ASRA Pain Medicine Update

Cite as: Abd-Elsayed A.  The evolution of wireless peripheral nerve stimulation. ASRA News 2021;46. https://doi.org/10.52211/asra080121.050.  

Since its introduction in the late 1960s, peripheral nerve stimulation (PNS) technology has improved dramatically in both the hardware of the device as well as the procedure.¹ The technology did not gain widespread popularity immediately because spinal cord stimulation was more commonly used for targeting peripheral nerves. PNS’s mechanism of action is complex and not completely understood, but gate control is one of the most accepted theories.² Another theory proposes that PNS directly changes the excitability of nerve fibers, inhibiting neurotransmitters and increasing the nociceptive stimulation threshold.³

The first PNS devices were rudimentary, and uniform description of the technical method for placing the electrodes of PNS near the target nerve had not been documented. Older reports described a surgical approach by making an incision near the target nerve. Although surgeons may have felt comfortable with the technique, many pain physicians felt unprepared. Implantable pulse generators (IPGs) were necessary with the early PNS devices, but implanting the IPG was technically challenging because of its bulky nature in relation to the affected nerve.⁴

Recently, the U.S. Food and Drug Administration approved the use of wireless PNS devices, negating the need for IPGs and rendering the procedure less complicated and more suitable for PNS in locations where implanting a generator could be challenging. No surgical incisions are required, so wireless devices can be placed in the office setting, which may increase PNS accessibility and lower costs.

Wireless stimulation conducts high power densities to the leads placed in close approximation to the nerve. The technology had to overcome some challenges associated with the energy transport and tissue conductivity: As the energy moves through tissues, it can get dispersed before reaching the nerve, reducing its efficacy in stimulation.^5,6 However, several published case reports, case series, retrospective studies, and a few randomized trials demonstrate the efficacy of PNS for peripheral neuralgias.^7–10

Implantation of a wireless system entails placing one or more leads close to the nerve using ultrasound guidance. An external antenna and generator are applied to the skin, near the lead, to provide energy which, in turn, will neuromodulate the nerve.

The use of PNS is rapidly expanding in pain practices. Wireless devices provide a new spectrum of neuromodulation and make it possible to neuromodulate any nerve throughout the body. PNS is indicated for chronic pain resulting from underlying peripheral neuralgias. The diagnosis can be made by history, physical examination, neurophysiological testing, and response to diagnostic nerve block, and patients should undergo a psychological evaluation.

The technology will likely continue to evolve with additional advancements in waveform and programming capabilities. Future systems may not require direct contact between the skin and external antenna or generator, providing the ability to stimulate from a distance. With further research, PNS’s scope of use may expand to other indications, including headaches and functional disorders such as urinary incontinence. Wireless PNS may be a potential treatment for a wide variety of disease pathologies. 

Alaa Abd-Elsayed, MD, MPH, FASA, is a physician in the anesthesiology department at the University of Wisconsin School of Medicine and Public Health in Madison.

References

1. Slavin KV. History of peripheral nerve stimulation. In Slavin KV, ed. Peripheral Nerve Stimulation. Basel, Switzerland: Karger; 2011:1–15. 
2. Melzack RA, Wall PD. Pain mechanisms: a new theory. Science 1965;150:971–9. 
3. Ellrich J, Lamp S. Peripheral nerve stimulation inhibits nociceptive processing: an electrophysiological study in healthy volunteers. Neuromodulation 2005;8:225–32. https://doi.org/10.1111/j.1525-1403.2005.00029.x. 
4. Yearwood TL, Perryman LT. Peripheral neurostimulation with a microsize wireless stimulator. In Slavin KV, ed. Stimulation of the Peripheral Nervous System. The Neuromodulation Frontier. Basel, Switzerland: Karger; 2016:168–91.
5. Schuder J, Stephenson H Jr, Townsend J. High-level electromagnetic energy transfer through a closed chest wall. Inst Radio Engrs Int Conv Record 1961;9:119–26. 
6. Deer TR, Pope JE, Kaplan M. A novel method of neurostimulation of the peripheral nervous system: the StimRouter implantable device. Tech Reg Anesth Pain Manag 2012;16(2):113–7. https://doi.org/10.1053/j.trap.2013.02.007. 
7. Dodick DW, Silberstein SD, Reed KL, et al. Safety and efficacy of peripheral nerve stimulation of the occipital nerves for the management of chronic migraine: long-term results from a randomized, multicenter, double-blinded, controlled study. Cephalalgia 2015;35(4):344–58. https://doi.org/10.1177/0333102414543331.
8. Mekhail NA, Estemalik E, Azer G, et al. Safety and efficacy of occipital nerves stimulation for the treatment of chronic migraines: randomized, double-blind, controlled single-center experience. Pain Pract 2017;17(5):669–77. https://doi.org/10.1111/papr.12504
9. Saper JR, Dodick DW, Silberstein SD, et al. Occipital nerve stimulation for the treatment of intractable chronic migraine headache: ONSTIM feasibility study. Cephalalgia 2011;31(3):271–85. https://doi.org/10.1177/0333102410381142
10. Serra G, Marchioretto F. Occipital nerve stimulation for chronic migraine: a randomized trial. Pain Physician 2012;15(3):245–53. https://pubmed.ncbi.nlm.nih.gov/22622909.