Stroke Lesion Volume and Injury to Motor Cortex Output Determines Extent of Contralesional Motor Cortex Reorganization

• Authors: Cathrin Buetefisch, Emory University; MW Haut, West Virginia University; KP Revill, Emory University; S Shaeffer, Emory University; L Edwards, Emory University; DA Barany, Emory University; Samir Belagaje, Emory University; Fadi Nahab, Emory University; N Shenvi, Emory University; Kirk Easley, Emory University
• Journal Title: NEUROREHABILITATION AND NEURAL REPAIR
• Volume: Volume 37, Number 2-3
• Publisher: SAGE PUBLICATIONS INC | 2023-02-14, Pages 119-130
• Type of Work: Article | Post-print: After Peer Review
• Publisher DOI: http://doi.org/10.1177/15459683231152816
• Subjects: Health Sciences, Medicine and Surgery; Health Sciences, Radiology; Health Sciences, Public Health
• Keywords: Science & Technology; Life Sciences & Biomedicine; Clinical Neurology; Rehabilitation; Neurosciences & Neurology; stroke; motor cortex; upper extremity paresis; reorganization; TMS; MRI; CORTICOSPINAL TRACT LESION; CORTICAL EXCITABILITY; HAND FUNCTION; RECOVERY; BRAIN; HEMISPHERE; THRESHOLD; NORMALIZATION; INHIBITION; INFARCTION

Abstract

Background: After stroke, increases in contralesional primary motor cortex (M1CL) activity and excitability have been reported. In pre-clinical studies, M1CL reorganization is related to the extent of ipsilesional M1 (M1IL) injury, but this has yet to be tested clinically. Objectives: We tested the hypothesis that the extent of damage to the ipsilesional M1 and/or its corticospinal tract (CST) determines the magnitude of M1CL reorganization and its relationship to affected hand function in humans recovering from stroke. Methods: Thirty-five participants with a single subacute ischemic stroke affecting M1 or CST and hand paresis underwent MRI scans of the brain to measure lesion volume and CST lesion load. Transcranial magnetic stimulation (TMS) of M1IL was used to determine the presence of an electromyographic response (motor evoked potential (MEP+ and MEP−)). M1CL reorganization was determined by TMS applied to M1CL at increasing intensities. Hand function was quantified with the Jebsen Taylor Hand Function Test. Results: The extent of M1CL reorganization was related to greater lesion volume in the MEP− group, but not in the MEP+ group. Greater M1CL reorganization was associated with more impaired hand function in MEP− but not MEP+ participants. Absence of an MEP (MEP−), larger lesion volumes and higher lesion loads in CST, particularly in CST fibers originating in M1 were associated with greater impairment of hand function. Conclusions: In the subacute post-stroke period, stroke volume and M1IL output determine the extent of M1CL reorganization and its relationship to affected hand function, consistent with pre-clinical evidence. ClinicalTrials.gov Identifier: NCT02544503.