Chronic pain treatments may get boost from high-tech imaging

SAN JOSE, Calif. — High-tech brain imaging could improve treatments for chronic pain, new research suggests.

Researchers from Uppsala University in Sweden and Harvard University have found that PET and MRI images can pinpoint cellular and molecular changes in the body and brain that accompany chronic pain. The scientists used chemical tracers that concentrate in the regions where chronic pain affects body and brain tissue. Measuring changes in the concentration of the tracers during a patient’s treatment can show how well a therapy works, Harvard neuroscientist Clas Linnman said February 13 at the annual meeting of the American Association for the Advancement of Science.

“The images are good predictors of whether drugs in clinical trials for chronic pain are going to work,” Linnman said. Providing such information early in drug development could make the process of developing medications for chronic pain more efficient, he said.

Scientists struggled for decades to identify changes to the structure and chemistry of the brain that occur with chronic pain. Recent studies have begun to identify molecules and proteins that hint at where and how chronic pain reshapes nerve cells and changes amounts of various proteins in the brain (SN: 6/30/12, p. 22). One of the most recent studies, published January 12 in Brain, found that glial cells, which support and protect nerve cells, can also play a role in chronic pain.

In the study, researchers measured amounts of a radioactive tracer attached to the translocator protein, which is linked with inflammation, in the brains of people with and without chronic pain. The translocator protein acts as a marker for the activity of glial cells. Images combining PET and MRI scans showed that healthy people had less translocator protein in their brains than people with chronic back pain did (SN Online: 1/13/15).

Marco Loggia, a neuroscientist at Massachusetts General Hospital in Charlestown, led that study. He agrees with Linnman that tracking the levels of the protein in chronic pain patients’ brain as they are treated could help scientists identify which therapies are most effective. Imaging may also help in developing new drugs that act on the translocator protein to reduce glial cell activation and reduce pain, said Loggia, who was not at the meeting.

Combining PET with MRI “gives us a whole new perspective on pain,” Linnman said, explaining that the images let scientists look at the anatomy affected by chronic pain.

When it comes to treating patients, such advanced imaging may not be necessary, said neuroscientist A. Vania Apkarian of Northwestern University’s Feinberg School of Medicine in Chicago. Scientists can already use standard functional MRI scans to identify people with chronic pain and those at risk of chronic pain. The same technologies can measure the effectiveness of treatments — even those as basic as placebo sugar pills.

“We are not yet at a position to push a button and get a response,” he said, “but we are moving toward individualized treatment pathways.”