It’s been too long since we provided an update about the pain-management benefits of peripheral nerve simulation (PNS). To refresh your memory, this technology uses implanted electrodes to directly stimulate the nerves at the furthest reaches of the residual limb—ie, closest to the amputation site. The approach has shown promise in managing both short-term post-amputation pain and chronic, long-term pain, but it’s still relatively new and investigational.
Multiple initiatives related to PNS have been making headlines lately, and it’s all good news. The biggest and best story on the PNS front comes courtesy of Veterans Affairs, which recently published some boffo clinical results. So let’s begin with that item:
VA Study Shows PNS Relieves Post-Amputation Pain
The bulk of the available research data on PNS is focused on chronic pain that’s unrelated to limb loss (e.g. back pain, CRPS, arthritis, etc.). This spring, the VA released one of the few studies that measures the effects of PNS on amputees in particular. Published in the journal Pain Management, the paper showed that amputees receiving PNS as part of their post-amputation rehab experienced less pain and required fewer opioid medications than amputees who received standard post-amputation care, sans PNS.
The study used a commercially available PNS system developed by SPR Therapeutics. Dubbed the SPRINT system, it uses temporary implants that only stay in the patient’s body for 60 days. SPRINT implants do not wrap directly around the nerve endings, as in other forms of PNS, and users can control the intensity (but not the frequency) of nerve stimulation.
The VA’s study cohort included 16 participants, all of them veterans. Eight of the subjects had Sprint’s PNS system implanted as part of their post-amputation rehabilitation; the other eight, representing the control group, followed the VA’s standard rehab protocols. All but one of the participants were men, and all had lower-limb amputations (9 above-knee, 7 below-knee). All but two of the subjects required amputation as a complication of diabetes or another vascular disease. The participants’ average age was 72, and about a third of them were already using opioids to manage pain prior to their amputation.
Let’s get to the data: In the PNS group, 100 percent of the patients reported a pain reduction of 50 percent or more after eight weeks of rehab. Only half the patients in the control group experienced the same level of pain relief. Even more striking was the pattern of opioid dependence. Within the PNS group, opioid doses decreased by 60 percent compared to pre-operative levels, whereas the control group witnessed a 200 percent increase. A third striking feature of this data: One-fourth of the patients in the control group had to be readmitted to the hospital; none of the PNS patients required rehospitalization.
While the study was focused on the 12 weeks immediately following amputation, the authors argue that those are critical weeks with long-lasting effects. Multiple studies have established that poorly managed pain correlates with unsuccessful prosthetic adaptation, lack of mobility, adverse employment outcomes, and overall low quality of life. “Achieving lower pain scores at earlier time points may help improve rehabilitation outcomes for amputees,” they conclude.
The authors add that further research is needed involving larger cohorts of patients. But this small study’s data are highly suggestive—particularly the enormous impact PNS appears to have in reducing opioid dependence. A quick check at clinicaltrials.gov showed several active projects investigating PNS’s potential benefits for amputees, including one at the University of Michigan that is actively recruiting.
PNS Device for Neuropathic Foot Pain Gets FDA Clearance
A California company called DyAnsys got FDA clearance last month for a PNS-based device engineered specifically to blunt the pangs of peripheral nerve pain stemming from diabetes.
The product, known as First Relief, operates on a basis not unlike the theory underpinning shiatsu massage. It delivers nerve stimulation to a specific pressure point (or points) on the ear, which maps to the part of the body where your pain is actually located. The device tucks behind your ear like a hearing aid, delivering pulses continuously over a period of days.
If (like us) you’re having a hard time understanding how a current flowing through your ear can ease pain in your feet, maybe it’s best to just focus on the data. A double-blind clinical trial involving 63 patients showed marked decreases in overall pain, pain-related insomnia, anxiety, and functional limitations. View the results for yourself.
While First Relief isn’t commercially available yet, it’s expected to hit the market soon. We’ll be keeping tabs on DyAnsys’s website for announcements.
Mayo Clinic Publishes PNS Guidelines for Pain Management Teams
“As PNS has increased in frequency of use, there has been a unique opportunity and need for a higher degree of [nurse practitioner and physician assistant] involvement in the care and management of this patient population,” notes the introduction of this paper published last week in the Journal of Pain Research. Patients often get more face-time with NPs and PAs than with the actual doctor, the authors note, so it’s imperative for these care-team members to have a good working knowledge of PNS. And it’s just as important for prospective patients to have the same knowledge, so they can investigate PNS in true partnership with their provider.
That begins with recognizing the categories of patients who are well-suited to get relief from PNS. The paper then offers guidelines for evaluating, on a case-by-case basis, whether PNS has a decent chance of success in achieving the patient’s goals. “Practitioners should be able to have an informed discussion with patients regarding currently available PNS systems and weigh the risks versus benefits of each system for the specific needs of the patient,” the article notes. “Once it is certain the patient is a good candidate for PNS and the patient agrees they are interested in this therapy, an appointment can be arranged with a PNS implanting physician.”
Further sections of the paper establish best practices for monitoring the effectiveness of PNS systems after they’re activated, troubleshooting any side effects that may occur, and preparing patients to take ownership of their own pain-management over the medium and long term. The mere fact the Mayo Clinic invested resources in a publication of this type shows how rapidly PNS is moving into the mainstream. The authors conclude: “It will be imperative, moving forward, . . . to stay up to date on evidence-based research regarding PNS therapies, best practices related to care of PNS patients and new PNS device offerings.”