Spinal Cord and Peripheral Nerve Stimulation for Painful Disorders

Mechanism of Action of Peripheral Nerve Stimulation for Chronic Pain: A Narrative Review

The use of stimulation of peripheral nerves to test or treat various medical disorders has been prevalent for a long time. Over the last few years, there has been growing evidence for the use of peripheral nerve stimulation (PNS) for treating a myriad of chronic pain conditions such as limb mononeuropathies, nerve entrapments, peripheral nerve injuries, phantom limb pain, complex regional pain syndrome, back pain, and even fibromyalgia. The ease of placement of a minimally invasive electrode via percutaneous approach in the close vicinity of the nerve and the ability to target various nerves have led to its widespread use and compliance. While most of the mechanism behind its role in neuromodulation is largely unknown, the gate control theory proposed by Melzack and Wall in the 1960s has been the mainstay for understanding its mechanism of action. In this review article, the authors performed a literature review to discuss the mechanism of action of PNS and discuss its safety and usefulness in treating chronic pain. The authors also discuss current PNS devices available in the market today.

Peripheral Nerve Stimulation for Lower Extremity Pain

Peripheral nerve stimulation (PNS) is rapidly increasing in use. This interventional pain treatment modality involves modulating peripheral nerves for a variety of chronic pain conditions. This review evaluated its use specifically in the context of chronic lower extremity pain. Studies continue to elucidate the utility of PNS and better define indications, contraindications, as well as short- and long-term benefits of the procedure for the lower extremity. While large, prospective evidence is still lacking, the best available evidence suggests that improvements may be seen in pain scores, functionality, and opioid consumption. Overall, evidence synthesis suggests that PNS for the lower extremities may be a viable option for patients with chronic lower extremity pain.

Incidence of Temporary Peripheral Nerve Stimulator Lead Tip Retention: A Retrospective Review of 80 Lead Placements

OBJECTIVES

The primary objective of this study was to determine the current rate of lead fracture during temporary percutaneous peripheral nerve stimulator (PNS) lead removal at the Mayo Clinic Rochester Division of Pain Medicine.

MATERIALS AND METHODS

A retrospective review of electronic medical records was performed for patients implanted with a temporary percutaneous PNS device between January 1, 2018, and December 31, 2020. Patients were included if they underwent temporary percutaneous PNS system implant, with planned lead removal at 60 days. Data collection included date of implant, diagnosis, peripheral nerve target(s), number of leads, and lead tip status at the time of removal (intact vs fractured).

RESULTS

Fifty patients underwent a total of 80 temporary percutaneous PNS leads placed during the time frame analyzed. Of the 80 temporary percutaneous PNS leads implanted, there were five lead fractures at the time of intentional lead removal.

CONCLUSIONS

This retrospective review of 50 patients with 80 temporary percutaneous PNS leads implanted for chronic peripheral neuropathic pain resulted in a 6.25% rate of retained lead fragment at the time of lead removal by the provider at the end of 60-day treatment. This fracture and retention rate is consistent with previous published retrospective data on PNS, which has shown a 3% to 21% lead fracture rate during intentional lead removal.

Successful application of spinal cord stimulation in a patient with refractory bilateral meralgia paresthetica

We present a 38-year-old morbidly obese male who presented with functionally limiting bilateral anterior thigh pain consistent with meralgia paresthetica. His symptoms had been unresponsive to conservative measures which included physical therapy, oral medications and multiple nerve blocks. Patient underwent a trial of spinal cord stimulation (SCS), experiencing 70% of pain relief. He then underwent permanent SCS implant. At subsequent follow-ups 3 and 6 months later, he continued to report 70% improvement of his pain, as well as improved function and quality of life. To our knowledge, this is only the second reported case of successful treatment of meralgia paresthetica with SCS, and the first in a morbidly obese patient.

Peripheral Nerve Stimulation: The Evolution in Pain Medicine

Electrical stimulation of peripheral nerves has been utilized for a variety of indications for over five decades [...].

