The Impossibility of Measuring Pain

The Pain TestDoctors have no idea how much their patients are suffering. That’s about to change – by Susannah Locke

Ally Niemiec could have lost a kidney because doctors didn’t believe she was in pain. It was last fall, and one of at least a dozen times that her rare kidney disease had sent her to the emergency room. She recognized the pain. She knew something was wrong

But when she turned up in an Atlanta emergency room that Saturday afternoon, vomiting and doubled over, no one believed her. They looked at her pain medication records and decided she had a drug abuse problem. “They told my mother that I needed to go to rehab and was a drug addict,” she says. The hospital wouldn’t give her any narcotic pain medication and refused to do an x-ray, ultrasound, or CT scan. That time, Niemiec was lucky enough to have other options. She left for another hospital, where they treated her pain and then removed her kidney stone the next morning.

One problem has been that her kidney disorder, renal tubular acidosis type 1, is described in medical journals as not painful. But to her, it was. Since she was 13, she’s had about 100 kidney stones and 18 surgeries to remove them. At one point, her pain was so bad that she couldn’t drive and had to leave her job. She went from doctor to doctor trying to get help. When her pain got really bad, she didn’t find adequate treatment for three long years.

“There’s nothing more horrific than a doctor looking you in the eye and saying there’s nothing wrong with you when you’re in debilitating pain,” she says. “To me, it’s a form of torture.”

Eventually, she got a spinal cord implant that uses electrical signals to block her kidney pain. Now she’s 24 years old and works at a tech startup. But many others continue to suffer.

The most cutting-edge test for pain is a doctor holding a piece of paper with a bunch of frowny and smiley faces on it or asking you how bad you feel on a scale of 1 to 10,

And as Niemiec can attest, the subjectiveness of the scale causes problems — it only works if the doctor believes you, and relying only on trust can threaten people’s lives.

A more objective pain test could transform pain medicine and lead to new treatments for people who suffer. It could weed out people lying in order to get drugs. And it could prove to doctors that people like Niemiec are really in pain.

Despite pain’s importance, it is quite difficult to define. And that difficulty underlies much of the disagreement about whether objective pain testing is even possible.

So although the mechanisms for what usually causes pain — certain receptors on certain neurons — are fairly well known, pain is still not defined as a physical thing that your body does. Your neurons could be firing off pain signals like crazy, but as long as you don’t feel pain (like if you’ve popped an Advil or are under anesthesia), you’re not in pain. If you feel pain, you are in pain.

Mackey, the Stanford pain specialist, got his PhD in electrical engineering and also an MD.

Working with pain patients, he often found himself using needles to block pain. (One common treatment for chronic pain is a temporary injection of anesthetic into the body, which stops pain signals from reaching the brain.) But it wasn’t working for everyone.

Those observations got him interested in the brain side of things, the psychology side, and how things like anxiety, fear, and empathy influence pain. “It was around this time that this field of neuroimaging was being established, which allows us to open up windows into people’s brains to see where pain is processed and perceived.”

Researchers have documented discriminatory patterns in how health-care workers treat pain. Women are more likely to have their pain dismissed as not real. And one study found that female emergency room patients with abdominal pain were less likely to be given strong pain meds than men were.

And until the last couple of decades, doctors thought that many people with chronic pain were faking it. Roger Fillingim is a psychologist at the University of Florida who studies pain. He describes patients saying that just the feeling of a long-sleeved shirt on their arm was painful: “We used to call that crazy.” Now, doctors know that a lot of chronic pain is actually real. For example, fibromyalgia, which causes pain throughout the body, was in the crazy category, too. Now it’s known to affect roughly 15 million people in the United States.

The problems with pain medication

A better pain test is one thing that could help real pain patients prove themselves — and weed out the liars.

The research on brain imaging

In the past few years, researchers have published studies showing that fMRI could determine whether someone is in pain

Then in 2014, Mackey published another paper that looked at patients with chronic back pain, using still MRI images to examine brain structures rather than brain activity. He was able to produce an algorithm that guessed with 76 percent accuracy whether or not a brain was from a chronic back pain patient. A similar study published the same year identified people who had chronic pelvic pain with 73 percent accuracy.

