Transcutaneous Spinal Cord Stimulation: Advances in an Emerging Non-Invasive Strategy for Neuromodulation

Hofstoetter, Ursula S.; Minassian, Karen

doi:10.3390/jcm11133836

Cited by 10 publications

(5 citation statements)

References 16 publications

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“…The goal will be to convert the immediate changes in MEP size observed in this study into adaptive changes in the sensorimotor system that persist, taking advantage of the capacity of the spinal cord for plasticity (Wolpaw, 2010). We will also explore whether paired stimulation requires epidural electrodes or whether non‐invasive methods could be used (Gad et al., 2018; Hofstoetter & Minassian, 2022). This research deepens our understanding of SCS and may inform neurorehabilitation intervention based on associative stimulation of brain and spinal cord in humans.…”

Section: Discussionmentioning

confidence: 99%

Timing‐dependent synergies between motor cortex and posterior spinal stimulation in humans

McIntosh,

Joiner,

Goldberg

et al. 2024

The Journal of Physiology

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Volitional movement requires descending input from the motor cortex and sensory feedback through the spinal cord. We previously developed a paired brain and spinal electrical stimulation approach in rats that relies on convergence of the descending motor and spinal sensory stimuli in the cervical cord. This approach strengthened sensorimotor circuits and improved volitional movement through associative plasticity. In humans, it is not known whether posterior epidural spinal cord stimulation targeted at the sensorimotor interface or anterior epidural spinal cord stimulation targeted within the motor system is effective at facilitating brain evoked responses. In 59 individuals undergoing elective cervical spine decompression surgery, the motor cortex was stimulated with scalp electrodes and the spinal cord was stimulated with epidural electrodes, with muscle responses being recorded in arm and leg muscles. Spinal electrodes were placed either posteriorly or anteriorly, and the interval between cortex and spinal cord stimulation was varied. Pairing stimulation between the motor cortex and spinal sensory (posterior) but not spinal motor (anterior) stimulation produced motor evoked potentials that were over five times larger than brain stimulation alone. This strong augmentation occurred only when descending motor and spinal afferent stimuli were timed to converge in the spinal cord. Paired stimulation also increased the selectivity of muscle responses relative to unpaired brain or spinal cord stimulation. Finally, clinical signs suggest that facilitation was observed in both injured and uninjured segments of the spinal cord. The large effect size of this paired stimulation makes it a promising candidate for therapeutic neuromodulation. imageKey points Pairs of stimuli designed to alter nervous system function typically target the motor system, or one targets the sensory system and the other targets the motor system for convergence in cortex. In humans undergoing clinically indicated surgery, we tested paired brain and spinal cord stimulation that we developed in rats aiming to target sensorimotor convergence in the cervical cord. Arm and hand muscle responses to paired sensorimotor stimulation were more than five times larger than brain or spinal cord stimulation alone when applied to the posterior but not anterior spinal cord. Arm and hand muscle responses to paired stimulation were more selective for targeted muscles than the brain‐ or spinal‐only conditions, especially at latencies that produced the strongest effects of paired stimulation. Measures of clinical evidence of compression were only weakly related to the paired stimulation effect, suggesting that it could be applied as therapy in people affected by disorders of the central nervous system.

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Section: Discussionmentioning

confidence: 99%

Timing‐dependent synergies between motor cortex and posterior spinal stimulation in humans

McIntosh,

Joiner,

Goldberg

et al. 2024

The Journal of Physiology

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“…The goal will be to convert the immediate changes in MEP size observed in this study into adaptive changes in the sensorimotor system that persist, taking advantage of the spinal cord's capacity for plasticity (Wolpaw, 2010) . We will also explore whether paired stimulation requires epidural electrodes or whether non-invasive methods could be used (Gad et al, 2018;Hofstoetter & Minassian, 2022) . This research deepens our understanding of spinal cord stimulation and may inform neurorehabilitation intervention based on associative stimulation of brain and spinal cord in humans.…”

Section: Discussionmentioning

confidence: 99%

Timing dependent synergies between motor cortex and posterior spinal stimulation in humans

