Abstract T MP37: Fractional Anisotropy Changes in the Acute Stroke Phase Only Modestly Predict Motor Outcome at 3 Months

Abstract

Background: A decrease in fractional anisotropy (FA) of the ipsilesional corticospinal tract (CST) distal to ischemic stroke lesions in chronic stroke patients has been associated with poor motor outcome, but in the acute phase no clear FA trends have been observed or used to make outcome predictions. Methods: This study followed 40 patients with first-ever ischemic stroke, measuring motor impairment with the Upper Extremity Fugl-Meyer (UE-FM) acutely and at 3 months. Images obtained <3 days after stroke, including FA, were overlaid with a probabilistic CST (blue in Figure 1) derived from healthy subjects to define a cerebral peduncle region of interest ROI and a “nearest slice” ROI (green line in Figure 1), the second slice downstream from the stroke lesion (red in Figure 1). Ipsilesional and contralesional CST FA values as well as Apparent Diffusion Coefficient (ADC) values of regions of interests were compared using a laterality index and related to 3-month motor outcome. Results: Asymmetry between ipsilesional and contralesional CST FA values was significant different between patients with bad motor outcome and good outcome, with lower FA of the ipsilesional CST in the bad outcome group. No such asymmetry was seen for the cerebral peduncle ROI using either FA or ADC values. The FA laterality index for the nearest slice ROI was a significant but modest predictor of 3-month motor outcome (R2=0.186, p=.02), with the best predictive value offered by the combination of this imaging variable and the initial motor impairment (R2=0.696, p=.01). Conclusion: FA changes of the CST can be detected near the ischemic lesion in the acute phase after stroke, but these changes offer only modest predictive value for eventual motor outcome.