Fibromyalgia and Chronic Pain
Daniel J. Clauw
John F. Beary III
Fibromyalgia (FM) is a painful, noninflammatory condition characterized by a history of widespread pain, and diffuse tenderness on examination.
The hallmark of FM appears to be a central disturbance in pain processing that is largely unexplained by psychological factors.
Functional imaging studies have confirmed that when patients with FM are given a low-pressure stimulus (that would not be felt as painful by a control subject), they not only experience pain, but also have activations in the pain-processing regions of the brain.
FM frequently coexists with other conditions. Approximately 25% of patients with rheumatoid arthritis (RA), lupus, osteoarthritis (OA), and hepatitis C also have FM.
Three types of treatment have been demonstrated in randomized, controlled trials to be of benefit for the spectrum of FM illness: symptom-based pharmacotherapy, aerobic exercise, and cognitive behavioral therapy (CBT).
Fibromyalgia (FM) is a painful, noninflammatory condition characterized by a history of widespread pain, and diffuse tenderness on examination. Although FM is defined on the basis of pain and tenderness, most individuals with FM also display a number of nondefining symptoms, including fatigue, sleep disturbances, headaches, or memory difficulties.
In fact, it has become increasingly clear that there is considerable overlap between FM and “systemic” conditions such as chronic fatigue syndrome, as well as other “organ-specific” syndromes such as migraine headache, tension headache, irritable bowel syndrome, temporomandibular disorders, and mitral valve prolapse.
In 1990, the definition of FM was redefined by a subcommittee of the American College of Rheumatology (ACR). The new definition requires a history of chronic widespread pain (pain lasting for more than 3 months in all four quadrants of the body plus the axial skeleton), and the finding of 11 or more positive results on the 18 tender points examined.
Chronic musculoskeletal pain can result from a central non-nociceptive mechanism such as in FM, from peripheral nociceptive mechanisms such as in mechanical osteoarthritis (OA) or in inflammatory rheumatoid arthritis (RA), or from neuropathic pain mechanisms such as in diabetic neuropathy.
FM tender points are discrete regions of the body where a 4-kg pressure is applied with digital palpation, and if the individual experiences pain when this area is pushed, it is considered a “positive” tender point. Even when this definition was originally adopted, it was stated that these criteria were not meant to be strictly applied in clinical practice. Only about half of the patients seen in clinical practice who clearly present with FM will meet these strict criteria; many individuals have pain that is more limited in distribution, or have fewer than 11 tender points.
The usefulness of the “tender points” concept is currently being debated, because it is now clear that the primary problem in FM is a generalized disturbance in pain processing. Patients with FM are more tender throughout the entire body, even in control areas such as the thumbnail or forehead. The tenderness is diffuse rather than regional, and not just confined to certain types of tissues (i.e., muscle).
Tender points merely represent regions of the body, such as the lateral epicondylar area, where even normal individuals are more tender. When a patient with FM is stimulated at these tender points, the pain is likely to be amplified as compared to a control subject.
The precise cause for FM remains unclear. There have been numerous studies suggesting that there is a strong familial aggregation of FM, although no studies have differentiated whether this is due to hereditary or shared environmental influences.
It is also clear that there are a number of environmental “stressors”, including physical trauma, infections, autoimmune disorders, endocrine conditions, and emotional stress, that seem to be capable of “triggering” the development of FM.
There have been several types of physiologic abnormalities that have been identified in individuals with FM and related conditions that may help explain the basis of symptoms. The hallmark of FM appears to be a central disturbance in pain processing that is largely unexplained by psychological factors. The evidence for this comes from numerous studies employing various types of experimental pain testing paradigms, as well as from objective abnormalities of neurotransmitters (e.g., substance P) in the cerebrospinal fluid of patients with FM.
Most recently, functional imaging studies have confirmed that when patients with FM are given a low-pressure stimulus (that would not be felt as painful by a control subject), they not only experience pain, but also have activations in the pain-processing regions of the brain, again confirming augmented central processing of pressure, heat, and other stimuli. There have also been a number of abnormalities in both neuroendocrine and autonomic function that have been identified in subgroups of patients with FM.
Although the dualistic notion that any illness is either “organic” or “functional” should be abandoned, because of the realization that all illnesses likely have a biological basis, this debate still continues with respect to FM and other related conditions. It is likely that in many individuals this illness begins as primarily a neurobiological problem, and in some individuals never progresses past this point because of appropriate treatment, good coping skills, and adequate support systems. But in other individuals,
with chronicity of symptoms, concurrent psychological, psychiatric, and behavioral factors either develop or become more prominent.