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Pain on the Scales: Measure We Must



Illustration by Bryce Hendry, copyright 2024.

 

This is the second post in my three-part series on the history of pain (you can read the first post here). In the 19th century, the scientific study of anatomy, physiology, and pain reached new heights. As with other bodily processes, a clinically useful measurement scale became a prominent research goal. This post looks at two 20th-century highlights of the quest for valid pain measurement. The search had an unexpected result that raised fresh questions about the nature of pain.


As a lifelong sports fan, I’ve drawn an analogy between an unlikely sports star and a key point of the history of pain. In the case of football player Brock Purdy, intensive measurement of his physical capabilities missed the attributes that would define his career; in the same vein efforts to quantify pain have shown how resistant it can be to measurement.


In 1989, physician Dennis Turk compared efforts to measure pain to a hunter pursuing an animal no one has ever seen. “Everyone is sure the beast exists because it has been raiding the poultry coops, but no one can describe it,” Turk wrote. “Since the forest contains many animals, the hunter is going to find a variety of tracks.”

  

In 2022, pro football’s San Francisco 49ers chose quarterback Brock Purdy with the very last pick – number 256 -- in the annual draft of college players.


What connects an unlikely sports star to the history of pain measurement?


The ties are about what we can measure and what we can’t. It’s about a downside of overly exuberant faith in numbers in medicine and beyond. We’ll return to Purdy. Let’s begin with pain measurement.


At first, Turk’s comparison might sound wrong in two ways. Every day, millions of people see, and endure, what pain does to them and to people they know. In addition, there are many scales and questionnaires that clinicians were using in 1989 and use today to assess pain. So what was Turk getting at? His analogy had to do with pain’s enduring mysteries and its basic nature. These mysteries include a knack for puzzling origins, diverse forms, random locations, and erratic behavior. Clinicians know well that “…a considerable amount of pain presents without explainable medical pathology.”


Turk’s comparison also evoked one of pain’s mysteries: how someone’s pain is tied to their attitudes, history, beliefs, circumstances, and personality. Today, the notion that pain is enmeshed with highly individual parts of ourselves is widely accepted.There’s an ironic link between the ascent of pain-as-subjective and the history of trying to measure it. It was the efforts to quantify pain that showed how key attributes resisted numerical capture. The more we measured pain, the more its individuality, its variability, and its depth came into focus.  


Let’s start by defining some terms and sketching the backdrop.  


Acute and Chronic Pain – Related, But Different


Today doctors are very good at treating acute pain that is over in a few days or a week – post-injury, post-illness, post-surgery. Before the mid-1900s, this was most of the pain doctors saw. But as people lived longer, and as war-related, industrial, vehicular, and recreational injuries piled up, chronic pain – the kind that lingers after healing, that lasts more than three months, that may not be fully traceable – became the bulk of what doctors treated.  


This shift defined pain’s larger clinical and social transformation after 1945. The understanding, treatment, and experience of pain all changed. Pain morphed from a rote, well understood event (acute) into a clinical condition defined by variability and complexity (chronic). Pain evolved from symptom to syndrome.


It’s a rich story that efforts to quantify pain helped to write.


A Measurement Backstory


Pain has been part of healers’ and patients’ lives forever. Attempts to understand and measure it are just as old. In the 1850s, physician Constantine Hering (1800-1880) advised colleagues on assisting patients who lived far away. He suggested asking them to describe their discomfort, where it hurt, how long it has hurt, if there have been any changes in the pain, and what helped or didn’t. Hering provided a list of words doctors could use to help patients describe their conditions. This was a forerunner of a pain scale this post examines.


In 1989, anesthesiologist Thomas E. Rudy described the state of pain measurement as follows:


Over the past 20 years, pain measurement has gained considerably in both maturity and spheres of usefulness … There has been a proliferation of measures, scales, questionnaires, inventories, observational techniques, and other assessment strategies to quantify pain and/or the cognitive, behavioral, affective, and physiological consequences of the pain experience.


Let’s look at two efforts that moved pain measurement to the point Rudy described.


Between 1930 and 1950, James Hardy, Harold G. Wolff, and Helen Goodell created what they termed “a new method for measuring pain thresholds.” Based at Cornell, they sought to identify biophysical constants in how people responded to pain. They focused on isolating what they called the sensation of pain – the proximate event, or stimulus – from a person’s reaction to it. They believed pain was divisible this way, both in theory and in how it worked. They defined the pain threshold as the “least perceptible intensity of pain.” Their goal was to locate a person’s threshold and to create a scale in which uniform increases from this threshold could be sized to measure pain.


