Clinical Review

Chronic Pain: How to Approach These 3 Common Conditions

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Fibromyalgia, osteoarthritis, and low back pain require multimodal, evidence-based treatment plans. Tailoring those plans to the underlying mechanisms of pain is key.


 

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Case 1 Lola, 28, has a history of muscular aches and joint pain throughout her body, fatigue, and mental fogginess. A rheumatologist diagnosed fibromyalgia, but Lola just moved to your town and is establishing care. She is feeling desperate because her pain has worsened and the medication previously prescribed (gabapentin 300 mg tid) is no longer working. She asks to try oxycodone.

Case 2 Matt is a 59-year-old truck driver with severe hip osteoarthritis (OA). His orthopedist recommended against hip replacement at this time because of his young age and a heart condition that makes him high risk. His pain makes sitting for long periods very difficult. He presents to you for help because he is worried he will be unable to continue working.

Case 3 Keith is a 56-year-old construction worker who has been experiencing back pain for many years. The pain has become more debilitating over time; it is now constant, and Keith can hardly make it through his work day. He has been getting hydrocodone/acetaminophen from urgent care centers and emergency departments, but he isn’t sure it is helping and is coming to you to assume his pain management.

Chronic pain (defined as > 3 mo in duration) is a complex, heterogeneous condition affecting an estimated 116 million US adults.1 Much of the management of chronic pain occurs in primary care settings, placing family practice providers (FPPs) on the frontlines of two epidemics: that of chronic pain and that of the abuse and misuse of opioid pain medications.

To improve communication about the risks and benefits of opioid therapy and the safety and effectiveness of pain treatments in general, many professional organizations, health care institutions, and recently the CDC, have published guidelines on the use of opioids for nonmalignant chronic pain.2 With these guidelines in mind—and in light of the latest evidence—we propose the following paradigm for the treatment of chronic pain. A critical aspect is determining the underlying pathophysiology of a patient’s pain in order to develop a well-rounded, multimodal, evidence-based treatment plan. Detailed here is the application of this approach to the treatment of three common diagnoses: fibromyalgia, osteoarthritis, and low back pain.

LOOK TO THE CENTRAL AND PERIPHERAL NERVOUS SYSTEM

Acute pain begins with activation of peripheral nociceptors at the site of injury. This causes depolarization up the spinal cord and through the brain stem to higher cortical centers where the pain is perceived and localized. Descending neural pathways transport both excitatory and inhibitory information from the brain to the periphery via the spinal cord, which either increases or decreases the perception of pain.3

When damage/injury doesn’t correlate with the perception of pain

Until recently, it was assumed that chronic pain worked much the same way as acute pain and was caused by ongoing nociceptive input in the periphery, but research has shown us that the central nervous system (CNS) can play a large role in the modulation of nociception. This new understanding comes from the lack of evidence pointing to any pain state in which the degree of nociceptive input correlates with the degree of pain experienced.

For most patients with chronic pain, regardless of their diagnosis, there is some degree of alteration in the processing of nociceptive signals by the CNS contributing to the experience of pain.4 This alteration is thought to result from peripheral nociceptive signaling persisting past the point of tissue healing, leading to a hypersensitivity of nerve fibers, which then continue to respond to low, or absent, sensory stimuli.

Central sensitization is when this hypersensitivity develops in the superficial, deep, and ventral cord nerves. When this happens, pain is often accompanied by systemic symptoms such as fatigue and slowed cognitive processing, often with little to no actual stimulation of the peripheral nociceptors.3

Table 1 lists the possible mechanisms of pain, which can be broken down into four categories: peripheral nociceptive (inflammatory or mechanical), peripheral neuropathic (underlying damage to a peripheral nerve), central (when the CNS is the primary entity involved in maintaining the pain), or any combination of the three.4

Mechanisms of Pain image

As pain becomes chronic, multiple mechanisms overlap

It is important to remember that for any single pain diagnosis, there is likely to be—at least initially—a principle underlying mechanism generating the pain. But as the pain becomes chronic, an overlap of multiple mechanisms develops, with central sensitization often playing a more dominant role than peripheral stimulation (regardless of the diagnosis).

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