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Published on: October 11, 2024
Distinguishing Distinct Neural Systems for Proximal vs Distal Upper Extremity Motor Control After Acute Stroke
David J Lin1, Richard Hardstone2, Julie A DiCarlo2
1From the Center for Neurotechnology and Neurorecovery (D.J.L., R.H., J.A.D., S.M., H.J., K.S.E., K.R., L.R.H.), Department of Neurology, Massachusetts General Hospital, Harvard Medical School; Division of Neurocritical Care (D.J.L., L.R.H.), Department of Neurology; Stroke Service (D.J.L., S.P.F., L.H.S., L.R.H.), Department of Neurology, Massachusetts General Hospital, Boston; VA RR&D Center for Neurorestoration and Neurotechnology (D.J.L., L.R.H.), Rehabilitation R&D Service, Department of VA Medical Center, Providence, RI; Division of Neurocritical Care (S.B.S.), Department of Neurology, Brigham and Women's Hospital, Harvard Medical School; Department of Occupational Therapy (H.J., K.S.E.), MGH Institute of Health Professions, Boston, MA; Department of Rehabilitation (P.B.), Exercise and Nutrition Sciences, University of Cincinnati College of Allied Health Sciences, OH; Department of Biostatistics (J.G.), Columbia University Mailman School of Public Health, New York, NY; Department of Occupational Therapy (J.R.), Massachusetts General Hospital, Boston; School of Engineering (L.R.H.), Brown University, Providence, RI; and Department of Neurology (S.C.C.), University of California, Los Angeles, California Rehabilitation Hospital. dlin7@mgh.harvard.edu.
Background And Objectives:
The classic and singular pattern of distal greater than proximal upper extremity motor deficits after acute stroke does not account for the distinct structural and functional organization of circuits for proximal and distal motor control in the healthy CNS. We hypothesized that separate proximal and distal upper extremity clinical syndromes after acute stroke could be distinguished and that patterns of neuroanatomical injury leading to these 2 syndromes would reflect their distinct organization in the intact CNS.
Methods:
Proximal and distal components of motor impairment (upper extremity Fugl-Meyer score) and strength (Shoulder Abduction Finger Extension score) were assessed in consecutively recruited patients within 7 days of acute stroke. Partial correlation analysis was used to assess the relationship between proximal and distal motor scores. Functional outcomes including the Box and Blocks Test (BBT), Barthel Index (BI), and modified Rankin scale (mRS) were examined in relation to proximal vs distal motor patterns of deficit. Voxel-based lesion-symptom mapping was used to identify regions of injury associated with proximal vs distal upper extremity motor deficits.
Results:
A total of 141 consecutive patients (49% female) were assessed 4.0 ± 1.6 (mean ± SD) days after stroke onset. Separate proximal and distal upper extremity motor components were distinguishable after acute stroke (p = 0.002). A pattern of proximal more than distal injury (i.e., relatively preserved distal motor control) was not rare, observed in 23% of acute stroke patients. Patients with relatively preserved distal motor control, even after controlling for total extent of deficit, had better outcomes in the first week and at 90 days poststroke (BBT, ρ = 0.51, p < 0.001; BI, ρ = 0.41, p < 0.001; mRS, ρ = 0.38, p < 0.001). Deficits in proximal motor control were associated with widespread injury to subcortical white and gray matter, while deficits in distal motor control were associated with injury restricted to the posterior aspect of the precentral gyrus, consistent with the organization of proximal vs distal neural circuits in the healthy CNS.
Discussion:
These results highlight that proximal and distal upper extremity motor systems can be selectively injured by acute stroke, with dissociable deficits and functional consequences. Our findings emphasize how disruption of distinct motor systems can contribute to separable components of poststroke upper extremity hemiparesis.
