Targeted transcutaneous spinal cord stimulation promotes persistent recovery of upper limb strength and tactile sensation in spinal cord injury: a pilot study

Abstract

Long-term recovery of limb function is a significant unmet need in people with paralysis. Neuromodulation of the spinal cord through epidural stimulation, when paired with intense activity-based training, has shown promising results toward restoring volitional limb control in people with spinal cord injury. Non-invasive neuromodulation of the cervical spinal cord using transcutaneous spinal cord stimulation (tSCS) has shown similar improvements in upper-limb motor control rehabilitation. However, the motor and sensory rehabilitative effects of activating specific cervical spinal segments using tSCS have largely remained unexplored. We show in two individuals with motor-complete SCI that targeted stimulation of the cervical spinal cord resulted in up to a 1,136% increase in exerted force, with weekly activity-based training. Furthermore, this is the first study to document up to a 2-point improvement in clinical assessment of tactile sensation in SCI after receiving tSCS. Lastly, participant gains persisted after a one-month period void of stimulation, suggesting that targeted tSCS may lead to persistent recovery of motor and sensory function.

Wireless control of nerve growth using bipolar electrodes: a new paradigm in electrostimulation

“…, supporting body weigh in a static standing position, or volitional ankle flex) is lost when the AC stimulation is stopped. 45–47 A similar response was observed for AC lumbar spinal stimulation to facilitate gait in Parkinson's. 62 Therefore, the specific combination of protocol and electrode material defines the outcome of electrostimulation, with DC schemes seeming to favour cell growth and repair.…”

“…This concept has been leveraged to manage symptoms for diverse neurological diseases including Parkinson's, depression, epilepsy, and migraine. 43,44–51 It may also be the basis for other recent applications in which implanted electrode arrays were used to effectively bypass damaged spinal cord regions to overcome functional deficits in clinically functionally complete (total loss of sensory and motor function below the injury) spinal injured patients. 44–47…”

“…Sufficiently large extracellular potentials can alter a cell's membrane potential or influence the threshold required for firing action potentials, but smaller, physiological scale potentials steer neuron growth cone direction and branching, direct migration of neurons, control neural stem cell fates, control glial cell orientation and behaviour, and influence immune and inflammatory mechanisms. 2,4,47,52–55 Furthermore, when an injury has occurred, the existence of new endogenous directional fields suggests that regeneration may be enhanced with the help of external fields that modify scar tissue. Implanted materials used to apply larger potentials always have a foreign body response, inducing inflammation and fast encapsulation, which results in an enhanced impedance.…”

“…However, AC stimulation (∼300 Hz) is used more often to restore function by acting on spared nerve pathways which may include central pattern generators. 45–47 Intriguingly, when using AC stimulation, the improvement depends on the continued presence of the stimulus rather than affecting a chronic improvement. For example, functional recovery ( e.g.…”

Effects of non-invasive cervical spinal cord neuromodulation by trans-spinal electrical stimulation on cortico-muscular descending patterns in upper extremity of chronic stroke

“…Attempts have been made in applying tsES to improve neural transmission across the lesional sites after SCI for motor restoration in the upper limbs ( Inanici et al, 2021 ). For example, previous studies have demonstrated that tsES could immediately modulate the excitability of spinal cord circuits and facilitate voluntary control of the triceps muscle in SCI individuals by using rectangular stimulation waveform with 1 ms bursts of 10 kHz carrier frequency at the level of C5-C6 interspinous space ( Chandrasekaran et al, 2023 ). tsES has also been applied to the spinal cord at the C3-C6 spinal segments to assist in fine motor control of upper limbs, i.e., hand pinch and grip strength, in patients with cervical SCI ( Inanici et al, 2018 ).…”