Study Claims Progress on Measuring Pain

(March 4) -- British researchers say they may have figured out a way to measure pain.

The findings in a small study by the researchers at King's College London are the latest in a centuries-old debate over how to, and whether we even can, quantify physical pain.

The researchers used functional magnetic resonance imaging (fMRI) scans, which measure changes in blood flow caused by neural changes to the brain. The imaging has been used to assess brain damage from strokes or Alzheimer's and even detect liars in criminal investigations.

The scans also can pinpoint areas of the brain that react to physical pain, because of differing levels of oxygenation in circulating blood. Oxygen rushes to a brain region as its neural pathways pick up on discomfort, so pain can be detected when scans note that particular regions are more oxygenated than others.

The scans are already used to detect discomfort, but until now, no one has made a claim to be able to quantify pain levels using the scanners.

Usually, fMRI scans are analyzed simply by evaluating where blood is flowing. But Tara Renton and her team used arterial spin labeling (ASL), which offers an analysis that actually measures how much blood is moving into different brain regions.

The team tested the method by scanning 16 men during wisdom teeth surgery. They found that the quantity of oxygenated blood flow corresponded to the self-described pain levels of each individual.

Renton and her team have yet to publish the research, but they consider themselves the first to quantitatively assess pain via fMRI scans.

Robert Coghill, a professor of neurobiology and anatomy at Wake Forest University, said the team is the first to announce results of fMRI analysis using ASL. "Researchers and doctors have wanted objective assessments like these for years," he told AOL News.

Coghill is working on similar fMRI analysis to determine how chronic itching affects different pain response areas of the brain. "This is the wave of the future," he said.

That pain still can't be objectively quantified might sound surprising, given advances in medical diagnostic technology. But doctors, surgeons and scientists still depend on subjective descriptions of pain for key decisions.

Subjective approaches are a "reasonable guesstimate," according to David Borsook, head of the Pain and Analgesia Imaging and Neuroscience division at McLean Hospital in Boston. "There is a great variation in responses," he told New Scientist.

The implications for pain-assessment brain scans are diverse and include choices between different drugs or dosages, counseling or even medical intervention to eliminate pain, based on knowledge of where, how and when it strikes.

That would be especially true for those who can't express themselves or assess their pain out loud: infants, people in a vegetative state and even animals.

Still, shortcomings to the fMRI analysis remain. Individual brain responses can vary through the day, and from person to person. A particular level of blood oxygenation in one might rank as a 10 on the pain scale, but elicit only a five for another.

"Highly sensitive individuals will always experience greater brain activation, so there's tremendous personal variation that comes into play here, even with accurate brain scanning," Coghill said, adding that researchers would need to systematize the method before applying it in clinical settings.

The uncertainties that remain also point to a potentially larger downfall of the fMRI technique. If pain is so, well, personal, then doesn't that lead us back to a reliance on subjectivity to quantify such an exceptionally individual experience?

Whatever the answer, the progress in pain diagnostics comes the same week that MIT researchers announced they are using fMRI scans to track neurotransmitters as they move through the brain. Given that several brain chemicals, like serotonin and glutamate, are directly responsible for pain response, it looks like fMRI scans could soon be offering pain assessment and relief.