56.
Chapter 49 Fibromyalgia
Manual of Rheumatology and Outpatient Orthopedic Disorders
Chapter 49 Fibromyalgia
Daniel J. Clauw and John F. Beary, III
Definition
Etiology and pathogenesis
Epidemiologic characteristics
Physical findings
Symptoms
Diagnostic testing
Treatment
Prognosis
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 persons with FM also display a number of non-defining symptoms, including fatigue, sleep disturbances, headaches , and memory difficulties. In fact, it has become increasingly clear that considerable overlap exists between FM and systemic conditions (e.g., chronic fatigue syndrome) as well as organ-specific syndromes (e.g., migraine headache , tension headaches, irritable bowel syndrome, temporomandibular disorders, and mitral valve prolapse syndrome).
I. Definition. In 1990, FM was redefined by a subcommittee of the American College of Rheumatology. The new definition requires a history of chronic widespread pain ( lasting longer than 3 months in all four quadrants of the body plus the axial skeleton) and the finding of tenderness in 11 or more of 18 points on examination. Tender points are discrete regions of the body. If a patient experiences pain when 4 kg of pressure is applied with digital palpation to any one of these points, it is considered a positive tender point. Patients whose chronic pain and tender points are confined to one quadrant of the body are diagnosed as having regional myofascial disorder .
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 have FM meet these strict criteria; in many cases, pain is more limited in distribution, or fewer than 11 tender points are noted. The usefulness of tender points is presently being debated because it is now clear that the primary problem in FM is a generalized disturbance in pain processing. Patients with FM exhibit more tenderness throughout the entire body, even in control areas such as the thumbnail or forehead. The tenderness is diffuse rather than regional and is not confined to certain types of tissues (i.e., muscle). Tender points merely represent regions of the body, such as the lateral epicondylar area, that are normally more tender. When a patient with FM is stimulated, the pain is likely to be amplified compared with that in a control subject.
Another problem with tender points is that in population-based studies, the number of tender points displayed by a patient is highly correlated with various measures of distress. In contrast, other methods of assessing tenderness, such as the use of a pressure gauge, are much less influenced by psychologic factors.
II. Etiology and pathogenesis. The precise cause for FM remains unclear. Numerous studies suggest a strong familial aggregation of FM, although none has established whether heredity or shared environmental influences are the cause. It is also clear that a number of environmental stressors, including physical trauma, infection, autoimmune disorders, endocrine conditions, and emotional stress, seem to be capable of triggering the development of FM.
Several types of physiologic abnormalities have been identified in persons 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 paradigms for pain testing. Abnormalities of neurotransmitters (e.g., substance P) in the cerebrospinal fluid of FM patients, and of cerebral areas involved in pain processing, such as the thalamus (seen on single-photon emission tomography ), provide further, objective evidence. A number of abnormalities in both neuroendocrine and autonomic function have also been identified in subgroups of FM patients.
Although the dualistic notion that any illness is either organic or functional should be abandoned , because of the realization that all illnesses are likely to have a biologic basis, this debate continues with respect to FM. It is likely that this illness usually begins as a primarily physiologic problem, and it never progresses past this point in some cases because of appropriate treatment, good coping skills, and adequate support systems. In other cases with chronic symptoms, however, concurrent psychological, psychiatric, and behavioral factors become more prominent. Examples of such factors, which portend a worse prognosis, include maladaptive illness behaviors, secondary gain issues (e.g., litigation, compensation), and concurrent mood disorders.
III. Epidemiologic characteristics. Approximately 2% to 4% of the population in industrialized countries (e.g., the United States, Canada, Israel, and Germany) suffers from FM, as defined by the American College of Rheumatology criteria. However, these population-based studies suggest that it may be better to consider FM as the end of a spectrum rather than as a discrete, unique illness. For example, both the pain and tenderness domains are continuously distributed across a wide range in the population. Approximately 10% of the U.S. population suffers from chronic widespread pain, and 20% from chronic regional pain; both symptoms occur approximately 1.5 times more commonly in female patients. A wide continuum of tenderness can be noted within the population, so that some patients are very tender and others quite nontender. Women are more sensitive to cutaneous pressure than are men, and in fact are 10 times more likely to have 11 tender points than men. Because the American College of Rheumatology definition uses an arbitrary cutoff of 11 tender points to define the subset of patients with chronic widespread pain who meet FM criteria, FM is diagnosed predominantly in women.
Other studies have demonstrated that FM frequently coexists with other conditions. Approximately 25% of patients with rheumatoid arthritis, lupus, ankylosing spondylitis, osteoarthritis , hepatitis C, and a number of other conditions display concurrent FM.
These data suggest that it may be better to consider FM as a construct that helps explain chronic pain in the absence of a peripheral inflammatory or mechanical stimulus. This central or non-nociceptive pain occurs commonly throughout the entire body (in FM), in a single region of the body (e.g., temporomandibular syndrome, myofascial pain syndrome), or concurrently with other medical conditions ( especially those characterized by chronic pain).
IV. Physical findings. The physical examination findings in FM are classically normal except for the presence of diffuse tenderness. Occasionally, patients will also display mild muscle weakness, perhaps because of pain or disuse.
