Acupuncture and Pain (continued)
Building an Evidence Base: Clinical Research Progress
"Our goal is to build a house of evidence," explains long-time NCCAM grantee Brian Berman, M.D., director of the Center for Integrative Medicine at the University of Maryland School of Medicine.
To date, much of the progress in clinical research on acupuncture has come from an interdisciplinary approach that includes experts in acupuncture, clinical trial methodology, biostatistics, and relevant diseases such as osteoarthritis or carpal tunnel syndrome.
"What we've learned so far is that the most promising area for using acupuncture is pain," says Dr. Nahin. Clinical studies are showing acupuncture's efficacy for some types of pain, such as back, osteoarthritis, and postoperative pain. For example, a systematic review supports the use of acupuncture for postoperative pain management. An NCCAM-supported Phase III clinical trial led by Dr. Berman showed that acupuncture relieved pain and improved function in patients with knee osteoarthritis when it was used with standard medical care, including anti-inflammatory medications and opioid pain relievers. In a large study published in 2009, researchers found that people suffering from chronic low-back pain who received acupuncture or simulated acupuncture treatments fared better than those receiving only conventional care. Pilot studies have looked at acupuncture in posttraumatic stress disorder and chemotherapy-induced nausea and vomiting. And, the Cochrane Collaboration reviewed 11 randomized trials and found that acupuncture may be a valuable option for patients suffering from tension headaches.
But these clinical outcomes may involve more than acupoints and needles. Other aspects of the acupuncture experience may play important roles in healing, including reassurance provided by the practitioner, expectation of benefit, and the sensory experience elicited by acupuncture needling, which has been called de qi and variously described as aching, dull pain, tingling, or a heaviness. In several recent studies researchers have carefully designed their studies to compare true acupuncture to simulated acupuncture and have tried to mimic the sensory experience of true acupuncture so that patients would be unaware of whether they were receiving true or simulated acupuncture. In some of these studies, such as the 2009 study on low-back pain, both simulated acupuncture and real acupuncture produced greater benefit than standard therapy.
The study led by Dr. Napadow examined the effects of acupuncture in patients with carpal tunnel syndrome. In these participants, nonpainful stimulation of finger 3 on the right hand produced hyperactivation in the left primary sensorimotor cortex. After acupuncture, this hyperactivity was reduced. By V. Napadow, Ph.D.; used with permission
Acupuncture's Effect on the Brain
Fascinating results regarding the possible use of acupuncture are coming out of clinical trials, but what are the mechanisms of action behind these effects? For example, NCCAM-supported researchers are tapping into the power of genomic techniques to look at what is happening at the cellular level and study acupuncture's effect in the expression of genes involved in pain. Researchers are also harnessing cutting-edge technologies to uncover pathways in the brain involved in the body's response to acupuncture.
"We wanted to know if the brain was involved in the process and how it was involved," says Bruce Rosen, M.D., Ph.D., principal investigator of an NCCAM Center of Excellence on Acupuncture and Brain Activity at Harvard Medical School. And the time is right to approach these questions. Powerful imaging techniques—fMRI (functional magnetic resonance imaging), PET (positron emission tomography), and MEG (magnetoencephalography)—are now available to reveal areas of the brain affected during pain and to map the impact of acupuncture in patients experiencing pain.
"With the advent of noninvasive brain imaging we were able to begin looking at human brain response to acupuncture and start to evaluate potential mechanisms in humans," says Dr. Napadow. And they found differences in this brain response between people with chronic pain and healthy controls.
For example, in research on carpal tunnel syndrome, which can cause pain and numbness due to compression of nerves in the wrist, Dr. Napadow and colleagues performed fMRI before and after acupuncture and found that patients with carpal tunnel syndrome responded to acupuncture differently from healthy controls. Their studies, published in 2007, showed that the brain of patients with carpal tunnel syndrome responded to acupuncture needling with greater activation in an area of the brain known as the hypothalamus and deactivation in another area known as the amygdala. These two areas of the brain are involved in behavior, emotions, long-term memory, and maintenance of a persistent pain state.
A number of aspects of the acupuncture experience probably contribute to the neural effects and quite possibly to the clinical benefit. Researchers have learned that the direct effects of acupuncture may be amplified by the expectation of benefit. "We found that expectation itself is a powerful modulator of the brain," says Dr. Rosen. "Expectation seems to be as powerful an influence on reduction in pain as acupuncture needling, though it appears to work in a different network in the brain that may be complementary."
