A new peripheral nerve stimulation system is providing long-lasting pain relief for patients with phantom limb pain.
On May 4, 2014, David Nipple was riding his motorcycle near his former home in Franklin, Tennessee, when the intoxicated driver of a Chevrolet Tahoe crossed into his lane and hit him. Nipple’s left leg was severed above his knee at the scene. He was taken to a Nashville hospital for acute care, although medical workers didn’t think he’d make it. Fortunately, he survived; however, Nipple’s new life was marked by excruciating phantom limb pain.
“It felt like my leg was reliving the accident,” he says. “I felt tons of pressure pushing my left foot to the right, and the femur being pushed to the left, just as it happened during the accident.”
Nipple says at that time his pain level was at a 10. It was so bad that he sometimes couldn’t sleep—for days. He found most pain medications ineffective and was reluctant to take them anyway. He assumed he would have to live with the pain.
Then one day, nearly a year after his accident, Nipple came across a Facebook post about a clinical trial for those suffering from phantom limb pain. Curious, he filled out the application and was accepted into the trial. Thankfully, he went on to experience significant pain relief as a result.
A New Method of Nerve Stimulation
The clinical trial Nipple participated in was for SPRINT PNS, a peripheral nerve stimulation system. Unlike spinal cord stimulators, which stimulate centrally at the spine, the SPRINT system focuses on peripheral nerves, where it is able to have a greater impact on nearby sources of pain.
“We’re doing something a little different in targeting the peripheral nerves in the area causing the pain,” says Maria Bennett, president, CEO and founder of SPRINT’s creator, SPR Therapeutics. “The spinal cord stimulators work more centrally, which often means patients with phantom limb pain are going to receive less relief.”
Until the introduction of peripheral nerve stimulators, the only option for locally applying nerve stimulation was through the adaptation of spinal cord stimulator leads, says Christopher Gilmore, MD, one of the physicians involved in the SPRINT clinical trial. This method posed problems, however.
“Ergonomically, the spinal cord stimulator leads aren’t designed to be used there, so we received suboptimal results,” he says. “But now, with a device like SPRINT, we have a much more ergonomic and specific therapy for peripheral stimulation, and I think that dedication to the periphery is what is allowing us to see long-term results with these devices.”
Bennett explains that SPRINT is applied through a thread-like wire that is pre-loaded into a needle. The needle introducer goes through the skin and deploys the wire in proximity to the target nerve that’s causing the pain, and the needle is then removed. A portion of the wire stays inside the body, and a portion of it exits the body and is connected to an external stimulator that’s worn on the skin. After that, patients go home with the system. The doctor can program three different modes for them to use within their therapeutic range—low, medium or high.
Patients with phantom limb pain who have participated in the trial have seen significant improvements in their pain. Nipple, who was treated by Dr. Gilmore during the trial, says his pain went from a 10 to a 2.
“In a case just recently, one of our team members saw a woman who had had amputation pain for decades, and it was the first time in decades she experienced relief from pain,” says Bennett.
According to Bennett, this system can address both phantom limb pain and residual limb pain. “We have done a significant amount of research in lower extremity amputees, folks who have had amputation below the knee,” she says. “Traditional systems have had some success in residual limb pain, but it’s been very difficult to have any sort of relief in phantom limb pain. SPRINT is a device that treats both.”
While SPRINT’s main advantage is targeted pain relief, it does have other benefits. Unlike spinal cord stimulators, which require permanent implantation, this system is inserted subcutaneously and is removed after approximately 60 days of use.
“This therapy doesn’t require anything to be permanently implanted,” says Dr. Gilmore. “That means patients don’t have to fully commit to a permanently implanted device.”
Despite the short-term use of the device, the SPRINT system has shown long-lasting outcomes. “The results of the study demonstrate that the pain relief far outlasts the duration of the temporary implant,” says Dr. Gilmore. “The patients not only realized significant pain relief when the system was on, but there was also a carryover of sustained pain relief that occurred after the device was removed.”
Dr. Gilmore points out that the patients he treated during the trial ranged from those who had undergone previous interventions that had failed to those who had only been exposed to conventional medical management. He says he has seen the long-term pain relief in patients last for many months—and even several years, in some cases.
“Patients report significant pain relief, but pain can be subjective,” says Bennett. “So the most compelling data has been related to how the device has impacted patients’ quality of life.”
Bennett says it has also been important to evaluate how the system affects patients’ abilities to wear prosthetics without any pain. “It can be used pretty early after amputation, helping patients be more active and adapt more quickly to prosthetics,” she says.
The Veterans Administration in Richmond, Virginia, initiated a study on the SPRINT device in acute amputee pain immediately following amputation and has started using the device for those undergoing amputations.
“Earlier intervention is always better—especially earlier in the pain cycle,” says Bennett. “If you can use it earlier, there’s a greater likelihood of having that carryover effect.”
Nipple received treatment with the SPRINT device in 2015, before he received his prosthetic. And now, about two years following his treatment, he’s still experiencing reduced pain. “My pain level has remained where it was when it dropped during the treatment,” he says. “I’ve been impressed. I’ve had a couple of experiences where the pain came back, but it didn’t last. I’ve got no complaints.”
Patients can undergo a second treatment period with the device if their pain returns.
“In many patients, the treatment may not need to be repeated,” says Bennett. “However, in some cases, patients experience a return in pain over time. In the trials, those patients who did experience a return of pain and participated in a second trial with the device were able to have the carryover effect that then lasted for years.”
The large majority of patients in the studies have had favorable responses, but due to each patient’s individual pathology and anatomy, it can be difficult to predict a patient’s outcome. Both Bennett and Dr. Gilmore point out that the temporary nature of the device makes it less risky for a patient to try. Because it’s a short-term treatment—and less expensive and invasive than a spinal cord stimulator—it doesn’t require as costly or permanent a commitment.
SPR Therapeutics received FDA approval for the device last year and is now engaged in a limited launch of the device.
In addition to phantom limb pain, SPRINT has also been used to manage lower back pain, post-stroke shoulder pain, peripheral neuropathic pain and pain following knee-replacement surgery.
“There are patients who didn’t think they could be helped who are now getting back to normal lives,” says Bennett.
“With the pain that hit me before the therapy, I didn’t want to do anything, ” Nipple says. “Sometimes I would just sit there crying. But now that’s changed. I can get out. I sleep better. I can enjoy my life more since I’m not in agony over phantom pain. I ride a Spider now (a three-wheeled motorcycle)—I have 23,000 miles on it and rode it all the way to Wisconsin. If I were still having the phantom pain issues, there’s no way I could’ve done that. I’m able to live my life again.”
Visit sprtherapeutics.com to learn more about the SPRINT device, the data behind it and the clinicians who offer it.