Do you know cervical transcutaneous electrical stimulation (ctSCS) with and without peripheral stimulation for the treatment of the upper limb?

It is one of the topics we will cover in our training “Electrical stimulation of the upper extremities to enhance functionality” thanks to Bersch-Porada Ines (https://cen-academy.com/courses/electrical-stimulation-of-the-upper-extremities-to-enhance-functionality/)

Cervical Transcutaneous Spinal Cord Stimulation (ctSCS) is a non-invasive neuromodulation technique that uses electrical currents applied to the skin over the cervical (neck) region to target and modulate neural activity within the spinal cord. It has shown promise in treating conditions related to spinal cord injuries, motor function recovery, and certain chronic pain syndromes. The application of this therapy with or without peripheral stimulation can have different effects on the nervous system, depending on the mechanisms involved.

Here’s an overview of ctSCS with and without peripheral stimulation:

1. ctSCS Without Peripheral Stimulation

In this configuration, electrical stimulation is applied to the cervical region without additional stimulation to peripheral nerves or muscles. The objective is to directly modulate the activity of the spinal cord circuits, which can influence neural pathways connected to motor control, sensory processing, and autonomic functions.

Key Features:

• Focus: Primarily targets the spinal cord to influence neural pathways.
• Mechanisms: It aims to modulate spinal cord excitability and connectivity between the spinal cord and brain, possibly by recruiting spinal interneurons and modulating sensory inputs.
• Applications: Recovery of motor function in spinal cord injury patients, chronic pain management, modulation of autonomic nervous system functions, and sensory restoration.
• Effects: Studies have demonstrated improvements in motor function, particularly in individuals with incomplete spinal cord injuries, where ctSCS alone may activate dormant neural pathways that can enhance motor responses.

2. ctSCS with Peripheral Stimulation

Peripheral stimulation involves applying electrical stimulation to the peripheral nerves or muscles along with ctSCS. The peripheral stimulation can be applied to the upper or lower limbs or other areas to complement and amplify the effects of spinal cord stimulation.

Key Features:

• Combined Modulation: By simultaneously stimulating the spinal cord and peripheral nerves, this method seeks to maximize neuromodulatory effects and enhance neuroplasticity.
• Mechanisms: In this combined approach, the electrical impulses activate both the spinal circuits and the peripheral sensory pathways, creating a more comprehensive neurophysiological effect. The peripheral input may provide additional afferent (sensory) feedback to the central nervous system, thereby reinforcing the effects of ctSCS on motor recovery and sensory improvements.
• Applications: Typically used in patients with spinal cord injuries, neurodegenerative diseases, or motor impairments, this combination can improve rehabilitation outcomes by strengthening muscle responses, enhancing proprioception, and promoting greater motor function.
• Effects: Studies have shown that when peripheral stimulation is combined with ctSCS, patients often experience improved motor recovery, enhanced sensory function, and better control of voluntary movements. It can accelerate neuroplasticity and improve the functional outcomes of rehabilitation programs.

Differences Between the Two Approaches

• Stimulation Focus: ctSCS alone: Focuses primarily on modulating spinal cord circuits. ctSCS with peripheral stimulation: Engages both spinal and peripheral nervous systems, offering a more integrative approach.
• Neuroplasticity: Peripheral stimulation can enhance the neuroplastic effects of ctSCS by providing additional sensory inputs, possibly resulting in more robust and long-lasting motor recovery.
• Functional Outcomes: Patients undergoing combined ctSCS and peripheral stimulation may experience faster and more significant improvements in motor function, as well as enhanced sensory perception, compared to ctSCS alone.

Clinical Relevance

The choice between using ctSCS alone or in combination with peripheral stimulation often depends on the clinical goals:

• For patients with incomplete spinal cord injuries, combining ctSCS with peripheral stimulation might be more beneficial for motor recovery, as it can activate multiple neural pathways.
• In chronic pain management, ctSCS alone may be sufficient, as it primarily modulates spinal excitability without the need for additional peripheral input.

