Title:
Intensive Locomotor-Related Skill Training and TDCS Neuromodulation to Improve Walking and Balance Function in Persons with Chronic Spinal Cord Injury
Intensive Locomotor-Related Skill Training and TDCS Neuromodulation to Improve Walking and Balance Function in Persons with Chronic Spinal Cord Injury
Author(s)
Evans, Nicholas H.
Advisor(s)
Field-Fote, Edelle C.
Nichols, T. Richard
Nichols, T. Richard
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Abstract
Spinal cord injury (SCI) results in immediate and persistent impairments in sensory and motor function below the neurological level of injury. Improved walking function is a priority among persons with SCI (PwSCI). Rehabilitation strategies aimed at recovery of walking function are primarily directed toward activation of spinal neural networks despite evidence demonstrating that human bipedal locomotion involves both spinal and supraspinal contributions. Additionally, the cost and long-term accessibility of existing locomotor training approaches limits participation in ongoing training once individuals are discharged from the clinical setting. Consequently, training interventions aimed at enhancing corticospinal drive to motoneurons of the lower limb muscles and that can be feasibly carried out in the home or community setting, either with or without supervision, may be advantageous. These interventions may have value both for promoting long-term recovery of walking function beyond initial rehabilitation, and/or for preserving gains in walking function acquired during rehabilitation.
Considering the need to explore alternative interventions that can be feasibly implemented beyond initial rehabilitation and the need to develop interventions that expand the range of neural targets subserving bipedal walking, this thesis explores the following questions: (1) Do persons with motor-incomplete SCI (PwMISCI) demonstrate improvements in lower limb motor function and walking performance following an intensive, high-velocity locomotor-related motor skill training (MST) intervention?; (2) Does enhancing corticospinal drive through the addition of non-invasive brain stimulation (i.e., transcranial direct current stimulation [tDCS]), delivered to the motor cortex and cerebellum, augment the effects of lower limb motor training in this population?; (3) Are there specific characteristics of walking performance that are most influenced by high-velocity locomotor-related motor skill training among PwMISCI?
Twenty-six individuals with chronic (≥11months), motor-incomplete SCI were enrolled in a multi-day intervention study with parallel group design, wherein participants were randomized to either a motor skill training plus sham tDCS condition (MST+tDCSsham) or a motor skill training plus active tDCS condition (MST+tDCS). Measures of walking function and gait quality were collected over five consecutive days and between-groups differences in the effects of training were compared. Three consecutive days of MST was associated with significant improvements in walking speed, walking distance, and spatiotemporal gait characteristics (i.e., cadence, stride length), stronger limb trailing limb angle (TLA), and intralimb coordination of the weaker leg. Measures of balance function and perceived fear of falling were also improved; however, concurrent application of tDCS with MST was not associated with greater improvement in outcomes compared to motor training alone. Additionally, among those walking outcomes that were positively influenced by MST intervention, between-day (offline) effects contributed to a greater proportion of total change in outcomes compared to within-day (online) effects.
Given the diminished capacity of PwMISCI to produce high step frequencies along with a relatively intact ability to modulate step length, we anticipated that participants in the study would present with diminished step length-frequency coordination (i.e., higher Walk Ratio [step length/step frequency ratio] values) compared to previous reports in non-injured adults. Furthermore, we anticipated that MST emphasizing high-velocity lower limb movements would be associated with improvements in step length-frequency coordination mediated in large part by improvements in the capacity to increase step frequency. Additionally, given that baseline walking speed may influence outcomes, we divided the study sample into slow versus fast walkers to account for differences that may be attributable to differences in walking speed. Among the full study sample, we observed higher Walk Ratio values among PwMISCI than previous reports in other neurological populations; however, values among fast walkers were comparable to non-injured adults. Slow walkers demonstrated greater variability in the Walk Ratio with higher values associated with slower walking speed. Following MST, increases in walking speed among slow walkers coincided with a decrease in the Walk Ratio, mediated primarily through an effect on step frequency suggesting a mechanism by which high velocity MST may improve walking function among PwMISCI with greater mobility deficits.
According to the findings, we conclude that a brief intensive, high-velocity MST designed to overcome limitations of existing locomotor training approaches was effective at improving measures of overground walking function and balance in PwMISCI, that concurrent application of tDCS failed to augment the effects of MST, that between-day (offline) change in outcomes contributed to observed improvements to a greater extent than within-day (online) change, and that the high-velocity nature of MST may have contributed to improvements in walking speed among more impaired individuals through a greater effect on step frequency compared to step length.
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Date Issued
2023-07-25
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Resource Type
Text
Resource Subtype
Dissertation