Sensory restoration by epidural stimulation of the lateral spinal cord in upper-limb amputees

eLife, 2020 · DOI: https://doi.org/10.7554/eLife.54349 · Published: July 21, 2020

Simple Explanation

This study explores using spinal cord stimulation (SCS) to create sensations in missing limbs of amputees. SCS, a method used for chronic pain, involves placing a device near the spinal cord to stimulate nerves. Four individuals with upper-limb amputations participated in experiments involving spinal cord stimulation for up to 29 days. They reported feeling electrical buzzing, vibration, or pressure in their missing limb during the stimulation. The intensity of the sensations could be adjusted by changing the strength of the electrical signals, suggesting a way to provide nuanced sensory feedback.

Study Duration

Up to 29 days

Participants

Four people with upper-limb amputation

Evidence Level

Not specified

Key Findings

1
Epidural spinal cord stimulation (SCS) evoked somatosensory percepts that were perceived as emanating from the missing arm and hand.
2
Stimulation evoked sensory percepts in consistent locations in the missing hand regardless of time since amputation or level of amputation.
3
Increasing stimulus amplitude increased the perceived intensity linearly, without increasing area of the sensations.

Research Summary

The study demonstrates the potential of epidural SCS as a method for restoring sensation in individuals with upper-limb amputations, with sensations localized to the missing limb. The evoked sensations were generally stable over the 29-day testing period, with only minor changes in location and area. While many sensations were paresthetic, some were described as more naturalistic. The ability to modulate percept intensity without increasing the area of the evoked sensations is important for providing graded feedback via a prosthetic device.

Practical Implications

Prosthetic Design

SCS can be incorporated into advanced prosthetic designs to provide sensory feedback, enhancing control and usability.

Clinical Translation

Given that SCS is already an FDA-approved and widely used technique, this research provides a pathway for clinical adoption of SCS for sensory restoration in amputees.

Neuroprosthetic Development

Percutaneous SCS devices can be used as a tool for development of somatosensory neuroprosthetic systems, especially for research projects focused on advanced prosthetic control.

Study Limitations

1
The sensory percepts evoked in this study were sometimes more diffuse than those reported in other studies using peripheral neurostimulation approaches.
2
The relationship between the locations of the electrodes and that of the evoked percepts showed marked inter-subject variability and deviation from expected dermatomes.
3
This study focused on characterizing the sensations evoked by SCS but did not demonstrate that those sensations could be used as part of a closed-loop neuro-prosthetic system.

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