Upper-Extremity Peripheral Nerve Stimulators

Abstract

Chronic pain conditions are some of the most challenging problems upper-extremity surgeons face and often require a multimodal approach including neuromodulation. Peripheral nerve stimulation (PNS) is one of these modalities, delivering electrical stimulation to peripheral axons to modulate the spinal cord and block out nociceptive signals from the extremity. This blockade leads to long-lasting effects in both the peripheral and central nervous systems. Not only does PNS decrease peripheral pain signals but it also decreases the peripheral inflammatory response and assists with central nervous system plasticity for long-term pain control. Although PNS was initially developed in the 1960s, it has been underrepresented in the literature largely due to the advent of spinal cord stimulation and the lack of Food and Drug Administration-approved hardware for PNS. However, for upper-extremity pain, PNS provides notable benefits over spinal cord stimulation devices, as PNS allows for safer, more specific, and often more effective pain control. As clinicians attempt to limit narcotic use, therapies such as PNS have been revisited and are gaining popularity. We present a narrative review of PNS; discuss its mechanism of action, indications, and surgical technique; and provide a summary of the available literature for the upper-extremity surgeon. Peripheral nerve stimulation offers a solution for chronic, debilitating pain recalcitrant to other treatment modalities.

Keywords: Hand; Nerve stimulator; Neuroma; Pain; Peripheral nerve.

Figure 1

The gate theory of pain control, as originally proposed by Melzack and Wall. Both somatosensory Aβ-fibers and nociceptive C-fibers synapse on to projection neurons, which send output to the brain. Projection neurons received inhibitory modulation by inhibitory interneurons, which are modulated by Aβ-fiber and C-fiber activity. The presence of somatosensory input excites the inhibitory interneuron that inhibits the projection neuron, “closing the gate” for nociceptive input. Nociceptive input at high enough intensities instead downregulates interneuron activity and thus keeps the gate “open” for signal transmission to the brain. Although the concept of gated nociceptive output is widely considered valid, the specifics of the circuit and molecular mechanisms remain controversial. Reprinted with permission (RightsLink License Number 5218290125994) from Kral et al.

Figure 2

An image of a percutaneous PNS showcases the 3 components of the system: the external pulse transmitter (EPT) and electrode patch, the implanted lead, and the patient programmer. In the top portion of the image is the EPT on top of the electrode patch. Whenever the patient wishes to trigger stimulation for pain relief, they place the electrode patch on their forearm’s skin, directly overlying the trajectory of the implanted lead. The EPT is subsequently attached to the electrode patch, delivering neuromuscular electrical field stimulation through the electrode patch to the implanted lead. In the middle portion of the image is one of the leads that were implanted parallel to the patient’s left median nerve. In the bottom portion of the image is the patient programmer, which the patient and the medical staff use to adjust the stimulation parameters after implantation. Reprinted with permission (RightsLink License Number 5218290570729) from Ferreira-Dos-Santos et al.

Figure 3

A PNS device placed over a volunteer’s forearm skin shows the trajectory of the leads implanted in the patient. Reprinted with permission (RightsLink License Number 5218290570729) from Ferreira-Dos-Santos et al.

Figure 4

Open placement of a tibial nerve stimulator. Although this intraoperative photograph demonstrates a paddle lead, cylindrical electrodes may also be used. Reprinted with permission (RightsLink License Number 5218291114657) from Stuart and Winfree.