This pilot study investigates the effects of reducing pain medication including opioids and anticonvulsants, on spinal cord sensitivity during closed-loop spinal cord stimulation (SCS). Patients with Persistent Spinal Pain Syndrome Type 2 (FBSS/FNSS) will undergo a standard 21-day SCS trial with the Evoke closed-loop system, followed by permanent implantation if successful. Neurophysiological responses (activation plots, conduction velocity, chronaxie, rheobase) and patient-reported outcomes (VAS, activity, sleep, medication intake) will be collected during the trial and up to 6 months after implantation. The goal is to evaluate the relationship between medication tapering and spinal cord sensitivity
Candidate for SCS and scheduled for trial with Evoke system.
Diagnosis of FBSS or FNSS (PSPS-T2).
Gabapentin ≥150 mg
Pregabalin ≥75 mg
Active disruptive psychiatric disorder or condition impacting pain perception or compliance.
Progressive neurological disease (MS, CIDP, progressive arachnoiditis, progressive diabetic neuropathy, brain/spinal tumor, severe spinal stenosis).
Coagulation disorder, platelet dysfunction, progressive vascular disease, or uncontrolled diabetes with procedural risk.
Active systemic or local infection.
Belgian patients selected for spinal cord stimulation (SCS) with Failed Back Surgery Syndrome ( FBSS )
Cohort
Prospective
Spinal Cord Stimulation with Evoke Closed-Loop System
Other interventionAll patients undergo a 21-day trial with Evoke closed-loop SCS. If successful, patients receive a permanent implant. Assessments include activation plots, conduction velocity, chronaxie, rheobase, VAS pain, sleep, activity, and medication intake.
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.
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.
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.
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.
Changes in sleep and activity scores
Participants will be required report their sleep and activity scores using a 10 cm visual analog scale (VAS) where 0 refers to no sleep and no activity at all and 10 refers to sleeping very well through the night and being very active. The resultant VAS score, expressed in cm, will be compared across study visits.
