Peripheral transcutaneous electrical nerve stimulation and gait analysis in rats with spinal cord injury

Electrical stimulation strategies are investigated in the literature to recover sensorimotor impairments in spinal cord injury. In this study, transcutaneous electrical nerve stimulation (TENS) (pulse width: 0.3 ms, pulse frequency: 2 Hz, amplitude: 2 × motor threshold, duration: 30 min. at 3 days/week) was applied bilaterally to the tibial nerve rats with spinal cord injury (SCI). The study included sham (n=10), SCI (n=15), NS-sham (n=6), and NS-SCI (n=18) with endpoints at day 1 (D1), day 7 (D7), month 1 (M1), month 2 (M2). After T8-T9 laminectomy, contusion-type SCI was induced by using a computer-controlled custom-made impactor device (contactor diameter: 2.3 mm, peak force: 0.9-2 N, displacement: 1.75 mm, duration: 0.5 s). The severity (moderate-to-severe) of the injury and recovery was measured Basso, Beattie ve Bresnahan (BBB) locomotor rating scale. The mechanical withdrawal threshold was measured by von Frey filaments. DeepLabCut system was used to track each paw from high-speed (120 fps) video recordings and gait parameters (stance/swing/stride durations, limb duty factor, stride length, footprint area) were extracted in Matlab before detrending for speed. Average BBB scores were significantly decreased after the injury (D1: 0). The recovery was higher at NS-SCI (BBB: 17.5) than SCI (BBB: 8) (p = 0.003) at M2. vF scores also improved but were not statistically different between SCI and NS-SCI (p = 0.495). In gait parameters, the facilitative effect of TENS was observed up until D14; however, there was a reversal trend in limb duty factor and footprint area after D14. Overall, TENS had positive effects on locomotor function and stepping after SCI. However, synchronized application of TENS with stepping may have better results in terms of gait parameters in future studies.