High-frequency Alternating Current Stimulation for Neurophatic Pain in Spinal Cord Injury

Effectiveness and Safety of Transcutaneous Electrical Stimulation With 40 kHz Alternating Currents in People With Spinal Cord Injury and Neuropathic Pain. A Randomised, Double-blind, Parallel Pilot Study With Placebo Control

To investigate the safety and effectiveness of transcutaneous electrical stimulation with 40 kHz alternating currents combined with standard treatment compared to placebo electrical stimulation plus standard treatment for neuropathic pain in people with spinal cord injury.

Study Overview

• Status: Completed
• Conditions: Neuropathic Pain; Spinal Cord Injuries (SCI)
• Intervention / Treatment: Device: Active group 40 kHz; Device: Sham intervention

Detailed Description

Neuropathic pain affects more than a third of people with spinal cord injuries, reducing their quality of life, and the effectiveness of current treatments is limited. The latest research on healthy volunteers has shown that transcutaneous electrical stimulation with high-frequency blocking currents could have a potential effect on pain, proving to be a safe intervention.

To investigate the safety and effectiveness of transcutaneous electrical stimulation with 40 kHz alternating currents combined with standard treatment compared to placebo electrical stimulation plus standard treatment for neuropathic pain in people with spinal cord injury.

Design: Parallel, randomised, double-blind, placebo-controlled pilot clinical trial.

Participants and location: People with spinal cord injury over the age of 18, with a history of more than three months, neuropathic pain at the level of injury and/or below the level of injury, and pain intensity ≥ 30 mm on the visual analogue scale (VAS) for pain. Participants with any contraindications for the application of transcutaneous electrical stimulation will be excluded. The study will be conducted at the National Hospital for Paraplegics in Toledo.

Intervention: Participants will be randomly assigned to two intervention groups:

Active group (n=15) transcutaneous electrical stimulation with 40kHz alternating currents and Placebo group (n=15) simulated stimulation. The duration of the session in both interventions will be 20 minutes, 10 sessions, over two weeks (5 sessions/week).

Main variables and measurement instruments: The main variable will be the Spanish version of the Neuropathic Pain Symptom Inventory. Secondary variables will be pain perception, which will be assessed using a daily record of spontaneous pain with the VAS scale. The intensity of pain evoked by mechanical stimuli will be assessed using the VAS scale, and pain evoked by thermal stimuli will be assessed using a quantitative sensory test with a Peltier thermode. An ad hoc questionnaire has been designed to assess adverse effects. The assessments will be carried out at four time points: before the intervention, during the intervention, immediately after the intervention, and one week after the intervention.

• Study Type: Interventional
• Enrollment (Actual): 30
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Spain
  • Toledo, Spain, 45005
    • Hospital Nacional de Parapléjicos

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• People with spinal cord injuries of any aetiology affecting the D1 spinal cord level or lower (paraplegia)
• With injury grade A, B, C, or D according to the ASIA (American Spinal Injury Association) Impairment Scale (AIS)
• Time since spinal cord injury ≥ 3 months
• A score of ≥ 4 points on the Dolour Neuropathique 4 (DN4) scale
• Neuropathic pain at the level of the injury (within the dermatome at that level and up to three dermatomes below) and/or below the level of the injury (more than three dermatomes below)
• Duration of pain ≥ 1 month
• Average pain perception score ≥ 30 mm on the visual analogue scale (VAS) in the week prior to eligibility, with a daily record of 5 days (Monday to Friday) in the morning.
• Be able to understand instructions and assessment tools
• Agree to participate in the study and sign the informed consent form

Exclusion Criteria:

• Cauda equina injuries
• Brain injuries or other central nervous system injuries concomitant with spinal cord injury
• A value of 100 mm in any of the daily records collected in the week prior to eligibility
• Having any contraindications for the application of transcutaneous electrical stimulation: cardiac pacemaker or any other implanted electrical device, epilepsy, pregnancy, active malignant tumours in the area of application of the stimulation, and wounds or skin damage in the area of stimulation
• History of psychiatric illness
• Major depression
• Spinal cord injury caused by autolysis
• Changes in medication prescribed for the treatment of pain and spasticity during the study
• Acute nociceptive pain in any area of the body during the study

