Using electrical stimulation for the control of pain with an implanted device onto the spinal cord and in the epidural space was done for the first time in 1971. This began after the publishing of Melzack and Wall’s renown work on the “gate control theory” of pain. The theory proposed that nerves carrying painful peripheral stimuli travel into the dorsal horn of the spinal cord. Further, the “gate” may be manipulated or closed by other electrical impulses to the area. Since the initial device in 1971, technology and understanding of neuromodulation has greatly changed, and there are new developments coming to the field.
Spinal cord stimulation (SCS) is an advanced form of pain management. It is an implantable system that uses electrical signals to the spine to modulate pain signals traveling through the spine. The exact mechanism is unknown, but somehow the signal generated by the stimulator modifies pain signals such that one does not perceive their normal pain quality. In the simplest terms, it is a pacemaker for the spine, pacing out pain signals. Since it is an implantable device, versus a simple form of treatment like physical therapy or medication, it is not considered a first line of treatment, but something to consider if other treatments have failed. For pain management professionals, it is a treatment that should be considered before less successful treatments like multilevel spine decompressions or fusions. The cost effectiveness of this treatment is far superior to most lumbar surgeries and is typically more successful in controlling pain.
Spinal cord stimulation is used for a variety of painful conditions. In the United States, the most common use is for pain that continues after back surgery. It is also used for neuropathic (nerve damage) type pain in the extremities, complex regional pain syndrome, and extremity pain that is unlikely to be managed with back surgery. In Europe, it is also often used for ischemic vascular pain in the legs and also for angina. Occasionally it is used for peripheral nerve pain, especially for migraines caused by occipital nerve irritation.
Advantages of Spinal Cord Stimulation
The advantage of SCS is that it often can control pain that no other treatment has been able to impact. When performed by an experienced interventional pain physician, the pain relief success rate should be above 60% with a complication rate less than 5%. Problems that may occur range from stimulator lead movement, damage from the needle used to insert the electrodes and infections. That said, complications are rare. The newer units have long lasting batteries, and one company makes units that are MRI compatible. Further, before any implant, a trial is done to see if the technology is helpful and to ensure it does not change the anatomy in the body.
As the technology has improved, there have been some new techniques discovered on spinal cord stimulation. The first technique is high frequency and high density stimulation. The unit is programmed at a very high rate, and the patient does not actually feel the stimulation to the spine. The electrical impulses block the pain signals at the spinal level and there may be some indication that it may also begin changing the central brain perception of pain signals. Several different brands of stimulators can perform this type of function; whether one brand is better than another is not clear.
The second new development is a very specific burst pattern of stimulation. This pattern is thought to mimic the transmission of certain pain signals and may be more effective in some individuals in blocking pain with less actual sensation of the electrical signals from the stimulator unit. Again, it is thought to also change the brain’s ability to perceive excessive pain signals in chronic pain patients, resetting the brain to a more normal pain sensitivity. The last new technique is for a special electrode that allows for specific nerve root ganglion positioning of the electrode to block an isolated nerve pain generator.
Spinal cord stimulation is an excellent technology to block pain signals. Our knowledge and ability to use these techniques to help diminish pain is expanding rapidly. Government and insurance approval has slowed some of the new technology and proven techniques, but hopefully these will be approved in the future to treat pain. The future for these technologies is bright and these provide a good option when simpler methods do not work.
Thomas Cohn, MD
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