Recovery cycles of posterior root-muscle reflexes evoked by transcutaneous spinal cord stimulation and of the H reflex in individuals with intact and injured spinal cord

PLoS ONE, 2019 · DOI: https://doi.org/10.1371/journal.pone.0227057 · Published: December 26, 2019

Simple Explanation

This study examines how reflexes in leg muscles respond to repeated stimulation of the spinal cord in people with and without spinal cord injuries. The reflexes studied were the H reflex and the posterior root-muscle (PRM) reflex. The researchers compared how these reflexes recover after an initial stimulation, using paired pulses with varying intervals between them. The key finding was that PRM reflexes showed different recovery patterns between the two groups, suggesting that spinal cord injury affects how these reflexes are regulated.

Study Duration

Not specified

Participants

10 neurologically intact volunteers and 10 individuals with traumatic, chronic spinal cord injury

Evidence Level

Not specified

Key Findings

1
The recovery cycles of H reflexes did not differ significantly between neurologically intact individuals and those with SCI.
2
PRM reflexes exhibited stronger suppression in the neurologically intact group compared to the individuals with SCI.
3
Within the neurologically intact group, the PRM reflexes showed a stronger suppression than the H reflexes.

Research Summary

This study compared the recovery cycles of H reflexes and posterior root-muscle (PRM) reflexes in individuals with and without spinal cord injury (SCI). The findings indicate that PRM reflexes, but not H reflexes, differ significantly in their recovery patterns between the two groups, suggesting different underlying spinal mechanisms. The study also found differences in PRM reflex recovery between thigh and lower leg muscles, potentially reflecting variations in motor control.

Practical Implications

Spasticity Measurement

PRM-reflex depression tested with paired pulses could serve as a sensitive measure for spasticity and motor recovery after SCI.

Motor Control Studies

The differences between H-reflexes and PRM reflexes highlight the need to consider heteronymous Ia facilitation when using PRM reflexes in motor control studies.

Antispasticity Therapies

Understanding the spinal inhibitory mechanisms probed by transcutaneous SCS could help in developing more effective antispasticity therapies.

Study Limitations

1
Sample size may limit generalizability.
2
The influence of antispasticity medications on reflex excitability was not fully controlled.
3
Not specified

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