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Single Case Reports in Peripheral Nerve Stimulation

Advancements in peripheral neuromodulation may offer an alternative to spinal cord stimulation when previous trials fail.

Editor's Note: Dr. Jameson, who serves as treasurer of the Women in Neuromodulation Committee of the North American Society for Neuromodulation (NAMS), is creator of the Women Neuromodulators Conference, which will hold its inaugural event this June  21-22, 2019 in Coeur d'Alene, Idaho.

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Typically, patients living with chronic pain conditions are started on conservative care that may include medications and physical therapy before they progress into more invasive treatments, such as nerve blocks, epidural injections, nerve cryoablation, or adhesiolysis of the nerves. When these treatments fail, the next step is often a trial of spinal cord stimulation (SCS), which may or may not relieve the entire area of pain distribution.1

Over the past few years, significant advances in SCS technology as it relates to peripheral nerve stimulation (PNS) have allowed clinicians to utilize this therapy much earlier in the treatment paradigm. As a result, patients may be able to avoid side effects of other less efficacious modalities, such as medications, and may find relief from their pain much sooner than may otherwise be offered.

PNS may serve as a viable option in those cases where SCS is unsuitable. The treatment involves placement of electrodes underneath the skin to deliver electric energy to the target nerves or nerve endings in the area of pain distribution. Even though PNS is a relatively new strategy in the neuromodulation realm, the literature to date supports its effective analgesic property.2-7

Deer published a multicenter, randomized, double-blinded, partial crossover study addressing the safety and efficacy of the StimRouterTM neuromodulation system for 94 patients with chronic pain of peripheral nerve origin (upper or lower extremity or trunk).The patients were assigned to A StimRouterTM group (n = 45) or A control group (n = 49). Efficacy was evaluated for three months; safety was evaluated for one year. Primary outcomes included pain relief and safety. At three months, the StimRouterTM group reported 27.2% pain reduction compared to 2.3% in the control group. Fifty-one percent of patients did not follow-up at one year. No serious adverse events were reported related to the device. A significant limitation of the study is the small sample size and large loss of follow-up.

When it was first introduced, PNS was considered to be cumbersome, involving the implantation of a battery. Technologic advances have enabled a minimally invasive approach that uses an external battery. The new wireless system is far more user-friendly for the physician and the patient. Below, two brief retrospective cases describe the successful treatment of refractory shoulder pain and knee pain with peripheral nerve stimulation.

Case #1

Patient is a 71-year-old female with s/p right mastectomy, chronic lymphedema, and right shoulder replacement that presented to the clinic for chronic right shoulder pain that radiated into her scapula and posterior aspect of her right tricep. She reported bicep weakness as well. The patient had significant swelling in this arm and had been diagnosed with lymphedema. She had tried multiple intra-articular injections in the past, as well as pain medications and extensive physical therapy without significant improvement. She reported that her pain was significantly worse with any movement of her shoulder and that she was unable to perform daily activities, such as laundry, cleaning, and shopping.

The patient underwent a diagnostic suprascapular nerve block with 80% relief performed from a posterior approach. She then underwent a peripheral nerve stimulator trial. This trial was also performed from a posterior approach with the patient in the prone position. Two leads were placed in the vicinity of the suprascapular nerve path both above the spine and into the notch (see Figure 1). The leads were tested and found to cover 100% of the patient’s painful distribution.

Two 8-contact trial leads placed in the vicinity of the suprascapular nerve capturing 100% of the painful area.

The patient returned after 5 days of trial reporting 100% relief of her shoulder pain. She was able to move the shoulder and perform activities such as laundry and shopping without pain. She no longer required short-acting narcotics. She was subsequently implanted. At 6-month follow-up, the patient continued to report complete relief. She has since weaned off all narcotics and has been working on improving her mobility of the shoulder with the assistance of physical therapy.

 

Case #2

Patient is a 72-year-old female with a history of a left common peroneal neuropathy as a result of multiple knee surgeries as well as peroneal nerve release. The patient had trialed numerous medications, physical therapy, and SCS without relief. She underwent a diagnostic block with 70% pain relief. She then underwent a peripheral nerve stimulator trial. The lead was placed with the electrodes spanning the width of the fibular head (see Figure 2). The lead was tested and found to cover 100% of the patient’s painful distribution.

The patient returned after 5 days and reported 60% relief of her pain. She was able to walk with far less pain and sleep without interruption. She was subsequently implanted. At six-month follow-up, she reported 70% relief of her symptoms with improved function and a 50% decrease in her opioid consumption.

One 8-contact trial lead placed over the fibular head capturing 100% of the painful area.

 

Discussion

Wireless PNS has been shown to provide effective pain control in a limited target area.9-10 The system eliminates many of the drawbacks experienced with older PNS technology and allows for a unique way to target the peripheral nerves. Wireless PNS devices do not recruit motor fibers and, therefore, do not cause contraction or spasm of the muscles.8 In addition, because there is no implanted pulse generator, many potential complications, such as persistent pocket site pain, may be avoided.

Adverse events related to PNS typically include infection and lead migration.11 Fortunately, most of these complications are minor and do not represent any threat to the life or neurological function of the patient.11 Because of the simplicity of insertion, low adverse events, and cosmetic acceptability compared to present day systems, minimally invasive wireless technology may provide an inviting treatment option for comparable pain relief in patients with a wide variety of peripheral nerve symptoms. The technical aspect of the procedure mirrors many other procedures. With the improved technology of the new symptoms, the ease of placement has improved and can be easily integrated into interventional pain practices.

Last updated on: May 29, 2019
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