The Potential of Corticospinal-Motoneuronal Plasticity for Recovery after Spinal Cord Injury

Curr Phys Med Rehabil Rep., 2020 · DOI: 10.1007/s40141-020-00272-6 · Published: September 1, 2020

Spinal Cord Injury Neurology Neurorehabilitation

Simple Explanation

This review focuses on a neuromodulation method pairing transcranial magnetic stimulation over the primary motor cortex with transcutaneous electrical stimulation over a peripheral nerve. This pairing aims to induce plasticity at corticospinal-motoneuronal synapses, potentially improving motor function recovery after spinal cord injury. The two stimuli are applied at precise inter-stimulus intervals to reinforce corticospinal synaptic transmission using principles of spike-timing dependent plasticity.

Study Duration

Not specified

Participants

Humans with chronic incomplete spinal cord injury

Evidence Level

Not specified

Key Findings

1
Recovery of sensorimotor function after spinal cord injury largely depends on transmission in the corticospinal pathway.
2
Transmission in residual corticospinal axons can be assessed using non-invasive transcranial magnetic stimulation which combined with transcutaneous electrical stimulation can be used to improve voluntary motor output.
3
These two stimuli are applied at precise inter-stimulus intervals to reinforce corticospinal synaptic transmission using principles of spike-timing dependent plasticity.

Research Summary

We discuss the neural mechanisms and application of this neuromodulation technique and its potential therapeutic effect on recovery of function in humans with chronic spinal cord injury. The review focuses on paired corticospinal-motoneuronal stimulation (PCMS) and its efficacy in inducing plasticity of residual corticospinal projections. PCMS combined with exercise training showed that corticospinal drive and maximal voluntary contraction (MVC) in targeted muscles increased after PCMS with or without exercise but not after sham-PCMS with exercise

Practical Implications

Therapeutic Potential

PCMS could be a valuable tool for promoting functional recovery after SCI, particularly when combined with exercise.

Clinical Translation

Further research is needed to optimize PCMS protocols for clinical use, including assessing lower stimulation intensities and exploring different stimulation frequencies.

Mechanism Understanding

Further investigations are needed to understand underlying mechanisms, optimal dose, size and duration of effects along with applicability out of laboratory settings.

Study Limitations

1
Effectiveness of PCMS depends on precise timing between TMS and peripheral nerve electrical stimulation
2
Current PCMS protocols in humans with SCI use 100% of maximal stimulator output (MSO) of TMS
3
Evidence for the combined use of AIH and PCMS is presently limited

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