Effect of TENS on Spasticity

Overview

The purpose of this clinical trial is to evaluate whether Transcutaneous Electrical Nerve Stimulation (TENS) is effective in reducing spasticity in adults with post-stroke spasticity. The primary research question is whether TENS can reduce the severity of spasticity. The effectiveness of TENS will be assessed by comparing spasticity-related outcomes measured before, during, and after the intervention. Participants will first undergo a one-hour baseline monitoring period, during which assessments will be conducted at 10-minute intervals. This will be followed by a 30-minute TENS intervention and a two-hour follow-up period, with assessments performed every 10 minutes. One participant will repeat this protocol once daily for three consecutive days, whereas the remaining three participants will undergo the procedure on a single occasion.

Post-stroke spasticity is a common consequence of upper motor neuron lesions and is characterized by increased muscle overactivity and exaggerated stretch reflex responses. It can negatively affect motor function, daily activities, and quality of life in stroke survivors. Transcutaneous electrical nerve stimulation (TENS) is a non-invasive and widely used rehabilitation modality that may modulate spinal and supraspinal neural mechanisms through activation of sensory afferent pathways. Although previous studies have reported potential benefits of TENS for spasticity management, findings remain inconsistent because of methodological heterogeneity, variability in stimulation parameters, and differences in individual treatment responses. The purpose of this study is to evaluate the effects of sensory-level TENS on wrist flexor spasticity and spinal motor neuron excitability in individuals with chronic post-stroke spastic paresis. Specifically, the study will examine whether TENS influences clinical spasticity, the duration of any observed effects, the magnitude of treatment-related changes, and the reproducibility of these effects across participants. Two complementary single-case experimental designs will be used. First, a withdrawal/reversal design (ABABA with washout periods) will be employed to evaluate the causal effects of TENS on outcome measures. Second, a nonconcurrent multiple-baseline design across participants will be used to assess the consistency of intervention effects across individuals. TENS will be applied over the paretic wrist flexor muscles for 30 minutes using symmetrical biphasic rectangular pulses (100 Hz, 200 μs). Stimulation intensity will be adjusted to a clearly perceived sensory level without visible muscle contraction or discomfort. The primary outcomes are clinical spasticity, assessed by muscle reaction angle during rapid passive stretch, and spinal motor neuron excitability, assessed by the Hmax/Mmax ratio obtained from flexor carpi radialis H-reflex recordings. Repeated measurements will be performed throughout the experimental phases to evaluate immediate and time-dependent changes associated with TENS application. This study is expected to provide individual-level evidence regarding the effects and temporal characteristics of sensory-level TENS in chronic post-stroke spasticity.