Lower Motoneuron Dysfunction Impacts Spontaneous Motor Recovery in Acute Cervical Spinal Cord Injury

Area of Science:

• Neurology
• Spinal Cord Injury Research
• Motor Neuron Diseases

Background:

• Paresis following spinal cord injury (SCI) results from damage to both upper and lower motoneurons (LMNs), influencing neurological recovery.
• Understanding the specific role and impact of LMN dysfunction is crucial for predicting motor function outcomes after acute cervical SCI.

Purpose of the Study:

• To investigate the extent and severity of LMN dysfunction in acute cervical SCI.
• To determine the relationship between LMN dysfunction and upper extremity motor recovery.
• To explore the correlation between LMN dysfunction, spinal cord myelopathy, and MRI findings.

Main Methods:

• Prospective, monocentric, longitudinal observational study design.
• Electromyography (EMG) to assess LMN dysfunction via spontaneous activity and motor unit action potential discharge rates.
• Standardized neurological examinations for motor recovery assessment (acute and chronic stages).
• Correlation analysis with spine MRI findings (T2-weighted hyperintense signals).

Main Results:

• LMN dysfunction was most prevalent at the lesion center and correlated with MRI-detected myelopathy severity.
• Increased LMN dysfunction severity was associated with more pronounced paresis in both acute and chronic SCI stages.
• While muscles with LMN dysfunction showed some recovery, those without LMN dysfunction had a greater potential for full strength recovery.
• Evidence of peripheral reinnervation was observed in muscles with LMN dysfunction, suggesting a compensatory mechanism.

Conclusions:

• LMN dysfunction is a significant contributor to motor impairment and influences recovery patterns in acute cervical SCI.
• Assessment of LMN dysfunction using EMG can help refine prognostication of motor recovery.
• Peripheral reinnervation plays a role in the spontaneous recovery of muscles affected by LMN dysfunction.