Motor Control of Human Spinal Cord Disconnected from the Brain and Under External Movement

Abstract

Motor control after spinal cord injury is strongly depending on residual ascending and descending pathways across the lesion. The individually altered neurophysiology is in general based on still intact sublesional control loops with afferent sensory inputs linked via interneuron networks to efferent motor outputs. Partial or total loss of translesional control inputs reduces and alters the ability to perform voluntary movements and results in motor incomplete (residual voluntary control of movement functions) or motor complete (no residual voluntary control) spinal cord injury classification. Of particular importance are intact functionally silent neural structures with residual brain influence but reduced state of excitability that inhibits execution of voluntary movements. The condition is described by the term discomplete spinal cord injury. There are strong evidences that artificial afferent input, e.g., by epidural or noninvasive electrical stimulation of the lumbar posterior roots, can elevate the state of excitability and thus re-enable or augment voluntary movement functions. This modality can serve as a powerful assessment technique for monitoring details of the residual function profile after spinal cord injury, as a therapeutic tool for support of restoration of movement programs and as a neuroprosthesis component augmenting and restoring movement functions, per se or in synergy with classical neuromuscular or muscular electrical stimulation.

Does galvanic vestibular stimulation decrease spasticity in clinically complete spinal cord injury?

“…However, the reported changes in spasticity after GVS in two out of seven SCI patients reported here are in contrast to the lower prevalence of medium latency responses in the erector spinae muscles below the level detected by Iles et al (2004) in only two of nine patients or the presence of vestibular-evoked myogenic potentials reported by Squair et al (2016) in two of 16 AIS-A patients. Thus, the accumulated evidence is consistent with broader neuro-physiological observations suggesting traces of somato-sensory (Finnerup et al, 2004;Awad et al, 2015;Wrigley et al 2018) and motor preservation (Sherwood et al, 1992;McKay et al, 2004;Dimitrijević et al, 2015;Mayr et al, 2016) is patients classified as having the AIS-A injury, which is also supported by the autopsy studies (Kakulas and Kaelan, 2015).…”

Current Principles of Motor Control, with Special Reference to Vertebrate Locomotion

“…Intrathecal electric stimulation of afferents and particularly the dorsal columns or peripheral stimulation have been shown to promote locomotor activity or facilitate other movements (19,88,89,241,243,330,404,405,462). Currently, this approach seems to be the most promising way to elevate the excitability in the spinal cord networks of spinal cord injury patients to a degree so that the remaining brain stem fibers from LGPi can initiate the locomotor activity, particularly if combined with locomotor training.…”

Activity-Based Therapy Targeting Neuromuscular Capacity After Pediatric-Onset Spinal Cord Injury

“…Ongoing research points to the benefit of neuromodulatory techniques (eg, transcutaneous electrical spinal stimulation and epidural stimulation) as potential effective tools to enhance neural drive and central state of excitability. 3,54,55 Such stimulation in combination with AB-LT has provided the catalyst for achievement of over ground walking in adults with complete SCI 56 and demonstrated potential for other motor improvements. 57 The accessibility of transcutaneous spinal stimulation makes it appealing for use with the pediatric population; specific study of its safety, feasibility, and efficacy in children post SCI is needed.…”