Dorsal root ganglion stimulation

Scenario

A 21-year-old woman presented in referral for treatment of a severe lower extremity pain. She had initially been treated after a horseback riding injury with a nondisplaced fracture of the fibula. Despite good bone healing, she had persistent pain of the limb and developed coldness to touch, skin discoloration, atrophy of the skin, shininess and excessive hair growth, and hyperhidrosis. She was diagnosed with complex regional pain syndrome (CRPS), type I. She did meet all criteria for this diagnosis and had been treated appropriately with physical therapy, lumbar sympathetic blocks, anticonvulsants, nonsteroidals, and low-dose opioids. She was a college student and did not do well with medications because of side effects and did not respond long term to injection or physical therapy. She had an electromyography/NCS which showed no abnormalities and had a three-phase bone scan that was inconclusive.

On evaluation, the patient had pain from her knee to her toes including the bottom of her foot. She had allodynia and obvious changes in her skin, hair, and nails. At this time, I confirmed the diagnosis of CRPS type I and discussed treatment options. We did extensive patient education and considered different stimulation options including burst, high frequency, and tonic. After this discussion, we went over the option of dorsal root ganglion (DRG) stimulation and the United States investigational device exemption (IDE) study that led to the approval. Her history and presentation was consistent with the patients in the study. Based on this discussion, she opted to move forward with a trial of DRG stimulation. Based on her pain distribution, we opted for a lead to be placed at L4 and L5.

• Variation : The patient has a disuse injury from lack of activity and weight bearing -- In this setting, the use of any form of stimulation may be overly aggressive. Options would include a tunneled catheter for a few weeks to increase tolerance to therapy, a tunneled stimulation trial, or potentially a 30-day cognitive program. In some of these settings, the placement of a permanent DRG stimulation device will lead to a reduction in pain levels and a tolerance to exercise. If the patient responds in this fashion and can undergo extensive therapy and desensitization training, they can often return to a normal status. In this setting, the device can be removed. We generally recommend a 6-month therapy hiatus to assure there is no relapse, before the explant.

• Variation : The patient has a peripheral nerve injury as the primary issue -- In some settings, a patient will have an injury of a peripheral nerve such as the superficial peroneal, tibial, or sural nerve and subsequently have an allodynic limb that develops signs of atrophy from disuse. In this setting, the use of peripheral nerve blocks and oral medications often fails. In this patient population, there is also a very low success rate of topicals, bracings, and alternative methods. Patients in this group can be treated with peripheral nerve stimulation (PNS) of the primary pain generator. Difficulties can arise from difficulty wearing a radiofrequency device in the lower extremity, and also problems may arise in devices that must couple to a Bluetooth system. Because of the limitations in these current devices, we would still move forward with DRG stimulation in the majority of these patients with the diagnosis of primary nerve injury or causalgia. The targets would be L5 or S1 for the foot, L4 or L5 for the area from the knee to the top of the foot, and L3 or L4 for the knee and surrounding structures. An alternative could be spinal cord stimulation (SCS) particularly if the anatomy does not merit a PNS device or DRG system.

• Variation : The patient has more widespread symptoms consistent with a radicular component in addition to the peripheral nerve injury -- Just as the patient with primary nerve injury, someone presenting with more than one pain generator is more complex. In this setting, after trying the conservative therapies noted in this discussion, additional workup is needed. A magnetic resonance imaging scan of the spine should be obtained, and consideration of a curative surgical lesion should be discussed. Even in this setting, the CRPS must be considered and may lead to worsening with any surgery including spine surgery. In this case, we would consider SCS as a primary implant method, with DRG as a potential backup. This is important because recent studies have shown that DRG lead placement at T12 or L2 may give considerable relief of both discogenic back pain and postsurgical pain.