Miscellaneous peripheral nerve stimulations

Scenario

A 39-year-old man presented to the emergency room (ER) at his local hospital with obesity and severe localized pain in the right groin after doing some cleanup and sweeping in his garage the previous weekend. After examination by ER staff and a consultation from the general surgeon on call, it was identified that he likely had a nonincarcerated inguinal hernia defect. He was told to gently push in the region where there was a faintly noted bulge in the painful region and to try ice over the area or even lying flat with his head lower than his pelvis to try to reduce the hernia if the pain persisted at times. He was given some hydrocodone for more severe pain on an as-needed basis and told to make an appointment with the general surgeon as an outpatient in follow-up as he may want to consider surgical repair electively to prevent the possibility of an incarcerated bowel loop in the future, particularly if the pain only briefly subsides in the meantime.

Over the subsequent 2 weeks, he had little respite from the pain, which was worse with standing or bending forward and coughing. He required a refill of the hydrocodone from his primary care physician (PCP). As his appointment with the general surgeon neared, he began to have pain in the same area on the left side. Although not quite as severe or constant, it was nonetheless quite distracting as well, and he found himself spending much of his time out of work and lying flat in bed. Eventually, he was seen again by the general surgeon who felt there was a need to repair both hernias, one with mesh. He was scheduled for surgery within the next week where there was an opening in the schedule from a cancellation. Surgery seemed to go relatively smoothly, and both hernias were definitively repaired. Other than some brief urinary retention after the surgery which required an extra day with a catheter, he was discharged to home.

Unfortunately, over the next few weeks, he developed an infection in the mesh repair and a recurrence of the hernia on the opposite side repair requiring a revision. All told, he underwent three further surgeries in the inguinal regions to address all the complicating developments, in addition to the original repair surgery, over the ensuing 8 weeks. After fully recovering and well healed, he returned for a follow-up with the general surgeon and complained that he had started to feel a burning type of pain, sometimes very severe, in the area of both groins, near but deep to his incisions. The pain was not quite the same in nature as the pain he had had when the hernias initially presented. Ice was somewhat helpful at times, but he could not maintain the application of ice all day long, and ibuprofen was ineffective.

His surgeon suggested that he may have some localized nerve damage from the multiple surgeries and scar in both areas. This was uncommon but not rare and often subsides over time or is treatable with antiinflammatories or gabapentin. He was prescribed gabapentin, initially 300 mg/night for 5 days, followed by 300 mg three times per day times 5 days, and then finally 600 mg three times per day. He tried this with ice and rest. Initially, he was groggy during the day with the gabapentin. This persisted for about 3 days but then subsided, and he had no side effects from the gabapentin. However, after taking the 1800 mg/day for a week, he realized there was little to no effect on his groin pains. In fact, during the month or so since the pain had begun, the pain had instead intensified and was unrelenting. He was referred to a pain specialist. Several injections that included bupivacaine and a steroid solution were tried on each side over a period of a couple months, with only 6–8 hours of benefit. He was told that the initial benefit was helpful in appreciating that there was likely a nerve tethering or entrapment from the prior surgeries in each region and that the benefit was from the bupivacaine, which of course then wore off within a matter of hours.

At this juncture, now many months out from the repair of the hernias and complications, and even longer since his original hernia presentation, he had been diagnosed with a neuropathic pain syndrome following from the bilateral hernia repairs and refractory to conservative care. His pain physician suggested that he try peripheral stimulation and a localized trial could be performed first to test whether this might alleviate some or all of the pain. The patient agreed, and an externalized trial was arranged in the clinic for roughly an hour of time. Sticky external electrodes were applied overlying the span of the area where the pain was primarily concentrated in each groin. The regions generally were areas of approximately 2 cm by about 4–5 cm, and a bipole was made and tested using the Ojemann Cortical Stimulator and an adapter for connecting these disposable leads. Within about 30 seconds, it was clear that a significant amount of the pain in each area could be eliminated and this relief maintained as long as the stimulation was “on”. Two different frequencies seemed to be ideal for the two areas, and different amplitudes were found that were comfortable, but the patient was told he likely would benefit from implanted leads and an implantable pulse generator (IPG) for long-term therapy.

• Variation : The external stimulation trial is not helpful -- While the use of clinic-based, outpatient external stimulation is convenient and reasonably predictable for determining likely benefit from an implanted peripheral lead and IPG, it is sometimes difficult to obtain reliable results in the clinic. Leads may become detached frequently, and the patient needs to be checked on often enough so as not to waste time if the leads had come off and the patient thinks they are getting no relief. However, external stimulation is less helpful in some cases where an implanted system may still work well. Some would advocate placing the system even without a trial. There is no standard of care, although third-party payors may approve or decline to cover these procedures with or without a trial.

• Variation : External stimulation is helpful but by using a portable TENS unit instead -- An alternative to using a modified connector to the Ojemann Cortical Stimulator is simply to use a typical portable TENS unit. The main drawback of this approach is that the electrodes provided with most TENS units are much larger than is practical for many areas of the body, particularly on the face. Other regions, however, may allow them to work well, and this could be an alternative method for trialing. An additional advantage of using a TENS unit is that should the trial be successful, it provides a noninvasive therapy for the patient in and of itself. Perhaps the patient had n’t tried a TENS unit previously, and this brief trial using one shows them how effective it can be. The damaged nerve or nerves are often not very deep below the surface of the skin, and the electrical fields can be adjusted adequately to achieve the same result in many cases.