Fibromyalgia is characterized by widespread pain, fatigue, disturbed sleep, and cognitive dysfunction. It is common (prevalence, 2%-3%), particularly among individuals of lower socioeconomic status and/or educational level. Prevalence increases with age, peaking around the seventh decade. The female-to-male ratio is approximately 3:1.
Early paradigms of fibromyalgia as an inflammatory or psychosomatic condition have yielded to an understanding of fibromyalgia as a disorder of pain processing. It is likely a form of “central sensitization,” in which the pain centers of the brain and spinal cord are hyperresponsive. Allodynia (a heightened sensitivity to stimuli that are not normally painful) and hyperalgesia (an increased response to painful stimuli) are common. An additional characteristic feature is “wind-up,” or temporal summation. When repeatedly exposed to a mildly uncomfortable stimulus, patients with fibromyalgia experience progressively additive pain, indicating that the stimuli are both persistent and inadequately damped.
Men with fibromyalgia frequently do not experience tender points, and tender points are no longer included in fibromyalgia classification criteria.
The underlying changes seen in the neurologic system are complex. Ascending fibers from the dorsal root ganglia convey inappropriately strong or persistent signals to hypothalamic pain centers. Patients with fibromyalgia have higher cerebrospinal fluid levels of the pain-promoting neurotransmitters substance P and glutamate, along with sensitization of glutamate receptors. Concurrently, descending inhibitory pathways utilizing adrenergic neurotransmitters (serotonin, norepinephrine) are impaired. The resultant circuit of chronic pain is self-sustaining but may be amplified by both psychic distress and peripherally generated tissue pain (such as arthritic joint pain). Genetic influences are a focus of ongoing investigation.
The characteristic clinical features of fibromyalgia are widespread chronic pain (including hypersensitivity to painful stimuli), fatigue, and sleep disorders (both disrupted and nonrestorative sleep). These are frequently accompanied by impaired cognitive function, mood disorders, and symptoms such as headache, gastrointestinal symptoms, and paresthesia. Although the diagnosis of fibromyalgia traditionally centered on the presence of specific tender points elicited on physical examination, tender point examination is subject to physician expertise (such as appropriate application of force). In addition, male patients report tender point pain less frequently than female patients, leading to possible underdiagnosis. Two instruments are now available to aid in the diagnosis of fibromyalgia: one from the American Pain Society (APS) and the FDA, called Analgesic, Anesthetic, and Addiction Clinical Trial Translations Innovations Opportunities and Networks (ACTTION)-APS Pain Taxonomy (AAPT) (Figure 32), and one based on the 2010 American College of Rheumatology Preliminary Diagnostic Criteria (Table 16). A diagnosis of fibromyalgia obtained by using these tools is valid irrespective of other diagnoses. A diagnosis of fibromyalgia does not exclude the presence of other clinically important illnesses.
Treatable alternative diagnoses that may provoke or be mistaken for fibromyalgia include hypothyroidism, hypoadrenalism, and depression.
Optimal management of fibromyalgia requires a holistic approach, including education, exercise, and psychosocial support. Pharmacotherapy is often warranted, although nonpharmacologic measures remain a cornerstone of treatment.
Patients should be educated regarding the disease, with validation that the symptoms are real and that the painful areas are not injured and will not lose function. Aerobic exercise can improve well-being and function as well as reduce pain. Because patients initially experience postexercise pain that may threaten their willingness to continue, exercise must be introduced gradually and supported encouragingly. Strength training may also be helpful. Although the evidence base supporting their use is modest, alternative medicine approaches, including yoga, tai chi, acupuncture, and massage, may also help alleviate symptoms.
Patients with fibromyalgia should be assessed for psychosocial stressors and psychiatric illness, including a history of trauma. If present, referral for psychological care is mandatory, because psychic distress may both promote and result from fibromyalgia. Cognitive behavioral therapy has shown modest benefit in reducing pain, negative mood, and disability.
Choice of pharmacologic therapy is based on symptom profile, patient comorbidities, and medication side effects because few trials directly compare the efficacy of medications. Effective pharmacologic therapies target the underlying pathophysiology and inhibit the ascending pain pathways, enhance the descending inhibitory pathways to the dorsal roots, or inhibit release of the pain-promoting neurotransmitter glutamate.
The antiepileptic agents gabapentin and pregabalin (the latter FDA approved) inhibit α2δ calcium channels to inhibit glutamate release. They have been shown to improve quality of life and decrease pain.
Tricyclic antidepressants (TCAs) (such as amitriptyline) raise norepinephrine levels and have documented benefit, although efficacy may wane with time. TCAs induce drowsiness, with potential benefit for disordered sleep. The muscle relaxant cyclobenzaprine, another tricyclic, may be useful in patients with muscle spasms. Selective serotonin reuptake inhibitors have little benefit alone but may complement the activity of TCAs.
Among the more effective fibromyalgia therapies are the dual serotonin-norepinephrine reuptake inhibitors (SNRIs), including the FDA-approved agents duloxetine and milnacipran. They or a TCA may be particularly appropriate in the patient with concomitant depression.
Tramadol, which has a complex mechanism of action, has shown some benefit and may be considered as a second-line approach. Finally, in some cases, combination pharmacologic therapy may be helpful.
Evidence does not support the benefit of NSAIDs for fibromyalgia, and pure opioids should not be used.
Fibromyalgia is a chronic disease, and the patient and physician should understand that the benefit of treatment will likely be partial and palliative, rather than complete or curative. Nonetheless, proper treatment can help most patients manage and cope with their symptoms as well as maintain function and autonomy.