Pain Doctors Offer Varied Opinions on PNS Applications

by Jeremy Koff, senior consulting editor

November 2024 issue

Peripheral nerve stimulation has rapidly gained traction as a promising intervention for treating chronic pain conditions, showing potential to improve patient outcomes with less reliance on pharmacologic treatments. Despite this rise in interest, considerable variability remains in its clinical application. A recent survey of 94 pain physicians, published in the journal Neuromodulation, sought to shed light on the clinical practices surrounding PNS, providing an important snapshot of current trends and revealing the areas in need of further standardization and validation.

This article summarizes those results while integrating previous PNS market research conducted by Neurotech Reports and industry experience from the editorial staff.

Patient Selection and Targeted Conditions

The survey was designed by Jay Karri from the University of Maryland, Amitabh Gulati, from Sloan Kettering in New York, and Ryan D’Souza from the Mayo Clinic, and highlights that while PNS is widely used to treat both nociceptive and neuropathic pain, significant variation exists in its application depending on the specific pain etiology. For nociceptive conditions, the authors found that PNS is most commonly used to treat major joint osteoarthritis (77.7%) and chronic axial low back pain (64.9%). However, the application for chronic neck pain remains divided, with only 50% of respondents endorsing its use.

Neuropathic pain conditions, however, see more consistent use of PNS, with 95% of physicians utilizing it for peripheral neuralgias and 78% for pericranial neuralgias. Interestingly, cancer-related neuropathic pain, despite being an emerging area, saw 65% reporting its use, indicating room for growth in this area.

Target Nerves

The article looked at specific nerve targets and frequency of those surveyed applying PNS to target nerves. For treating knee osteoarthritis, the primary targets included the supero-medial genicular (49% of those surveyed), supero-lateral genicular (41%), and saphenous (37%) nerves, followed by the infero-medial genicular (24%), femoral (19%), and infrapatellar branch of the saphenous nerve (15%). For treating ankle/foot CRPS with PNS, the most common targets were sciatic (54%), tibial (51%), and common peroneal (29%). For treating diffuse wrist/hand CRPS with PNS, the primary targets were terminal nerves in the proximal arm (57%), terminal nerves in the distal arm (35%), brachial plexus trunks in the supraclavicular region (26%), and brachial plexus cords in the infraclavicular region (22%).

Neurotech Reports’ own research on PNS supports many of these use cases. In unpublished market research by Neurotech Reports, we found the top PNS nerve targets for chronic pain to be the axillary nerve, followed by saphenous, intercostal, sciatic, suprascular, illionguinal and tibial nerve.

Nerve Blocks Prior to PNS

A significant proportion of respondents (76%) routinely perform nerve blocks before proceeding with PNS, using it as a tool to confirm the anatomical coverage of the painful area. These blocks are seen as a useful step for both diagnostic purposes and insurance requirements. Notably, 84% of respondents identified confirming coverage as a primary reason for using nerve blocks before PNS.

PNS vs. Other Neuromodulation Therapies

When it comes to treating CRPS, physicians often prefer PNS over other neuromodulation therapies. More than 71% of respondents indicated they would apply PNS before considering intrathecal drug delivery systems, while 56% and 52% favored PNS over dorsal root ganglion stimulation and spinal cord stimulation, respectively. This preference may reflect the safety profile and less invasive nature of PNS, as compared to other neuromodulation modalities.

PNS vs. Ablation

In the article, the authors reported that 19% of respondents would use RF ablation prior to PNS for treating nonsurgical lower back pain. Our research in this area yielded very mixed opinions on ablation vs PNS. “Radiofrequency ablation is severing the nerve supply to the stabilizing muscles of the spinal column, which has pretty profound negative effects that we see clinically,” said one orthopedic spine surgeon interviewed. But another ortho stated, “I think the nerves re-grow anyway. They are so small, so terminal that even though you destroy them, you don’t destroy everything. And at some point they re-grow after six months to a year or so. I don’t think it’s a big issue.” And then there is the business perspective, as stated by one implanter we spoke to: “Anything that you implant as a device is reimbursed a lot better than something you stick in as a needle.”

Imaging and Stimulation Modalities

Imaging guidance plays a crucial role in PNS procedures, and the authors reveal that ultrasound (75%) and fluoroscopy (67%) are the most commonly used methods for localizing peripheral nerve targets. Interestingly, electrical nerve stimulation is used by only 17% of respondents, suggesting that while it remains an available tool, most practitioners rely on imaging for precision.

Adverse Events and Practice Adjustments

Regarding adverse events, most clinicians reported they would not change their PNS utilization following minor complications, such as skin reactions or minor infections. However, 59% would reduce PNS usage if faced with major complications, such as lead fractures or skin erosion. This reflects the relatively favorable safety profile of PNS, but also highlights areas where improvements in device durability could further boost clinical confidence.

Form Factor

The article did not address form factor, which according to Neurotech Reports’ proprietary research, plays a significant role in the target nerve and which PNS system clinicians adopted.

In our market research, IPG size and wearability of externals directed doctors to use one system or another for a target nerve. The form factor also impacted the type of pain targeted with a particular system. One neurosurgeon we spoke to summarized it succinctly: “Patients that have, not a permanent pain, not the acute pain, not the chronic pain, but the intermediate pain, see a pain that will last for weeks but has an end to it. Like for instance, somebody has a shoulder replacement. They need to do physical therapy in the recovery, and temporary PNS could enhance the physical therapy. I’m not talking about the implantable one, I’m talking about the injectable PNS.

Market Growth

The market growth of the PNS sector was outside the scope of the published survey. SCS systems have been used for decades off label for PNS applications. But with new dedicated PNS systems coming on the market, that is likely to change. One interventional anesthesiologist we spoke to said that dedicated PNS systems are taking about 10 to 15 percent of their practice in terms of neuromodulation but they expect that to increase over the next couple years.” Neurotech Reports projects that the PNS market will grow at a compound rate of 41% between 2023 and 2028.

Conclusions and Future Directions

The survey results underscore the significant variability in PNS practices and highlight the need for more standardized clinical guidelines. Future research should focus on understanding the drivers behind this variability and work toward developing more robust frameworks for patient selection, procedural approaches, and long-term management of PNS patients. Given that some PNS systems are suitable for acute, “intermediate” pain, and post-surgical recovery, more work is needed in these promising areas for PNS.

The rapid expansion of PNS technologies—and their demonstrated efficacy across diverse pain conditions— will require a unified approach to PNS utilization will be key to optimizing outcomes and ensuring broader adoption of this promising therapy. As noted by NANS president Corey Hunter, “I hope that commercial payers in the U.S. will finally accept that PNS has a place in the treatment of chronic pain and should no longer be considered “experimental.” With increasing support by the implant community, the PNS future is bright.