The Brain

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The Brain A Tiny Key to a Terrible Lock
Scientists have traced chronic pain to a defect in one enzyme in asingle region of the brain. Could this be a decisive turn in the battle against pain?
by Carl Zimmer; illustration by Bryon Eggenschwiler
From the June 2011issue; published online June 16, 2011 

For tens of millions of Americans, pain is not just an occasional 
nuisance—a stubbed toe, a paper cut—but a constantand torturous companion. Chronic pain can be focused on an arthritic knee or a bad back, diffused throughout the body, or even located virtually in an amputatedlimb. It can linger for years. And it can transform the world so that merely the light brush of a finger is an agonizing experience. The daily devastation canbe so intense that people with chronic pain are up to six times as likely as those who are pain-free to report suicidal thoughts.
Despite the toll, chronic painhas been relatively neglected by 
doctors. Perhaps that’s because it seems less real to them than other, more tangible medical disorders. With no equivalent ofa stethoscope 
or thermometer to measure pain objectively, they have had to rely 
entirely on their patients’ testimony.
As neuroscientists learn more aboutthe biological basis of pain, the situation is finally beginning to change. Most remarkably, unfolding research shows that chronic pain can cause concrete,physiological changes in the brain. After several months of chronic pain, a person’s brain begins to shrink. The longer people suffer, the more gray matter they lose.