A new implantable spine stimulation device has received high marks in an ongoing prospective study, delivering significant pain relief without paresthesia, a common adverse effect of conventional spinal stimulation.
The study was one of several highlighted posters at the American Academy of Pain Medicine 27th Annual Meeting, held in Washington, DC.
The results were presented by Adnan Al-Kaisy, MB ChB, FRCA, consultant in pain medicine and clinical lead of the Pain Management & Neuromodulation Centre of Guy's and Thomas' Hospital in London, United Kingdom.
"Spinal cord stimulation has been around for 40 years and is the preferred treatment for patients with failed back syndrome surgery," Dr. Al-Kaisy told Medscape Medical News in an interview, "But unfortunately it produces paresthesia, with reports in the literature of up to 71% of patients experiencing that adverse effect."
The new technology, known as the Nervo System (Nervo), uses super high-frequency stimulation that suppresses the sparse fibers of the lower back, Dr. Al-Kaisy said. The frequency is so high — up to 10 kHz — that patients experience none of the usual tingling sensations associated with cord stimulation. "They don't feel anything apart from their pain getting better. And that makes this approach unique," he said.
Dr. Al-Kaisy and his colleagues are conducting a prospective trial at Guy's and St. Thomas' Hospital, as well as at a center in Belgium.
"Between us, we've recruited about 75 patients who are suffering from severe lower back pain," Dr. Al-Kaisy said.
In a preliminary part of the trial, the investigators temporarily inserted leads from the device into the patients' spines between T8-T11 and assessed the effects for up to 4 weeks. "We followed them to see if their pain improved, if they had improvement in function, if they were able to reduce their medication."
If the results of the temporary insertion were successful, the device was permanently implanted and patients were provided a remote control so they could adjust the stimulation as desired.
In the poster presentation, Dr. Al-Kaisy presented data on 30 patients who had completed the preliminary trial and had been implanted with the device.
With follow-up averaging 2.4 months, visual analog scale (VAS) scores for back pain were reduced from 7.6 to 1.7 cm, a decrease of 77.1% (P < .05), he reported. VAS scores for leg pain were decreased from 7.9 to 1.0 cm (89.4%; P < .05). The investigators also used the Oswestry Disability Index to assess how back pain affected patients' everyday lives. That measure improved from 61 (P < .001) to 44 (P < .001).
Use of the device reportedly also improved patient function without movement-induced shocking. "When patients used the system overnight they reported no change in stimulation when they adjusted their sleeping positions. So that gave them less pain at night and improved quality of sleep," Dr. Al-Kaisy said.
He noted that with the use of conventional spinal cord stimulation, if paresthesia over the lumbar dermatomes can't be obtained, the pain can't be treated successfully. "This device changes that paradigm. Besides providing sustained analgesia, it avoids paresthesia, and that's a major advantage," he said.
There were a few adverse effects noted with use of the device. Two patients implanted reported nerve irritation and 1 reported the development of a hematoma, Dr. Al-Kaisy said.
The device does have a technological drawback, Dr. Al-Kaisy said. "Since the stimulation is on 24/7, it requires a significant amount of power. Because of that, the patient has to plug in and recharge the battery every day." However, he said, none of the patients in the cohort complained about that limitation. "They regard it as a good deal, I think."
Dr. Al-Kaisy emphasized that the data he presented were preliminary. Even so, he said, "We think the device is a significant advance in the treatment of lower back pain because conventional spinal cord stimulation has been around for decades and it's never produced the quality of pain relief that we've seen in these patients," he said.
The device is not yet approved for use by the US Food and Drug Administration. It received approval in Europe late last year.
Funding for the study was provided, in part, by Nervo of Menlo Park, California. Dr. Al-Kaisy has disclosed no relevant financial relationships.
American Academy of Pain Medicine (AAPM) 27th Annual Meeting: Poster 202. Presented March 26, 2011.
Steven Fox • Medscape Medical News © 2011 WebMD, LLC