equally well. These results suggest that the healthy CST template could be a surrogate structure for defining tract-based ROIs with which to measure stroke patients' FA metrics, avoiding the necessity for CST tracking in individual patients. CST template-based automated quantification of structural integrity would greatly facilitate implementation of practical clinical applications of diffusion tensor imaging.
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ABSTRACT: This study examined the relationship between fractional anisotropy (FA) values of magnetic resonance-diffusion tensor imaging (DTI) and motor outcome (1 month after onset) in 15 patients with hemiparesis after ischemic stroke of corona radiata lesions. DTI data were obtained on days 14-18. FA values within the cerebral peduncle were analyzed using a computer-automated method. Motor outcome of hemiparesis was evaluated according to Brunnstrom stage (BRS; 6-point scale: severe to normal) for separate shoulder/elbow/forearm, wrist/hand, and lower extremity functions. The ratio of FA values in the affected hemisphere to those in the unaffected hemisphere (rFA) was assessed in relation to the BRS data (Spearman rank correlation test, P < .05). rFA values ranged from .715 to 1.002 (median = .924). BRS ranged from 1 to 6 (median = 4) for shoulder/elbow/forearm, from 1 to 6 (median = 5) for wrist/hand, and from 2 to 6 (median = 4) for the lower extremities. Analysis revealed statistically significant relationships between rFA and upper extremity functions (correlation coefficient = .679 for shoulder/elbow/forearm and .706 for wrist/hand). Although slightly less evident, the relationship between rFA and lower extremity function was also statistically significant (correlation coefficient = .641). FA values within the cerebral peduncle are moderately associated with the outcome of both upper and lower extremity functions, suggesting that DTI may be applicable for outcome prediction in stroke patients with corona radiata infarct.
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Magnetic resonance diffusion tensor fractional anisotropy (DTI-FA) is often used to characterize neural damage after stroke. Here we assessed the relationship between DTI-FA and long-term motor outcome in patients after middle cerebral artery (MCA) infarction.
Fractional anisotropy (FA) maps were generated from diffusion tensor brain images obtained from 16 patients 14-18 days postinfarction, and tract-based spatial statistics (TBSS) analysis was applied. Regions of interest were set within the right and left corticospinal tracts, and mean FA values were extracted from individual TBSS data. Hemiparesis motor outcome was evaluated according to Brunnstrom stage (BRS: 1-6, severe-normal) for separate shoulder/elbow/forearm, hand, and lower extremity functions, as well as the motor component score of the Functional Independence Measure (FIM-motor: 13-91, null-full) 5-7 months after onset. Ratios between FA values in the affected and unaffected hemispheres (rFA) were assessed by BRS and FIM-motor scores.
rFA values were .636-.984 (median, .883) and BRS scores were 1-6 (median, 3) for shoulder/elbow/forearm, 2-6 (median, 3) for hand, and 3-6 (median, 5) for the lower extremities. FIM-motor scores were 51-90 (median, 75). Analysis revealed significant relationships between rFA and BRS data (correlation coefficient: .687 for shoulder/elbow/forearm, .579 for hand, and .623 for lower extremities) but no significance relationship between rFA and FIM-motor scores.
The results suggest that DTI-FA is applicable for predicting the long-term outcome of extremity functions after MCA infarction.
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