Neuroregenerative Effects of Intraspinal Microstimulation (ISMS) Following Spinal Cord Injury (SCI)

Background Intraspinal microstimulation (ISMS) is a novel electrical stimulation technique that has demonstrated mobility restoration in animals with spinal cord injury (SCI). This project investigated: 1) the capacity of ISMS to restore functional walking in rats with SCI through 4 weeks of stimulation, and 2) the degree of walking deficit caused by ISMS surgery. Methods Thirteen Sprague Dawley rats were divided into three groups: 1) rats with hemi-section SCI (hSCI) and no implants (control group), 2) rats with hSCI and passive ISMS implants (ISMS sham group), and 3) rats with hSCI and implants with active electrical stimulation (ISMS group). All groups were trained to walk on a horizontal ladder and their performance was quantified pre- and post-surgery. Results We hypothesized that the rats with active ISMS implants would demonstrate the greatest improvement in functional walking compared to both control groups, and that the ISMS sham group would underperform the most. The preoperative functional walking scores of control, sham and ISMS rats were 5.7±0.2, 5.5±0.3 and 5.7±0.1, respectively (7-point scale; mean ± standard error). The post-surgery scores were 3.2±0.9, 2.6±0.6 and 3.3±0.8 for control, sham, and ISMS rats, respectively. Conclusions As the difference between the post-surgery functional walking scores of ISMS and control rats was not statistically significant, this may indicate that four weeks of ISMS stimulation is not enough to cause rehabilitative effects. Additionally, the ISMS sham group demonstrated impaired functional walking compared to the hSCI control group as predicted. Future studies will employ a larger sample size to fully elucidate this trend and utilize thinner microwires to mitigate cellular damage.