Published October 20, 2020
Editor’s note: Neuroscientist Vitaly Napadow, PhD, is director of the Center for Integrative Pain Neuroimaging and an associate professor at the Martinos Center for Biomedical Imaging at Massachusetts General Hospital and Harvard Medical School, Boston, US. Napadow uses imaging technology to study how acupuncture changes the brain to alleviate chronic pain and is also a practicing acupuncturist himself. In this RELIEF interview, he spoke with freelance writer Stephani Sutherland to discuss the evidence for a beneficial effect of acupuncture on pain, how acupuncture might be working to reduce pain, and much more. Below is an edited transcript of their conversation.
What is acupuncture, and how is it used?
Acupuncture has been around for about 2,500 years or so; it is just one part of traditional Chinese medicine, which also includes herbs and other interventions. Currently, it involves the insertion of fine metallic needles into specific locations on the body. There’s a really long history of acupuncture, and it’s developed a lot over time. There is a theory behind it in terms of traditional Chinese medicine, but a lot of it is based on a sort of empiricism: if a certain body location was stimulated, and this person got better, let’s try that again – and again and again. Things that were successful were retained and placed within an updated medical philosophical construct. This is how medicine developed in the pre-scientific age.
What is acupuncture used to treat, and what does the evidence say about how effective it is for pain?
Acupuncture became popularized in the West in the 1970s after a thaw in the political relationships between the United States and China. That spurred a lot of interest in acupuncture in the scientific community. This was happening at the same time that endogenous opioid receptors [specialized proteins to which the body’s own natural opioids attach] were first discovered. And so, a lot of the very early theories around acupuncture centered on endogenous opioid receptors and endorphins [a type of endogenous opioid]. Because of that link, the vast majority of research in acupuncture, and a lot of the clinical trials evaluating acupuncture, have been in the pain field. So we know a lot more about acupuncture for pain than we do about acupuncture for other disorders.
The most definitive evidence we have comes from a meta-analysis [a type of statistical analysis that brings together results from multiple studies]. That data showed that acupuncture significantly reduced pain across musculoskeletal, headache and migraine conditions and other chronic pain disorders. This effect was significant relative to “sham acupuncture” – and I’ll get into that in a second – but relatively small, on par with the effect of non-steroidal anti-inflammatory drugs, known as NSAIDS. When acupuncture was compared to usual treatment controls and not to a placebo sham acupuncture, the effect size was significantly larger.
So then we get into the interesting conundrum of placebo effects in acupuncture, and what are the proper control treatments. Acupuncture, as any medical device, is very difficult to develop a control for; it’s not a pill. So, different forms of sham acupuncture as a control have been tried over the years, such as sticking the needle into a location that was close to, but not at the exact location where you’re supposed to stick it into.
Then a guy named Konrad Streitberger developed a sham acupuncture needle called the Streitberger needle. He got this idea when he was in China studying martial arts, where they used these practice swords. He was also interested in theater – the idea of a stage dagger where somebody gets stabbed and they die, but they’re not really dead because it’s theater. So he took that idea and developed the Streitberger needle, which is a sham acupuncture needle, where the pointy part of the needle disappears into the hilt of the acupuncture needle, so when pressed against the skin it looks like the needle is entering the skin but actually it’s not penetrating the skin. It was ingenious – a brilliant idea at the time. But unfortunately, it was not based on any understanding of the mechanisms of how acupuncture might be working. So even with a sham acupuncture needle, you are stimulating the skin receptors, which allow for the detection of various sensory stimuli over that acupuncture location, and that certainly produces a physiological response, which may or may not be clinically effective.
Acupuncture research has been held back by trying to come up with a sham acupuncture treatment compared with other device-based therapies that have not been tested as rigorously in large trials. It has also been held back by the baggage of the traditional Chinese medicine theoretical framework, which was developed from a philosophical standpoint in a pre-scientific age. That framework can best be thought of as a system of correspondences with our current understanding of anatomy and physiology – an idea suggested by acupuncturist Stephen Birch a decade or so ago. So when modern scientists look at it, they say, “well, that can’t work, it must be a placebo.” However, if you actually look at acupuncture for the procedure that it is, and not at the philosophical constructs that it comes from, you see it in a completely different light, which is how I approach it from a scientific research point of view.
