Preliminary outcome of spinal cord stimulation for incomplete spinal cord injury patients

Introduction: Spinal cord injury (SCI) causes devastating sensory and motor dysfunction and life-long sensorimotor impairment. Epidural electrical stimulation (EES) has been shown recovery of voluntary control of lower limb motor function for patients with American Spinal Injury Association (AIS) A or B. This study aimed to investigate whether EES improves lower limbs function for the cervical level of chronic SCI patients with AIS C or D as well.

Methods: Four cervical level chronic SCI patients with AIS C or D were enrolled (AIS C = 2, AIS D = 2), and the range of post-injury years was from 1.5 to 10 years, and the average age was 56.25 ±7 years at the time of implant. Three individuals revealed gait instability and walking with assistance and one could not stand or walk independently with minimal motor activity. They received an individualized rehabilitation program plus multi-mode electrical stimulation treatment for 36 weeks. This study used surface electromyography (EMG) to measure lower limb muscles and applied GAITRite walkway systems to evaluate gait.

Results: The improvement percentage of walking gait was more than 30% for patients with 1.5 to 3 injury years (35% - 92%). In contrast, the patient with 10 years SCI showed trivial improvement. Nevertheless, the analysis results of muscular activity indicated a significant increase (P < 0.05) under EES treatment. Moreover, one patient with AIS C improved to AIS D.

Conclusion : We observed that EES enables faster recovery of lower limb function for patients with C or D, but there were still some factors lead to variable improvement. We found that longer duration injury (injury year≧10 years) might cause EES to improve neuroplasticity obscurely in corticospinal motor circuitry. However, EES for activating spinal cord circuitry under EMG analysis all showed significant enhancement. We suggested that SCI patients with long-term injury might need combinational therapeutic approaches to facilitate effectiveness of EES and enhance corticospinal circuit motor plasticity.