Detection and Predictive Value of Fractional Anisotropy Changes of the Corticospinal Tract in the Acute Phase of a Stroke

Abstract

Background and Purpose A decrease in fractional anisotropy (FA) of the ipsilesional corticospinal tract (CST) distal to stroke lesions in the subacute (e.g., 30 days) and chronic phase has been correlated with poor motor outcomes, but it is unclear whether FA values obtained within the acute stroke phase (here defined as 80 hours after onset) can predict later outcome. Methods Fifty-eight patients underwent an assessment of motor impairment in the acute phase and at 3 months using the Upper Extremity Fugl-Meyer (UE-FM) assessment. FA values, obtained within 80 hrs after stroke onset, were determined in two regions of interest: cerebral peduncle (CP) and a stretch of the CST caudal to each stroke lesion (Nearest-5-Slice – N5S)). Results The FA laterality index (FA-LI) for the CP-ROI was a poor predictor of 3-months outcome (R2 =0.044, p=0.137), while the slope over the FA-LIs of the N5S showed a relatively weak but significant prediction (R2=0.11, p=0.022) with the affected side having lower FA values. Initial UE-FM (R2=0.69, p<0.001) and the weighted CST lesion load (wCST-LL) (R2=0.71, p<0.001) were strong predictors of 3-months outcome. In multivariate analyses controlling for initial UE-FM, wCST-LL, and Days-of-Therapy, neither the FA-LI of the CP nor the slope over the FA-LI of the N5S significantly contributed to the prediction of 86% of the variance in the UE-FM at 3 months. Conclusions FA reductions of the CST can be detected near the ischemic lesion in the acute stroke phase, but offer minimal predictive value to motor outcomes at 3 months.

Motor Recovery Prediction With Clinical Assessment and Local Diffusion Homogeneity After Acute Subcortical Infarction

“…These results are consistent with prior reports that CST FA at a single time point within the first week after stroke has limited value in predicting long-term motor outcome. [9][10][11]21 Together, these findings suggest that FA of the ipsilesional CST in the acute period of subcortical infarction has limited value in predicting long-term motor improvement, whereas LDH offers good predictive value. …”

“…1,4 In addition, diffusion tensor imaging (DTI) studies have reported that the use of fractional anisotropy (FA) of corticospinal tract (CST) alone to predict future motor function of the upper extremity in patients with stroke in the acute period is also unreliable. [8][9][10][11] Researchers have proposed that more accurate prognoses may be made by combining behavioral tests with magnetic resonance imaging (MRI) determinations of the functional or structural integrity of the ipsilesional corticomotor tract. 12,13 However, it has been reported that on the base of initial impairment, adding functional MRI task-related brain activation patterns (during hand closure task) to their prediction model did…”

Prediction of Walking and Arm Recovery after Stroke: A Critical Review

“…FA asymmetry index values of <0.15 and <0.25 have been used to predict arm recovery [49,73,98]. Recent studies that have used neuroimaging predictors to predict arm recovery have also measured “early fiber number ratio” [102] and “weighted corticospinal lesion load” [103,104] as markers of corticospinal tract integrity.…”

“…When this claim is made explicitly it is often supported by reference to the proportional recovery model or poorly conducted prognostic studies, rather than models which have shown good predictive accuracy [25,42]. In addition, comparisons of predictive accuracy of models based on clinical data and models based on neurophysiological or neuroimaging data consistently demonstrate that prediction models based on clinical data have similar or higher predictive accuracy in predicting arm recovery [75,99,103,104,110]. When neurophysiological or neuroimaging data are added to models containing clinical data the increase in predictive accuracy is small [75,99,110] (e.g., increments in r 2 of 5%–9% [75,99])—probably too small to justify the expense and inconvenience of these investigations.…”

“…In these patients it may be hard to conduct clinical assessments that involve self-reporting or performance of complex tasks. However, studies that have predicted arm recovery with neurophysiological and neuroimaging data have often excluded patients with cognitive deficits [49,73,98,99,100,101,103,104,109]. Moreover, patients with previous strokes or contraindications to TMS or MRI are also often excluded from TMS and MRI studies [49,73,75,98,99,100,101,102,103,109,110].…”