Neurophysiological Effects of Medication Tapering During Treatment With Spinal Cord Stimulation

Assessment of Neurophysiological Effects of Medication Tapering During Treatment With ECAP Controlled Closed-loop Spinal Cord Stimulation Trial Periods

This study is being conducted in patients who will receive a spinal cord stimulator. This device helps manage chronic neuropathic pain in the trunk and/or limbs. The patients will receive a spinal cord stimulator that is available, notified, and reimbursed in Belgium, which uses a special technology automatically adjusting the intensity of the stimulation. This is called a closed-loop system.

The closed-loop system stimulates the Beta fibers in the spinal cord and simultaneously measures their response. Based on the measured response, the stimulation strength is automatically adjusted. In Belgium, after implant of the leads the effect must first be evalauted for 3 weeks before implanting the Internal Pulse Generator; this is called the trial period. Only if the trial is successful, the patients will receive a permanent implant.

The primary goal of the study is to evaluate how different types of pain medication influence the neurophysiological response of the Beta fibers during spinal cord stimulation. Patients will be divided into three groups, based on the medication they are taking before receiving a spinal cord stimulator:

• patients not taking any pain medication,
• patients taking strong opioids,
• patients taking anticonvulsant medication.

As part of the study, patients will follow the normal clinical schedule. During visits, they will be asked questions about their pain, sleep, medication use, and activity. The study will end one month after the patient receives the permanent spinal cord stimulator implant.

Study Overview

• Status: Recruiting
• Conditions: Persistent Spinal Pain Syndrome Type 2 (PSPS-T2), Lower Spine; Spinal Cord Sensitivity to Neurostimulation; Neurophysiological Sensitivity to Spinal Cord Stimulation
• Intervention / Treatment: Other: Spinal Cord Stimulation with Evoke Closed-Loop System

Detailed Description

Chronic neuropathic pain, particularly in patients with Persistent Spinal Pain Syndrome Type 2 (PSPS-T2, formerly FBSS), remains a major therapeutic challenge. Spinal cord stimulation (SCS) is an established therapy for patients with refractory pain. In Belgium, a 21-day trial period with an externalized epidural lead is mandatory before permanent implantation. During this trial, pain relief, improved sleep, increased activity, and reduction in pain medication intake must be documented in order to qualify for a permanent implant.

The Evoke™ Closed-Loop SCS system (Saluda Medical) is a CE-marked device used within its licensed indication in this study. This system uniquely records Evoked Compound Action Potentials (ECAPs) from the spinal cord, allowing continuous monitoring of neural activation. Closed-loop algorithms adjust stimulation output in real time based on measured ECAPs, thereby aiming to deliver consistent therapy within each patient's therapeutic window.

Recent pilot data and case reports have suggested that reductions in pain medication, particularly strong opioids and anticonvulsants, may alter spinal cord sensitivity to stimulation and ECAP parameters. A prospective pilot study performed at ZAS St. Augustinus Hospital (Belgium) demonstrated measurable changes in spinal cord sensitivity after medication reduction in patients implanted with the Evoke system. These findings suggest that medication tapering may influence neurophysiological responsiveness to SCS and highlight the importance of documenting this relationship systematically.

Study Design

This is a multicenter, open-label, prospective observational study enrolling 50 patients scheduled for SCS with the Evoke closed-loop system. Patients will be stratified into three groups according to baseline pain medication use:

1. Patients with no strong opioids or anticonvulsants (control group, n≈10).
2. Patients with monotherapy of strong opioids (n≈20).
3. Patients with monotherapy of anticonvulsants (n≈20).

All participants will undergo a 3-week trial with one or two epidural leads (T7 level). If the trial is successful, patients will proceed to permanent implantation of the closed-loop stimulator. Assessments will occur at baseline, each week during the trial, at permanent implantation, and one month post-implantation.

Assessments

• Documentation of medication use (daily/weekly via Belgian Pain Platform [BPP] and clinical verification).
• Pain intensity (VAS), sleep, and activity (BPP).
• Activation plots (relationship between current output and ECAP amplitude anchored by patient-reported thresholds and maximum tolerable perception).
• Neurophysiological parameters: conduction velocity, chronaxie, rheobase.

Endpoints

• Primary endpoint: Effect of pain medication group on changes in spinal cord sensitivity to stimulation during the SCS trial, assessed through activation plots and medication intake.
• Secondary endpoints:
• Change in pain intensity (VAS) from baseline to post-trial.
• Reduction in pain medication intake during the trial and one month after implantation.
• Changes in sleep and activity.
• Additional neurophysiological outcomes (conduction velocity, chronaxie, rheobase).

