Peripheral Nerve Stimulator

Anatomy and Physiology

The determination for the appropriate location for the placement of a peripheral nerve stimulator lead depends on the area in which analgesia is necessary. Because the anatomy and approach to this technique are similar to that of continuous peripheral nerve block, percutaneous peripheral nerve stimulator placement could theoretically be in any location commonly used for peripheral nerve block.[12] Cadaveric studies have shown that tibial nerve, peroneal nerve, sciatic nerve, and lateral sural nerve are all acceptable locations in the lower extremity and radial nerve, median nerve, and ulnar nerve would be feasible locations for peripheral nerve stimulator placement in the upper extremity.[13][11] However, peripheral nerve stimulation may be used effectively at other sites. The ideal placement of a peripheral nerve stimulator lead is parallel to a nerve.

Indications

Indications of a peripheral nerve stimulator include all conditions that result in neuropathic pain in a dermatomal distribution of a particular nerve. Examples of such conditions are but not limited to-

1) Median/ulnar/radial neuropathy

2) Occipital neuralgia [14][15]

3) Cluneal nerve pain

4) Pudendal neuralgia

5) Femoral/sciatic/obturator neuropathy

6) Brachial/lumbar plexus neuropathy

7) Meralgia paresthetica

8) Lumbar/cervical radiculitis

9) Intercostal neuralgia

Contraindications

Absolute contraindications to the placement of a peripheral nerve stimulator include allergy to any component of the stimulator or patient refusal. Relative contraindications include coagulopathy and local infection near the access site.[12]

Equipment

Necessary equipment for placing a peripheral nerve stimulator include ultrasound for identification of target nerve, equipment to maintain sterility of the procedure, appropriate needles for monopolar lead placement, and a sterile dressing. Any ultrasound machine with either a curved array transducer or linear array transducer may be used.[13] A sterile transducer sleeve should be utilized for this procedure as well. A small volume of local anesthetic for skin anesthesia is the recommended procedure. A monopolar needle electrode for testing optimal lead placement is also recommended. An introducer needle and stimulator lead serve to place the peripheral nerve stimulator. A machine for delivering electrical stimulation is necessary for testing the lead and providing continuous stimulation. The procedure requires the use of sterile gloves, surgical cap, and mask at a minimum and skin prep with chlorhexidine is recommended — and placement of a sterile dressing over the lead to maintain its position is also standard procedure.

Personnel

Personnel trained in placement of peripheral nerve stimulators can typically perform this procedure alone or with a single assistant. Anesthesiologists, pain management providers, or certified registered nurse anesthetists generally perform this procedure.

Preparation

Preparation for this procedure begins with obtaining informed consent from the patient.  The patient’s anatomy is assessed using ultrasound, and the desired location for lead placement is determined. The skin is prepped with alcohol containing solution, ideally chlorhexidine unless a contraindication to its use is present. Personnel will don personal protective equipment, sterile gloves and place sterile drapes to expose the insertion site.

Technique or Treatment

The provision of anesthesia to the insertion site is by injecting a local anesthetic under ultrasound guidance along the track of proposed needle insertion. A skin wheal is raised to ensure adequate cutaneous anesthesia. A monopolar needle is inserted under ultrasound guidance up to 0.5cm to 1cm from the target nerve. An electrical stimulator is attached to the needle to deliver a test stimulation. Inducing uncomfortable local sensations is associated with superficial needle placement, and distal discomfort or muscle contractions are associated with too deep of needle placement. Readjustment of the stimulator needle continues until muscle contractions and discomfort are no longer present. The monopolar needle then gets withdrawn and the introducer needle pre-loaded with the stimulator lead is placed in the same location. The needle is then removed over the stimulator lead. Once the needle is withdrawn, the lead can be attached to a stimulator, and a surface electrode is placed on the ipsilateral limb. Appropriate placement results in comfortable sensations in the desired region without muscle contraction via the electrical stimulation. Upon confirmation of placement, the lead is secured in place with a sterile dressing.[13]

Complications

Pain during the procedure, infection, lead migration, fracture, or misplacement, allergic dermatitis, stimulation intolerance, and hematoma formation are possible complications of peripheral nerve stimulators.[12]  The most common complication is lead migration, with incidence increasing with chronic stimulators in place. Infections may also occur in about 4 to 10% of cases, which may require antibiotic therapy, removal of the lead, or both. Long-term nerve damage is a rare, but serious complication that can result from peripheral nerve stimulators.[16]

Clinical Significance

Placement of peripheral nerve stimulators for analgesia could significantly change practice patterns for health care providers and could substantially impact patient satisfaction and quality of life.[17] Some studies suggest that peripheral nerve stimulators can successfully treat post-operative and acute pain with minimal need for opioid pain medications.[11][13] The concept of replacing opioids for this type of pain management holds promise in light of the current opioid crisis in America. The use of peripheral nerve stimulators can provide regional anesthesia without systemic effects common with most pain medications. Peripheral nerve stimulators can also provide pain relief for patients with chronic neuropathic pain who have contraindications to spinal cord stimulator placement and provide lasting relief without adverse effects of pain medications. While peripheral nerve blocks with local anesthetic medications may result in motor weakness, Ilfeld and colleagues suggest that peripheral nerve stimulation may avoid this “undesirable” effect.[11] There are still gaps in knowledge in this area, and more research is necessary, but initial studies show promise in peripheral nerve stimulation as an adjunct to current pain management practices. 

Enhancing Healthcare Team Outcomes

Peripheral nerve stimulator placement can improve patient safety by providing non-narcotic analgesia options for patients. With the integration of pain management specialists, surgeons, nursing care, and patients, the use of peripheral nerve stimulators may be a successful option for analgesia for both chronic and acute post-operative pain.