Growing worries about the dangers of overusing opioid pain medications have generated new interest in spinal cord stimulation (SCS), a pain treatment that has been around for decades. Also called neurostimulation or neuromodulation, the technique uses low-voltage electrical currents—emanating from a surgically implanted device—to directly stimulate nerves and block the sensation of pain.
Several SCS devices have been developed and heavily marketed in recent years, with new models currently being tested in clinical trials. All employ a similar approach. A small stimulation device, powered by a rechargeable battery, is implanted under the skin, usually just above the buttocks. Attached to the device are thin wires that send a mild electrical current to electrodes positioned near nerves that are the source of the pain. A handheld remote control allows users to activate the device and adjust the intensity.
Researchers don’t know exactly why SCS seems to ease pain. One theory holds that by stimulating large nerves, SCS blocks smaller nerves from transmitting pain signals. But studies have shown that SCS can provide relief even weeks after the electrical currents are stopped, suggesting that the technique may ease pain in multiple ways. The devices don’t come without risks, however—some of which can be serious.
Evidence is limited
How effective is SCS in easing back pain? The evidence most often cited comes from randomized studies done in the early 2000s, involving people who had back surgery and still suffered significant pain afterward—a condition called failed back surgery syndrome.
In a trial of 50 people with the syndrome, SCS was more effective than follow-up back surgery at reducing pain by more than 50 percent. Another randomized trial, which included 100 people, found that SCS was more effective than conventional pain management for easing pain in individuals who suffered persistent pain after surgery for a herniated disc.
It’s important to note that both studies were managed and funded by the makers of the devices that were being tested. Neither study included a sham procedure or turned off the stimulators without the participants’ knowledge, so the studies didn’t include true controls. And 26 to 32 percent of the participants experienced complications. Follow-up studies have confirmed both the relative benefits and potential risks of SCS for people with failed back surgery syndrome.
To date, no studies have looked specifically at whether SCS is as effective for low back pain in people who have not had surgery.
The risks of SCS
Like most treatments, electrical stimulation has drawbacks. Implantation surgery requires general anesthesia, which has its own risks. As with any surgery, there’s a danger of infection during wound healing. Also, over time, the electrodes can move out of position or the electrical stimulator can fail, leading to further surgery to reposition the electrodes or replace the device. Although rare, the most dangerous complication is spinal epidural hematoma, or bleeding around the nerves of the spine, which can cause paralysis if not treated quickly. In some cases, stimulation simply stops providing relief, and pain returns.
To better understand the risks, a study published in the journal Pain Medicine in 2018 followed 256 people who had SCS devices implanted during the period of 2002 to 2015 at a single pain center. Half of the people received SCS after failed back surgery. Another 25 percent had complex regional pain syndrome, a nerve disorder that causes intense burning pain, usually in the extremities. The rest were given SCS for other pain conditions, such as neuropathy, a nerve problem that causes pain, numbness, tingling, swelling, or muscle weakness in different parts of the body.
When the researchers assessed how the participants fared, they found that 30 percent had had their devices removed, a procedure called explantation. The reasons included infections, inflammation, hardware malfunctions, and in some cases, inadequate pain relief. Most of the problems, the study found, arose during the first few years after SCS devices were implanted.
A more recent investigation was published in the journal Regional Anesthesia and Pain Medicine in 2019. It examined complications reported to the U.S. Food and Drug Administration (FDA) related to a particular kind of SCS that is gaining popularity, called dorsal root ganglion stimulation (which targets a specific cluster of spinal nerves). Reviewing reports from May 1, 2016, to December 31, 2017, the investigators identified 979 procedures that led to complications. Almost half were related to problems with the device itself. One in four were complications from the surgical procedure. Most of the rest of the reported complications were from people who were dissatisfied with the outcome. The majority of complications were managed with additional surgery (488 cases) rather than explantation (161 cases).
Although the use of SCS in modern medicine has been around for decades, researchers are still testing new ways to employ electricity to stimulate nerves and ease pain. Proponents believe that innovations currently in clinical trials will dramatically improve this approach to pain management.
For example, most of the SCS devices used today deliver low-frequency electrical pulses, but there’s growing interest in high-frequency SCS. In preliminary studies, high-frequency SCS appears to be more effective for low back pain—defined as at least 50 percent pain reduction—than low-frequency stimulation.
Another new approach is designing devices that deliver short bursts of stimulation, rather than continuous electrical current. Again, preliminary studies suggest that this approach may result in greater pain relief.
Technological advances may also improve physicians’ ability to place electrodes in the ideal location to stimulate nerves involved in pain. Advanced algorithms based on three-dimensional anatomical models are being tested that take into account how different structures in the spine conduct electricity. The goal is to deliver just the right amount of stimulation to the exact part of the nerve involved.
Is SCS an option for you?
Given technologies currently available, the bottom line is that SCS can help some people when other treatments have failed. But not everyone benefits. And the risk of complications that can lead to the removal of the device is a cause of concern.
Still, if you have chronic back pain that hasn’t been helped by other treatments, including surgery, it might be worth talking to your doctor about SCS. In evaluating whether SCS is right for you, your doctor will take into account several critical health factors. If you have a pacemaker, your doctor will need to determine that the SCS device’s electrical signals don’t interfere. If you take anti-clotting medication, you will be at higher risk of bleeding at the site where the device is implanted. Your medication regimen may need to be adjusted before and after surgery to prevent bleeding. Your doctor will also review your history of back pain. The longer someone has suffered from chronic back pain, the less likely SCS is to help, the evidence suggests.
If you and your doctor decide that SCS is appropriate, the first step is a three- to seven-day trial run in which temporary electrodes are implanted, using local anesthesia, and connected to an external current generator that has one or more customized stimulation programs. The trial period allows your doctor to determine whether the device is working and what stimulation program is best for you. If you’re getting adequate pain relief, then a permanent SCS device will be implanted under general anesthesia.
The batteries of implantable SCS devices need to be recharged, which is typically done by placing a recharging unit over the skin where the device is implanted. Eventually, the battery itself needs to be replaced.
Medicare and most private insurers cover SCS in back pain patients, but typically only after other treatments have failed to help ease pain. Since other coverage restrictions apply, it’s wise to confirm with your insurer before deciding on SCS.