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Double

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: Experimental: 40 kHz; Alternating current stimulation with a 40kHz frequency with a transcutaneous approach, 20 minutes for each intervention.	Device: Active group 40 kHz; For experimental electrical stimulation, two stainless steel electrodes with conductive gel will be applied over the bilateral spinal roots with a separation between electrodes of at least 2 cm and a distance between the medial edge of each electrode and the spinous process of at least 1 cm. The upper third of the electrode will be placed above the level of spinal cord injury where the participant will have preserved sensitivity, and the remaining two thirds in the lesion and/or infralesional area. An unmodulated rectangular alternating or biphasic electrical current with a frequency of 40 kHz will be applied. The intensity of the current will be adjusted individually, increasing it until the participant reports a sensation of 'strong but comfortable tingling' just below the motor threshold. Every two minutes, the intensity of the current will be adjusted if the tingling sensation decreases. The electrical current will be applied for 20 minutes in two 10-minute phases.
Sham Comparator: Sham stimulation; Sham stimulation via transcutaneous approach will be delivered only for the first 30 seconds, following the same procedures as the 40kHz group.	Device: Sham intervention; Placebo stimulation will be performed using the same electrical current device, the same electrode placement, and the same stimulation parameters as in the experimental stimulation, but the current intensity will be increased only during the initial 30 initial seconds and the final 30 seconds of the session, with the current intensity set to 0 mA for the rest of the intervention (20 minutes).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain perception - NPSI	It will be assessed using the Spanish version of the Neuropathic Pain Symptom Inventory (NPSI), and the result will be taken as the change from baseline at different time points. This questionnaire has a score ranging from 0 to 100 points, with a higher score indicating greater severity of neuropathic pain symptoms. Regarding the psychometric properties of this questionnaire, it has been shown that the areas under the receiver operating characteristic curves were greater than 0.85 and all reliability coefficients were greater than 0.70.	Prior to the intervention (Baseline), during the intervention after five sessions (Day 5), after the intervention (Day 10) and one week after the end of the intervention (Day 15)