Peripheral Nerve Stimulation for the Treatment of Meralgia Paresthetica

Meralgia paresthetica is a condition caused by entrapment of the lateral femoral cutaneous nerve at the level of the inguinal ligament. This nerve is a purely sensory nerve and provides innervation to the anterolateral portion of the thigh. The condition can lead to numbness, paresthesia, dysesthesia, and pain over the anterolateral aspect of the thigh, which are exacerbated with walking, standing, and hip extension. First-line treatment for MP includes conservative measures such as weight loss and eliminating tight-fitted clothing. Neuropathic pain medications and corticosteroid injections are also treatment options for some patients with significant pain complaints. In more refractory cases, surgical intervention can be considered. Peripheral nerve stimulation has also been shown to be a helpful treatment modality for patients with refractory meralgia paresthetica. Here we report our experience utilizing peripheral nerve stimulation in patients with significant pain complaints related to refractory meralgia paresthetica.

Astrocytes contribute to pain gating in the spinal cord

Various pain therapies have been developed on the basis of the gate control theory of pain, which postulates that nonpainful sensory inputs mediated by large-diameter afferent fibers (Aβ-fibers) can attenuate noxious signals relayed to the brain. To date, this theory has focused only on neuronal mechanisms. Here, we identified an unprecedented function of astrocytes in the gating of nociceptive signals transmitted by neurokinin 1 receptor–positive (NK1R+) projection neurons in the spinal cord. Electrical stimulation of peripheral Aβ-fibers in naïve mice activated spinal astrocytes, which in turn induced long-term depression (LTD) in NK1R+ neurons and antinociception through activation of endogenous adenosinergic mechanisms. Suppression of astrocyte activation by pharmacologic, chemogenetic, and optogenetic manipulations blocked the induction of LTD in NK1R+ neurons and pain inhibition by Aβ-fiber stimulation. Collectively, our study introduces astrocytes as an important component of pain gating by activation of Aβ-fibers, which thus exert nonneuronal control of pain.

Mechanism of Action of Peripheral Nerve Stimulation

PURPOSE OF REVIEW

The number of applications for peripheral nerve stimulation (PNS) in the pain management field is ever-growing. With the increasing number of clinical applications for peripheral nerve stimulation, the purpose of this article is to review the mechanism of action surrounding PNS, the recent literature from January 2018 to January 2021, and pertinent clinical outcomes.

RECENT FINDINGS

The authors searched articles identified from PubMed (January 2018-January 2021), Cochrane Central Register of Controlled Trials databases (January 2018-January 2021), and Scopus (January 2018-January 2021) databases, and manually searched references of identified publications. Broad MeSH terms and Boolean operators were queried in each search, including the following terms and their respective synonyms: peripheral nerve stimulation, mechanism of action, biochemical pathway, and pain pathway. 15 consensus articles were selected for in-depth review and inclusion for qualitative analysis. PNS may activate and modulate higher central nervous system (CNS) centers, including the dorsal lateral prefrontal cortex, somatosensory cortex, anterior cingulate cortex, and parahippocampal areas. Neuromodulatory effects from PNS may also extend into the spinal columns. Also, PNS may lead to changes in endogenous neurotransmitters and affect the plasticity of NMDA pathways.

Peripheral Nerve Stimulation: A New Treatment for Meralgia Paresthetica

BACKGROUND

Meralgia paresthetica is a condition caused by entrapment of the lateral femoral cutaneous nerve that leads to paresthesia along the anterolateral portion of the thigh. Because of advancements in neuromodulation, peripheral nerve stimulation (PNS) has been considered a new treatment option for meralgia paresthetica. Newer PNS technology targets peripheral nerves directly yet in a minimally invasive manner. We report a case in which a PNS device provided more than 12 months of complete pain relief in a patient with meralgia paresthetica and helped the patient avoid a neurolysis procedure.

CASE PRESENTATION

A 57-year-old male presented to clinic with a 6-year history of "painful numbness [and] burning" along the right lateral thigh. He rated his pain as 8 out of 10, which decreased to a rating of 2 out of 10 with the use of gabapentin, but unwanted side effects motivated him to seek alternative treatment. On the basis of his history, physical exam, and imaging results, he was diagnosed with meralgia paresthetica. He was offered neurolysis; however, after seeing a pain specialist, he agreed to the implantation of a SPRINT peripheral nerve stimulator. After the implantation procedure, his pain reduced to 0 out of 10, and his quality of life improved, with better sleep and less somnolence. The device was removed after 60 days, as planned. He continued to have complete resolution of pain at 12 months after the date of device implantation.

CONCLUSION

With recent advancements, PNS can be used to treat meralgia paresthetica in an effective yet minimally invasive manner. As newer PNS technology becomes more familiar to physicians and pain specialists, it is likely to be used as a mainstay treatment for meralgia paresthetica.