Researchers have found a way to measure pain

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Clinical Research Assistant Kevin Jackson uses AlgometRx Platform Technology on Sarah Taylor's eyes to measure her degree of pain at the Children's National Medical Center in Washington, Monday, Dec. 10, 2018. Children's National Medical Center is testing an experimental device that aims to measure pain according to how pupils react to certain stimuli. (AP Photo/Manuel Balce Ceneta)

Is the pain stabbing or burning?

On a scale from 1 to 10, is it a 6 or an 8?

When investigating pain, the basic procedure for clinics everywhere is to give a patient the McGill Pain Questionnaire.

This was developed in the 1970s by two scientists, Dr. Ronald Melzack and Dr. Warren Torgerson, both of McGill University in Montreal, and is still the main tool for measuring pain in clinics worldwide.

Melzack and his colleague Dr. Patrick Wall of St Thomas’ Hospital in London had already galvanized the field of pain research in 1965 with their seminal ‘gate control theory’, a ground-breaking explanation of how psychology can affect the body’s perception of pain.

In 1984 the pair went on to write Wall and Melzack’s Textbook of Pain, the most comprehensive reference work in pain medicine. It’s gone through five editions and is currently over 1,000 pages long.

In the early 1970s, Melzack began to list the words patients used to describe their pain and classified them into three categories: sensory (which included heat, pressure, “throbbing” or “pounding” sensations), affective (which related to emotional effects, such as “tiring,” “sickening,” “grueling” or “frightful”) and lastly evaluative (evocative of an experience – from “annoying” and “troublesome” to “horrible,” “unbearable” and “excruciating”).

You don’t have to be a linguistic genius to see there are shortcomings in this lexical smorgasbord.

For one thing, some words in the affective and evaluative categories seem interchangeable—there’s no difference between “frightful” in the former and “horrible” in the latter, or between “tiring” and “annoying”—and all the words share an unfortunate quality of sounding like a duchess complaining about a ball that didn’t meet her standards.

But Melzack’s grid of suffering formed the basis of what became the McGill Pain Questionnaire.

The patient listens as a list of “pain descriptors” is read out and has to say whether each word describes their pain—and, if so, to rate the intensity of the feeling.

The clinicians then look at the questionnaire and put check marks in the appropriate places.

This gives them a number, or a percentage figure, to work with in assessing, later, whether a treatment has brought the patient’s pain down (or up).

A more recent variant is the National Initiative on Pain Control’s Pain Quality Assessment Scale (PQAS), in which patients are asked to indicate, on a scale of 1 to 10, how “intense”—or “sharp,” “hot,” “dull,” “cold,” “sensitive,” “tender,” “itchy,” etc.—their pain has been over the past week.

The trouble with this approach is the imprecision of that scale of 1 to 10, where a 10 would be “the most intense pain sensation imaginable.” How does a patient “imagine” the worst pain ever and give their own pain a number?

Middle-class British men who have never been in a war zone may find it hard to imagine anything more agonizing than toothache or a tennis injury. Women who have experienced childbirth may, after that experience, rate everything else as a mild 3 or 4.

Pain can be either acute or chronic, and the words do not (as some people think) mean “bad” and “very bad.”

Acute pain means a temporary or one-off feeling of discomfort, which is usually treated with drugs; chronic pain persists over time and has to be lived with as a malevolent everyday companion.

But because patients build up a resistance to drugs, other forms of treatment must be found for it.

The Pain Management and Neuromodulation Centre at Guy’s and St Thomas’ Hospital in central London is the biggest pain center in Europe.

Heading the team there is Dr. Adnan Al-Kaisy, who studied medicine at the University of Basrah, Iraq, and later worked in anaesthetics at specialist centers in England, the USA and Canada.

Who are his patients and what kind of pain are they generally suffering from? “I’d say that 55% to 60% of our patients suffer from lower back pain,” he says.

“The reason is, simply, that we don’t pay attention to the demands life makes on us, the way we sit, stand, walk and so on.

We sit for hours in front of a computer, with the body putting heavy pressure on small joints in the back.”

Al-Kaisy reckons that in the UK, the incidence of chronic lower back pain has increased substantially in the last 15–20 years, and that “the cost in lost working days is about £6–7 billion”.

