Effect of TENS on Spasticity

Official title

The Effect of Transcutaneous Electrical Nerve Stimulation on Spasticity: A Single-Subject Experimental Study

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.

Detailed description

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.

Interventions

• Device Transcutaneous electrical nerve stimulation (TENS)
  Transcutaneous electrical nerve stimulation (TENS) will be applied over the projection area of the paretic wrist flexor muscles (flexor carpi radialis) for 30 minutes. Stimulation parameters will consist of symmetrical biphasic rectangular pulses at a frequency of 100 Hz and a pulse duration of 200 μs. Stimulation intensity will be adjusted to produce a clearly perceived sensory sensation without visible muscle contraction or discomfort.

Primary outcome measures

• Angle of Muscle Reaction [Time frame: From baseline assessment through completion of study participation (1 to 3 days, depending on the assigned experimental design).]
• Hmax / Mmax ratio [Time frame: From baseline assessment through completion of study participation (1 to 3 days, depending on the assigned experimental design).]

Eligibility criteria

Inclusion criteria

• Age between 18 and 70 years
• Post-stroke wrist flexor spasticity scored as Grade 2 or 3 on the Australian Spasticity Assessment Scale (ASAS), specifically selecting patients whose passive stretch resistance (post-catch response) can be easily overcome to ensure accurate and unconfounded electrophysiological evaluation.
• At least 6 months post-stroke (chronic phase).
• Provision of voluntary, written informed consent prior to study enrollment.

Exclusion criteria

• Age <18 or >70 year
• Contraindications to transcutaneous electrical nerve stimulation (e.g., implanted electronic devices, history of epilepsy, or localized skin lesions preventing electrode placement)
• Concomitant wrist contracture or pain sufficient to impede clinical evaluation
• Structural abnormalities of the elbow joint obstructing median nerve stimulation
• Median nerve neuropathy or injury in the affected upper extremity.
• Non-stable dosage of antispastic medications within the 2 weeks prior to baseline
• Initiation of medications affecting nerve conduction (e.g., antidepressants, anticonvulsants, anesthetics) within the past month; patients on a stable dose for >1 month remain eligible
• Botulinum toxin injection in the target spastic muscles within the preceding 3 months
• History of neurolytic procedures targeting spasticity in the affected limb.
• History of orthopedic or neurological surgery targeting spasticity in the affected limb
• Cognitive impairment severe enough to compromise adherence to study protocols
• Inability to maintain the required testing positions for the upper extremity joints (shoulder, elbow, forearm, and wrist)
• Pregnancy or breastfeeding
• Presence of active malignancy at or near the treatment area.

Criteria are shown verbatim from the registry (in English). Final eligibility is always assessed by the study center.

Healthy volunteers: No

Study design

Allocation

N/A

Model

Single group

Masking

Open label

Primary purpose

Treatment

Study locations

Turkey (Türkiye) · 1 center

• Izmir Katip Çelebi University — Izmir

Publications

• Lance JW. Symposium synopsis. In: Feldman RG, Young RR, Koella WP, editors. Spasticity: Disordered Motor Control. Chicago: Year Book Medical Publishers; 1980. p. 485-494.
• Chen B, Yang T, Liao Z, Sun F, Mei Z, Zhang W. Pathophysiology and Management Strategies for Post-Stroke Spasticity: An Update Review. Int J Mol Sci. 2025 Jan 5;26(1):406. doi: 10.3390/ijms26010406. PMID 39796261
• Tate RL, Perdices M. Introduction to single-case experimental designs: historical overview and basic concepts. In: Tate RL, Perdices M, editors. Single-Case Experimental Designs for Clinical Research and Neurorehabilitation Settings: Planning, Conduct, Analysis and Reporting. New York: Routledge; 2019. p. 3-20.
• He J, Luo A, Yu J, Qian C, Liu D, Hou M, Ma Y. Quantitative assessment of spasticity: a narrative review of novel approaches and technologies. Front Neurol. 2023 Jul 5;14:1121323. doi: 10.3389/fneur.2023.1121323. eCollection 2023. PMID 37475737
• Childers MK, Biswas SS, Petroski G, Merveille O. Inhibitory casting decreases a vibratory inhibition index of the H-reflex in the spastic upper limb. Arch Phys Med Rehabil. 1999 Jun;80(6):714-6. doi: 10.1016/s0003-9993(99)90178-8. PMID 10378501
• Katz RT, Rovai GP, Brait C, Rymer WZ. Objective quantification of spastic hypertonia: correlation with clinical findings. Arch Phys Med Rehabil. 1992 Apr;73(4):339-47. doi: 10.1016/0003-9993(92)90007-j. PMID 1554307
• Burke D. Clinical uses of H reflexes of upper and lower limb muscles. Clin Neurophysiol Pract. 2016 Apr 7;1:9-17. doi: 10.1016/j.cnp.2016.02.003. eCollection 2016. PMID 30214954
• Gracies JM, Bayle N, Vinti M, Alkandari S, Vu P, Loche CM, Colas C. Five-step clinical assessment in spastic paresis. Eur J Phys Rehabil Med. 2010 Sep;46(3):411-21. PMID 20927007

Identifiers

NCT: NCT07669649 · 2026-KAE-0019

Primary sources (government registries)

• ClinicalTrials.gov (US NIH)

View this study on ClinicalTrials.gov ↗