The mystery of chronic pain
Why do some people develop chronic pain following an injury while others do not?
The question has remained a mystery to both doctors and scientists.
Chronic pain affects millions of people. People who suffer from severe, chronic pain know only too well how it can utterly disrupt and damage day-to-day life. Pain can make it a challenge to get through each day let alone to enjoy even the simplest daily activities.
Chronic pain has historically been misunderstood. The medical profession used to believe that pain could only be a manifestation of an underlying injury or disease. As such, doctors focused on treating the underlying cause of the pain, with the belief that once the injury or disease was cured the chronic pain would then disappear.
If no underlying cause could be found for the pain, then the patient was often told that, “the pain must be in your head”. Unfortunately, some doctors still practice in this manner, having no appreciation for the unique difficulties experienced by sufferers of chronic pain.
A new study led by researchers at the Rehabilitation Institute of Chicago (RIC) and Northwestern University Feinberg School of Medicine has revealed that the risk of a patient developing chronic pain is determined by the brains anatomical properties, and not the initial injury.
“While simple, the logic of addressing problems at the site of an injury to remove pain has resulted in only limited success,” said senior study author Marwan Baliki, PhD, research scientist at RIC and an assistant professor of physical medicine and rehabilitation at Feinberg. “The central processes of chronic pain have largely been ignored, so our research team set out to better understand the brain’s role.”
The researchers found that patients who developed chronic pain had a smaller hippocampus and amygdala compared with those who recovered. The hippocampus is the primary brain region involved in memory formation and retention, while the amygdala is involved in the processing of emotions and fear. In addition to changes in size, these regions also showed differences in connections to the rest of the brain, particularly to the frontal cortex, an area involved in judgment.
The study’s results challenge long-standing views of the science of pain, establishing that the gross anatomical properties of the brain determine the most risk for developing chronic pain.
The results pave the way for the development of a different approach for the prevention and treatment of chronic pain.
The full study, “Corticolimbic anatomical characteristics predetermine risk for chronic pain,” will be published in the June edition of Brain. In addition to Apkarian, Baliki and Vachon-Presseau, study authors include Pascal Tétreault, Bogdan Petre, Lejian Huang, Sara E. Berger, Souraya Torbey, Alexis T. Baria, Ali R.Mansour, Javeria A. Hashmi, James W. Griffith, Erika Comasco, and Thomas J. Schnitzer.