Combining Spinal Cord Transcutaneous Stimulation with Activity-based Training to Improve Upper Extremity Function Following Cervical Spinal Cord Injury.

Recovery of upper extremity (UE) function is the top priority following cervical spinal cord injury (SCI); even partial function restoration would greatly improve the quality of their life and thus remains an important goal in SCI rehabilitation. Current clinical therapies focus on promoting neuroplasticity by performing task-specific activities with high intensity and high repetition. Repetitive training, paired with functional electrical, somatosensory, or transcranial magnetic stimulation, has been evaluated to augment functional recovery in chronic SCI, but improvements were modest. Evidence has demonstrated that the non-invasive spinal cord transcutaneous stimulation (scTS) can increase the excitability of spinal circuits and facilitate the weak or silent descending drive for restoration of sensorimotor function. Currently, we are conducting a multicenter randomized clinical trial to investigate the efficacy and potential mechanisms of scTS combined with activity-based training (ABT) to facilitate UE function recovery in individuals with tetraplegia. The preliminary outcomes from our four individuals with complete and incomplete injury demonstrated that the combination of scTS and ABT led to immediate and sustained (for up to 1-month follow-up) UE function recovery. Notably, one individual with motor complete injury showed a 5-fold improvement in UE function quantified by the Graded Redefined Assessment of Strength, Sensibility, and Prehension following scTS+ABT, as compared to receiving ABT alone. These functional gains were also reflected in the increased spinal excitability by measuring the scTS-evoked muscle response of UE motor pools, suggesting physiological evidence of reorganization of the non-functional, but surviving spinal networks after spinal transcutaneous stimulation.Clinical Relevance-This study offered the preliminary efficacy of combining scTS and ABT to facilitate UE function recovery following cervical SCI.

Spinal Cord Stimulation with Activity-Based Training: Effect on Spasticity.

Spasticity is common after a spinal cord injury (SCI). Pharmacological treatments for spasticity often have adverse effects on neurorehabilitation. Spinal cord transcutaneous stimulation (scTS) and activity-based training (ABT) have been shown to be useful tools for neurorehabilitation which can lead to improved function for people with SCI. Our preliminary data suggests that neuromodulation of the spinal circuitry may result in attenuating spasticity.Clinical Relevance- Spasticity effects 65-70% of individuals following SCI, this technique of using ABT with scTS may allow for improvements in limiting spasticity.

Spinal Cord Transcutaneous Stimulation Enables Volitional Knee Extension in Motor-complete SCI.

Non-invasive spinal cord transcutaneous stimulation (scTS) is often applied to one or multiple spinal segments and may improve motor control after spinal cord injury (SCI). The purpose of this pilot study was to apply tonic scTS to an individual with motor-complete spinal cord injury (SCI) in order to initiate and maintain volitional control during a specific lower-extremity motor task. The participant's legs were placed in a gravity-neutral position, and he was asked to extend his knee, with and without the presence of tonic scTS. Our results show intentional voluntary control of knee extension with scTS (with no assistance). Our preliminary findings highlight how scTS neuromodulation of the spinal circuitry has the potential to restore motor function for people with motor-complete SCI. Clinical Relevance- This investigation is critical to better understand the neuromodulatory effects of tonic scTS for augmentation of voluntary-induced muscle activations in individuals with motor-complete SCI.

Corticomuscular Connectivity during Walking in Able Bodied and Individuals with Incomplete Spinal Cord Injury.