McIntosh,

Joiner,

Goldberg

et al. 2023

Preprint

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Electrical stimulation of the brain and spinal cord can strengthen sensorimotor circuits and improve movement through associative plasticity. Current paired stimulation paradigms target the motor system alone or sensorimotor connections in cortex. We developed a paired stimulation approach in rats that targets sensory and motor connections in the cervical spinal cord. Since the circuits necessary for paired stimulation are conserved between species, we hypothesized that paired stimulation of motor cortex and posterior cervical spinal cord in humans would produce synergistic muscle responses but only when stimulation is properly timed. In 59 individuals undergoing clinically indicated cervical spine surgery, the motor cortex was stimulated with scalp electrodes and the spinal cord with epidural electrodes while muscle responses were recorded in arm and leg muscles. Spinal electrodes were placed over either the posterior or anterior spinal cord, and the interval between cortex and spinal cord stimulation was varied. Pairing stimulation between the motor cortex and posterior, but not anterior, spinal cord stimulation produced motor evoked potentials that were over five times larger than brain stimulation alone. This strong augmentation occurred when descending motor and spinal afferent stimuli were timed to converge in the cervical spinal cord. Paired stimulation also increased the selectivity of muscle responses relative to unpaired brain or spinal cord stimulation. Finally, paired stimulation effects were present regardless of the severity of myelopathy as measured by clinical signs or spinal cord imaging. The large effect size of this paired stimulation makes it a promising candidate for therapeutic neuromodulation.Significance StatementPairs of stimuli that alter nervous system function typically target the motor system alone or the sensorimotor convergence in cortex. In humans undergoing clinically indicated surgery we tested a paired brain and spinal cord stimulation paradigm that we developed in rats to target sensorimotor convergence in the cervical spinal cord. Arm and hand muscle responses to paired stimulation were six times larger than brain or spinal cord stimulation alone and more selective to the targeted muscles when applied to the posterior but not anterior spinal cord. The paired stimulation effect was independent of the degree of myelopathy, suggesting that it could be applied as therapy in people affected by spinal cord injury.

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“…However, the use of FES alone to promote standing has several disadvantages: first, FES needs to be delivered and controlled over multiple muscle groups [11]; second, peripheral neuromuscular stimulation, such as FES, inevitably results in fatigue as it recruits the fastest and most fatigable muscle fibers first [12]. Transcutaneous Spinal Stimulation (TSS), another noninvasive electrical stimulation technique, has recently received much attention from clinicians and researchers [13][14][15][16]. TSS can produce motor responses via Ia afferents -α-motoneuron synapses in multiple spinal segments, but also is capable to activate other neural components within the spinal cord, including interneurons, ascending sensory fibers in the dorsal columns, descending motor tracts, and other polysynaptic pathways [17][18][19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Combining transcutaneous spinal stimulation and functional electrical stimulation increases force generated by lower limbs: When more is more

Steele,

Vette,

Martin

et al. 2023

Preprint

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BackgroundTranscutaneous Spinal Stimulation (TSS) has been shown to promote activation of the lower limb and trunk muscles and is being actively explored for improving the motor outcomes of people with neurological conditions. However, individual responses to TSS vary, and often the muscle responses are insufficient to produce enough force for self-supported standing. Functional electrical stimulation (FES) can activate individual muscles and assist in closing this functional gap, but it introduces questions regarding timing between modalities.MethodsTo assess the effects of TSS and FES on force generation, ten neurologically intact participants underwent (1) TSS only, (2) FES only, and (3) TSS + FES. TSS was delivered using four electrodes placed at T10–T11 through the L1–L2 intervertebral spaces simultaneously, while FES was delivered to the skin over the right knee extensors and plantarflexors. For all conditions, TSS and FES were delivered using three 0.5 ms biphasic square-wave pulses at 15 Hz. During the TSS + FES condition, timing between the two modalities was adjusted in increments of ¼ time between pulses (16.5 ms).ResultsWhen TSS preceded FES, a larger force production was observed. We also determined several changes in muscle activation amplitude at different relative stimulus intervals, which help characterize our finding and indicate the facilitating and inhibitory effects of the modalities.ConclusionsUtilizing a delay ranging from 15 to 30 ms between stimuli resulted in higher mean force generation in both the knee and ankle joints, regardless of the selected FES location (Average; knee: 112.0%, ankle: 103.1%).

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Transcutaneous Spinal Cord Stimulation: Advances in an Emerging Non-Invasive Strategy for Neuromodulation

Abstract: Recent studies of epidural electrical spinal cord stimulation have shown the enabling and, in some cases, the recovery of motor functions thought to be irreversibly lost due to severe spinal cord injury [...]

Cited by 10 publications

References 16 publications

Timing‐dependent synergies between motor cortex and posterior spinal stimulation in humans

Timing‐dependent synergies between motor cortex and posterior spinal stimulation in humans

Timing dependent synergies between motor cortex and posterior spinal stimulation in humans

Combining transcutaneous spinal stimulation and functional electrical stimulation increases force generated by lower limbs: When more is more

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