Going back to this large clinical trials meta-analysis, we’re talking about 20,000 subjects; there were very large studies put into this analysis. So when people say we just don’t have enough clinical research on acupuncture, it’s just not the case. There’s so much research that’s been done. It doesn’t uniformly show that acupuncture is an amazing panacea that will help every patient, but on the other hand we do have to look at that literature and take it for what it is – which is that acupuncture is indeed effective for chronic pain.
So how do researchers think that acupuncture has beneficial effects?
There are different forms of acupuncture and different ways that the needle can be stimulated. It can be stimulated by mechanical energy such as inserting the needle and then twisting it or lifting it and pressing it. It can be stimulated by heat, where the needle is inserted and then you put an herb over top of the needle, and then you light that herb on fire – that’s called moxibustion. And you have electroacupuncture, where you attach electrodes to two or more needles, and you pass current between those needles. All of these things have been called acupuncture, but these different forms of acupuncture might have very different mechanistic pathways by which they’re working to impact the nervous system and pass energy into it.
There is very interesting research into what’s happening at the site of the needle and in the peripheral nervous system, and then in the central nervous system [brain and spinal cord], which is where I come in, because I’m a neuroimager; I study what’s happening in the brain. However my research is also informed by my background as a trained acupuncturist, and I’ve practiced acupuncture at the pain management center for Brigham and Women’s Hospital and Harvard Medical School since 2006. One afternoon a week I’m there running an acupuncture clinic embedded in this very conventional medical center.
Clinically speaking, acupuncture is sometimes used directly to treat a muscle ache or a tight muscle in your neck or back; the needle could be inserted right at that location because you have, say, a knot. So, one way you can use acupuncture is to take the needle, stick it in at that location, and stimulate it. That induces a biological response to this very small injury that’s happening in response to the needle entering the body. That can serve, over the long term, to increase blood flow to that area and break up that knot and reduce the pain because you’re also reducing local inflammation, which is irritating the nerve.
But, if you were using acupuncture to treat, say, a toothache, the acupuncture targets are not local at the mouth; they’re in the hand. So, the location of stimulation is very distant from the location of the pain. In fact, a lot of acupuncture is practiced with needles being inserted away from the site of the pain.
So, when you’re using acupuncture for treating local pain, the effect could be very local, affecting local receptors and the tissue milieu. Whereas if you’re treating a toothache and you’re stimulating the hands, I would say that is much more likely to be mechanistically driven through the peripheral nervous system at the location where you’re sticking the needle and then on to the brain, serving to dampen pain sensations that may be felt somewhere else in the body.
What have you been working on in your research with brain imaging?
We’ve completed multiple studies with acunpuncture now. For instance, we’ve been trying to understand how acupuncture works by studying people with carpal tunnel syndrome. As opposed to fibromyalgia or low back pain, carpal tunnel syndrome is a chronic pain disorder where a singular nerve is affected, the median nerve, which is compressed at the wrist.
In a 2017 study, we randomized patients to either getting electroacupuncture directly at this location versus getting acupuncture at a place far away from that location, on the ankle on the opposite side of the body, where local mechanisms are less relevant and acupuncture would probably be acting through the central nervous system. We used Streitberger needle acupuncture as a sham intervention. We found that while both local and distal acupuncture and sham acupuncture reduced pain in carpal tunnel syndrome, it was only real acupuncture that had physiological effects.
To measure those effects, we did nerve conduction studies, where you measure the speed of an impulse over the median nerve at the wrist. In carpal tunnel syndrome patients, that speed is reduced; it’s much slower because of changes happening at the nerve. We saw that real acupuncture can affect that objective biological outcome; it did improve it somewhat. However, we also found differences between carpal tunnel syndrome patients and healthy controls in the primary somatosensory cortex, the part of the brain that receives sensory information. In the people with carpal tunnel, the cortex had been remapped somewhat. We found that real acupuncture, both local and distal, changed that remapping in the brain in a beneficial direction.
