Both pain relief and neurological improvements persisted in patients with diabetic neuropathy 2 years after they began receiving treatment with 10 kHz of spinal cord stimulation, according to research that released early, prior to its presentation at the annual meeting of the American Academy of Neurology.
Dr Erika Petersen
The data represent the longest follow-up available for spinal cord stimulation at a frequency higher than the 60 Hz initially approved for diabetic neuropathy by the Food and Drug Administration, according to lead author Erika A. Petersen, MD, a professor of neurosurgery and the residency program director at the University of Arkansas for Medical Sciences, Little Rock.
“You would expect that somebody who continues to have diabetes for 24 months and has neuropathy would have worse neuropathy after 2 years, and what we’re seeing is that people were stable or better in terms of their nerve function at 2 years,” Dr. Petersen said in an interview. “So that’s really revolutionary.”
Encouraging preliminary findings
The findings are “promising and preliminary,” John D. Markman, MD, a professor in neurology and neurosurgery, vice chair for clinical research, and director of the Translational Pain Research Program at the University of Rochester (N.Y.) Medical Center, said in an interview. Dr. Markman, who was not involved in this study, said that, though the results are encouraging, it’s “less clear how much of [the pain improvement] is due to what we would consider to be on-target, pain-relieving benefit from stimulation versus other factors like expectation.” The crossover rate and amount of reduction in pain intensity are promising, but “I think that excitement is weighed against the fact that this is an open-label study.”
An underused treatment
Although spinal cord stimulation has been around since the late 1960s, its use only picked up steam in the 2000s, when it became more frequently used to treat chronic nerve damage related to neuropathic pain syndromes, Dr. Petersen explained. The FDA approved the treatment’s new indication for diabetic neuropathy in 2015, and data from Abbott and Medtronic have shown benefits from spinal cord stimulation at 60 Hz, but some patients are uncomfortable with the vibration or tingling feelings the devices can cause at that frequency.
“They describe creepy crawlies or ants crawling over the feet, or pins and needles, and painful sensitivity,” Dr. Petersen said. “You create a vibration feeling in the same zone where they already have those feelings of buzzing and pain and vibration, and it’s sometimes actually even more uncomfortable and less satisfying to them in terms of relief” with the spinal cord stimulation at 60 Hz, she said, “so there’s a lot of attrition in terms of who will actually use it.”
At 10 kHz, however, “people don’t feel any vibration or tingling associated with it; it just jams the signal of the pain,” she said. The difference between the frequencies is like that between “a lifeguard whistle and a dog whistle.”
Testing high-frequency stimulation
The new findings included the 24-month follow-up data from a randomized controlled trial that assessed the effectiveness of high-frequency spinal cord stimulation for painful diabetic neuropathy. The original 216 participants enrolled in the trial had diabetic neuropathy symptoms for at least 12 months and either could no not tolerate or did not respond to medications. Enrollment criteria also included lower-limb pain intensity of at least 5 on a 0-10 visual analogy scale and hemoglobin A1c of no more than 10%.
For the first 6 months of the trial – before crossover was offered – participants were randomly assigned to receive either 10 kHz of spinal cord stimulation along with conventional medical management or to receive conventional medical management alone. The 6-month data from 187 patients, as reported in April 2021 in JAMA Neurology, revealed that 79% of those receiving spinal cord stimulation experienced at least 50% improved pain relief without worsening of their baseline neurologic deficits, compared with only 5% of those receiving only conventional treatments.
Average pain levels increased 2% in the control participants compared with a decrease of 76% in those with the spinal cord stimulation devices. In addition, 62% of the patients receiving spinal cord stimulation demonstration neurologic improvement in reflexes, strength, movement and sensation, compared with 3% of those in the control group. The study’s findings led the FDA to approve the device using 10 kHz.
At 6 months, 93% of control patients crossed over to receiving spinal cord stimulation while none with the devices opted to stop their spinal cord stimulation. The 12-month data revealed that 85% of those receiving spinal cord stimulation experienced at least 50% pain relief, with the average pain relief at 74%. Patients also reported statistically significant improved quality of life as well as less interference with sleep, mood, and daily activities from pain.
Two years after baseline, patients’ pain relief was maintained with average 80% improvement, and 66% of patients showed neurologic improvement since baseline. Though no patients had devices removed because of ineffectiveness, five patients’ devices were removed because of infection while infections in three other patients resolved.
“Being able to offer something that is not a pharmaceutical, without the side effects, that shows an even longer durability to that response is a really important finding at this point,” Dr. Petersen said.
Among the estimated 37 million Americans with type 1 or 2 diabetes, approximately one quarter of them experience some level of painful diabetic neuropathy, but medication and other medical management strategies are not always adequate in treating their pain. After a 1-week trial of spinal cord stimulation, the devices are implanted under the skin and rechargeable through the skin for up to 10 years, after which they can be replaced.
An appropriate candidate for spinal cord stimulation would be someone for whom existing non-invasive pain relief options, including medications, are ineffective or intolerable, Dr. Petersen and Dr. Markman both said. An adequate trial of medication is not “one size fits all” and will vary by each patient, added Dr. Markman, who is also interested in whether this study’s participants were able to have a reduction in use of pain relief medications.
“I think there’s a significant number of patients out there who can benefit from this, so I think that’s why it’s promising and exciting,” Dr. Markman said. “I do think it’s important to see if this actually allows them to be on less medication or whether stimulation turns out to be another treatment in addition to their baseline treatments.” The challenge is identifying “which patients are most likely to be benefiting from this and which are most likely to be harmed.”
Aside from infection from implantation, other possible risks include pain at the battery site and, in rare cases, a need for reoperation because of migration of the leads, he said.
Improvement in symptom severity and quality of life
After the wound from the implant has completely healed, Dr. Petersen said patients using the devices do not have any activity restrictions outside of magnetic interference, such as MRIs. “I’ve had people go back-country kayaking, scuba diving, fishing with their grandkids, all sorts of all sorts of things. If patients need to go through a scanner of any kind, they should ask whether it’s safe for pacemakers since these devices are like a “pacemaker for pain.
“I had a patient bring solar chargers with him so that he could recharge his battery in the backwoods while kayaking because that’s the level of improvement in pain that he got – from barely being able to walk down the hall to feeling comfortable being off the grid and active again,” Dr. Petersen said. “Those kinds of improvements in quality of life are massive.”
The study findings may also suggest that spinal cord stimulation can benefit a broader population of patients experiencing neuropathic pain, Dr. Markman said.
“There’s an extraordinary unmet need for treatments for neuropathy, and one important question here is the extent to which diabetic peripheral neuropathy and the response that we’re seeing here is a proxy for a broader effect across many neuropathies that are caused by other conditions other than diabetes,” Dr. Markman said. “There’s a lot of reason to think that this will be helpful not just for diabetes-related neuropathic pain, but for other types of neuropathic pain that have similar clinical presentations or clinical symptom patterns to diabetic peripheral neuropathy.”
The study was funded by Nevro, who manufactures the devices. Dr. Petersen and Dr. Markman both reported consulting with, receiving support from, holding stock options with, and serving on the data safety monitoring boards and advisory boards of numerous pharmaceutical companies.
This article originally appeared on MDedge.com, part of the Medscape Professional Network.
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