Preservation of functional descending input to paralyzed upper extremity muscles in motor complete cervical spinal cord injury

Pawan Sharma; Ahmed Naglah; Sevda Aslan; Fahmi Khalifa; Ayman El-Baz; Susan Harkema; Jessica D'Amico

doi:10.1016/j.clinph.2023.03.003

Preservation of functional descending input to paralyzed upper extremity muscles in motor complete cervical spinal cord injury

Clin Neurophysiol. 2023 Jun:150:56-68. doi: 10.1016/j.clinph.2023.03.003. Epub 2023 Mar 17.

Authors

Pawan Sharma¹, Ahmed Naglah², Sevda Aslan³, Fahmi Khalifa⁴, Ayman El-Baz⁵, Susan Harkema⁶, Jessica D'Amico⁷

Affiliations

¹ Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY 40202, USA. Electronic address: pawan.sharma@louisville.edu.
² Department of Bioengineering, University of Louisville, Louisville, KY 40202, USA. Electronic address: ahmed.naglah@louisville.edu.
³ Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY 40202, USA. Electronic address: sevdacaslan@gmail.com.
⁴ Department of Bioengineering, University of Louisville, Louisville, KY 40202, USA; Department of Electrical and Computer Engineering, Morgan State University, Baltimore, MD 2125, USA. Electronic address: fahmi.khalifa@morgan.edu.
⁵ Department of Bioengineering, University of Louisville, Louisville, KY 40202, USA. Electronic address: ayman.elbaz@louisville.edu.
⁶ Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, Louisville, KY 40202, USA; Frazier Rehabilitation Institute, University of Louisville Health, Louisville, KY 40202, USA. Electronic address: susan.harkema@louisville.edu.
⁷ Kentucky Spinal Cord Injury Research Center, University of Louisville, Louisville, KY 40202, USA; Department of Neurological Surgery, University of Louisville, Louisville, KY 40202, USA; Glenrose Rehabilitation Hospital, Department of Medicine, University of Alberta, Edmonton, Alberta T5G 0B7, Canada. Electronic address: damico1@ualberta.ca.

PMID: 37004296
DOI: 10.1016/j.clinph.2023.03.003

Abstract

Objective: Spinal cord injury (SCI) is classified as complete or incomplete depending on the extent of sensorimotor preservation below the injury level. However, individuals with complete SCIs can voluntarily activate paralyzed lower limb muscles alone or by engaging non-paralyzed muscles during neurophysiological assessments, indicating presence of residual pathways across the injury. However, similar phenomena have not been explored for the upper extremity (UE) muscles following cervical SCIs.

Methods: Eighteen individuals with motor complete cervical SCI (AIS A or B) and five age-matched non-injured (NI) individuals performed various UE events against manual resistance during functional neurophysiological assessment (FNPA), and electromyographic (EMG) activity was recorded from UE muscles.

Results: Our findings demonstrated i) voluntary activation of clinically paralyzed muscles as evident from EMG readouts, ii) increased activity in these muscles during events engaging muscles above the injury level, iii) reduced spectral properties of paralyzed muscles in SCI compared to NI participants.

Conclusions: Functional EMG activity in clinically paralyzed muscles indicate presence of residual pathways across the injury establishing supralesional control over the sublesional neural circuitry.

Significance: The findings may help explain the neurophysiological basis for UE recovery and can be exploited in designing rehabilitation techniques to facilitate UE recovery following cervical SCIs.

Keywords: Discomplete injury; Reinforcement techniques; Residual motor control; Spinal cord injury; Upper extremity.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Cervical Cord*
Electromyography / methods
Humans
Lower Extremity
Muscles
Spinal Cord Injuries*
Upper Extremity