Spinalcord stimulation (SCS) with a closed-loop system that uses recorded evokedcompound action potentials (ECAPs) is superior to a fixed-output, open-loopsystem for patients with chronic back and leg pain, according to study resultspublished in Lancet Neurology.

While SCS has been a well-established treatment for chronic pain for more than 50 years, the results are suboptimal. The major challenge in SCS is the changing distance between the stimulating electrodes and their spinal cord target, because while the spinal cord changes position within the cerebrospinal fluid with every movement, the electrode is fixed in the epidural space.

Theavailable SCS systems are open-loop systems and do not measure or adjust forchanges in the electrical field strength reaching the spinal cord, leading tounpredictable inhibition of pain-processing pathways. An ECAP-controlled,closed-loop system can change the stimulation output current as needed.

Thegoal of the current double-blind, randomized-controlled study was to comparethe safety and efficacy of ECAP-controlled, closed loop SCS with that of fixed-output,open-loop SCS for patients with chronic back and leg pain.

Thestudy included patients with chronic intractable pain of the back and legs whowere refractory to conservative therapy and on stable medications. Theparticipants were randomly assigned to receive ECAP-controlled closed-loop SCSor fixed-output, open-loop SCS.

Theprimary objective was to show noninferiority, and then to test the superiority,of closed-loop SCS compared with open-loop SCS. The primary outcome, tested at3 and 12 months after the permanent implant, was a composite outcome thatincluded the proportion of patients who responded to SCS with a 50% reductionin overall back and leg pain as determined by visual analog scale score, withno increase in analgesics.

Thestudy enrolled 134 participants: 67 were assigned to closed-loop(investigational) group and 67 to open-loop (control) group.

Inthe intent-to-treat population, the percentage of responders with 50% reductionin overall back and leg pain and no increase in pain medications at 3 monthswas 82.3% (51 of 62 patients) in the closed-loop group vs 60.3% (38 of 63 patients)in the open-loop group. At 12 months the response rates were 83.1% (49 of 59patients) and 61.0% (36 of 59 patients), respectively. Noninferiority was demonstratedat 3 months (P <.0001) and 12 months (P <.0001), as wassuperiority (3 months, P =.0052; 12 months, P =.0060).

Thetype, nature, and severity of adverse events were similar between treatmentgroups. There were 23 adverse events in 13 patients (19%) in the closed-loopgroup and 11 adverse events in 11 patients (16%) in the open-loop group. Themost common study-related adverse events were lead migration, implantable pulsegenerator pocket pain and muscle spasm or cramps.

LawrencePoree, MD, MPH, PhD, Director of Neuromodulation Service, Division of PainMedicine at University of California, San Francisco and the senior author ofthe study commented that these are impressive clinical outcomes forcomprehensively managing patients pain effectively over the long term. Themore than 50 percent of closed-loop patients who reached high responder statusof greater than or equal to 80% reduction in overall pain also demonstratedclinically meaningful changes in secondary patient-reported outcomes,emphasizing the value of achieving this high threshold.

Closed-loopspinal cord stimulation provided greater levels of spinal cord activation,within the therapeutic window, which suggests a mechanistic explanation for thesuperior results. Although preliminary, we believe this is the first step inthe field of neuromodulation, moving towards a mechanism-based, personalisedtherapy founded on an objective outcome measure, concluded theresearchers.

Disclosure: This clinical trial was supported by Saluda Medical. Please see the original reference for a full list of authors disclosures.

Reference

Mekhail N, Levy RM, Deer TR, et al. Long-term safety and efficacy of closed-loop spinal cord stimulation to treat chronic back and leg pain (Evoke): a double-blind, randomised, controlled trial [published online ahead of print, 2019 Dec 20]. Lancet Neurol. 2019;S1474-4422(19)30414-4. doi:10.1016/S1474-4422(19)30414-4

This is part 1 of a 2 part feature. In part 2 Neurology Advisor interviews Nagy Mekhail, MD, PhD, Professor at the Cleveland Clinic Lerner College of Medicine, Director of Evidence-Based Pain Medicine Research and Education in the Department of Pain Management at the Cleveland Clinic, and first author of this study.

See the article here:
Closed-Loop Spinal Cord Stimulation for the Management of Chronic Back and Leg Pain [Part 1] - Neurology Advisor