New insights into pain mechanisms

Dec 7 2005

Long treated as a side effect, pain is now widely recognized as an integral part of patient care.

While the last decade has brought extraordinary advances in the unravelling of pain mechanisms at the molecular level, evaluating and alleviating pain remains an ongoing challenge for physicians, particularly rheumatologists. The December 2005 issue of Arthritis & Rheumatism offers a timely examination of pain as it pertains to rheumatology practice.

"Rheumatologists are increasingly required to address pain as a specific symptom," notes leading author Mary-Ann Fitzcharles, M.D., of Montreal General Hospital, McGill University. "Pain management is no longer simply a quick fix with a single pill, but rather an approach to the patient as a whole biopsychosocial being."

What is rheumatic pain? How is it affected by inflammation? How is it linked to a patient's psychological state? Drawing on the latest research into this complex factor, Dr. Fitzcharles and her collaborators demystify both the process and the experience of pain for patients with rheumatoid arthritis (RA) and related diseases. Pain mechanisms are not hard wired, but constantly in a state of change. But neurotransmitters and inflammatory molecules make rheumatic pain feel chronic. Rheumatic pain, as the authors explain, is transmitted by not only the central nervous system, but also receptors in the joint tissue and cartilage. Because rheumatic pain travels through small, slow-conducting fibers, it is perceived as a pervasive aching rather than as acute, localized stabs. Inflammation also plays a role in activating pain pathways that usually lie dormant – comprising as many as one-third of the total number of pain-transmitting nerves. What's more, molecular evidence suggests that stress and depression may increase a rheumatic patient's production of pain-provoking inflammatory agents.

How can a rheumatologist accurately assess a patient's pain? As Dr. Fitzcharles acknowledges, clinical evaluation of pain is difficult and subjective. In addition to using time-honored tools – namely, the visual analogue scale of pain severity and patient questionnaires – in real-life practice, the rheumatologist must take cues from the patient during the interview and examination, heeding spontaneous movement, musculoskeletal structure, and verbal complaints, as well as consider the patient's psychosocial history and coping strategies.

Beyond the prescription of a pill, what works to relieve rheumatic pain? "There is no gold standard regarding the ideal management of chronic pain in rheumatic diseases," observes Dr. Fitzcharles. "Ideal pain management should encompass a wide range of both pharmacological and nonpharmacological interventions." The authors culminate with a comprehensive review of complementary treatment approaches, including:

• Exercise. According to studies, regular physical activity not only maintains muscle tone and helps to improve function, but also induces the production of endogenous opioids – endorphins and other natural painkillers.

• Herbal and dietary supplements. For example, decreased pain has been recorded among RA patients receiving supplementation with an omega-3 enriched diet for 12 months. This dietary change reduced the need for antirheumatic medication.
• Topical applications. Used for centuries as home remedies, healing ointments have shown clinical promise for the care of rheumatic conditions. In one recent study, topical diclofenac performed as well as ingested diclofenac in relieving knee joint pain.

• Opioid analgesics. The cornerstone of pain management in cancer, opioids are increasingly prescribed for patients with musculoskeletal pain. However, only limited data support the long-term use of opioids in patients with rheumatic pain. It is not clear, as yet, if opioids provide sufficient benefit to counterbalance the possible harmful effects.

"Rheumatologists will need to become familiar and comfortable with the use of newly developed strategies for pain management to ensure optimal treatment," Dr. Fitzcharles concludes. "Improved function and rehabilitation, and not simply palliation, should be the main goal of pain management in rheumatologic practice."