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Pain perception - VAS	A daily assessment (Monday to Friday) will be carried out in the morning of self-perceived pain using the visual analogue scale (VAS) (0 mm no pain and 100 mm maximum imaginable pain). The result will be taken as the change from baseline in the weekly mean value of self-perceived pain.	Baseline (-5 to 0 days), week 1 treatment (days 1-5), week 2 treatment (days 6-10) and post-treatment week (days 11-15).
Change in pain threshold evoked by mechanical stimuli	The change in pain threshold evoked by mechanical stimuli will be assessed at and below the level of injury-specifically, within the dermatome of the lesion and up to three dermatomes below, and in areas more than three dermatomes below the lesion. Mechanical allodynia will be evaluated using the SenseLab™ Brush-05 (Somedic, Sweden), with two 40 mm brush strokes applied 2 seconds apart. Pinprick pain will be assessed using three stimuli with a 512 mN Von Frey filament no. 12 (OptiHair 2, Germany). In both cases, pain intensity will be rated using a 0-100 mm Visual Analogue Scale (VAS).	Prior to the intervention (Baseline), during the intervention after five sessions (Day 5), after the intervention (Day 10) and one week after the end of the intervention (Day 15)
Change in pain threshold evoked by thermal (cold and heat) stimuli	The change in pain threshold evoked by thermal (cold and heat) stimuli will be assessed at and below the level of injury-specifically, within the dermatome of the lesion and up to three dermatomes below, and in areas more than three dermatomes below the lesion. Thermal pain thresholds will be measured using a 32 × 32 mm Peltier thermode (TSA 2, MEDOC, Israel), with temperature changes from a 30 °C baseline at 1 °C/s. Heat and cold pain thresholds will be recorded using the method of limits, taking the average of three consecutive stimuli. For safety, maximum and minimum cut-offs will be set at 50 °C and 0 °C, respectively.	Prior to the intervention (Baseline), during the intervention after five sessions (Day 5), after the intervention (Day 10) and one week after the end of the intervention (Day 15)
Patient's Overall Impression of Change	A record of the Global Patient Change Rating Scale will be made at post-treatment and during follow-up with respect to the baseline situation. This scale consists of 7 items ranging from '1 = much better' to '7 = much worse'.	During the intervention after five sessions (Day 5), after the intervention (Day 10) and one week after the end of the intervention (Day 15)
Percentage of participants responding to treatment	The percentage of participants responding to treatment will be evaluated as those who achieve a reduction in pain in the weekly Visual Analog Scale average ≥ 30% and ≥ 50% after treatment and at follow-up.	Baseline (-5 to 0 days), week 1 treatment (days 1-5), week 2 treatment (days 6-10) and post-treatment week (days 11-15).
Pain interference with sleep	Pain interference with sleep will be reported in a daily morning log (Monday to Friday) using the VAS scale (0 mm = pain does not interfere with sleep and 100 mm = pain completely interferes with sleep) The result will be taken as the change from baseline in the weekly mean value of pain interference with sleep.	Baseline (-5 to 0 days), week 1 treatment (days 1-5), week 2 treatment (days 6-10) and post-treatment week (days 11-15).
Spasticity	To this end, the Modified Ashworth Scale will be used to assess resistance to passive movement in the knee joint bilaterally. The Modified Ashworth Scale ranges from a minimum score of 0 to a maximum score of 4 and is used to assess the degree of muscle spasticity. Higher scores indicate worse outcomes.	Prior to the intervention (Baseline), during the intervention after five sessions (Day 5), after the intervention (Day 10) and one week after the end of the intervention (Day 15)
Frequency of spasms	The Penn Spasm Frequency Scale ranges from a minimum score of 0 to a maximum score of 4 and evaluates the frequency of muscle spasms. Higher scores indicate worse outcomes, reflecting more frequent and severe spasms.	Prior to the intervention (Baseline), during the intervention after five sessions (Day 5), after the intervention (Day 10) and one week after the end of the intervention (Day 15)
Adverse events	Adverse effects related to the electrical current will be recorded using an ad hoc questionnaire specifically designed for this study.	Week 1 treatment (days 1-5), week 2 treatment (days 6-10)

Other Outcome Measures

Outcome Measure	Measure Description	Time Frame
Success of blinding	The success of blinding the participants and evaluators will be assessed using a question with five response options: "What type of intervention do you think you have received?": "I strongly believe that I received an experimental treatment / I slightly believe that I received an experimental treatment / I strongly believe that I received a placebo / I slightly believe that I received a placebo / I don't know / No answer	Day 10

Collaborators and Investigators

• Sponsor: University of Castilla-La Mancha
• Collaborators: Hospital Nacional de Parapléjicos de Toledo
• Investigators: Principal Investigator: Juan Avendaño-Coy, PhD, Castilla La Mancha University

Study record dates

Study Major Dates

• Study Start (Actual): January 30, 2026
• Primary Completion (Actual): April 7, 2026
• Study Completion (Actual): April 7, 2026

Study Registration Dates

• First Submitted: November 17, 2025
• First Submitted That Met QC Criteria: January 15, 2026
• First Posted (Actual): January 22, 2026

Study Record Updates

• Last Update Posted (Actual): April 13, 2026
• Last Update Submitted That Met QC Criteria: April 7, 2026
• Last Verified: April 1, 2026

More Information

Terms related to this study

• Keywords: Neuropathic pain; Spinal cord injury; High-frequency alternating current stimulation
• Additional Relevant MeSH Terms: Pain; Neurologic Manifestations; Central Nervous System Diseases; Nervous System Diseases; Wounds and Injuries; Neuromuscular Diseases; Peripheral Nervous System Diseases; Trauma, Nervous System; Spinal Cord Diseases; Pathological Conditions, Signs and Symptoms; Signs and Symptoms; Neuralgia; Spinal Cord Injuries
• Other Study ID Numbers: SCI-Neuromodest-gifto

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No