Duration of Participation Each patient will participate from baseline assessment through 1 month after permanent implantation. Study exit occurs either at completion or upon withdrawal (e.g., unsuccessful trial phase or medical reasons).

Burden and Risks The primary and secondary endpoints involve assessments routinely performed in SCS trials. Additional neurophysiological measurements (conduction velocity, chronaxie, rheobase) may add 5-10 minutes to a follow-up visit. Risks are limited to those normally associated with SCS implantation. There is no direct benefit to participants, but data may inform future research and optimization of medication management during SCS therapy.

• Study Type: Observational
• Enrollment (Estimated): 50

Contacts and Locations

• Study Contact: Name: Pieter Van Looy; Phone Number: +32 3 443 48 72; Email: pieter.vanlooy@zas.be

Study Locations

• Belgium
  • Wilrijk, Belgium, 2610
    • Recruiting
    • Brai²n - ZAS Augustinus
    • Contact: Pieter Van Looy; Phone Number: +32 3 443 48 72; Email: pieter.vanlooy@zas.be
    • Principal Investigator: Tony Van Havenbergh, MD

Participation Criteria

Eligibility Criteria

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

• Sampling Method: Probability Sample

Study Population

Belgian patients selected for spinal cord stimulation (SCS) with Persistent Spinal Pain Syndrome Type 2 (lower spine).

Description

Inclusion Criteria:

• Patient deemed a suitable candidate for SCS and routinely scheduled to undergo a trial phase with the Evoke SCS system.
• Diagnosis of Persistent Spinal Pain Syndrome Type 2 (lower spine).
• Current medication use:
• No strong opioids or anticonvulsants, or other analgesics
• Monotherapy with a strong opioid, or
• Monotherapy with an anticonvulsant.
• Willing and able to provide written informed consent to participate, based on a voluntary agreement after a full explanation of the study.
• Age ≥ 18 years at the time of enrollment.
• Willing and able to comply with study requirements, procedures, and follow-up visits.

Exclusion Criteria:

• Evidence of an active disruptive psychological or psychiatric disorder, or other condition significant enough to impact pain perception, compliance with intervention, or ability to evaluate outcomes (as determined by the investigator in consultation with a clinical psychologist).
• Current diagnosis of a progressive neurological disease such as multiple sclerosis, chronic inflammatory demyelinating polyneuropathy, rapidly progressive arachnoiditis, rapidly progressive diabetic peripheral neuropathy, brain or spinal cord tumor, or severe/critical spinal stenosis.
• Current diagnosis or condition such as coagulation disorder, bleeding diathesis, platelet dysfunction, progressive peripheral vascular disease, or uncontrolled diabetes mellitus that presents excess risk for the procedure (as determined by the investigator).
• Active systemic or local infection.
• Pregnancy.
• Within 6 months prior to enrollment: significant untreated addiction to dependency-producing medications or a history of substance abuse (including alcohol or illicit drugs).

Study Plan

How is the study designed?

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Without strong opioids or anticonvulsants or other analgesic drugs; Patients with Persistent Spinal Pain Syndrome Type 2 (PSPS-T2) (lower spine) who are not taking any analgesic medication.	Other: Spinal Cord Stimulation with Evoke Closed-Loop System; All participants will undergo trial stimulation with the Evoke ECAP-controlled closed-loop spinal cord stimulation system, followed by permanent implantation if the trial phase is successful. Neurophysiological parameters (activation plots, conduction velocity, chronaxie, rheobase) will be assessed alongside patient-reported outcomes (pain intensity, sleep, activity, medication use).
Monotherapy with strong opioids; Patients with Persistent Spinal Pain Syndrome Type 2 (PSPS-T2) (lower spine) treated with analgesic monotherapy consisting of strong opioids (e.g., morphine, oxycodone, hydromorphone, fentanyl, methadone, oxymorphone).	Other: Spinal Cord Stimulation with Evoke Closed-Loop System; All participants will undergo trial stimulation with the Evoke ECAP-controlled closed-loop spinal cord stimulation system, followed by permanent implantation if the trial phase is successful. Neurophysiological parameters (activation plots, conduction velocity, chronaxie, rheobase) will be assessed alongside patient-reported outcomes (pain intensity, sleep, activity, medication use).
Monotherapy with anticonvulsants; Patients with Persistent Spinal Pain Syndrome Type 2 (PSPS-T2) (lower spine) treated with analgesic monotherapy consisting of anticonvulsants (e.g., gabapentin, pregabalin, carbamazepine, lamotrigine, topiramate).	Other: Spinal Cord Stimulation with Evoke Closed-Loop System; All participants will undergo trial stimulation with the Evoke ECAP-controlled closed-loop spinal cord stimulation system, followed by permanent implantation if the trial phase is successful. Neurophysiological parameters (activation plots, conduction velocity, chronaxie, rheobase) will be assessed alongside patient-reported outcomes (pain intensity, sleep, activity, medication use).

