Christopher J. Winfree, MD, FAANS
Department of Neurological Surgery, Columbia University
New York, NY
Neurosurgeons have played an important role in the management of neuropathic pain since the inception of the field of neurological surgery over a century ago. Most early neurosurgical pain therapies were ablative in nature. The non-ablative neuromodulation strategies were introduced in the 1960s and have been a valuable tool for neurosurgeons for the treatment of chronic neuropathic pain.
Spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS) have been used for decades to treat one particular type of neuropathic pain, called complex regional pain syndrome. Unfortunately, there are some limitations to the effectiveness of the surgical techniques, and thus, they only are effective in a fraction of the patients considered to be good candidates for the procedures.
Some experimental studies have implicated the dorsal root ganglion (DRG) as the site of some significant pathophysiology in the origin and persistence of neuropathic pain in patients with complex regional pain syndrome (CRPS). Thus, the DRG makes an attractive target for neurostimulation therapy. If we could target the DRG with stimulation, then perhaps we could utilize DRG stimulation to treat CRPS.
Since the early 2000s, neurosurgeons have been placing electrodes along the spinal nerve roots and DRGs to treat pain confined to the spinal dermatomes. This technique is called spinal nerve root stimulation (SNRS). Distal lower extremity pain in the setting of CRPS is generally confined to the L4-S1 dermatomes and is particularly well-suited to treatment with SNRS. The electrodes used in SNRS procedures are repurposed SCS stimulator electrodes, designed for placement in the epidural space over the dorsal columns. The spaces along the spinal nerve roots and DRGs, however, are curved and somewhat more confined. Thus, the relatively thick and stiff SCS electrodes have a suboptimal configuration for placement along the nerve roots. They can be difficult to place for the surgeon, and uncomfortable to use by the patient. Not surprisingly, outcomes were poor with SNRS techniques.
Recently, neurosurgeons have played a role in the development of a new form of neurostimulation, called DRG stimulation, that has proven to be more effective in the treatment of CRPS (and other dermatomal pain syndromes) than other types of neurostimulation. DRG stimulation targets the spinal nerve roots with small, percutaneously-placed electrodes, which limit stimulation to very focused regions of the body such as the lower legs and feet. The electrodes, which were designed specifically for placement along the DRG, are smaller, thinner, and easier to place along the spinal nerve root than SCS electrodes. The stimulation paresthesia overlap is easier to obtain initially and maintain long-term, unlike SCS and PNS. Patients also report better pain relief with DRG stimulation than with other forms of neurostimulation.
A recent clinical trial, called the ACCURATE Study, highlighted the use of DRG stimulation in patients with CRPS. This was a prospective, randomized, multi-center, controlled clinical trial comparing DRG stimulation to SCS in patients (N = 152) with lower extremity CRPS at 1-year of follow-up. The DRG patients reported 74 percent reduction in pain compared with the SCS patients who reported a 53 percent reduction in their pain. Also, the DRG stimulation restricted stimulation paresthesias to the painful area in 95 percent of patients, while SCS could only restrict the paresthesias to the painful area in 61 percent of patients.
DRG stimulation has become an important, evidence-based strategy for the treatment of severe, medically refractory CRPS. Working with our pain management colleagues, neurosurgeons continue to develop, test and utilize novel pain management strategies for patients with chronic neuropathic pain.
Editor’s note: During the month of September, we encourage everyone to join the conversation online by using the hashtag #painfacts.