Investigating the relationship between anatomic and metabolic changes in the motor cortex and upper-extremity hemiparesis in individuals with chronic subcortical stroke

Hemiparesis is one of the most prevalent chronic disabilities after stroke, particularly in subcortical stroke. Neuroimaging has provided important morphological insight in to the mechanisms associated with hemiparesis in individuals with stroke. Assessing morphological changes within the primary motor cortex may provide valuable information of the neural events that underlie upper-extremity (UE) hemiparesis in chronic stroke. The purposes of this study were to 1) evaluate anatomical and metabolic changes in the motor cortex, and 2) examine the relationship between anatomical and metabolic changes and hemiparetic arm use in individuals in the chronic stage of stroke recovery. Seventeen individuals with chronic (>6 months) subcortical ischemic stroke and eleven neurologically healthy controls were recruited. Single voxel proton magnetic resonance spectroscopy (H1MRS) was performed to measure metabolite concentrations of total N-acetylaspartate (tNAA) and glutamate+glutamine (Glx). FreeSurfer software package (http://surfer.nmr.mgh.havard.edu) was used to quantify cortical thickness of the precentral gyrus. Upper-extremity motor performance was assessed using the Wolf Motor Function Test (WMFT) and the Motor Activity Log Quality of Movement scale (MAL-QOM) and upper-extremity motor activity was assessed using activity counts from wrist-mounted accelerometers. Results demonstrated a significant decrease in tNAA and Glx concentration in the hand area of the primary motor cortex in the stroke group, particularly within the ipsilesional hemisphere. Precentral gyrus cortical thickness was also decreased in the ipsilesional hemisphere of the stroke group. Parametric correlation analysis revealed a significant positive correlation between precentral gyrus thickness and tNAA concentration bilaterally. Multivariable regression analyses revealed that, after accounting for age and post-stroke duration, the combination of ipsilesional metabolite concentration (tNAA and Glx) and ipsilesional cortical thickness was associated with hemiparetic UE motor performance, but not UE motor activity in individuals in the chronic stage of stroke recovery. The observed link between structural and neurochemical changes in the stroke-affected brain and hemiparetic UE motor performance during the chronic phase of recovery may improve the understanding of the underlying neural mechanisms that support motor impairment after stroke.Medicine, Faculty ofGraduat