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4 Articles in this Series
Introduction
Individualizing Pain Treatment: Start with Gender?
Simplifying Pain Self-Management for Patients
The Interactions of Emotions and Chronic Pain
To Treat Pain Better, Underlying Mechanisms Are Key

To Treat Pain Better, Underlying Mechanisms Are Key

with Roger Fillingim, PhD, and Kevin Lancer, PhD

Roger Fillingim, distinguished professor and director of the Pain Research & Intervention Center of Excellence at the University of Florida in Gainesville, focused on how physicians and other healthcare providers may move toward mechanism-based pain assessments, at the 2018 American Pain Society (APS) Scientific Summit.1 Understanding mechanisms of pain was the focus of the annual meeting.

“There are multiple biopsychosocial mechanisms that need to be considered,” said Dr. Fillingim. “The better we get at identifying the mechanistic target, the better we get at the development of successful treatments for chronic pain.”

It is also important to understand that these mechanisms interact. “If we don’t know what the mechanisms are, we are shooting in the dark,” he told Practical Pain Management.

Pain Mechanisms: A Closer Look

A mechanism, he explained, consists of entities and activities organized in a way that they are responsible for the phenomenon—in this case, pain. All of these processes and events that may contribute causally to the pain experience need to be taken into account when assessing a patient.

As a clinical example, Dr. Fillingim shared the case of a 65-year-old man involved in a car accident that left him in chronic pain. The low back pain, which became chronic after the accident, was due not only to the vehicle smashup, it was found, but also to two previous unsuccessful surgeries. Add these experiences to related litigation and financial stress, a less than high school education, panic disorder, depression, and a myocardial infarction, and it was easy to see many biological and psychological factors at work, said Dr. Fillingim.

Using knee osteoarthritis (OA) as another example, Dr. Fillingim said the condition is classically viewed as peripherally based. As a result, treatments may often take this approach, including the use of nonsteroidal anti-inflammatory drugs, injections, and joint replacements.1

However, his research, and that of others, has suggested that there may be distinct subgroups or phenotypes based on experimental pain sensitivity in older adults with knee OA.3 While some patients report low pain sensitivity to pressure pain, their reported pain levels range across a spectrum, with groupings differing by race, gender, somatic reactivity, and catastrophizing.

When individuals present with both genetic risk factors for pain and psychological conditions, such as the tendency to catastrophize, they seem to be “at particularly increased risk of severe pain,” Dr. Fillingim explained.

Persons with a higher pain sensitivity, along with the
catechol-O-methyltransferase (COMT) haplotype, a genetic variant, for example, are more likely to have temporomandibular joint disorders, Dr. Fillingim said,4 as well as other pain-related issues such as shoulder pain.

“This is a gene by psychology interaction,” he said. Therefore, clinicians working to treat chronic pain may keep these factors in mind when presented with similar cases:

  • biological, such as disease severity
  • psychological, such as mood, affect, stress, and coping
  • social, such as economic factors, social support, and social environment.2

Overall, clinicians should seek to address all biopsychosocial factors, and consider the mixture of central and peripheral pain in patients, Dr. Fillingim told PPM.

Perspective

Kevin Lancer, PhD, a psychologist at Malcom Randall VA Medical Center in Gainesville, Florida, who attended Dr. Fillingim’s APS talk agreed that “good pain treatment is complex.” It requires a multifaceted approach, he said, which looks at medical and psychological aspects. ‘‘The trend in the past has been to be very mechanical [with pain patients],” he said. “Give a medicine, give a treatment. What the patient is looking for is the absence of pain.”

The reality is that the healthcare team often provides a patient with tools to manage their pain, without considering all the mechanisms or working toward an absence of pain. Patients with chronic pain often have multiple morbidities, Dr. Lancer said, and a single-site pain problem may quickly turn into multiple sites, complicating treatment. For instance, knee pain that is not tended to may begin to affect the hips, the back, and lead to inactivity and weight gain.

At that point, the patient in pain may need a variety of treatments, including help to manage sleep apnea, relaxation, and exercise despite their pain. “If you do all those [interventions] and combine them, you actually get the effect of pain management,’’ Dr. Lancer said.

Sources

1. Fillingim R. Taking Aim is Easier When You Know the Target. Presented at American Pain Society Scientific Summit, March 4-6, 2018, in Anaheim, California.

2. Fillingim, RB. Individual differences in pain: understanding the mosaic that makes pain personal. Pain. 2017;158(4):S11-S18.

3. Cardoso JS, et al. Experimental pain phenotyping in community-dwelling individuals with knee osteoarthritis. Pain. 2016;157(9):2104-2114.

4. Diatchenko L, et al. Genetic basis for individual variations in pain perception and the development of a chronic pain condition. Human Molec Gen. 2005;14:135-143.

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