Soleus H and Lower Limb Posterior Root Muscle Reﬂexes During Stepping After Incomplete SCI

Frontiers in Rehabilitation Sciences, 2022 · DOI: 10.3389/fresc.2022.789333 · Published: May 13, 2022

Spinal Cord Injury Physiology Rehabilitation

Simple Explanation

This study aimed to understand how spinal cord injuries affect the way muscles coordinate during walking, using reflexes as indicators. Researchers compared two types of reflexes in people with and without spinal cord injuries while they were standing and stepping with robotic assistance. The study found that spinal cord injuries disrupt the normal modulation of these reflexes during walking, potentially due to impaired brain control over spinal cord activity.

Study Duration

Not specified

Participants

15 subjects with SCI and 10 without injury

Evidence Level

Not specified

Key Findings

1
Both the soleus H and soleus PRM reﬂex amplitudes were higher relative to the non-injured group and modulated less during the step cycle in SCI subjects.
2
Modulation of the soleus H reﬂex, but not soleus PRM reﬂex, correlated to the lower extremity motor scores in individuals with SCI.
3
The SCI group had a signiﬁcantly lower modulation index, indicating less step cycle related modulation, compared to the NI group for the soleus PRM reﬂex (p < 0.01) and H reﬂex (p = 0.027, t-test).

Research Summary

The study compared soleus H-reflexes and posterior root muscle (PRM) reflexes during robotic-assisted stepping in individuals with and without motor-incomplete spinal cord injury (SCI). Results indicated that both H and PRM reflexes modulate with the step cycle in non-injured individuals, but only the soleus H-reflex significantly modulated in the SCI group. The ability to modulate H-reflexes, but not PRM reflexes, was related to lower extremity motor scores, suggesting altered supraspinal regulation of segmental excitability after SCI.

Practical Implications

Rehabilitation Strategies

Locomotor training may be more effective for individuals with better step cycle-related reflex modulation, emphasizing the need to assess and improve this modulation in SCI rehabilitation.

Biomarkers for SCI

H and PRM reflexes can be used as biomarkers to assess the therapeutic effects of interventions in SCI, where normalization of their modulation indicates recovery of spinal circuit function.

Improved Motor Control Quantification

Better methods are needed to quantify post-SCI motor control patterns, potentially incorporating both H and PRM reflexes, to tailor and optimize rehabilitation strategies.

Study Limitations

1
The relationship of the soleus H and PRM reﬂex has not been clearly established
2
The modulation of these PRM reﬂexes has not been evaluated while walking with body weight support after motor incomplete SCI.
3
Small sample sizes in each group may limit the generalizability of the findings.

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