Differential modulation of trunk muscle activation using thoracic epidural spinal stimulation

Area of Science:

• Neuroscience
• Rehabilitation Medicine
• Biomedical Engineering

Background:

• Epidural spinal stimulation (ESS) shows potential for improving trunk control after spinal cord injury (SCI).
• Previous ESS studies focused on lower thoracic levels, potentially missing optimal stimulation sites for trunk muscles based on innervation patterns.

Purpose of the Study:

• To investigate trunk muscle activity using ESS at various stimulation locations above the thoracic spine.
• To determine the optimal stimulation sites for evoking trunk muscle responses.

Main Methods:

• Implanted an electrode array above the thoracic spine in 13 participants.
• Systematically varied stimulation location along rostrocaudal and mediolateral axes.
• Quantified ESS-evoked responses in trunk muscles, including motor thresholds (MTs) and latencies.

Main Results:

• Ipsilateral ESS between T6-T10 vertebrae activated all trunk muscles.
• Stimulation between T8-T10 vertebrae yielded lower MTs and shorter latencies.
• Ipsilateral stimulation produced significantly greater response amplitudes and faster responses compared to contralateral stimulation.

Conclusions:

• Provides quantitative evidence on the impact of ESS amplitude and location on trunk muscle activity.
• Suggests both afferent and efferent pathways contribute to ESS-evoked muscle activation.
• Results can guide electrode placement for improved trunk control in SCI rehabilitation.