Cortical thickness and metabolite concentration in chronic stroke and the relationship with motor function

Article type: Research Article

Authors: Jones, Paul W.^a | Borich, Michael R.^b | Vavsour, Irene^c | Mackay, Alex^d | Boyd, Lara A.^{e; f; *}

Affiliations: [a] Graduate Program in Neuroscience, University of British Columbia, Wesbrook Mall, Vancouver, Canada | [b] Division of Physical Therapy, Department of Rehabilitation Medicine, Emory University School of Medicine, Clifton Road NE, Atlanta, Georgia, USA | [c] Department of Radiology, University of British Columbia, Vancouver, Canada | [d] Department of Physics, University of British Columbia, Agricultural Road, Vancouver, Canada | [e] Department of Physical Therapy, University of British Columbia, Wesbrook Mall, Vancouver, Canada | [f] Centre for Brain Health, University of British Columbia, Wesbrook Mall, Vancouver, Canada

Correspondence: [*] Corresponding author: Lara Boyd, PT, PhD, University of British Columbia, Department of Physical Therapy, 212-2177 Wesbrook Mall, Vancouver, British Columbia, V6T 1Z3, Canada. Tel.: +1 604 827 3369; E-mail: lara.boyd@ubc.ca.

Abstract: Background: Hemiparesis is one of the most prevalent chronic disabilities after stroke. Biochemical and structural magnetic resonance imaging approaches may be employed to study the neural substrates underpinning upper-extremity (UE) recovery after chronic stroke. Objective: The purposes of this study were to 1) quantify anatomical and metabolic differences in the precentral gyrus, and 2) test the relationships between anatomical and metabolic differences, and hemiparetic arm function in individuals in the chronic stage of stroke recovery. Our hypotheses were: 1) the Stroke group would exhibit reduced precentral gyrus cortical thickness and lower concentrations of total N-acetylaspartate (tNAA) and glutamate+glutamine (Glx) in the ipsilesional motor cortex; and 2) that each of these measures would be associated with UE motor function after stroke. Methods: 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 tNAA and Glx in the precentral gyrus in both ipsilesional and contralesional hemispheres. Surface-based cortical morphometry was used to quantify precentral gyral thickness. Upper-extremity motor function was assessed using the Wolf Motor Function Test (WMFT). Results: Results demonstrated significantly lower ipsilesional tNAA and Glx concentrations and precentral gyrus thickness in the Stroke group. Ipsilesional tNAA and Glx concentration and precentral gyrus thickness was significantly lower in the ipsilesional hemisphere in the Stroke group. Parametric correlation analyses revealed a significant positive relationship between precentral gyrus thickness and tNAA concentration bilaterally. Multivariate regression analyses revealed that ipsilesional concentrations of tNAA and Glx predicted the largest amount of variance in WMFT scores. Cortical thickness measures alone did not predict a significant amount of variance in WMFT scores. Conclusion: While stroke impairs both structure and biochemistry in the ipsilesional hemisphere our data suggest that tNAA has the strongest relationship with motor function.

Keywords: Stroke, human, metabolite, motor function, cortical thickness

DOI: 10.3233/RNN-150623

Journal: Restorative Neurology and Neuroscience, vol. 34, no. 5, pp. 733-746, 2016