Comparing prognostic strength of acute corticospinal tract injury measured by a new diffusion tensor imaging based template approach versus common approaches.

BACKGROUND: Long-term motor outcome of acute stroke patients with severe motor impairment is difficult to predict. While measure of corticospinal tract (CST) injury based on diffusion tensor imaging (DTI) in subacute stroke patients strongly predicts motor outcome, its predictive value in acute stroke patients is unclear. Using a new DTI-based, density-weighted CST template approach, we demonstrated recently that CST injury measured in acute stroke patients with moderately-severe to severe motor impairment of the upper limb strongly predicts motor outcome of the limb at 6 months. NEW METHOD: The current study compared the prognostic strength of CST injury measured in 10 acute stroke patients with moderately-severe to severe motor impairment of the upper limb by the new density-weighted CST template approach versus several variants of commonly used DTI-based approaches. RESULTS AND COMPARISON WITH EXISTING METHODS: Use of the density-weighted CST template approach yielded measurements of acute CST injury that correlated most strongly, in absolute magnitude, with 6-month upper limb strength (rs=0.93), grip (rs=0.94) and dexterity (rs=0.89) compared to all other 11 approaches. Formal statistical comparison of correlation coefficients revealed that acute CST injury measured by the density-weighted CST template approach correlated significantly more strongly with 6-month upper limb strength, grip and dexterity than 9, 10 and 6 of the 11 alternative measurements, respectively. CONCLUSIONS: Measurements of CST injury in acute stroke patients with substantial motor impairment by the density-weighted CST template approach may have clinical utility for anticipating healthcare needs and improving clinical trial design.

Corticospinal tract diffusion abnormalities early after stroke predict motor outcome.

BACKGROUND: Prognosis of long-term motor outcome of acute stroke patients with severe motor impairment is difficult to determine. OBJECTIVE: Our primary goal was to evaluate the prognostic value of corticospinal tract (CST) injury on motor outcome of the upper limb compared with motor impairment level and lesion volume. METHODS: In all, 10 acute stroke patients with moderately severe to severe motor impairment of the upper limb underwent diffusion tensor imaging (DTI) and testing of upper limb strength and dexterity at acute, subacute, and chronic poststroke time points. A density-weighted CST atlas was constructed using DTI tractography data from normal participants. This CST atlas was applied, using a largely automated process, to DTI data from patients to quantify CST injury at each time point. Differences in axial diffusivity (AD), radial diffusivity (RD), and fractional anisotropy (FA) of the ipsilesional CST relative to the contralesional CST were measured. RESULTS: Acute loss in CST AD correlated most strongly and significantly with subacute and chronic strength and dexterity and remained significant after adjusting for acute motor impairment or lesion volume. Subacute loss in CST FA correlated most strongly with chronic dexterity, whereas subacute behavioral measures of limb strength correlated most strongly with chronic strength measures. CONCLUSIONS: Loss in acute CST AD and subacute CST FA are strong prognostic indicators of future motor functions of the upper limb for stroke patients with substantial initial motor impairment. DTI-derived measure of CST injury early after stroke may have utility in health care planning and in design of acute stroke clinical trials.