New and emerging neuromodulation devices are becoming a preferred non-opioid alternative for treating chronic pain. Spinal cord stimulation (SMS) is one of these options, however for some patients, it isn’t sufficiently effective for Complex Regional Pain Syndrome in the lower extremities – areas such as the hand, chest, abdomen, foot, knee or groin. Since early 2016, the FDA has approved an additional alternative – dorsal root ganglion (DRG) stimulation. It can help manage chronic pain in those lower extremities even when other therapies have failed.
The concept behind dorsal root ganglion stimulation is nearly identical to traditional spinal cord stimulation. With both options, a small device, similar to a pacemaker, is implanted in the body and pain signals are masked before the reach the brain. However, there is a key difference. With spinal cord stimulation, leads are placed in the general region of the spinal cord, while dorsal root ganglion therapy targets selective nerve fibers on the dorsal root ganglion, which is a cluster of neurons (a ganglion) in a dorsal root of a spinal nerve. Dorsal root ganglion neuromodulation offers a highly-directed stimulation field, which can limit stimulation to a specific pain area.
Because the layer between the lead wires and the dorsal root ganglion cells is so narrow, dorsal root ganglion stimulation uses only about 10 percent of the energy required for traditional spinal cord stimulation. That, in turn, leads to longer-lasting batteries. In addition, the pattern of stimulation for dorsal root ganglion stimulation is constant, where the pattern of spinal cord stimulation can vary according to body position. As a result, dorsal root ganglion stimulation pain relief is much more consistent by comparison.
Who Is a Good Candidate?
Dorsal root ganglion stimulation can be effective for people who have pain that is concentrated in the lower limbs and may be an option if a patient has:
- Chronic pain that has lasted 6 months or more
- Little or no relief from traditional neurostimulation, surgery, pain medications, nerve blocks or other pain management therapies
- Isolated chronic pain in a lower part of the body, such as the foot, knee, hip or groin, following an injury or surgical procedure
- Diagnosis of having Complex Regional Pain Syndrome (CRPS) and have not found relief with rehabilitative physical therapy
Any patient who is considered a good candidate for dorsal root stimulation therapy must go through a thorough screening process before undergoing the procedure.
Dorsal Root ganglion stimulation does not work for everyone. Some find the neurostimulation sensation to be uncomfortable, and for others, the treatment doesn’t fully address their areas of pain. As a result, before a dorsal root stimulator is permanently implanted, a trial stimulation is always performed first. If the trial does not live up to expectations, the trial wires can be removed in a simple office procedure with almost no discomfort and without damaging the dorsal root ganglion and nerves.
With the trial procedure, a patient receives an external test stimulator in a simple outpatient procedure where temporary leads are placed via a needle using flouroscopy for guidance. During a three- to ten-day trial period, patients receive stimulation through these thin, temporary lead wires which are connected to an external trialing cable and an external test stimulator. A trial is considered successful when it results in pain relief of at least 50% accompanied by an improvement in function.
The trial leads are always removed at the trial’s conclusion. If the trial procedure has been successful, a permanent implantation is scheduled to be performed at a later date.
Permanent implantation is done as a minimally invasive outpatient procedure. During this procedure, the generator is placed underneath the skin and flouroscopy is used to determine where the electrodes are placed. Long term success with this procedure is often determined by how skilled a surgeon is when placing and anchoring the electrodes to minimize movement over time as the patient actively goes about their life post-procedure.
After the implantation, the healthcare team monitors the healing process and adjusts the settings on the stimulation device to optimize the therapy and pain control. After slight adjustments in the first few weeks, the settings on the dorsal root ganglion stimulator are often stable.