From the Archives: The State of Pain Research

cerebrum_0612_painNearly four years ago, we ran a news story that asked, “Is the neuroscientific study of pain lagging?” From the 2011 story, by Kayt Sukel:

Earlier this year, scientists, politicians and other healthcare advocates came together to share their hopes for the next decade of neuroscience research at the One Mind for Research (OMR) Summit in Boston. At a session highlighting the neurobiological consequences of war, Clifford J. Woolf, a pain researcher at Harvard Medical School and Children’s Hospital Boston, stated, “We have made enormous progress in promoting survival…but, in fact, an area that has really lagged behind relates to the pain associated with combat injury.”

The word that many locked on to in that statement was lagged. In a variety of publications and meetings in the past few years, the idea that the study and treatment of pain, particularly chronic or neuropathic pain, is somehow behind where it should be keeps coming to the surface—and that is whether it’s pain associated with combat, cancer, or some other disease state. But with more than a dozen research journals dedicated solely to the topic of pain and thousands of new pain-related papers being published each year, does a word like lagged accurately reflect the state of its study?

The researchers Kayt talked to said it did, and explained some of the challenges, from relying (or discounting) patients’ reports of pain to trying to translate a human perception into animal models.

That same year, though, we did a Q&A with Jack W. Tsao on his investigation into mirror therapy for phantom limb pain:

My colleagues and I have been working with amputees at Walter Reed Army Medical Center for the past five years to investigate Phantom Limb Pain (PLP), which is the sensation that an amputated limb is still present, with painful sensations appearing to emanate from it. An amputee may feel, for example, that the limb is frozen in an uncomfortable position, or he or she may experience burning, stabbing, shooting, or electrical shock-like pain.

Mirror therapy (MT) was first reported in the mid-1990s by a neurologist named V.S. Ramachandran at the University of California-San Diego, who studied a small series of upper-extremity amputees who were years or decades post-amputation. In this study, MT successfully relieved PLP in about 60 percent of the group (9 of 15 patients). In the decade that followed, nobody ever did a randomized, controlled trial to see if MT actually works or not. So in 2005, our group conducted the first controlled trial of MT, in which we split subjects into three groups: one group received mirror therapy; one group underwent the same process as the mirror therapy group but with a mirror that was covered with a cloth to prevent the reflection of the limb moving, and a third group closed their eyes and visualized their phantom limb moving.  We showed that MT clearly is better than the two control therapies.

Proving one therapy works is great, but we need more treatments, too. The next year we asked David Borsooki to weigh in for Cerebrum. In his essay, “A Future without Chronic Pain,” he described some promising advances and recommended steps to facilitate new treatments, including establishing integrated clinical neuroscience centers bridging the gap between bench and bedside.

Chronic pain is an enormous public health challenge that deserves immediate focus and attention. … A layered approach could be a strategy for immediate, intermediate, and long-term progress. For example, significant research investment and focus on surgically induced neuropathic pain could have early benefits. Doctors in the United States perform an estimated 48 million inpatient surgeries each year; these are open laboratories in which to collect and evaluate data and implement clinical trials. Our knowledge of the transition from acute to chronic pain is based not on scientific evidence but on an arbitrary timeline; clearly, for conditions such as surgically induced neuropathic pain, the initial surgical trauma (even while under anesthesia) is the initiating event that progresses to chronic neuropathic pain in substantial numbers of patients.

Approaching chronic pain as a national emergency would allow for a better future in terms of both treatments for chronic pain, costs to society, and individual well-being. It is time to take an honest look at where we are, get rid of unnecessary and unproven treatments, and advance neuroscience to the patient in the form of better treatments. Pain neuroscience has never been so exciting or well positioned in terms of the potential it offers to change the current impasse. But it will take bold decisions to put into place a vision and plan of action.

In the area of reporting and measuring pain, I’ve recently heard reports that researchers using imaging can identify “signatures of pain.” Researcher Clas Linnman and others  described how they combine PET and MRI imaging to see such signatures during the annual meeting of the American Association for the Advancement of Science (AAAS) in San Jose.  “With imaging we can describe different aspects of the pain experience, even down to the molecular level. We can say more than just ‘less pain,’” he said. Here’s Linnman explaining the method (video credit: AAAS/Carla Schaffer):

Imaging also could be used to see if a treatment is working and, perhaps, to predict which drugs would help which type of patients. Kayt reported on a data-mining proof of principle experiment in which researchers fed imaging data into an algorithm to see if it could “decode the patterns” of relief from pain.

Four years on, there has been some progress. Still, as I heard from panelists at last month’s  Neuroscience and Society (Neuroseries) event at AAAS’s headquarters in Washington, DC, we still have a ways to go to help people suffering with chronic pain (videocast).  The need for relief is mighty: As many as 100 million people in the US have chronic pain, more than have diabetes, heart disease, and cancer combined.

—Nicky Penttila

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