Spinal Cord Imaging Markers and Recovery of Volitional Leg Movement With Spinal Cord Epidural Stimulation in Individuals With Clinically Motor Complete Spinal Cord Injury

Front. Syst. Neurosci., 2020 · DOI: 10.3389/fnsys.2020.559313 · Published: October 21, 2020

Spinal Cord Injury Neuroimaging Neurology

Simple Explanation

This study explores how spinal cord epidural stimulation (scES) can help people with complete spinal cord injuries regain some voluntary leg movement. Researchers used MRI to look at the spinal cord damage in 13 individuals before implanting an epidural stimulator. They analyzed the amount of spared tissue in different regions of the spinal cord and how it related to the recovery of motor control. The ability to generate force exertion and movement was not correlated to any neuroimaging marker. Spared tissue of speciﬁc cord regions signiﬁcantly and importantly correlated with some aspects of motor control.

Study Duration

Not specified

Participants

13 individuals with chronic, clinically motor complete and sensory complete or incomplete SCI

Evidence Level

Not specified

Key Findings

1
The amount and location of spared spinal cord tissue at the lesion site were unrelated to the ability to generate volitional lower limb movements with scES.
2
Spared tissue of the anterior spinal cord was negatively correlated with EMG amplitude of the left soleus muscle during left ankle dorsiflexion attempts.
3
The amount of isolated activation of the right medial hamstrings was directly related to the spared tissue of the lateral right cord during right lower limb flexion attempts.

Research Summary

This study investigated the relationship between spinal cord MRI markers and the recovery of volitional leg movement with spinal cord epidural stimulation (scES) in individuals with clinically motor complete spinal cord injury. The study found that the amount and location of spared spinal cord tissue at the lesion site were not related to the ability to generate volitional lower limb movements with scES. However, spared tissue of specific cord regions was related to some aspects of motor control, suggesting that supraspinal inputs through spared spinal cord regions that differ across individuals can result in the generation of lower limb volitional movements prior to any training when epidural stimulation is provided.

Practical Implications

Personalized scES parameter selection

The findings highlight the importance of individual-specific characteristics in the extent of motor function recovery promoted by scES, suggesting personalized approaches to scES parameter selection may be crucial.

Targeted Rehabilitation Strategies

The study suggests that interventions aimed at improving intra- and inter-limb coordination of motor pools may be a valuable approach for promoting motor recovery after SCI, potentially through neural reorganization involving inhibitory and excitatory interneurons.

Further Research Directions

Future studies should focus on detailing the spared tissue of specific white matter pathways using higher resolution MRI, and pairing imaging and neurophysiology markers to provide further mechanistic insights on the recovery of volitional leg movements promoted by epidural stimulation after severe spinal cord injury.

Study Limitations

1
The imaging approach provides an estimate of spinal cord damage location based on MRI, and spinal cord lesion itself distorts the spinal cord dimensions in the axial plane.
2
The epidural stimulation implants utilized in this study are not 3T-MRI compatible which limit longitudinal assessment.
3
The level of optimization of scES parameters might have been slightly differed across participants.

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