Spatiotemporal Distribution of Electrically Evoked Spinal Compound Action Potentials During Spinal Cord Stimulation

Neuromodulation, 2023 · DOI: 10.1016/j.neurom.2022.03.007 · Published: July 1, 2023

Simple Explanation

Spinal Cord Stimulation (SCS) is used to treat chronic pain, but how it works is unclear. This study uses spinal evoked compound action potentials (ECAPs) to understand how SCS affects the spinal cord. Two 24-contact electrode arrays were placed on the spinal cords of four sheep to record ECAPs during SCS. The researchers looked at how the ECAPs changed in different areas of the spinal cord and how they related to muscle activity. The study found that ECAPs have a triphasic shape and that their distribution changes depending on where the stimulation is applied. These ECAPs correlate with muscle activity, suggesting they can be used to understand how SCS affects sensorimotor networks.

Study Duration

6 Months

Participants

4 Sheep

Evidence Level

Not specified

Key Findings

1
Distinct regions of lateral stimulation resulted in simultaneously increased ECAP and EMG responses compared to stimulation at adjacent lateral contacts.
2
Spinal ECAP responses and EMG responses demonstrated preferential ipsilateral recruitment during lateral stimulation as compared to midline stimulation.
3
EMG responses were correlated with stimulation that resulted in increased ECAP amplitude on the ipsilateral side of the electrode array.

Research Summary

This study investigates the spatiotemporal distribution of spinal ECAPs during SCS in sheep, examining how these ECAPs relate to lower extremity motor responses. The researchers found that spinal ECAP morphology is triphasic and modulated by the location of stimulation, with lateral stimulation resulting in increased ECAP and EMG responses on the ipsilateral side. The study suggests that spinal ECAPs can be used to investigate the effects of SCS on spinal sensorimotor networks and may inform strategies to optimize the clinical benefit of SCS.

Practical Implications

Optimize SCS Strategies

ECAPs can inform stimulation strategies for chronic pain management and restoration of sensorimotor function after SCI.

Understand Neural Mechanisms

Spinal ECAPs provide insights into the neurophysiological effects of SCS spatiotemporally across the spinal cord.

Develop Quantitative Techniques

ECAP recordings offer a quantitative method to measure the effects of SCS, potentially replacing subjective pain scales.

Study Limitations

1
Spinal anatomy can differ between sheep, such as in the number of lumbar vertebrae.
2
Relationship between the spatiotemporal distribution of ECAPs and behavior such as sensation can be difficult to evaluate in sheep.
3
Experiments were performed while the sheep were raised in the sling apparatus without any afferent feedback.

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