Electrical stimulation from a spinal cord implant can provide long-lasting relief for people with diabetic neuropathy, updated clinical trial results show.
"Two years after starting with using that stimulator device, they're still having the same quality of improvement as what we first saw," said lead researcher Dr. Erika Petersen. She is director of functional and restorative neurosurgery at UAMS (University of Arkansas for Medical Sciences) in Little Rock, Ark.
Approximately 37 million Americans have diabetes, and about one-quarter develop painful diabetic neuropathy, researchers explained in background notes.
Their diabetes does damage to small nerves, typically in their hands and feet, Petersen said. This causes a variety of painful sensations — burning, pins and needles tingling, and itching among them.
"I've had someone describe it to me as if they feel like they're walking on crushed glass when they put their feet on the floor. Even just having a sheet over their feet when they sleep at night is uncomfortable," Petersen said. "I have one patient who had to build a custom little tent frame for his blankets at the bottom of his bed with PVC pipes to prevent the sheets from brushing on his feet."
Spinal cord stimulators have been around for decades, used to treat various forms of pain.
In 2021, the U.S. Food and Drug Administration approved the use of a spinal cord stimulator device specifically to treat diabetic neuropathy in the legs and feet, Petersen said.
Electrical leads are placed into the spinal canal, and run back to a battery pack that is placed under the skin, Petersen explained.
"You can think of it like a pacemaker for pain," Petersen said. "The device delivers small impulses that change how the nerves within the spinal cord process the pain messages that are coming from the feet through the spinal cord up towards the brain, and helps them decrease how those pain messages are conducted."
For their clinical trial, Petersen and her colleagues recruited 216 people with painful diabetic neuropathy symptoms for at least a year who were no longer responding to medications.
Initially, half of the people received spinal cord stimulation for six months, while the other half received regular medical treatment (the "control" group).
At six months, people with the implant reported a 76% decrease in their pain and a 62% improvement in their motor function and reflexes, the results showed. By comparison, the control group had a 2% increase in pain and a 3% improvement in function.
After six months, those in the control group were given the option to receive an implant. More than 90% opted to get the stimulator, while no one with an implant asked to be switched to medication, the study authors reported.
The researchers continued to follow the patients, and now report that two years out 80% still have less nerve pain and 66% report continued improvement in motor function.
There also were no nerve damage issues associated with the stimulator, and the surgical risks were comparable to what are found in patients without diabetes who receive spinal stimulator implants for other conditions, Petersen said. Eight people had surgical infections related to the device, and five had to have their devices removed due to infection.
The results showed that spinal cord stimulation is a solid option to pursue if medications stop helping a patient with diabetic neuropathy, Petersen said.
"Over time, these medicines stop working as effectively, or people develop side effects. Some of the medicines are really expensive, and people just don't pay for them because it isn't worth it," Petersen said. "Up to about 70% of people taking Pregabalin, for example, will stop taking it within a year because of various problems with the medication."
The findings are scheduled for presentation at the American Academy of Neurology annual meeting, to be held April 22 to 27 in Boston. Findings presented at medical meetings should be considered preliminary until published in a peer-reviewed journal.
Dr. Michael Polydefkis, a professor of neurology with Johns Hopkins Medicine in Baltimore, agreed that the results are "exciting."
However, Polydefkis noted that the clinical trial results could have been influenced by a placebo effect, given that the people who received the implant knew that they were receiving special care.
"The placebo effect is notorious in pain studies," Polydefkis said.
Cleveland Clinic pain management expert Dr. Shrif Costandi found the clinical trial results persuasive as well.
"The findings are very promising, and it's providing an important tool to help those patients who are suffering and whose quality of life is being compromised by this chronic pain," Costandi said.
Still, Petersen and Costandi said medications should remain the front-line therapy for diabetic neuropathy. Patients should be offered the implant after drugs fail to diminish their pain.
"I think it makes sense to try medicines first, but I don't think that people should be on medicines for years and years and years if they're not helping," Petersen said. "I think that if you try medicines for a reasonable amount of time, that moving on to the stimulator is a good option."
Spinal cord stimulator implants can be pricey, costing tens of thousands of dollars, but following the FDA approval more insurers are moving to cover their cost, Petersen noted.
"So about 60% or more, last time I checked, of insurance companies are covering the device in the U.S., and that includes Medicare as well as commercial insurances," Petersen said. "Access is definitely improving, as far as that goes."
One nice thing is that patients can "test drive" spinal stimulation before receiving a permanent implant, Petersen said.
"The person gets the wires placed in through needle in an office procedure, and they wear an external device home for about a week so they can test drive and see what kind of response they have over that week and decide whether that benefit is enough for them to go forward with the permanent procedure," Petersen said.
"It's one of the few operations where my patients can actually test out what their results will be like before they actually have their operation, and it gives a really good idea as to whether it meets their expectations," she continued.
The clinical trial was funded by Nevro Corp., the maker of the spinal cord stimulation system.