Targeted-Plasticity in the Corticospinal Tract After Human Spinal Cord Injury

Neurotherapeutics, 2018 · DOI: https://doi.org/10.1007/s13311-018-0639-y · Published: June 26, 2018

Spinal Cord Injury Neurology Neuroplasticity

Simple Explanation

Spinal cord injuries (SCI) often impair sensorimotor function. This review discusses how noninvasive stimulation can target the corticospinal tract to boost motor output. The review explores how transcranial magnetic stimulation (TMS) and peripheral nerve electrical stimulation can induce plasticity in corticospinal projections. The paper highlights two emerging TMS protocols: one based on spike-timing dependent plasticity (STDP) and another mimicking the frequency of I-wave volleys.

Study Duration

Not specified

Participants

Humans with chronic incomplete SCI

Evidence Level

Review

Key Findings

1
A large proportion of individuals with clinically complete SCI show signs of spared connections, categorized as 'discomplete'.
2
PCMS can increase voluntary activation of low-threshold motor units, evidenced by increased EMG and force generation.
3
Pairs of TMS pulses mimicking late I-wave volleys increased corticospinal excitability and fine motor function in humans with incomplete cervical SCI.

Research Summary

This review addresses the potential for activating residual corticospinal projections after SCI to improve motor recovery. It discusses evidence showing that spinal cord injuries are rarely anatomically complete, with many individuals having 'discomplete' injuries. The review highlights emerging TMS protocols targeting the corticospinal tract, showing promise in enhancing motor output after SCI.

Practical Implications

Clinical Translation

The findings suggest that targeted TMS protocols, such as PCMS and I-wave stimulation, could be translated to clinical environments to enhance motor rehabilitation after SCI.

Personalized Interventions

The need for electrophysiological finesse in determining interstimulus intervals highlights the potential for personalized interventions tailored to individual patients' neurophysiological profiles.

Combination Therapies

Combining PCMS with voluntary contraction or acute intermittent hypoxia can augment the beneficial effects, suggesting the potential for multi-modal therapeutic approaches.

Study Limitations

1
Current PCMS protocols use high stimulation intensities, which might need adjustment for clinical use.
2
The need for electrophysiological finesse in determining interstimulus intervals for PCMS may limit its clinical applicability.
3
Further investigations are needed to determine the optimal dose, size, and duration of effects of these protocols outside laboratory settings.

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