Identification of critical areas for motor function recovery in chronic stroke subjects using voxel-based lesion symptom mapping

Abstract

IntroductionPrevious stroke studies using fMRI or lesion characterization methods to study the preservation of motor performance have been limited in defining anatomical structure critical for functional performance. This study attempts to overcome this limitation by using voxel-based lesion symptom mapping (VLSM) to identify specific anatomical regions required for preservation of motor function. MethodsForty-one moderate to moderately severe stroke subjects (upper extremity Fugl-Meyer between 28 and 50, Arm Motor Ability Test >35) were imaged with a 1 mm isotropic T1-weighted volumetric sequence, and their motor performance was assessed. The T1 volume images were normalized to a symmetric template using SPM5 and oriented so the lesion appeared in the left hemisphere. The lesioned areas were manually segmented on the normalized T1 image. All 3D lesion maps were entered into the VLSM analysis. Areas showing significant correlations with functional performance measures were identified using the false discovery rate corrected at p≤0.05. ResultsThe areas most correlated with a decrease in motor performance were at the junction of the corona radiata leading into the corticospinal tract. The Arm Motor Ability Test scores produced the most significant results, while the other measures showed similar anatomical patterns. ConclusionThe use of lesion symptom mapping in conjunction with behavioral measures produced anatomically specific results demonstrating that the area leading from the corticospinal tract to cortical motor areas is critical for maintaining hand motor performance after a stroke. This area may represent the joining of parallel redundant tracts that, when damaged, limit recovery potential.