Effects of lesion extent and location on upper limb function following hemispheric stroke

Abstract

A large proportion of stroke survivors present spastic paresis of the upper limb (UL). Therapeutic interventions result in large variance in the response of patients to the same treatment protocols, possibly stemming from differences in lesion characteristics, among other factors. Here we concentrated on the impact of lesion size and location on UL function following stroke, comparing the effect of right hemisphere damage (RHD) to that of left hemisphere damage (LHD). Clinical and lesion data for the current study were collected as part of a multicenter randomized, controlled trial (ENHANCE project; ClinicalTrials.gov, ID: NCT02725853 ). Two groups of patients with subacute stroke were compared: those with right hemisphere ( n = 8) and left hemisphere damage ( n = 15). Voxel-based lesion symptom mapping (VLSM) was employed to identify voxel clusters in the normalized brain where damage exerts a significant impact on the functioning of the hemiparetic UL, as revealed by the Functional Ability Scale of the short (streamlined) version of the Wolf Motor Function Test. Motor function of the hemiparetic UL was affected in LHD patients by damage to voxel clusters involving (a) cortical areas of the superior temporal regions and the insula, (b) white matter tracts, notably the superior and inferior fronto-occipital fascicles, the corona radiata and the internal capsule, and (c) the basal ganglia and thalamus. In the RHD group, VLSM analysis showed a different pattern where UL function was affected almost exclusively by damage to subcortical structures of the corona radiata, the capsular-putaminal region, the superior longitudinal fasciculus and the external capsule. Motor function of the hemiparetic upper limb in patients with subacute stroke was affected differently by damage to homologous structures in the left and right cerebral hemispheres.