Elsewhere, the clinic treats those suffering from severe chronic headaches and injuries from accidents that affect the nervous system.

Do they still use the McGill Questionnaire?

“Unfortunately yes,” says Al-Kaisy.

“It’s a subjective measurement.

But pain can be magnified by a domestic argument or trouble at work, so we try to find out about the patient’s life—their sleeping patterns, their ability to walk and stand, their appetite. It’s not just the patient’s condition, it’s also their environment.”

The challenge is to transform this information into scientific data. 

New study and solution….

Over and over, 17-year-old Sarah Taylor 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.

Scientists seek ways to finally take a real measure of pain
Julia Finkel, Associate Chief of Anesthesiology at Children’s National Medical Center in Washington, talks to her patient Sarah Taylor during a consultation, Monday, Dec. 10, 2018. Children’s National Medical Center is testing an experimental device that aims to measure pain according to how pupils react to certain stimuli. “If we can’t measure pain, we can’t fix it,” said Finkel, who invented the eye-tracking device. (AP Photo/Manuel Balce Ceneta)

Nor do self-ratings determine what kind of pain someone has—one reason for trial-and-error treatment.

Are opioids necessary?

Or is the pain, like Sarah’s, better suited to nerve-targeting medicines?

“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.

“We’re not creating a lie detector for pain,” stressed David Thomas of NIH’s National Institute on Drug Abuse, who oversees the research. “We do not want to lose the patient voice.”

Around the country, NIH-funded scientists have begun studies of brain scans, pupil reactions and other possible markers of pain in hopes of finally “seeing” the ouch so they can better treat it.

It’s early-stage research, and it’s not clear how soon any of the attempts might pan out.

“There won’t be a single signature of pain,” Thomas predicted.

“My vision is that someday we’ll pull these different metrics together for something of a fingerprint of pain.”

NIH estimates 25 million people in the U.S. experience daily pain.

Most days Sarah Taylor is one of them.

Now living in Potomac, Maryland, she was a toddler in her native Australia when the swollen, aching joints of juvenile arthritis appeared.

She’s had migraines and spinal inflammation. Then two years ago, the body-wide pain of fibromyalgia struck; a flare-up last winter hospitalized her for two weeks.

Scientists seek ways to finally take a real measure of pain
Acupuncture needles are applied on Sarah Taylor’s back during an acupuncture treatment at the Children’s National Medical Center in Washington, Monday, Dec. 10, 2018. Over and over, the 17-year-old struggled to make doctors understand her sometimes debilitating levels of pain, first from joint-damaging childhood arthritis and then from fibromyalgia. “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. Children’s National Medical Center is testing an experimental device that aims to measure pain according to how pupils react to certain stimuli. (AP Photo/Manuel Balce Ceneta)

One recent morning, Sarah climbed onto an acupuncture table at Children’s National, 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.

Consider the shooting hip and leg pain of sciatica:

“Everyone knows someone who’s been started on oxycodone for their sciatic nerve pain.

And they’ll tell you that they feel it—it still hurts—and they just don’t care,” Finkel said.

What’s going on?

An opioid like oxycodone brings some relief by dulling the perception of pain but not its transmission—while a different kind of drug might block the pain by targeting the culprit nerve fiber, she said.

Certain medications also can be detected by other changes in a resting pupil, she said.

Last month the Food and Drug Administration announced it would help AlgometRx, a biotech company Finkel founded, speed development of the device as a rapid drug screen.

Scientists seek ways to finally take a real measure of pain
Anesthesiologist and Acupuncture Specialist Sarah Reece-Stremtan applies acupuncture needle on Sarah Taylor’s forehead during an acupuncture treatment at the Children’s National Medical Center in Washington, Monday, Dec. 10, 2018. Over and over, the 17-year-old struggled to make doctors understand her sometimes debilitating levels of pain, first from joint-damaging childhood arthritis and then from fibromyalgia. “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. Children’s National Medical Center is testing an experimental device that aims to measure pain according to how pupils react to certain stimuli. (AP Photo/Manuel Balce Ceneta)

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.

Ultimately, NIH wants to uncover biological markers that explain why some people recover from acute pain while others develop hard-to-treat chronic pain.

“Your brain changes with pain,” Thomas explained. “A zero-to-10 scale or a happy-face scale doesn’t capture anywhere near the totality of the pain experience.”

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