This exploratory study used EEG as mobile imaging method to study cortico-muscular connectivity (CMC) during walking in able-bodied individuals (AB) and individuals with spinal cord injury (iSCI), while walking with and without exoskeleton walking robot (EWR) assistance. We also explored change in CMC after intensive training using EWR assistance in iSCI. Results showed no different in CMC within the AB group during walking with and without robot assistance. However, before training the iSCI subjects showed lower CMC during walking with robot assistance. The intensive 40 hours of walking training with EWR improved the walking function in iSCI participants allowing them to walk with robot assistance set to lower assistance level. This decrease in assistance level and improvement in walking function correlated with increase in CMC, reducing the difference in CMC during walking with and without EWR assistance. The findings suggest that high level of robot assistance and low walking function in iSCI correlates with weaker connectivity between primary motor cortices and lower extremity muscles. Further research is needed to better understand the importance of intention and cortical involvement in training of walking function using EWRs. Clinical Relevance - This study provides innovative data on CMC during walking and how it changes with EWR assistance and with training. This research is important to the clinical field to provide recommendations of how training of walking function can be delivered to maximize cortical engagement and improve rehabilitation outcomes.

A closed-loop self-righting controller for seated balance in the coronal and diagonal planes following spinal cord injury.

Spinal cord injury (SCI) often results in loss of the ability to keep the trunk erect and stable while seated. Functional neuromuscular stimulation (FNS) can cause muscles paralyzed by SCI to contract and assist with trunk stability. We have extended the results of a previously reported threshold-based controller for restoring upright posture using FNS in the sagittal plane to more challenging displacements of the trunk in the coronal plane. The system was applied to five individuals with mid-thoracic or higher SCI, and in all cases the control system successfully restored upright sitting. The potential of the control system to maintain posture in forward-sideways (diagonal) directions was also tested in three of the subjects. In all cases, the controller successfully restored posture to erect. Clinically, these results imply that a simple, threshold based control scheme can restore upright sitting from forward, lateral or diagonal leaning without a chest strap; and that removal of barriers to upper extremity interaction with the surrounding environment could potentially allow objects to be more readily retrieved from around the wheelchair. Technical performance of the system was assessed in terms of three variables: response time, recovery time and percent maximum deviation from erect. Overall response and recovery times varied widely among subjects in the coronal plane (415±213 ms and 1381±883 ms, respectively) and in the diagonal planes (530±230 ms and 1800±820 ms, respectively). Average response time was significantly lower (p < 0.05) than the recovery time in all cases. The percent maximum deviation from erect was of the order of 40% or less for 9 out of 10 cases in the coronal plane and 5 out of 6 cases in diagonal directions.

Estimating total maximum isometric force output of trunk and hip muscles after spinal cord injury.

Functional neuromuscular stimulation (FNS) can be used to restore seated trunk function in individuals paralyzed due to spinal cord injury (SCI). Musculoskeletal models allow for the design and tuning of controllers for use with FNS; however, these models often use aggregated estimates for parameters of the musculotendon elements, the most significant of which is maximum isometric force (MIF). Stimulated MIF for individuals with SCI is typically assumed to be approximately 50% of the values exhibited by able-bodied muscles, which itself varies between studies and individuals. A method for estimating subject-specific MIF during dynamic motions in individuals with SCI produced by electrical stimulation has been developed to test this assumption and obtained more accurate estimates for biomechanical analysis and controller design. A simple on-off controller was applied to individuals with SCI seated in the workspace of a motion capture system to record joint angles of three types of trunk motions: forward flexion, left and right lateral bending followed by returning, un-aided, to upright posture via neural stimulation delivered to activate the muscles of the hips and trunk. System identification was used with a musculoskeletal model to find the optimal MIF values that reproduced the experimentally observed motions. Experiments with five volunteers with SCI indicate that an MIF of the 50% able-bodied values commonly used is significantly lower than the identified estimates in 33 of 44 muscle groups tested. This suggests that the strengths of paralyzed muscles when stimulated with FNS have been underestimated in many situations and their true force outputs may be higher than the values suggested for use in simulation studies with musculoskeletal models. These findings indicate that subject-specific musculoskeletal models can more closely mimic the motions of subjects by using individualized estimates of MIF, which may allow the design and tuning of controllers while reducing the time spent with subjects in the loop.