Targeted Walking in Incomplete Spinal Cord Injury: Role of Corticospinal Control

Abstract

Locomotor recovery after incomplete spinal cord injury (iSCI) is influenced by spinal and supraspinal networks. Conventional clinical gait analysis fails to differentiate between these components. There is evidence that corticospinal control is enhanced during targeted walking, where each foot must be continuously placed on visual targets in randomized order. This study investigates the potential of targeted walking in the functional assessment of corticospinal integrity. Twenty-one controls and 16 individuals with chronic iSCI performed normal and targeted walking on a treadmill while electromyograms (EMGs) and kinematics were recorded. Precision (% of accurate foot placements) in targeted walking was significantly lower in individuals with iSCI (82.9±14.7%, controls: 94.9±4.0%). While the overall kinematic pattern was comparable between walking conditions, controls showed significantly higher semitendinosus activity before heel-strike during targeted walking. This was accompanied by a shift of relative EMG intensity from 90-120Hz to lower frequencies of 20-60 Hz, previously associated with corticospinal control of muscle activity. Targeted walking in iSCI individuals evoked smaller EMG changes, suggesting that the switch to more corticospinal control is impaired. Accordingly, mildly impaired iSCI individuals revealed higher adaptations to the targeted walking task than more-impaired individuals. Recording of EMGs during targeted walking holds potential as a research tool to reveal further insights into the neuromuscular control of locomotion. It also complements findings of preclinical studies and is a promising novel surrogate marker of integrity of corticospinal control in individuals with iSCI and other neurological impairments. Future studies should investigate its potential for diagnosis or tracking recovery during rehabilitation.

Immediate Effects of Transcutaneous Spinal Cord Stimulation on Motor Function in Chronic, Sensorimotor Incomplete Spinal Cord Injury

“…α-errors of p < 0.05 were considered significant. Prior to the data analysis, the two legs of each participant were grouped into more and less affected sides, based on the total lower extremity motor scores (LEMS) per leg [66][67][68]. In participant 7, total light touch sensory scores were additionally considered, as LEMS were equivalent in both legs.…”

Properties of the surface electromyogram following traumatic spinal cord injury: a scoping review

“…Similarly, wavelet analysis can characterize the time–frequency profile of the sEMG signal with good resolution and contribute to the understanding of targeted walking and corticospinal integrity. Using such techniques, it was shown that an increase of relative semitendinosus intensity in the 38-Hz band during the swing phase was related to targeted walking in SCI, likely reflecting greater corticospinal control before heel-strike during targeted walking [ 134 ].…”

MRI metrics at the epicenter of spinal cord injury are correlated with the stepping process in rhesus monkeys

“…PS mainly demonstrates whether the animal achieves the swing phase, whereas GS additionally estimates the stability and consistency of the stepping process. In primates, highly stable and consistent gait cycles (GS) require more precise supraspinal control than achieving swing (PS) [ 27 , 60 , 61 ]. The integrity of cortical projection pathways determines the degree of supraspinal control after SCI.…”