Recommendations of the Neuromodulation Appropriateness Consensus Committee (NACC), announced at the 11th World Congress of the International Neuromodulation Society (INS), address established therapies and preview emerging and potential future advances.
"Physicians concerned with delivering improved care for patients afflicted with chronic pain look for evidence supporting use of new and evolving therapies," said Dr. Timothy Deer, INS president-elect and director of the Center for Pain Relief in Charleston, W. Va. "A knowledge base continues to grow almost exponentially on programmable, reversible therapies - 'digital drugs' - that use devices to deliver targeted electrical stimulation to nerves to manage chronic pain symptoms."
The more than 60 leading experts who form the committee recognize that as neuromodulation devices and techniques evolve, so will recommendations about their use, based on accumulating evidence presented in peer-review journals and medical conferences, such as the biennial world congress of the INS, which uniquely spans the most comprehensive breadth of neuromodulation therapies.
Since the first spinal cord stimulation system (SCS) was implanted in 1967, the devices have advanced with new technological capabilities, including configuration of electrical leads for neurostimulation, miniaturization of components, electrical current delivery, battery capacity, and stimulation programming. Among recent refinements are the addition of accelerometers that adjust electrical current delivery with changes in posture; the availability in Europe of SCS systems designed for MRI compatibility; and surgical navigation that incorporates real-time synthesis of composite images.
"Patient satisfaction and pain control have increased with the advent of new methods of stimulation, such as directing electrical stimulation to the nerve bundle at the edge of the spine, the dorsal root ganglion (DRG), that is a gateway to transmission of sensory signals to the spine and brain," said Dr. Liong Liem, consultant in anaesthesiology and pain medicine at St. Antonius Hospital in the Netherlands, who collaborated on three abstracts being presented at the congress about this technique. Several abstracts indicate that DRG studies in groups of patients ranging in number from six to 32 appear promising, with early results showing an ability to relieve chronic pain in areas that were previously hard to treat, such as the upper limbs, groin or foot, with a lead migration rate of less than 3 percent.
One abstract at the congress presents a minimally invasive approach under development, a wirelessly powered device, measuring 1 cm x 0.8 mm, that is small enough for non-surgical implantation through a syringe to treat failed back surgery syndrome, sciatica, upper leg pain, or craniofacial pain through DRG stimulation.
While spinal cord stimulation may replace painful sensations of chronic pain with a tingling sensation called paresthesia, this sign of active stimulation does not occur with DRG stimulation. Likewise, a form of neurostimulation that uses high-frequency current (up to 10 kHz) also lacks the production of tingling paresthesia sensations. Both DRG stimulation for chronic intractable pain and high-frequency stimulation spinal cord stimulation have received CE mark approval for marketing in Europe. High-frequency SCS is subject to a randomized controlled clinical trial with more than 350 chronic pain patients in the United States that is expected to be completed in 2014.
Preclinical work has demonstrated that high-frequency stimulation of certain neurons (wide dynamic range neurons) can calm their hyperactivity and bring them closer to pre-injury states, said Dr. Jean-Pierre Van Buyten, consultant in pain medicine at the AZ Niklaas Multidisciplinary Pain Centre in Belgium.
A third method, burst stimulation, is reported to further reduce pain. According to an abstract at the congress, more than 60 percent of a group of 60 chronic pain patients found added relief from burst stimulation while participating in a study by Drs. Cecile de Vos, Marjanne Bom, and Mathieu Lenders of the University of Twente, and Sven Vanneste, Ph.D. and Dirk De Ridder, Ph.D. of Brai2n and the University Hospital Antwerp. Burst stimulation also may offer improved pain control for some patients with diabetic neuropathy.
Several abstracts at the June 8 - 13, 2013 world congress present studies that are planned, completed, or underway. Data from 10 clinical studies (of up to 42 patients each), seven case reports or series, and one preclinical trial are being reported regarding high-frequency stimulation. Two abstracts describe a recently initiated study of subcutaneous stimulation, SubQStim, in which up to 400 patients will be recruited at approximately 35 centers in Europe, Canada and Australia for a prospective, randomized, controlled trial in failed back surgery syndrome. Researchers are presenting an abstract at the congress about another trial, investigating multicolumn spinal cord stimulation for low back pain - the PROMISE (Prospective, Randomized Study of Multicolumn Implantable Lead Stimulation for Predominant Low Back Pain) study - that will take place at approximately 30 centers in Canada, Europe, and the United States. The Options trial of SCS for chronic pain in Australia and Europe, meanwhile, will look at optional, additional nerve stimulation in those patients, using four implantable pulse generator ports to independently power up to 32 electrical contacts on two or more leads.
In Berlin, Van Buyten is presenting two years of experience from one of the largest prospective studies of SCS. In it, 72 out of 82 patients (88 percent) who temporarily tried high-frequency SCS - including 15 out of 16 who had not had prior back surgery - had positive results and underwent permanent implantation.
He also will discuss a multi-institution feasibility trial in Europe that used neurostimulation to tone muscles that stabilize the lower back in chronic, nonspecific back-pain patients who failed physical therapy. Of 21 patients who completed the three-month stimulation trial, 84 percent improved work status and medication, 74 percent lowered pain scores, and 63 percent reduced disability scores.
Other congress presentations address new, potentially expanded or improved intervention opportunities for previously hard-to-treat pain in the feet, face, groin, low back, neck, chest, upper limbs, shoulders, and abdomen. Investigators will discuss results of using neurostimulation for pain from diseases such as swine flu, leprosy, and pancreatitis, or chronic conditions such as diabetic neuropathy, migraine and phantom limb pain.
Other variations in neurostimulation for pain that are under investigation include delivery of more energy-efficient waveforms that have the potential to extend useful device life, and fully external forms of neuromodulation using electrical nerve stimulation (ENS), or stimulation beneath the skin (percutaneous electrical nerve stimulation, PENS).
External devices being explored to deliver brain stimulation for pain treatment include repetitive transcranial magnetic stimulation and transcranial direct current stimulation.
Wireless programming of neurostimulators over the Internet is another development that has been reported for patients who have suffered strokes.
The NACC guidance also acknowledges emerging technologies that incorporate feedback control, such as closed loop stimulation that relies on sensors to adjust stimulation, for example, in response to the onset of an epileptic seizure. And, further in the future is the potential to selectively stimulate neurons for therapeutic effect by modifying them to respond to precise wavelengths of light - a research area known as optogenetics. The committee also recognizes the possibility of using regenerative medicine to repair neural networks, a possibility that is also in early stages of preclinical research.
Source: Neuromodulation Appropriateness Consensus Committee