Dorsal Root Ganglion (DRG) Stimulation
The dorsal root ganglion is a bundle of nerve cell bodies (i.e., a ganglion) located within the posterior region of various vertebrae along the spinal column and is adjacent to the dorsal nerve root. The primary function of the dorsal root ganglion is to transmit information regarding sensory function. As such, the dorsal root ganglion carries sensory neural signals from the peripheral nervous system to the central nervous system, which includes the spinal cord and brain.
Damage to or irritation of the dorsal root ganglion can lead to intractable symptoms of neuropathic pain that do not respond to typical treatments. This can lead to additional complications in the form of impairment in functioning for the individual. In these cases, more interventional approaches may be warranted, such as spinal cord stimulation or dorsal root ganglion stimulation.
Every year thousands of traditional spinal cord stimulation devices are implanted, which successfully treat conditions of intractable neuropathic pain, such as complex regional pain syndrome or failed back surgery. Evidence has suggested that a new technique for neuromodulation of the dorsal root ganglion, which is nearly identical to the technique used in spinal cord stimulation, may also result in effective management of chronic pain. Moreover, dorsal root ganglion stimulation is considered to be an ideal alternative for some pain conditions, as it more effectively targets the specific pain location.
What is DRG Stimulation
How DRG Stimulation is Performed
As noted above, dorsal root ganglion stimulation is almost identical to the traditional spinal cord stimulation procedure; however, the dorsal root ganglion is targeted, rather than the spinal cord. Thus, dorsal root ganglion stimulation involves implanting electrodes, which are uniquely designed for use on this type of nerve bundle. Along with the electrodes, a stimulation device is also implanted, which sends electrical impulses to the specified area of the dorsal root ganglion where the electrodes have been placed. In doing this, the transmission of pain signals from the peripheral nervous system, through the dorsal root ganglion, to the spinal cord and brain is interrupted, preventing the signal of pain from being perceived. Moreover, stimulating the nerve bundles with low intensity electrical impulses is also believed to reduce pain by replacing the sensation with a pleasant tingling sensation, known as paresthesia. The device itself generates electrical impulses from a battery and can be programed using an external handheld device. These batteries need to be changed approximately every two to five years.
By applying stimulation to the specific region of the dorsal root ganglion that is responsible for the pain, the result is much more effective pain relief, with less stimulation of the neural network in general. Thus, individuals are able to successfully feel relief from their debilitating symptoms of chronic pain, with less impact on surrounding areas.
Another benefit of dorsal root ganglion stimulation is related to the fact that the dorsal root ganglion lacks the protective membrane that is found on other peripheral nerve fascicles. Instead, the dorsal root ganglion is surrounded by a permeable connective tissue coating making it an ideal target for the application of neuromodulation.
The first application of dorsal root ganglion stimulation was conducted in 1991 in a sample of rats. These studies found that dorsal root ganglion stimulation resulted in favorable effects on the inflammatory responses of these rats. Since this study, a number of trials of dorsal root ganglion stimulation have been conducted and the FDA has now approved dorsal root ganglion stimulation for the treatment of certain pain conditions in humans.
Conditions Related to DRG Stimulation
Damage to the dorsal root ganglion can occur either by direct injury to the nerve bundle itself or by compression from local inflammation or infection. Irritation or damage to the dorsal root ganglion can result in symptoms of chronic pain.
Dorsal root ganglion stimulation has received approval from the FDA as an effective treatment for some types of chronic pain conditions, including complex regional pain syndrome. Complex regional pain syndrome is a type of chronic pain condition that can affect a specific area of the body following injury or trauma. It is linked with damage or irritation of the neural system, either through injury or compression from inflammation. Symptoms of complex regional pain syndrome can include prolonged and excessive pain that can cause the individual impairments in functioning. Other symptoms of complex regional pain syndrome can include mild to severe alterations in skin temperature, skin color, or swelling of the affected area. Individuals suffering from this condition may also suffer from depression as the result of loss of functioning.
Dorsal root ganglion stimulation may also be used to relieve post-amputation pain.
Risks Associated With DRG Stimulation
Neural stimulation of the dorsal root ganglion does involve some risk, as the dorsal root ganglion device is surgically implanted. Though very little is known about the consequences of injecting pain relieving medication within the dorsal root ganglion or the spinal cord, neuromodulation of the neural tissue within this area is believed to be safe and completely reversible. The procedure itself for implanting the device is regarded as safe and conducted in such a way as to avoid inflammation or additional pain to the individual. In fact, many may return to normal activities of daily function within several days.
Risks associated with the condition are considered to be mild in nature and generally include minor bleeding at the site of the injections, infection, neural injury, and local anesthetic systemic toxicity. Individuals may also have a reaction to the medication used during the procedure.
References
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Abram SE, Yi, J, Fuchs, A, Hogan QH. Permeability of injured and intact peripheral nerves and dorsal root ganglia.Anesthesiology 2006;105(1):146-153.
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Sapunar, D, Kostic, S, Banozic, A, & Puljak, L. Dorsal root ganglion: A potential new therapeutic target for neuropathic pain. J Pain Res 2012;5:31-38.
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Hu, SJ & Xing, JL. An experimental model for chronic compression of dorsal root ganglion produced by intervertebral foramen stenosis in the rat. Pain 1998;77(1):15-23.
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Schu, S et al. Spinal cord stimulation of the dorsal root ganglion for groin pain: A retrospective review. Pain Practice2015;15(4):293-299.
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Liem, L et al. One-year outcomes of spinal cord stimulation of the dorsal root ganglion in the treatment of chronic neuropathic pain. Neuromodulation: Technology at the Neural Interface 2015;18(1):41-49.
Conclusions
Chronic neuropathic pain can be quite debilitating and lead to impairments in functioning, as well as other associated conditions, such as depression. Dorsal root ganglion stimulation is a procedure for providing relief from symptoms of chronic pain resulting from neural injury or compression. This interventional approach is regarded as a relatively safe and effective procedure, with a low risk for side effects. The dorsal root ganglion is considered an ideal target for delivering pain relief, as the electrical stimulation may be applied to a more targeted area. Previous findings examining the effectiveness of dorsal root ganglion stimulation have found that this procedure results in many favorable outcomes for chronic neuropathic pain, which may last up to a year or more.