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Spinal cord sensitivity expressed in ECAP amplitude (µV) as a function of the SCS stimulation amplitude (mA).	Spinal cord sensitivity to spinal cord stimulation (SCS), will be assessed using activation plots describing the relationship between SCS stimulation current (mA) and the resultant Evoked Compound Action Potential (ECAP) amplitude (µV). Change is spinal cord sensitivity (µV/mA) will be compared between the SCS trial phase and at 1 month after permanent implantation across the different medication groups.	From start of SCS trial (baseline) to 1 month after permanent implantation.

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Change in pain intensity measured using a 10 cm Visual Analog Scale (VAS)	Participants will be required report their pain intensity using a 10 cm visual analog scale (VAS) where 0 refers to no pain at all and 10 refers to worst possible pain. The resultant VAS score, expressed in cm, will be compared across study visits.	From start of SCS trial (baseline) to 1 month after permanent implantation.
Change in pain medication intake measured via Belgian Pain Platform (BPP) and clinical verification	Reduction in analgesic medication dose (standardized daily dose or milligram equivalents, if applicable) will be documented using daily/weekly BPP entries and verified by clinical staff. Data will be compared between baseline, end of SCS trial, and 1 month after permanent implantation.	From start of SCS trial (baseline) to 1 month after permanent implantation.
Change in neurophysiological parameters such as conduction velocity (m/sec), rheobase (mA) and chronaxie (µs), measured using the Evoke system's neurophysiological assessment tools.	The following neurophysiological parameters will be measured using the Evoke system's neurophysiological assessment tools.; Conduction velocity (meter/sec): Changes in SCS neural conduction velocity (m/sec) will be compared across baseline, during the SCS trial phase, and 1 month after permanent implantation.; Rheobase (mA): This is the lowest electrical current amplitude (mA) that can stimulate a nerve or muscle. Changes in rheobase will be compared across baseline, during the SCS trial phase, and 1 month after permanent implantation.; Chronaxie (µs): The minimum pulse duration (µs) needed to excite a nerve or muscle when the current strength is set to double the rheobase. Changes in chronaxie will be compared across baseline, during the SCS trial phase, and 1 month after permanent implantation.	From start of SCS trial (baseline) to 1 month after permanent implantation.

Collaborators and Investigators

• Sponsor: Brai²n
• Investigators: Principal Investigator: Tony Van Havenbergh, MD, Brai²n / Department of Neurosurgery, ZAS Augustinus, Antwerp, Belgium

Publications and helpful links

General Publications

• Moens M, Crunelle CL, Putman K, Wuyts E, Bultinck F, Van Puyenbroeck H; PIANISSIMO consortium; Goudman L. Pain medication tapering for patients with Persistent Spinal Pain Syndrome Type II, treated with Spinal Cord Stimulation: A RCT-study protocol of the PIANISSIMO study. PLoS One. 2024 Aug 12;19(8):e0302842. doi: 10.1371/journal.pone.0302842. eCollection 2024.
• Nissen M, Ikaheimo TM, Huttunen J, Leinonen V, Jyrkkanen HK, von Und Zu Fraunberg M. Higher Preimplantation Opioid Doses Associated With Long-Term Spinal Cord Stimulation Failure in 211 Patients With Failed Back Surgery Syndrome. Neuromodulation. 2021 Jan;24(1):102-111. doi: 10.1111/ner.13297. Epub 2020 Oct 19.

Study record dates

Study Major Dates

• Study Start (Actual): February 3, 2025
• Primary Completion (Estimated): February 3, 2027
• Study Completion (Estimated): April 3, 2027

Study Registration Dates

• First Submitted: September 1, 2025
• First Submitted That Met QC Criteria: February 13, 2026
• First Posted (Actual): February 17, 2026

Study Record Updates

• Last Update Posted (Actual): February 17, 2026
• Last Update Submitted That Met QC Criteria: February 13, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Neuromodulation; Opioids; Spinal cord stimulation; Neurophysiology; Anticonvulsants; Closed-loop stimulation; Evoked Compound Action Potentials (ECAPs); Pain medication tapering
• Additional Relevant MeSH Terms: Therapeutics; Physical Therapy Modalities; Rehabilitation; Electric Stimulation Therapy; Spinal Cord Stimulation
• Other Study ID Numbers: Multicentric-ZAS-ECAP-01

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: NO
• IPD Plan Description: The international committee of medical journal editors believes there is an ethical obligtion to share data generated by interventional clinical trials. This is not considered an interventional clinical trial

Drug and device information, study documents

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