Case example and trial for peripheral nerve stimulation

Scenario

A 32-year-old woman had been involved in a farm equipment accident several years earlier and required reconstruction of her right upper extremity with multiple skin grafts and muscle transfers. She had lost one and a half fingers on her hand and had a fused elbow but remained able to feel some areas in her hand and forearm as well as most regions more proximally. However, she also had likely avulsive injuries in several nerve roots in her neck on the same side and had had multilevel posterior decompressive laminectomies in her cervical spine. She had been treated since the accident for multiple areas of pain which included her right hand, or at least a significant but focal part of it, several parts of her forearm distally, and also headaches and upper neck pains on the right side using a combination of medications and a retrograde percutaneous spinal cord stimulation (SCS) electrode at the C1-2 region on the right. That electrode was located above the prior laminectomy levels. The implantable pulse generator (IPG) for it was located in the right subclavicular region. She explains that despite all of these attempts to treat her pain, she obtains only modest relief from the SCS and only a point or two on a good day in her hand and arm from the medication. She does relate that when she has missed doses of gabapentin, missing an entire day once, she again develops quite noticeably more severe pain.

• Variation : The patient had no prior cervical surgery -- Given that this woman's pain syndrome involves one upper extremity and is fairly localized within the hand area, without prior posterior surgery to compromise the epidural space, it makes most sense to try a cervical SCS trial initially. In this case, the lead would best span the C5-7 levels. One can also consider adding peripheral stimulation to a previously placed SCS system (as in this case) to better cover the same area or provide a slightly different type of waveform to broaden the ability of the therapy to benefit the pain.

• Variation : The patient had no prior accident or derangement of anatomy and no cervical spine etiology -- Although one would need to consider the basis for the pain syndrome at all in a case without prior trauma or obvious pathology in the cervical spine (e.g., nerve impingement or cord injury), it is sometimes reasonable to consider that the patient may have a severe peripheral neuropathy wherein, if the patient is not diabetic, the etiology is often difficult to discern. Such pain syndromes can often respond to stimulation therapy, in fact they are at their root “neuropathic” by definition and should at least receive an SCS trial. As noted previously, without a distortion of anatomy, the epidural space is undisturbed and a trial can likely be performed. One can also consider a noninvasive externalized trial as described here. In either case, the fact that there is no prior trauma or obvious anatomical etiology would not in and of itself rule out stimulation therapy.

• Variation : The patient had bilateral hand numbness and pain, worse at night, and focal periscapular pain only -- This combination of symptoms does suggest the possibility of carpal tunnel syndrome, and in some cases, especially involving the upper extremity because of the increased frequency of entrapment neuropathies, this etiology should be first evaluated using an adequate electromyogram-nerve conduction study (EMG-NCS). However, the periscapular pain can be considered either a cervical root injury potentially with a particularly focal aspect to it or a peripheral distal branch injury leaving the patient with pain, often related to movement of that area or palpation. An externalized trial can be tried in this region. Success can be fleeting and difficult to maintain in the long term with scenarios such as this however.