This effort culminated in 1940, when they introduced a device called a dolorimeter. (Dolor is Latin for grief, sadness, or pain.) A 1000-watt incandescent lamp delivered the experimental pain. A lens focused a light beam onto a small square on a person’s forehead that had been blackened to neutralize the effects of natural skin-color differences. A rheostat controlled the heat “dosage.”


The dolorimeter was a hit. Historian Naomi Tousignant has described how the device “quickly became popular as an analgesic-testing technology…By 1950, over twenty research teams had published data generated by a dolorimeter.” Tousignant showed too how the dolorimeter was supplanted in the 1950s by the controlled clinical trial. The dolorimeter’s rise and fall took less than 20 years. Its importance for our story is as an experimentally sophisticated approach to measuring pain.


Use Your Words


A later development used very different constants – 78 adjectives organized into 20 subgroups – to create a clinically useful tool for measuring pain. There’s a lively history to the McGill Pain Questionnaire (MPQ). It was published in 1975 and was used widely for about 20 years.


The MPQ is a six-page questionnaire. It uses its adjective groupings, pictures, and questions to help patients describe what they are experiencing. It probes three pain dimensions: sensory (what the pain feels like), affective (how it makes the person feel), and evaluative (how intense the pain is).


Sensory qualities of pain include temporal, spatial, pressure, and thermal properties; affective dimensions are feelings of tension, fear, and autonomic responses; evaluative words describe the intensity of the experience. For example, a subclass of the sensory dimension groups the words “pinching, pressing, gnawing, cramping, crushing.”


The MPQ has five sections. After gathering a patient’s age, diagnosis, and current pain regimen, part 1 is a back-and-front outline sketch of a gender-neutral adult body on which the patient shows where the pain is. Other parts ask what the pain feels like, how it changes over time, and how strong it is. There’s a way to assign a number score, the pain rating index, to a person’s answers.


Since its introduction, the MPQ has generated a small library of research on its strengths, weaknesses, cross-cultural adaptability, and linguistic assumptions. Its influence in measuring pain has been substantial. By asking people to pick from a constant word set, the MPQ helped doctors and patients reach a shared understanding of a person’s pain. The MPQ gave patients unusual influence over a process that aspired to clinical credibility. By putting psychological factors on the same footing as physical ones, the MPQ operationalized an understanding of pain that brought subjectivity to new prominence.


Back to You, Brock


Here’s where Brock Purdy comes in. He’s the San Francisco quarterback who had been the last college player drafted in 2022.


For decades the occupant of this dead-last draft slot has been dubbed Mr. Irrelevant by the National Football League and its vast public, and with good reason. The majority of such draftees spend a few days at training camp before getting cut from the team. Only a select few make it through training camp to win a spot on the team.


Purdy is different. He has emerged as an outstanding performer at the most important position in the sport. His physical skills, poise, on-field intelligence, and improbable story have made him a Bay Area hero.


Purdy had qualities that not even intense scrutiny could detect. How many of us have been assessed as fully as pro football prospects? But with Purdy, scouts and coaches missed crucial factors – his drive, his discipline, his ability to learn quickly from mistakes – in part because these dimensions can’t be measured.


It’s the same with pain. Scientists and doctors are becoming more knowledgeable about how our nervous systems modulate painful stimuli. Still, pain’s mysteries remain. Its immense variability, even when associated with the same condition, is just one.  


As neuroscientist Richard Ambron showed in The Brain and Pain, numerous brain regions are involved in creating the pain experience. These regions are implicated as well in attention, memory, and our emotions. The specifics of how millions of neuronal circuits in the brain interoperate to produce pain – not to mention how our pain is connected to those other human dimensions -- remain obscure.


I’m guessing that personal dimensions of pain are themselves encoded in the endless electrochemical operations of our nervous and other bodily systems.  


So pain’s mysteries are unlikely to yield to quick resolution. The chasm between the word and the experience hints at this. We ask the same word to stand for a scraped knee as well as unbearable grief. This linguistic range expresses an understanding that pain is close to the heart of so much that makes us human.


The stories of people born with a very rare genetic inability to feel pain are invariably tales of suffering and early death. Our pain, for all its misery, is bound up with our survival. In torment can lie the seeds of redemption.  


That’s hard to measure. But it won’t stop Dennis Turk’s mythical hunters from pursuing the beast that is pain.


The concluding post in my pain series will look at a question that COVID has infused with fresh urgency: How do people experience and process the pain they feel from global events – e.g., natural disasters, wars, mass shootings? How do individual bodies deal with pain that we share?

  

  

  

  

  

  

  

  

 

 

 

 

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