Peripheral Nerve Stimulation Education and Psychological Evaluation

What is peripheral nerve stimulation?

It is important to educate the patient on all aspects of the implanted device, including expectation for pain relief, improved function, quality of life, and magnetic resonance imaging (MRI) compatibility. These should be clearly defined and, if possible, measured prior to and after implantation. Specific goals can be set and written down if necessary. The clinician should clearly state that total pain relief or return to pain state prior to disease state is not the expectation. Depending on site of implantation and device used, half of patients should expect approximately 50% pain relief.

In a small, 28-patient, 60-day trial with disposable PNS systems for postamputation pain, 67% of participants reported 50% or greater relief. In a case series targeting medial branch nerves for nonspecific low back pain, 6 of the 9 participants achieved an average of 80% pain relief. At 12-month follow-up, these same responders had greater than 50% pain reduction, significant reductions in disability, and improved quality of life, and 100% of participants reported satisfaction with the device.

Depending on your patient’s coping style, it may be beneficial to show a sample or pictures of the implant itself and the charging device if applicable. A brief explanation of the mechanism by which the patient will receive relief should also be covered. For example, the patient can be informed that PNS may work via a combination of blocking pain signals in nerves as well as decreasing concentrations of substances that contribute to pain.

Patient ambassador programs may also be helpful. Patients who have been treated with the device may share their experiences, both positive and negative, with the potential patient. If using an ambassador program, it is important to ensure voluntary participation and adherence to the Health Insurance Portability and Accountability Act. While there is no direct evidence for this practice, industry device companies and physicians’ offices have found that patient-to-patient interaction can offer insight into life with PNS. Keeping a log of patients who are willing to be ambassadors can be helpful. Device companies may also have an ambassador program that can be utilized.

Education should be provided on the definition of a successful trial. While this definition may differ from clinician to clinician, the Neuromodulation Appropriateness Consensus Committee (NACC) recommends that a successful trial be defined as the patient experiencing 50% or more pain relief during the trial. Ideally this reduction should occur in conjunction with increased activity and reduction in any opioid medications. Clinicians may choose to use objective measures to define success, such as walking tolerance, sleep, and ability to perform activities of daily living. These goals should be addressed with the patient prior to proceeding with a trial.

In addition, the basic components of the device should be explained. While devices differ, each has three basic components: a power source electrodes that are used to deliver the pulses to the peripheral nerve, and a remote-control device that allows the patient to adjust the settings of the device.

Patients also need to be educated about potential adverse events, including subcutaneous hematomas, seromas, skin erosions, pain and numbness at the implanted pulse generator site (if applicable), allergic reactions to surgical material, pruritus, infection, unwanted paresthesia, and muscle cramping. In addition, the chances of lead migration also need to be discussed. Large case series reported lead migration rates of between 2% and 15%. The same study reported lead fracture rates and lead infection rates as 2% to 5% and 1% to 6%, respectively.

What is peripheral nerve stimulation used for? What can and cannot peripheral nerve stimulation accomplish?

PNS interventions are seldom curative, and should be pursued as part of a multidisciplinary approach to chronic pain. Patients should expect to see objective changes in or stabilization of functional goals such as maintenance of or return to work status, improved activities of daily living, decreased use of medications, and measurable functional gains such as increased range of motion or muscle strength. Ideally, a patient would commit to an exercise or physical therapy program that monitors progress and functional improvement prior to and after implantation. This should be well documented and can serve the patient by showing clear functional goals achieved by PNS. It should also be explained that PNS therapies should not be relied on as a curative therapy and may not decrease pain.

Conditions treated with PNS can be discussed with the patient, including peripheral nerve and plexus pain, amputation pain, back pain, and headache and facial pain, as well as shoulder and limb pain (including post stroke pain). The clinician should be able to provide basic information about outcomes in each of these conditions ( Table 7.1 ).

There are certain circumstances in which caution should be exercised before considering proceeding with PNS. According to the NACC of the International Neuromodulation Society Using U.S. Preventative Task Force Criteria, when considering PNS for patients with active malignancies who may require MRI scanning to monitor disease progress, the use of neurostimulation is warranted for patients with moderate to severe neuropathic or mixed pain who are in remission or who have tumors expected to grow at a slow and often painful rate. The group rated the strength of the evidence as moderate. (Note that this recommendation did not consider stimulators that were MRI-compatible.) Furthermore, the NACC states that current data do not support the use of PNS in patients who cannot be taken off their anticoagulants or bridged safely for the proper duration of the trial of surgery.

What happens before the procedure?

Multiple steps should be taken prior to the procedure. Many physicians have adopted the NACC’s recommendations for infection control. Based on this guidance, education regarding smoking cessation should be provided. This education should include the increased risk of postoperative infection rate in smokers. Furthermore, reviewing and discussing any patient comorbidities is essential. Patients should be aware of the impact of comorbidities on the success of the treatment. For example, discussing the importance of tight glycemic control is necessary in patients with a history of diabetes mellitus. This discussion should include the increased risk of postoperative infection. If warranted, the impact of uncontrolled depression or anxiety on treatment outcomes should also be considered.

In addition, preoperative checklists can be helpful to address any medical issues and to evaluate proper implant location planning. Checklist items may be used to inquire about any active infections or history of prior infections requiring antibiotic prophylaxis, discussion of discontinuation of anticoagulation and any needed cardiac clearance, and review of potential trial and implant sites for infection or any inflammatory processes. Checklists are also useful to ensure patients have an understanding of the procedural process ( Box 7.1 ).