Transcutaneous spinal cord stimulation and motor responses in individuals with spinal cord injury: A methodological review

PLOS ONE, 2021 · DOI: https://doi.org/10.1371/journal.pone.0260166 · Published: November 18, 2021

Simple Explanation

Transcutaneous spinal cord stimulation (tSCS) is a non-invasive method where electrodes on the skin stimulate spinal circuits to facilitate motor responses. This review evaluates the methodology of studies using tSCS to generate motor activity in individuals with spinal cord injury (SCI). tSCS may enhance rehabilitation for people with neurological disorders, such as SCI. As this modality is under the relatively early stages of investigation with injured individuals, there is still much to learn about its implementation and clinical potential. The review outlines the parameters currently employed for tSCS to produce motor responses. To establish standardized procedures, further high-quality investigations are required, using consistent electrophysiological recording methods and reporting common characteristics of the electrical stimulation administered.

Study Duration

Not specified

Participants

173 participants with SCI

Evidence Level

Not specified

Key Findings

1
The overall quality of evidence was deemed to be poor-to-fair based on the Downs and Black Quality Checklist criteria.
2
The electrical characteristics were collated to establish the dosage range across stimulation trials. The methods employed by included studies relating to stimulation parameters and outcome measurement varied extensively.
3
Studies were divided into those using tSCS for neurophysiological investigations of reflex responses (n = 9) and therapeutic investigations of motor recovery (n = 16).

Research Summary

This review separated studies utilising tSCS into two broad categories: studies evaluating neurophysiological properties of stimulation at a spinal level and those using tSCS as a therapeutic modality for motor recovery. While publications in both categories have grown in number, the quality of the current evidence base is limited, and a large degree of methodological heterogeneity exists between studies. In particular, extensive variability in stimulation parameters and inconsistent processing and/or presentation of EMG signals make it difficult to draw meaningful conclusions about the effects of tSCS on motor engagement.

Practical Implications

Standardize Reporting

Future studies should standardize reporting of muscle activity and electrical parameters of tSCS, including electrode dimensions, location, charge polarity, phase duration, and stimulation frequency.

Improve Trial Quality

Enhance the quality of future trials by improving recruitment method reporting, intervention protocols, and using techniques like randomization and sham stimulation.

Safety Reporting

Explicitly detail the presence or absence of adverse events to provide a larger evidence base supporting safety and feasibility.

Study Limitations

1
Relevant studies may have been missed due to variance in terminology and lack of standardized nomenclature.
2
Studies using EMG outcomes were included; other studies detailing tSCS parameters may have been excluded.
3
Study outcomes were not possible to pool due to the heterogeneity of included experiments.

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