V. Symptoms. The character of the pain in FM is different from that in most other musculoskeletal conditions. Although most persons with FM have a few areas where they always experience pain, this condition is characterized by wide variation in the location and intensity of pain. Patients frequently report a worsening of pain in response to activity, weather changes, menstrual status, and stressors. Subjective weakness, morning stiffness, swelling (especially of the hands and feet), and nondermatomal dysesthesias or paresthesias frequently accompany the pain. Fatigue and difficulties with short term -memory and concentration are also often present.
VI. Diagnostic testing. FM is a diagnosis of exclusion because there are no predictably abnormal findings on laboratory or imaging studies in this entity. Initial testing in a patient suspected of having FM should include routine hematology and chemistry panels, thyroid function tests, and a determination of sedimentation rate or C-reactive protein. Unless specific signs and symptoms suggest the presence of illnesses such as rheumatoid arthritis (e.g., synovitis on examination) or systemic lupus, tests for antinuclear antibodies and rheumatoid factor have a very low predictive value and should be avoided. For example, it has been estimated that for every antinuclear antibody test ordered for a patient with the nonspecific complaints of myalgias, arthralgias, and fatigue, there will be at least 20 false-positive results for every true-positive result (i.e., a patient with an autoimmune disorder). Certain laboratory abnormalities occur more commonly in persons with this spectrum of illness than in the general population, such as elevated antibody titers to certain viruses (e.g., Epstein-Barr virus), positivity for antinuclear antibodies, and lipid abnormalities. However, these tests are neither sensitive nor specific for FM.
VII. Treatment. Three types of treatment have been best demonstrated in randomized, controlled trials to be of benefit within this spectrum of illness: symptom-based pharmacotherapy, aerobic exercise, and cognitive behavioral therapy . Perhaps the most important role of the physician is to educate the patient that FM is a chronic condition wherein pain occurs even though there is no damage to the body, and that no pill or magic herb is available to cure their illness. Patients with this condition rarely improve significantly unless they accept the fact that they need to play an active role in their own treatment, which should include daily exercise and appropriate life-style modifications.
- Pharmacotherapy. The class of drugs with established efficacy in FM is the tricyclic compounds ; cyclobenzaprine (Flexeril) and amitriptyline (Elavil) are the best studied. These medications are tolerated best if they are taken several hours before bedtime (to help prevent the hung-over feeling that patients often report). They must be started at low doses (e.g., half of a 10-mg tablet) and slowly escalated by 5 to 10 mg every 1 to 2 weeks until efficacy is established or a dose of 50 mg daily is reached. Because FM is not an inflammatory condition, antiinflammatory doses of nonsteroidal antiinflammatory drugs (NSAIDs) are neither necessary nor of much benefit. In addition to tricyclics, analgesics (e.g., low doses of NSAIDs, acetaminophen, or tramadol) may be helpful. In some instances, other classes of antidepressants, such as those acting on the adrenergic or dopaminergic systems (venlafaxine, bupropion) or on serotonin receptors may be effective.
- Aerobic exercise therapy can be extremely beneficial in FM and related conditions. Mildly affected persons can sometimes be adequately managed with these modalities alone. A graded, low-impact, aerobic exercise program is extremely beneficial. Patients should be instructed to begin with 5 to 10 minutes of low-impact exercise (e.g., water exercise, stationary bike, treadmill, walking) three to four times weekly and to increase this by 1 to 2 minutes a week. Beginning at high levels of exercise or escalating more rapidly is poorly tolerated and frequently will make the patient feel worse. The eventual goal should be 20 to 30 minutes of aerobic exercise four to five times weekly.
- Cognitive behavioral therapy is an education-based program that has been successfully used to treat a number of chronic medical conditions, including chronic pain states, FM, and chronic fatigue syndrome. These programs, which can be undertaken in an individual or group setting, focus on teaching techniques that reduce symptoms (e.g., biofeedback, relaxation exercises). Maladaptive illness behaviors that the patient (usually unknowingly) displays and that make the illness worse are identified and explained. An example is the tendency for patients to overdo it on good days, which will lead to several bad days.
VIII. Prognosis. Although FM is typically a chronic illness lasting for several years , life expectancy is not affected. Most afflicted persons can expect to lead a relatively normal life with appropriate management.
Bibliography
Bennett RM, et al. Group treatment of fibromyalgia: a 6-month outpatient program. J Rheumatol 1996;23:521.
Clauw DJ. Fibromyalgia: more than just a musculoskeletal disease. Am Fam Physician 1995;52:843.
Clauw DJ, Chrousos GP. Chronic pain and fatigue syndromes: overlapping clinical and neuroendocrine features and potential pathogenic mechanisms. Neuroimmunomodulation 1997;4:134.
Goldenberg DL, Felson DT, Dinerman H. A randomized controlled trial of amitriptyline and naproxen in the treatment of patients with fibromyalgia. Arthritis Rheum 1986; 29:1371.
Books@Ovid
Copyright 2000 by Lippincott Williams & Wilkins
Stephen A. Paget, M.D., Allan Gibofsky, M.D., J.D. and John F. Beary, III, M.D.
Manual of Rheumatology and Outpatient Orthopedic Disorders
EAN: N/A
Pages: 315