Closed-Loop Spinal Cord Stimulator Effective for Treatment of Chronic Pain

Results from the EVOKE study (NCT02924129) published inLancet Neurology show that a closed-loop spinal cord stimulation (SCS) system (Evoke System; Saluda Medica, Artarmon, Australia) provided long-term, statistically superior pain relief for individuals with chronic intractable back and leg pain. 

Those treated with closed-loop SCS had statistically superior overall back and leg pain relief with no increase in pain medications compared with open-loop SCS. Of those treated with closed-loop SCS, 83.1% (49/59) had at least 50% pain relief vs 61.0% (36 of 59) for those treated with open-loop SCS (P=.006). For participants using opioid medications, use was reduced or eliminated for 55% (17/31) of participants treated with closed-loop SCS vs 40% (12/30) of those treated with open-loop SCS. 

The closed-loop system maintained spinal cord activation within the therapeutic window 95.2% of the time vs 47% of the time for open-loop SCS.   
 
“This study provides robust evidence of outcomes in the treatment of overall pain, with superior patient responder rates with closed-loop SCS compared to the open-loop SCS control group,” said 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. “Beyond the clinical results, this study has important practical implications as it establishes that individual-specific therapeutic windows can be identified and targeted to maintain spinal cord activation at therapeutic levels and improve care long-term.”

“These are impressive clinical outcomes for comprehensively managing patients’ pain effectively over the long term,” said Lawrence Poree, MD, MPH, PhD, director, Neuromodulation Service, Division of Pain Medicine at University of California, San Francisco (UCSF). “The more than 50% of closed-loop patients who reached high responder status of greater than or equal to 80% reduction in overall pain also demonstrated clinically meaningful changes in secondary patient-reported outcomes, emphasizing the value of achieving this high threshold.”  

The trial enrolled 134 participants, age 18 to 80 years who had chronic, intractable pain of the back and legs. Inclusion criteria included a score of 60 or more out of 100 possible on the Visual Analog Scale (VAS), score of 41 to 80 on the Oswestry Disability Index (ODI), stable use of pain medications, and no prior experience with SCS. 

Participants were randomly assigned to receive closed-loop SCS or fixed-output or open-loop SCS. For both treatment groups, real-time SCS activation was determined from measured evoked compound action potentials (ECAPs).