Abstract 21: Motor Tract Impairment is an Independent Predictor of Lower Limb Motor Recovery

Abstract

Introduction: Initial motor impairment assessed in the acute stroke phase (as measured by the Fugl-Meyer (FM) Assessment) is a strong predictor of lower extremity (LE) motor impairment at 3 months (Smith et al., 2017). The predictive value of measures of motor tract integrity, lesion size and location is not known. For our analysis we combined two motor tracts that might be particularly important in the control of proximal leg muscles to create a canonical tract of the corticospinal tract proper (CST) and the corticorubrospinal tract (CRST)(Lindenberg et al., 2010; Rueber et al., 2012). In previous work (Feng et al., 2015) we have shown that weighted CST-Lesion Load (a combined variable of lesion size and location) is a significant predictor of 3 months outcome for the UE. Hypothesis: Weighted CST-CRST Lesion-Load (wCST/CRST-LL) can improve the FM-based predictions of lower limb motor recovery. Methods: Ischemic stroke patients with a upper limb paresis (UE-FM<66) and lower limb paresis (LE-FM<34) were assessed between 48-72h and 3 months poststroke with the FM scale. Lesion maps drawn on diffusion-weighted images were used to calculate lesion loads of a combined CST-CRST probabilistic tract derived from matched elderly healthy control subjects. Then, several variables that have been shown to predict outcome (e.g., FM, lesion load, age, hemisphere) were subjected to individual regression analyses. Significant variables (at p<0.05) were entered into a multiple regression model to assess predictors of lower limb motor recovery (i.e., actual difference in LE-FM between 3 months and initial stroke phase assessment). Results: Both baseline and 3-months follow-up were available for 134 patients. Initial motor impairment (FM-LE) and wCST/CRST-LL were independent strong predictors of lower limb motor recovery (respectively p<0.0001 and p=0.0005). Combining initial motor impairment and wCST/CRST lesion load was a much better model than FM-LE by itself (respectively R2=0.43 and R2=0.46, p=0.003) which was confirmed by the Akaike Information Criterion (AIC). Conclusion: wCST/CRST-LL, a combined measure of lesion size/location, adds significant power to a combined model with FM, but is also a strong predictor of lower limb motor recovery by itself.