Ouch! Scientists seek real way to measure pain
Sarah Taylor, 17, struggled to make doctors understand her sometimes debilitating levels of pain, first from joint-damaging childhood arthritis and then from fibromyalgia.
“It’s really hard when people can’t see how much pain you’re in, because they have to take your word on it and sometimes, they don’t quite believe you,” she said.
Now scientists are peeking into Sarah’s eyes to track how her pupils react when she’s hurting and when she’s not—part of a quest to develop the first objective way to measure pain.
“If we can’t measure pain, we can’t fix it,” said Dr. Julia Finkel, a pediatric anesthesiologist at Children’s National Medical Center in Washington, who invented the experimental eye-tracking device.
At just about every doctor’s visit you’ll get your temperature, heart rate and blood pressure measured. But there’s no stethoscope for pain. Patients must convey how bad it is using that 10-point scale or emoji-style charts that show faces turning from smiles to frowns.
That’s problematic for lots of reasons. Doctors and nurses have to guess at babies’ pain by their cries and squirms, for example. The aching that one person rates a 7 might be a 4 to someone who’s more used to serious pain or genetically more tolerant. Patient-to-patient variability makes it hard to test if potential new painkillers really work.
“It’s very frustrating to be in pain and you have to wait like six weeks, two months, to see if the drug’s working,” said Sarah, who uses a combination of medications, acupuncture and lots of exercise to counter her pain.
The National Institutes of Health is pushing for development of what its director, Dr. Francis Collins, has called a “pain-o-meter.” Spurred by the opioid crisis, the goal isn’t just to signal how much pain someone’s in. It’s also to determine what kind it is and what drug might be the most effective.
One morning, Sarah climbed onto an acupuncture table, rated that day’s pain a not-too-bad 3, and opened her eyes wide for the experimental pain test.
“There’ll be a flash of light for 10 seconds. All you have to do is try not to blink,” researcher Kevin Jackson told Sarah as he lined up the pupil-tracking device, mounted on a smartphone.
The eyes offer a window to pain centers in the brain, said Finkel, who directs pain research at Children’s Sheikh Zayed Institute for Pediatric Surgical Innovation. How? Some pain-sensing nerves transmit “ouch” signals to the brain along pathways that also alter muscles of the pupils as they react to different stimuli. Finkel’s device tracks pupillary reactions to light or to non-painful stimulation of certain nerve fibers, aiming to link different patterns to different intensities and types of pain.
Looking deeper than the eyes, scientists at Harvard and Massachusetts General Hospital found MRI scans revealed patterns of inflammation in the brain that identified either fibromyalgia or chronic back pain. Other researchers have found changes in brain activity—where different areas “light up” on scans—that signal certain types of pain. Still others are using electrodes on the scalp to measure pain through brain waves.