BB&T

Alon Mogilner, MD, director of functional and restorative neurosurgery at North Shore-Long Island Jewish Health System (Long Island, New York), has been using neurostimulation to treat chronic pain for about 10 years.

But doctors who don't do it have criticized the therapy, Mogilner told Biomedical Business & Technology, asking questions, such as "How do we know it really works?"

Thus Mogilner hopes a study published online Sept. 14 in the medical journal PAIN will increase awareness about neurostimulation therapy for chronic pain and encourage more doctors to prescribe it.

According to the study, neurostimulation improves chronic neuropathic leg and back pain, providing significantly more relief than conventional therapy alone.

The PROspective randomized Controlled trial of the Effectiveness of Spinal cord Stimulation (PROCESS) study, sponsored by Medtronic (Minneapolis), was the largest multi-center randomized controlled trial of neurostimulation therapy ever conducted, according to the company. And, Mogilner added, it is the first study to show pain relief long-term using neurostimulation therapy.

Neurostimulation therapy uses an implantable device to deliver electrical pulses to the epidural space in order to block pain signals traveling through the nervous system from reaching the brain, according to Medtronic.

One hundred patients were randomly assigned to receive conventional medical management or Medtronic neurostimulation therapy for a period of six months, with long-term follow-up to 24 months. Patients assigned to receive neurostimulation were allowed to receive conventional medical therapies, as needed, including oral medications, nerve blocks, steroid injections, physical and psychological therapy, and/or chiropractic care.

All patients in the study had undergone at least one anatomically successful spine surgery for a herniated disk but continued to experience moderate to severe pain in one or both legs, and to a lesser degree in the back, at least six months later.

"Basically, patients in this study were people who have persistent pain in their back or legs, it's nerve pain, related to a nerve injury, and they've been through other surgeries and taken medications that haven't worked and their quality of life is poor," Mogilner said.

The study's primary endpoint was the proportion of patients in each group reporting an improvement of at least 50% in leg pain relief after six months. Patients receiving Medtronic neurostimulation therapy with standard treatments were more than five times more likely (48% vs. 9%) to achieve a 50% or higher reduction in pain compared to patients receiving only standard therapy.

The neurostimulation therapy plus conventional medical management patients also improved quality of life, functional capacity and treatment satisfaction among patients than conventional medical management alone, the company noted.

For the most part, Mogilner said, the therapy is done after other procedures and medication have failed but what has changed is that it's being used earlier in the treatment.

"Now, it works, it's safe, it's easy to do, so it's being used earlier," he said.

After a year of therapy, the main complications among patients receiving neurostimulation therapy included electrode migration, infection, and loss of paresthesia. Medtronic noted that 24% of patients in this group experienced an event requiring surgery. Some patients in each group experienced non-device related events, including an adverse reaction to a drug or the development of a new illness, injury or condition, the company said.

"Patients with persistently disabling neuropathic pain in the back and legs represent one of the most difficult treatment problems in clinical practice, the real-world setting of our trial," said the study's principal investigator, Krishna Kumar, MD, clinical professor and chairman of the neurosurgery department at the Regina General Hospital of the University of Saskatchewan (Saskatoon, Canada). "Our findings show that neurostimulation offers patients in this situation a treatment option that can relieve their pain to a significantly greater degree than conventional medical management alone — and, as a result, helps restore quality of life and functional capacity as well. Neurostimulation therapy should therefore be added to the list of conventional treatments and routinely considered for appropriate patients."

According to Medtronic, neuropathic pain most commonly affects the back and legs. Associated with nerve damage or nervous system disease, neuropathic pain affects up to 8% of the population but is often underdiagnosed and undertreated. Of all pain types, it is among the most severe, chronic, disabling, costly and difficult to treat, the company noted.

"Medtronic offers a range of effective chronic pain management options, from minimally invasive spine surgery to neurostimulation and intrathecal drug therapy," said Richard Kuntz, MD, senior VP of Medtronic and president of the company's Neuromodulation business, which includes Global Pain Management. "We are committed to making ongoing investments across the company in clinical research and product development for the benefit of people with chronic pain and their physicians."

Medtronic's line of neurostimulation systems includes the RestoreAdvanced and PrimeAdvanced neurostimulators and the SynergyPlus+ system, which received FDA approval in 2005. In June the company reported FDA approval of its Specif 5-6-5 surgical lead for neurostimulation therapy, designed to improve the effect of the therapy on low back pain. The company's neurostimulation business also offers therapies for movement disorders, spasticity, overactive bladder, benign prostatic hyperplasia and gastroparesis.

Another company in the neurostimulation space, Advanced Neuromodulation Systems (ANS; Plano, Texas), a division of St. Jude Medical (St. Paul, Minnesota), is also using this type of technology for the treatment of lower back pain, as well as chest pain caused by angina.

Tom Hickman, VP of product management for ANS, agrees that the PROCESS study is a boost for the neurostimulation sector.

"We feel that this study really confirms the importance of neurostimulation therapy and the growing use of spinal cord stimulation for pain," Hickman told BB&T.

ANS also has several large ongoing studies to further validate the use of the therapy, Hickman said, though he declined to speak about any specific studies in process.

"We realize the importance of evidence-based medicine and obviously Medtronic does too. It's important for all participants to continue to bring evidence showing the efficacy and [value] of spinal cord stimulation and neurostimulation therapy," Hickman said.

These studies provide a vehicle, he said, for further education about the therapy and emerging technologies in the sector.

"I think it's going to bring more understanding, probably more importantly, for both the referring physician and the [physician performing the procedure]," Hickman said.

Spinal cord stimulators are similar in function and appearance to cardiac pacemakers, except that the mild electrical pulses from the device are sent to electrical leads near the spinal cord instead of the heart and the device is implanted in the patient's upper buttocks, rather than their chest. The pulses are intended to interrupt the pain signals as they travel to the brain, replacing painful sensations with a more pleasing sensation called paresthesia, according to ANS.

ANS' neurostimulation products include its Eon, Genesis, GenesisXP, and the Renew. The company also offers leads designed to allow physicians more programming options to address complex pain patterns when using spinal cord stimulators.

In July Boston Scientific (Natick, Massachusetts) reported the launch of its Precision Plus spinal cord stimulation system (SCS), a rechargeable SCS neuromodulation device for the treatment of chronic pain of the trunk, back and limbs. The company estimates about 5 million people may be candidates for SCS therapy.

According to Boston Scientific, Precision Plus provides physicians with electronically generated lead (EGL) scan, the only SCS lead scanning technology. EGL scan technology displays the relative position of implanted leads within seconds and without using fluoroscopy or X-ray. The information from EGL Scan can be used to increase programming accuracy, which can lead to improvements in patient outcomes and treatment office operating efficiencies, the company said.

In addition to treating chronic pain, some companies in the neurostimulation market are now using neurostimulation devices to treat movement disorders like Essential Tremor or Dystonia and psychological disorders including depression and obsessive-compulsive disorder.

Other companies involved in developing neurostimulation therapy devices are Northstar Neuroscience (Seattle), and Cyberonics (Houston).