Abstract 2856: Lesion load of Corticospinal Tract and Initial Motor Impairment in the Acute Stroke Phase Predict Motor Impairment 3 Months Post-Stroke

Abstract

Background: We use lesion-mapping techniques in combination with diffusion tensor imaging to quantitatively test the hypothesis that motor impairment 3 months post- stroke is inversely related to the lesion load of the corticospinal tract (CST) in the acute stroke phase. Methods: We prospectively followed up a cohort of 32 patients who presented with their first-ever acute ischemic stroke with various degree of motor deficit , had a MRI during the hospitalization, and had follow-up motor assessments using the Fugl-Meyer Upper Extremity Scale (FM-UE) at 3 months (+/- 2 weeks) after stroke. We calculated a CST-lesion load for each patient by overlaying the patient’s lesion map from diffusion weighted image with a probabilistic DTI tract constructed from 12 age-matched healthy subjects . Both raw and weighted (which accounts for the narrowing of the CST as it descends from the motor cortex to the posterior limb of the internal capsule) were calculated; weighted lesion-loads were calculated by multiplying the lesion-tract overlap on each slice by the ratio of the maximum cross-sectional area of the tract to the cross-sectional area of the tract on that particular slice). A multiple regression is fit to assess the predicted value of CST lesion load (raw or weighted), along with other variables such age, gender, lesion size, initial impairment, days of therapy known to have an possible effect on motor outcome. Results: CST-lesion load and initial motor impairment are found to be significant predictors of upper extremity motor impairment at 3 months post-stroke. Age, gender, lesion size or days of therapy does not have predictive value in our cohort study. The adjusted R² is 0.63 with initial impairment and raw lesion load in the regression model, and is 0.66 with initial impairment and weighted lesion load. Conclusions: Our data shows the degree of motor impairment at 3 months after a first-ever ischemic stroke can be predicted by the overlap of the lesion with the canonical CST derived from age-matched healthy control subjects and the initial motor impairment measured in the acute phase.