Pain control devices give out
Spinal cord stimulators are one of the few options for patients with extreme pain that no longer responds to drugs. Implanted near the base of the spinal cord, the devices deliver electrical impulses to specific nerves and block pain signals from reaching the brain.
Now researchers have found that, for one little-understood condition, the benefits of the devices diminish over time -- and disappear after three years.
The stimulators have long offered particular hope to patients with complex regional pain syndrome, an often-agonizing nerve disorder that can occur after surgery or an injury involving a limb. The condition, which can leave patients disabled and unable to work, affects about 200,000 Americans.
Treatments include a handful of drugs ranging in strength from acetaminophen to morphine. One in eight Americans with the disorder has received a spinal stimulator, which is often seen as a last resort. The device and the procedure to implant it cost around $20,000. Previous studies of stimulators showed clear benefits, but those trials lasted no more than two years.
The report, published as a letter in the New England Journal of Medicine’s June 1 issue, provided the first long-term look at the performance of spinal stimulators in patients with complex regional pain syndrome.
Dutch researchers tracked 54 patients for five years. Thirty-six patients received stimulators and physical therapy, and 18 received physical therapy alone.
Patients’ pain intensity was rated on a scale of 1 to 10. For the first two years, patients with stimulators reported more improvement than patients receiving only physical therapy. The difference between the groups was statistically significant.
After three years, however, the pain-alleviating effect of the device diminished and was no better than physical therapy, researchers found.
Patients in the stimulator group had pain intensity of 5.2 at the end of three years, down from 6.7 at the start of the study. The physical therapy group had pain intensity of 6.2, down from 6.9 when the clinical trial began.
There was no statistically significant difference in improvements seen between the groups.
Medtronic Inc., the Minneapolis-based manufacturer of the devices, said the stimulator models used in the study were outmoded and the method of rating pain was too subjective.
Still, Dr. Robert J. Schwartzman of Drexel University College of Medicine in Philadelphia said the study results mirrored his experience. Schwartzman said he no longer offers the devices to patients with complex regional pain syndrome. The study should discourage other doctors from using them, he said.
But Dr. Marius A. Kemler of the Academic Medical Center in Amsterdam, the lead author of the report, said he had not soured on spinal cord stimulators. Despite the disappointing results, he said, most patients in his study would opt for spinal cord stimulators if they could do it over, because they remain one of the only treatments available.
