Body Position Influences Which Neural Structures Are Recruited by Lumbar Transcutaneous Spinal Cord Stimulation

PLoS ONE, 2016 · DOI: 10.1371/journal.pone.0147479 · Published: January 21, 2016

Simple Explanation

Transcutaneous stimulation of the spinal cord is used to evoke reflexes and modulate sensorimotor function. This requires reliable stimulation of sensory fibers, but sometimes motor fibers are also activated. The study investigates how body position (supine, standing, prone) affects the stimulation of sensory versus motor fibers during transcutaneous spinal cord stimulation. The findings suggest that supine and standing positions primarily stimulate sensory fibers, while the prone position leads to concomitant motor fiber stimulation.

Study Duration

Not specified

Participants

10 able-bodied adults (6 female) aged 18–34 years

Evidence Level

Not specified

Key Findings

1
Responses to the second stimulus were decreased to 14% ±5% in the supine position, to 30%±5% in the standing, and to only 80%±5% in the prone position.
2
Response thresholds were lowest during standing and highest in the prone position, indicating that it takes less stimulation to evoke a response while standing and more while prone.
3
Response amplitudes were largest in the supine and smallest in the prone position, meaning the size of the evoked muscle responses was greatest when lying on the back and least when lying on the stomach.

Research Summary

The study investigated the influence of body position on the recruitment of neural structures during lumbar transcutaneous spinal cord stimulation in able-bodied individuals. The results showed that body position significantly affects the nature of the evoked responses, with supine and standing positions primarily stimulating sensory fibers, while the prone position leads to concomitant motor fiber stimulation. The authors recommend conducting spinal reflex or neuromodulation studies with subjects lying supine or in an upright position, as in standing or stepping, to selectively target sensory fibers.

Practical Implications

Clinical Practice

When using transcutaneous spinal cord stimulation for therapy or research, consider the patient's body position to selectively target sensory or motor fibers.

Study Design

Researchers should use supine or upright positions when aiming to evoke spinal reflexes or provide sensory drive for neuromodulation.

Future Research

Further imaging and computer simulations are needed to understand how body position affects root-fiber trajectories and optimize transcutaneous stimulation techniques.

Study Limitations

1
The study was conducted on able-bodied individuals, and the results may not be directly applicable to individuals with spinal cord injury.
2
The study did not directly visualize the root-fiber trajectories, relying on inferences based on EMG responses and existing anatomical knowledge.
3
The threshold intensity in the prone position may have been underestimated due to missing data points.

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