Limb segment vibration modulates spinal reflex excitability and muscle mRNA expression after spinal cord injury

Clin Neurophysiol, 2012 · DOI: 10.1016/j.clinph.2011.08.001 · Published: March 1, 2012

Spinal Cord Injury Physiology Rehabilitation

Simple Explanation

The study investigated the effect of limb vibration on spinal reflexes and muscle gene expression in individuals with and without spinal cord injury (SCI). Vibration of the lower leg was found to inhibit the H-reflex amplitude, a measure of spinal excitability, in both healthy individuals and those with SCI. The study also found that limb vibration altered the expression of certain genes in skeletal muscle that are associated with synaptic plasticity, which is the ability of connections between nerve cells to change.

Study Duration

Not specified

Participants

6 healthy adults and 7 individuals with sub-acute/chronic SCI

Evidence Level

Level 2: Experimental study

Key Findings

1
Segmental vibration resulted in H-reflex depression in both SCI and healthy control groups.
2
The SCI group showed rapid H-reflex recovery within the first 2 min after vibration whereas H-reflex in the control group appeared to remain at a depressed state for more than 2 min.
3
A short-term limb segment vibration had significant effects on genes associated with synaptic plasticity.

Research Summary

This study demonstrated that mechanical oscillation of a single paralyzed limb segment modulates the amplitude of the H-reflex and influences the degree of post-activation depression in healthy and those with complete SCI. H-reflex depression is likely caused by the sum of modulations via multiple sources within the spinal neuronal circuitry including presynaptic inhibition, postsynaptic inhibition, and post-activation depression mechanisms, but does not require supra spinal drive. In addition, specific gene signatures, known to mediate synaptic plasticity, were modulated by the mechanical oscillation.

Practical Implications

Rehabilitation Potential

Limb segment vibration may offer a long-term method to reduce spinal reflex excitability after SCI, potentially improving motor control.

Therapeutic Target

The modulation of specific genes associated with synaptic plasticity suggests a potential therapeutic target for promoting spinal neuronal plasticity in individuals with chronic SCI.

Spasticity Reduction

The study suggests that vibration-induced changes in spinal excitability are likely attributed to inhibitory modulations from multiple sources which may ultimately contribute to the velocity dependent increase in stiffness (spasticity) commonly observed in those with SCI.

Study Limitations

1
The study involved a small sample size, particularly for the muscle biopsy and mRNA analysis.
2
The study only examined the acute effects of vibration on muscle gene expression; long-term effects were not assessed.
3
The study did not linearly correlate H-reflex amplitude with gravitational acceleration.

Your Feedback

Was this summary helpful?

Back to Spinal Cord Injury