Imagine you are a doctor, and a patient comes into your office with a serious case of back pain. You begin by performing all the standard diagnostic tests, including an MRI and X-ray. Then, you perform an extensive interview. You ask about his psychological history, and rate his level of depression, fear and anxiety. You also assess him for a variety of risk factors that tend to correlate with back pain, including his job satisfaction, and whether or not he is involved in pertinent litigation. After this extensive medical evaluation, you try to predict how intense his back pain is and how long it will last. Unfortunately, your verdict won't be very useful. According to a 2005 paper in Pain, all of these parameters can only explain about 25 percent of the individual variance in chronic back pain.
But what if you tried a different diagnostic strategy? Instead of looking at the patient's back and asking him all sorts of personal questions, let's say you just study his brain. You measure a few brain chemicals, and then image his cortex in an fMRI machine. It turns out that this approach is much more effective. You are now able to predict about 80 percent of the variance associated with chronic back pain. Your judgments about his clinical condition have become significantly more reliable.
That, at least, is the message of a 2006 paper out of the Apkarian lab of Northwestern. The scientists, in a series of simple and well-controlled experiments, located the neural underpinnings of chronic back pain. The scientists found that chronic pain - unlike acute pain - activated brain regions typically associated with negative emotions and response conflict, like the mPFC and rostral ACC. It's as if the chronic pain had stopped being sensory in nature, and was instead built into the emotional brain. That's why it never went away.
But last week, Apkarian's lab came out with a promising paper in Pain that might help suppress those negative emotions. The researchers looked at D-Cycloserine, a drug originally designed for TB infections, but which has also been used to treat social phobias. (It's pretty amazing how many of our brain drugs are sheer accidents.) According to Apkarian's rodent studies, rats with chronic pain were living pain free lives after thirty days of pharmaceutical treatment. Apkarian is hoping to begin a clinical trial with chronic back pain patients later this year. "When we do this in a clinical trial, we expect people to say I still have the pain, but it's not bothering me anymore," Apkarian says. "We think they will have a physical awareness of the pain, but its emotional consequences will have decreased."
Obviously, there's a vast different between curing chronic pain in rats and humans. But I think trying to reduce the emotional component of chronic pain in the cortex is a fascinating and novel approach. Given the dismal success rate of more conventional medical approaches to chronic pain (i.e., surgery and opiate painkillers), it's time we start looking for new alternatives.
Comments (7)
While an interesting point, there is the risk of doctors going back to the old "it's all in your head". Chronic pain is a very serious problem, and, while it may be in part due to certain chemicals, still starts somewhere.
It's true, though, that chronic pain sort of builds up to take on a life of its own. I have chronic neuropathic pain, though, while chronic, it is not permanent. When the pain comes, it can take control of all thoughts and hang out for hours or days. Fortunately, some meds do work for this type of pain (I've found clonazepam to be best, though gabapentin is very good too, but I couldn't handle the side effects.) In my experience, you need to nip the pain in the bud before it builds up, because then it takes over the emotions. I can imagine that people who have no respite are always at that level.
Posted by: km | June 14, 2007 1:40 PM