Corticospinal tract lesion load: An imaging biomarker for stroke motor outcomes

Abstract

Objective: The aim of this work was to investigate whether an imaging measure of corticospinal tract (CST) injury in the acute phase can predict motor outcome at 3 months in comparison to clinical assessment of initial motor impairment. Methods: A two‐site prospective cohort study followed up a group of first‐ever ischemic stroke patients using the Upper‐Extremity Fugl‐Meyer (UE‐FM) Scale to measure motor impairment in the acute phase and at 3 months. A weighted CST lesion load (wCST‐LL) was calculated by overlaying the patient's lesion map on magnetic resonance imaging with a probabilistic CST constructed from healthy control subjects. Regression models were fit to assess the predictive value of wCST‐LL and compared with initial motor impairment. Results: Seventy‐six patients (37 from cohort 1 and 39 from cohort 2) completed the study. wCST‐LL as well as assessment of motor impairment (UE‐FM) in the acute phase correlated with motor impairment (UE‐FM) at 3 months in both cohort 1 (R 2 = 0.69 vs. R 2 = 0.67; p = 0.43) and cohort 2 (R 2 = 0.69 vs. R 2 = 0.62; p = 0.25). In the severely impaired subgroup (defined as UE‐FM ≤ 10 at baseline), wCST‐LL correlated with outcomes significantly better than clinical assessment (R 2 = 0.47 vs. R 2 = 0.11; p = 0.03). In the nonseverely impaired subgroup, stroke patients recovered approximately 70% of their maximal recovery potential. All stroke patients in both cohorts had poor motor outcomes at 3 months (defined as UE‐FM ≤ 25) when wCST‐LL was ≥ 7.0 cc (positive predictive value was 100%). Interpretation: wCST‐LL, an imaging biomarker determined in the acute phase, can predict poststroke motor outcomes at 3 months, especially in patients with severe impairment at baseline. Ann Neurol 2015;78:860–870