The Mechanistic Basis for Successful Spinal Cord Stimulation to Generate Steady Motor Outputs

Frontiers in Cellular Neuroscience, 2019 · DOI: 10.3389/fncel.2019.00359 · Published: August 9, 2019

Simple Explanation

Electrical stimulation of the spinal cord is showing promise for motor rehabilitation after spinal cord injury (SCI). With electrical stimulation, patients showed improved trunk control, standing, stepping, and urogenital function. Electrical stimulation was not eﬀective unless it included proprioceptive feedback generated from muscle length changes and load-bearing during stepping and standing, indicating that sensorimotor integration mediates these eﬀects. We therefore hypothesized that combined electrical stimulation of sensory and motor inputs in the transected spinal cord yields higher and more stable motor output than that generated by either input separately.

Study Duration

Not specified

Participants

53 male mice

Evidence Level

Not specified

Key Findings

1
EPSPs and coAPs of the S input exhibited progressive depression.
2
EPSPs and coAPs of the M input exhibited progressive facilitation.
3
Their combined eﬀect (S&M) generated higher EPSP and coAP amplitudes with steady proﬁles. This combined enhancement was magniﬁed at higher neuromodulatory states.

Research Summary

The current study provides comprehensive investigation of the plasticity, integration, and neuromodulation of electrically evoked sensorimotor inputs in spinal motoneurons, and the resultant motor output in absence of supraspinal inputs. Using electrophysiological recordings and computer simulations, we show that integration of electrically evoked sensory and motor inputs, despite having diﬀerent plasticity patterns, help generate a stronger and steadier motor output, which is more readily achievable at higher neuromodulatory states. Accordingly, these results provide, for the ﬁrst time, mechanistic explanation for the cellular processes contributing to the functional motor improvement observed in subjects with complete SCI when electrical stimulation is delivered.

Practical Implications

Improved Stimulation Protocols

The results can be leveraged into improved stimulation protocols, leading to improved restoration of movement and independence for SCI patients.

Understanding Sensorimotor Integration

This study mechanistically highlights the role of sensorimotor integration in generating steady motor outputs.

Clinical Applications

The data also suggest that dorsal root stimulation might be combined with spinal cord stimulation to improve the clinical outcome in patients who failed to independently stand and step with epidural stimulation alone.

Study Limitations

1
ex vivo spinal cord preparation represents a relatively low neuromodulatory state
2
Absence of supraspinal inputs
3
The motor inputs were activated by stimulation of the local motor circuits and remaining descending axons in the ventral funiculus of the sacral cord.

Your Feedback

Was this summary helpful?

Back to Spinal Cord Injury