Still images of brain structure like these could someday help chronic pain patients justify their condition, even though they don’t show brain activity itself.

All of these new studies are still firmly in the realm of science, not medicine. These tools are not ready for use on patients to determine a course of treatment. Mackey estimates that that might be 10 years away

In addition, most researchers don’t believe that there’s just one pain brain-activity pattern, but that different kinds of pain will end up producing different patterns. So, touching something hot might look different than the muscle pain of fibromyalgia, which might look different than chronic back pain. And that means that a lot more research will be needed before such technology could be used on the wide variety of painful health issues that exist.

The problems with an ‘objective’ pain test

They think that such scans should only be used to confirm someone’s pain, but never to go against their word and deny that they’re in pain when they say that they are. That’s because pain is defined as a subjective experience. And the brain scan is objective. So, to them, the brain scan is merely an objective marker of possible pain

Another reason for that stance is that a person could be feeling a kind of pain that they haven’t found the brain signature for yet.

And, says Mackey, “There is the potential for abuse. There’s always the potential for people misusing this technology for insurance purposes to deny care.

Another problem is that pain might be something that cannot be reduced to a bunch of neurons firing. “Some people believe that pain isn’t simply some sum or algorithm of brain activity, it’s an emergent property of brain activity,” says Fillingim. “And maybe we won’t figure out how the experience of pain emerges from some pattern of brain activity. And maybe the formula is different for different people.”

“Could we similarly look at someone’s brain and tell you how happy they are, how satisfied with life?” he asks. “These are all pretty high level experiences.”

But not everyone agrees. And Mark Sullivan is one of them. He’s a psychiatrist and bioethicist at the University of Washington who specializes in treating patients with chronic pain. He’s been one of the most vocal opponents of the drive to find objective measures of pain.

he says he’s concerned about people who are truly ill being denied workers’ compensation and social security because nothing can be found on a brain scan

Technology will march on, and someday, someone is going to start selling something called an objective pain test, whether or not that’s actually what it’s capable of.

And no matter how accurate the test is or isn’t, the images it produces could help pain become a more visible problem in health care. Pain isn’t something that someone can see, like a physical wound. It can take numerous forms, making it easier for medical practitioners to ignore.

44-year-old Californian Elizabeth Schenk is one of the many patients who’ve had doctors ignore her agony. She used to be a pilates instructor, but her chronic pain has brought her into a new career counseling people with pain problems. At its worst, her pain has been excruciating: “like someone was dragging a knife down my thigh,” and “like someone taking a hammer to my thumb,” and “a chisel to my spine.”

“What I’ve experienced in the medical world is that if they don’t see anything, they won’t do anything,” she says. But brain imaging can put an image to the invisible. It can give them something to see.  

And here is a medical news article pointing out how ineffective the current “Visual Analog Scale” for pain:

medwireNews – Pain medicine – Pain classification with VAS scores ‘doubtful’

Researchers advise caution when using cutoff points on the visual analogue scale (VAS) to classify mild, moderate or severe pain in clinical practice.

They found that a VAS cutoff score below 3.5 was consistently associated with mild pain, but the cutoff point between moderate and severe pain was less clear and subject to misinterpretation.

Also, VAS scores were, at best, only moderately associated with functioning and with Verbal Rating Scale (VRS) scores.

A VAS score of up to 3.4 cm similarly corresponded best with mild pain on the VRS, but the score for moderate pain was 3.5 to 7.4 and for severe pain 7.5 or above

The overlap between moderate and severe VAS cutoff points in terms of pain-related interference with functioning and verbal rating mean that a patient may score their pain on VRS as moderate but its impact on functioning could be severe, the researchers explain in Pain.  

2 thoughts on “The Impossibility of Measuring Pain

  1. Pingback: Problems with Neuroimaging for Chronic Pain | EDS and Chronic Pain News & Info

  2. Pingback: Biomarkers May (or may not) Indicate Chronic Pain | EDS and Chronic Pain News & Info

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