And so, it was interesting that while real and sham acupuncture reduced pain to an equal degree in these patients, it was the objective outcomes that really differentiated real versus sham acupuncture. That might be one of the reasons why it’s been so difficult to study acupuncture, because when you’re comparing it to sham acupuncture procedures, it’s very hard to find a signal between the two. But frankly, that’s the case for a lot of drugs, even with a very good sham condition, because the placebo effects for patient-reported pain are so large.
The field of placebo research overlaps with acupuncture, because placebo effects also work through endogenous mechanisms of pain modulation. And there is some overlap there with acupuncture, to a degree, as you are tapping into endogenous mechanisms of pain relief.
Can you say more about endogenous opioids, and how they affect pain?
Endogenous opioids are what are called neuromodulators, which are chemicals that are released in the brainstem and hypothalamus; we all have them. These are the body’s way of reducing pain perception, because sometimes it’s really important not to be distracted by pain. For example, if you’re running away from an animal that has injured you, you need to keep running. You’ve got to get away from that tiger, so you’ve got to dampen the pain so you can keep going.
From an evolutionary point of view, this is likely why these systems developed over time. We see them in everything from professional athletes playing soccer with a broken bone to soldiers undergoing all kinds of bodily harm and continuing to do their job. These endogenous control mechanisms release endorphins and other neuromodulators in the brain to control the pain.
So acupuncture engages that pain modulation system?
Acupuncture is interesting because it’s actually a very complex intervention. What I mean by that is that it operates on a bottom-up level, where you have a stimulus at a certain location on the body, and you have information that’s going up to the brain from the body due to the needle stimulation at peripheral locations. Once the information gets into the brainstem and into higher brain structures, it has effects on multiple systems, from somatosensory to cognitive to affective and reward circuitry.
But with acupuncture, there is also this very complex, ritualistic clinical interaction that’s happening between the acupuncturist and the patient. They spend a lot of time together, almost like psychotherapy. So there’s also potential endogenous pain modulatory mechanisms that are at play due to this interaction between the clinician and the patient. So what we call “therapeutic alliance” is a whole other potential mechanism by which acupuncture might also be reducing pain. Our research lab is trying to study both of these mechanisms.
How did you get interested in doing both acupuncture and acupuncture research?
My background is actually in biomechanical engineering, which during my PhD years got me into imaging. During that same time, I was going to night school for acupuncture on the side as a way to get away from research and coding; I had pretty much zero interest in acupuncture research at that time. After I graduated, I didn’t want to be a full-time acupuncturist, but at the same time, I really loved interacting with patients and being a clinician. It seemed like the natural step forward in my postdoc would be to get involved in acupuncture research, and I got involved in neuroimaging. That brought me into the pain imaging field, and now I consider myself more as a pain imager than strictly an acupuncture imaging scientist.
What would you say to someone with chronic pain considering acupuncture treatment?
The safety of acupuncture is very good; there’s a very low risk of serious side effects. Find an acupuncturist who’s reputable and make sure you’re seeing somebody who’s certified nationally or at the very least, state certified. More health insurers are starting to cover acupuncture.
Usually I tell patients to give it three to five treatments. You’re not going to be healed necessarily, but you should see some form of improvement in that time period. Typically, you’d go once a week for three to five weeks and then reevaluate after that how effective it’s been for you. It very well may help you; it may not. It’s something that has a good enough safety profile that it’s worth giving it a try.
Do you treat people with chronic pain and see improvements?
I work in what’s called a tertiary pain clinic, meaning these are patients who have gone through their primary care providers and various interventions have failed to control their pain, and so that’s why they’re coming into the pain clinic where I work. That’s a real difference from a walk-in clinic, and the success rates really differ compared to a tertiary pain clinic, where you’re dealing with somebody who has had long-standing pain. And the more chronic it is, the harder it is to combat that pain.
Having said that, even in that kind of setting, I’ve seen patients get better and so you need to have hope. As a patient, hope is a very important thing that you cannot lose, and acupuncture is one way that you can continue to try to reduce your pain and learn how to live with pain.
Stephani Sutherland, PhD, is a neuroscientist and freelance journalist in Southern California. Follow her on Twitter @SutherlandPhD