By Pat Anson, Editor

An international team of researchers is recommending against the use of brain imaging as a diagnostic test for chronic pain, saying the tests are “inappropriate and unethical.”

"It's not possible at this point in time to say with any degree of certainty that a person does or does not have chronic pain based on brain imaging," said Karen Davis, PhD, senior scientist at the Krembil Research Institute and a professor at the University of Toronto.

"The only way to truly know if someone is in pain is if they tell you because pain is subjective and it is a complex experience. No brain scan can do that."

In recent years, technological advances in brain imaging have led to an increased use of functional magnetic resonance imaging (fMRI) to search for brain-based biomarkers for chronic pain.

Demand for brain imaging is also growing for legal purposes, including the development of a potential “lie detector” test for chronic pain.

"Use of such tools would be inappropriate and unethical," said Davis. "This technology is not foolproof. There are vast issues of variability between people and even within a person at different times. As a result, brain imaging must not be used as a lie detector for chronic pain."

Davis and her colleagues say brain-based biomarkers should only be used to supplement -- not replace -- a patient’s own reports of pain, even if testing is improved and valid protocols developed. Their recommendations were published in the journal Nature Review: Neurology.

"We are working towards biomarkers for chronic pain, but the goal is not as a lie detector test but rather to help provide personalized pain treatment options for patients," Davis. “People outside of the field of imaging might be disappointed, but the fact of the matter is the technology cannot be used to support or dispute a claim of chronic pain."

According to a 2015 study at the University of Michigan, one in eight visits to a doctor for a headache or migraine end up with the patient going for a brain scan. Often a doctor will order an fMRI to ease a patient’s fear that they may have a brain tumor or some other serious health problem. Doctors may also order a test to protect themselves in case of a lawsuit. About 1 to 3 percent of brain scans of patients with repeated headaches identify a cancerous growth or aneurysm.

University of Michigan researcher Brian Callaghan, MD, identified 74 neurological tests and procedures that are often unnecessary. Many involve the use of imaging.

“The two biggest areas that might be done more than they should are imaging for low back pain and imaging for headaches,” Callaghan said. “It’s a big problem and it costs a lot of money – we’re talking a billion dollars a year on just headache imaging.”

Other researchers believe brain imaging can be used as a valuable diagnostic tool. In a small study at the University of Colorado Boulder, researchers used fMRIs to discover a “brain signature” that identifies fibromyalgia with 93 percent accuracy. They found three neurological patterns in the brain that correlate with the pain hypersensitivity typically experienced with fibromyalgia.