In summary, ctSCS with peripheral stimulation offers a more comprehensive approach to neuromodulation, likely to yield greater benefits in motor recovery and sensory function, while ctSCS alone provides targeted spinal modulation that can be effective in specific conditions like pain management or spinal cord injury rehabilitation. The use of one approach versus the other would depend on the specific condition being treated and the desired clinical outcomes.

Posteroanterior Cervical Transcutaneous Spinal Cord Stimulation: Interactions with Cortical and Peripheral Nerve Stimulation (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8623612/pdf/jcm-10-05304.pdf )

Provides a detailed exploration of how posteroanterior cervical transcutaneous spinal cord stimulation (TSCS) interacts with cortical and peripheral nerve stimulation. Some key points from the study:

1. Objective: The study aimed to explore how pairing cervical TSCS with other nervous system stimulations, such as motor cortex stimulation and median nerve stimulation, can enhance synaptic plasticity in circuits that serve hand function.
2. Novel Configuration: The researchers used a novel posteroanterior configuration for cervical TSCS, where the anode was placed anteriorly over C4–C5 and the cathode posteriorly over T2–T4. This configuration elicited muscle responses across multiple cervical myotomes, primarily activating sensory afferent circuits at lower intensities and motor efferents at higher intensities.
3. Participants: The study included 13 participants with chronic cervical spinal cord injury (SCI) and 15 able-bodied participants. It examined how TSCS facilitates hand muscle responses to motor cortex stimulation when timed appropriately with TSCS pulses.
4. Key Findings: Subthreshold TSCS enhanced hand muscle responses to motor cortex stimulation, especially when TSCS was timed to arrive at the cervical spinal cord synapses simultaneously or up to 10 milliseconds after the cortical stimulus. Single pulses of subthreshold TSCS did not significantly affect the amplitudes of H-reflex or F-wave responses from the median nerve.
5. Clinical Implications: The findings support the hypothesis that TSCS paired with appropriately timed cortical stimulation may enhance convergent transmission between descending motor circuits, segmental afferents, and spinal motor neurons serving the hand. However, larger studies are needed to confirm these results and explore potential rehabilitation applications.

Targeted transcutaneous cervical spinal cord stimulation promotes upper limb recovery in spinal cord and peripheral nerve injury (https://www.medrxiv.org/content/10.1101/2022.02.15.22269115v2.full.pdf )

Provides comprehensive insights into the rehabilitative potential of cervical transcutaneous spinal cord stimulation (tSCS). Some key takeaways:

1. Objective: This study aimed to investigate the effects of tSCS in restoring upper-limb motor function in patients with spinal cord injury (SCI) and peripheral nerve injury.
2. Participants: Two participants with motor-complete cervical SCI (C5 level) and one participant with peripheral nerve injury were included. tSCS was administered once a week for up to 31 sessions, paired with minimal physical therapy.
3. Findings: The study observed an up to 1136% increase in muscle force in SCI participants and 407% increase in hand strength in a participant with peripheral nerve injury. Improvements were seen in muscle recruitment and volitional control over targeted upper-limb muscles, especially in those with some baseline activity. Notably, tSCS resulted in sensory improvement, showing a 3-point increase in sensation in the hand of SCI and peripheral nerve injury participants.
4. Mechanism: The researchers employed a custom electrode array to stimulate specific cervical segments, targeting upper-limb motor nuclei effectively. This allowed for maximal recruitment of muscles linked to the desired motor functions.
5. Clinical Implications: tSCS shows promising potential for both SCI and peripheral nerve injury rehabilitation. Targeted stimulation may be crucial for improving the efficacy of the treatment, even with minimal physical therapy.
6. Sustainability: The benefits of tSCS persisted for up to a month without stimulation, suggesting that the intervention could lead to long-lasting motor improvements.

The study emphasizes that targeted non-invasive stimulation of the cervical spinal cord can significantly enhance upper-limb function in individuals with severe paralysis. It opens avenues for broader applications of tSCS in various neurological conditions.

José López Sánchez

CEO @ Centro Europeo de Neurociencias | Intensive Therapy Specialist