Where pain pills fail, electronic devices can deliver
Despite modern medicine’s pharmacy, chock-full of pain medicines, popping pills fails to stop many kinds of pain.
Thus, for certain kinds of debilitating pain, many doctors and patients turn to technology instead of pharmacology — electronic devices that confuse the pain signal before you even feel it.
Tiny wires implanted in the spinal cord can deliver electronic pulses that eliminate pain in two-thirds to three-quarters of patients deemed suitable for the surgery, says Dr. Brett Stacey, a pain physician at the Oregon Health and Science University in Portland. Though electrical stimulation treatments for pain have been around since the 1970s, doctors say these therapies, which can be life-changing, don’t reach as many people as they could.
Researchers are also experimenting with electrodes implanted at the site of the perceived pain, which could mean against a knee or elbow, or right in the brain in the case of severe, persistent headaches.
The best candidates for these kinds of treatments are people whose pain comes from nerve damage.
Normally, nerves send sensations of pain and touch from all over the body to the brain via the spinal cord; the brain then interprets a pain signal as pain and a touch signal as touch. However, when a nerve is injured — for example, in an accident — that transmission can get scrambled, causing some people to feel even a light touch as searing pain. This so-called neuropathic pain can make even sliding into a sweater or holding hands unbearable.
Electronic stimulation can also be helpful for patients suffering the aftereffects of spinal surgery as well as those who have pain after a bout with shingles.
The procedure basically tries to obstruct one electrical transmission — say, the nerve signal from a throbbing knee or lower back — with another electrical transmission, artificially delivered by a pacemaker-like device, to interfere with the pain message heading toward the brain.
“You substitute a different sensation for the pain,” says Dr. F. Michael Ferrante, director of the UCLA Pain Management Center.
People with these electrical implants say the pain is still there, but the replacement feeling, called paresthesia, overrides it. They describe the new feeling in various ways, as a warm or cool sensation, or like a tingling or a cat purring, Ferrante says.
Electrode implants do not work for all kinds of pain or for all people, and they carry the risks inherent in any surgical procedure, so doctors carefully select patients most likely to benefit. Usually they will consider electronic treatment when the standard medical pharmacopeia fails to soothe a person’s discomfort. That still makes for many candidates: By some estimates, medicines for pain don’t work in some one-fifth to one-third of people — although not everyone who is unsatisfied with medications has the type of pain amenable to electronic treatment either.
Doctors usually start with a trial stimulator, which does not require surgery, before permanently implanting a device in those who found the trial beneficial.
Surgeons place the electrodes in the epidural space, the outermost layer of the spinal canal. This is the same area anesthesiologists target with drugs in women during labor, for example. Wires inserted under the skin connect the electrodes to pacemaker-like device an inch or so in diameter, implanted in the abdomen. Patients get a remote control to modify their settings.
As with any surgical procedure, there is some risk. The surgical site might become infected, or the surgery could cause bleeding in the spine, potentially leading to neurological damage, says Dr. David Sibell, a pain medicine specialist also at Oregon Health and Science University. In addition, Sibell says, people who have these implants should avoid getting an MRI, which could damage the implant or cause it to heat up, damaging body tissues.
Pain specialists say that patients with neuropathic pain often report that, with stimulation, they can suddenly get dressed and go out; over several years, about half of patients report continuing pain relief, Stacey says. One woman, he remembers, was able to walk to her mailbox for the first time in a decade.
Stacey adds that more people could likely benefit from spinal cord stimulation. In particular, he says, there is potential to treat more people with back pain this way — but only once researchers determine who is most likely to find the stimulation useful.
Ferrante agrees that “not enough” people receive stimulation. Some doctors and patients may think it sounds too invasive, but “it’s really just a grandiose epidural,” he says.
Peripheral nerve stimulation, with the electrodes right next to the damaged nerve, is also rising in popularity, Ferrante says.
Beyond damaged nerves, researchers are considering electronic stimulation for headaches. One option is to implant electrodes deep in the brain, where they interfere with signals from the part that causes the pain of cluster headaches.
“That’s remarkably effective,” says Dr. Peter Goadsby, director of the UCSF Headache Center. However, it’s also invasive: “You have to drill a hole in the person’s head and stick an electrode in their brain.”
Goadsby is working on an alternative that would put the electrode on the edge of the brain, where the occipital nerve runs in the back of the head. This nerve connects to the part of the brain that interprets headache pain, so interfering with its activity can swap pain sensations for tingly paresthesia. Goadsby has used devices as small as a matchstick to generate the interfering signal, and they have little risk, he says.
This treatment could be effective for migraines as well as cluster headache but is still undergoing study. Researchers are working to figure out how best to use the therapy and who is most likely to benefit.
