Battling chronic pain

Implants short-circuit signals to the brain

October 14, 2007|By Chris Emery | Chris Emery,Sun reporter

The crash that grounded Linda Berl had nothing to do with the Piper Cherokee that she flew to shuttle needy Eastern Shore patients to local hospitals. What got her was a low-altitude tumble from the front porch of her Delaware home in 2001 that left her with a broken leg and persistent, debilitating pain.

"Sometimes I'll feel like my foot is on fire," she said. "It feels very deep, like it's in my bones."

The pain dominated Berl's life for years, but now the 47-year-old Smyrna resident hopes to return to flying with the help of a spinal cord stimulator -- a device that Johns Hopkins doctors implanted under the skin of her back to override pain signals traveling from her body to her brain.

The stimulators, which cost $30,000 to $40,000, are a last resort for patients who suffer from severe chronic pain that physical therapy and drugs can't relieve. And their use is increasing -- along with the debate over their effectiveness.

Experts say implant procedures have expanded about 20 percent annually in recent years. One manufacturer estimates that 40,000 devices have been implanted in the past year alone.

Some doctors say they should be used even more often -- and earlier in a patient's treatment. But skeptics say that evidence the devices work is shaky, and that their pain-fighting ability is often short-lived.

"What is not really known is the long-term effectiveness," said Judith A. Turner, a pain researcher at the University of Washington School of Medicine. "And with chronic pain, that is the real question."

Doctors typically use stimulators on patients who suffer chronic pain in their lower bodies. The pain may result from a number of conditions, including complications from lower-back surgery, an inflamed spinal cord and nerve damage from a leg injury.

Dr. Paul Christo, the Johns Hopkins surgeon who implanted Berl's stimulator, said the ancestors of these devices date back to Roman times, when doctors placed torpedo fish -- a species of electric ray -- under patients' feet to relieve pain from headache and gout.

In the 1960s, researchers developed stimulators that applied current directly to patients' spinal nerves through electrodes running along the spine. They believe the impulses override pain signals traveling along the spinal cord, much the way turning up the volume on your TV can help drown out the noise of a neighbor's radio.

"The theory holds that if you stimulate the large fibers of the spinal cord," Christo said, "it closed the gate to painful input from smaller fibers."

Authorities say early skepticism about stimulators gave way to overprescription for patients who got little real help from the devices. "There was a period of time when they were adopted enthusiastically and uncritically," said Dr. Richard B. North, a neurosurgeon at Sinai Hospital who has helped design spinal stimulators.

That, in turn, led to renewed skepticism that lingers today. "It's still underutilized, compared to other treatments for pain," North said.

But Turner argues that the stimulator's effectiveness is still in question -- in part because it's so difficult to determine whether pain relief is due to the therapy or to the power of positive thinking.. "It's impossible to tell if it's a real effect or a placebo effect," she said

Previous studies have suggested that effectiveness fades after two or three years, she said, and "the complication rate is fairly high.

"There have been some encouraging results for some patients in the short term," she added. "But we need to know more about the longer term."

In Berl's case, the stimulator has worked where other therapies have failed. The fall from her porch broke her leg, and doctors had to shore up the fracture with a large metal rod and several screws. When her agony failed to subside as she healed, doctors diagnosed complex regional pain syndrome (CRPS).

"I was insane with the pain -- I couldn't get away from it," she said. "I knew it should be disappearing, but it didn't."

The symptoms of CRPS were first described by Silas Weir Mitchell, a Civil War doctor who reported that soldiers complained of a terrible burning pain that lingered long after their gunshot wounds should have healed.

The exact cause of this chronic pain is still unknown. In some cases, it can be traced to nerve damage from trauma -- but the nerves often appear undamaged, and the pain can spread to an area much larger than the original injury.

One theory holds that the initial trauma accustoms sensory nerves to transmitting strong pain signals, a phenomenon known as "windup." The injury heals, but the nerves continue to bombard the brain with the pain messages.

A related mechanism, known as "central sensitization," may also be at play. Here, nerves higher up in the nervous system, in the brain or spinal cord, become oversensitized after an injury.

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