Transcutaneous spinal stimulation (TSS) and whole-body vibration (WBV) each have a robust ability to activate spinal afferents. Both forms of stimulation have been shown to influence spasticity in persons with spinal cord injury (SCI), and may be viable non-pharmacological approaches to spasticity management. In thirty-two individuals with motor-incomplete SCI, we used a randomized crossover design to compare single-session effects of TSS versus WBV on quadriceps spasticity, as measured by the pendulum test. TSS (50 Hz, 400 μs, 15 min) was delivered in supine through a cathode placed over the thoracic spine (T11-T12) and an anode over the abdomen. WBV (50 Hz; eight 45-s bouts) was delivered with the participants standing on a vibration platform. Pendulum test first swing excursion (FSE) was measured at baseline, immediately post-intervention, and 15 and 45 min post-intervention. In the whole-group analysis, there were no between- or within-group differences of TSS and WBV in the change from baseline FSE to any post-intervention timepoints. Significant correlations between baseline FSE and change in FSE were associated with TSS at all timepoints. In the subgroup analysis, participants with more pronounced spasticity showed significant decreases in spasticity immediately post-TSS and 45 min post-TSS. TSS and WBV are feasible physical therapeutic interventions for the reduction of spasticity, with persistent effects.

Background: Transcutaneous spinal stimulation (TSS) is a noninvasive stimulation approach to modulate spinal reflex circuit excitability after spinal cord injury (SCI) Posterior root muscle (PRM) reflexes can be used to characterize the change in excitability of spinal reflex circuits after TSS; these responses are likely influenced by stimulus parameters. Methods: We compared PRM reflex responses to 3 TSS conditions: single-site continuous (SS-CONT), single-site burst (SS-BURST), and dual-site continuous (DS-CONT). Stimulation (frequency: 50 Hz, intensity: 80% soleus reflex threshold[RT]) was delivered for 30 min. The cathode was placed over the thoracic spine (T11–T12) and anodes placed paraumbilically; a second cathode over the lumbar spine (L1/2 or L2/3) was used for DS-CONT. PRM reflex responses in the soleus were elicited by paired 1 ms monophasic conditioning–test stimuli at a 50 ms interstimulus interval via the T11–12 cathode and paraumbilical anodes. Soleus PRM reflex indices included RT, response amplitude at 1.2xRT (RA_1.2xRT), slope, area under the input–output curve (AUC). Paired-pulse indices were collected, including paired-pulse depression (PPD) and depression of the area under the curve (AUC_dep). To assess the correlation between biomechanical and electrophysiologic measures of soleus spasticity, the ankle clonus drop test first drop excursion (FDE) was measured. All indices were measured at baseline and immediately post-intervention. Results: In whole-group analyses, PPD and AUC_dep were significantly decreased. Significant decreases in PPD and AUC_dep were identified only after the SS-CONT condition. No significant changes were identified in other PRM reflex indices after any of the 3 TSS conditions. No relationships between baseline FDE and any PRM reflex parameter were identified at baseline. Conclusions: With stimulation intensity of 80% soleus RT, modulation of targeted spinal reflex circuits was observed only in the SS-CONT condition when the response of the conditioning and test stimuli were considered. In addition, stretch-induced spasticity of the soleus may not be consistent with electrophysiologic testing.

Background/Objectives: Transcutaneous spinal stimulation (TSS) is a noninvasive stimulation approach for spasticity reduction in people with spinal cord injury (SCI). We enrolled 17 individuals with SCI who experience lower extremity hyperreflexia for this randomized crossover study to compare single-session effects of 3 TSS conditions: single-site continuous (SS-CONT), single-site burst (SS-BURST), and dual-site continuous (DS-CONT). Methods: Each TSS condition was delivered for 30 min with participants in supine via a cathode over the thoracic spine (T11–T12) and an anode over the abdomen. A second cathode was placed over the lumbar spine (L1/2 or L2/3) for DS-CONT. SS-CONT and DS-CONT stimulation was delivered as continuous 50 Hz stimulation with a 1 ms pulse width. SS-BURST stimulation was delivered as 4 bursts/second of 50 Hz stimulation with a 1 ms pulse width. Pendulum test first swing excursion (FSE) and ankle clonus drop test first drop excursion (FDE) were measured at baseline and immediately post-intervention to assess quadriceps and soleus spasticity, respectively. FSE and FDE of the first trial (FSE_T1 and FDE_T1) and the average of 3 trials (FSE_avg and FDE_avg) were included in analyses. Subgroup analyses were performed based on baseline level of spasticity (high vs. low). Results: Between-condition analyses showed no significant differences; however, SS-CONT (FSE_T1 d = 0.30, FSE_avg d = 0.27) and DS-CONT (FSE_T1 d = 0.33, FSE_avg d = 0.12) stimulation demonstrated the largest effect sizes for FSE measures, and SS-CONT (FDE_T1 d = 0.32, FDE_avg d = 0.31) stimulation demonstrated the largest effect size for FDE measures. Significant fair correlations between baseline FSE measures and change in FSE were identified when all conditions were combined. A significant fair correlation between baseline FDE_T1 and change in FDE_T1 was identified when data were collapsed across conditions. In subgroup analyses, only participants with high baseline quadriceps spasticity showed a significant decrease in quadriceps spasticity with DS-CONT (∆FSE_T1 = 14.8 ± 13.0°), SS-BURST (∆FSE_T1 = 4.1 ± 4.5°), and with all conditions combined (∆FSE_T1 = 11.3 ± 16.5°, ∆FSE_avg = 7.2 ± 13.1°). For participants with low baseline soleus spasticity, DS-CONT stimulation significantly increased soleus spasticity (∆FDE_T1 = −12.2 ± 9.3°, ∆FDE_avg = −8.5 ± 8.4°). Conclusions: When data were collapsed across conditions, TSS did not result in a significant reduction in quadriceps or soleus spasticity. Continuous stimulation at both single- and dual-sites was associated with the largest effect on quadriceps spasticity when all participants were combined. Lastly, TSS reduced spasticity in a severity-dependent manner.