Fibromyalgia (FM) is characterized by chronic widespread musculoskeletal pain and tenderness. Although it is defined primarily as a pain syndrome, FM patients also commonly complain of associated neuropsychological symptoms of fatigue, unrefreshing sleep, cognitive dysfunction, anxiety, and depression. Patients with FM have an increased prevalence of other syndromes associated with pain and fatigue, including chronic fatigue syndrome (Chap. 389), temporomandibular disorder, chronic headaches, irritable bowel syndrome, interstitial cystitis/painful bladder syndrome, and other pelvic pain syndromes. Available evidence implicates the central nervous system as key to maintaining pain and other core symptoms of FM and related conditions. The presence of FM is associated with substantial negative consequences for physical and social functioning.
FM is far more common in women than in men, with a ratio of about 9:1. In population-based studies worldwide, there is general agreement that the prevalence rate is approximately 2–3%, with rates of closer to 5–10% in primary care practices. The prevalence data are similar across socioeconomic classes. Cultural factors may play a role in determining whether patients with FM symptoms seek medical attention; however, even in cultures in which secondary gain is not expected to play a significant role, the prevalence of FM remains in this range.
The most common presenting complaint of a patient with FM is “pain all over.” Patients with FM have pain that is typically above and below the waist on both sides of the body and involves the axial skeleton (neck, back, or chest). The pain attributable to FM is poorly localized, difficult to ignore, severe in its intensity, and associated with a reduced functional capacity. Pain should have been present most of the day on most days for at least 3 months.
The clinical pain of FM is associated with increased evoked pain sensitivity. In clinical practice, this is determined by a tender point examination in which the examiner uses the thumbnail to exert pressure of approximately 4 kg/m2, or the pressure leading to blanching of the tip of the thumbnail, on well-defined musculotendinous sites (Fig. 335-1). American College of Rheumatology classification criteria previously required that 11 of 18 sites be perceived as painful for a diagnosis of FM. In practice, tenderness is a continuous variable, and strict application of a categorical threshold for diagnosis specifics is no longer necessary. Increased pain sensitivity can be demonstrated not only for the mechanical pressure-induced pain used in the clinic but also for nonmuscular mechanical pressure, heat, cold, and other sensory stimuli; this reinforces the idea that the pathogenic mechanisms of FM are not related to specific musculoskeletal pathology but to altered pain processing. New criteria eliminate tender points and focus on clinical symptoms of widespread pain and neuropsychological symptoms.
Tender point assessment in patients with fibromyalgia.
Patients with FM often have peripheral pain generators that are thought to serve as triggers for the more widespread pain attributed to central nervous system factors. Potential pain generators such as arthritis, bursitis, tendinitis, neuropathies, and other inflammatory or degenerative conditions should be identified by history and physical examination. More subtle pain generators may include joint hypermobility and scoliosis. Patients also may have chronic myalgias triggered by infectious, metabolic, or psychiatric conditions that can serve as triggers for the development of FM. These conditions are often in the differential diagnosis of patients with FM, and a major challenge is to distinguish the ongoing activity of a triggering condition from FM as a consequence of a comorbid condition that should itself be treated.
In addition to widespread pain, FM patients typically complain of fatigue, stiffness, sleep disturbance, cognitive dysfunction, anxiety, and depression. These symptoms are present to varying degrees in most FM patients but are not present in every patient or at all times. Such symptoms may, however, have an equal or even greater impact on function and quality of life. Fatigue is highly prevalent in patients under primary care who ultimately are diagnosed with FM. Pain, stiffness, and fatigue often are worsened by exercise or unaccustomed activity (postexertional malaise). The sleep complaints include difficulty falling asleep, difficulty staying asleep, and early-morning awakening. Regardless of the specific complaint, patients awake feeling unrefreshed. Patients with FM may meet criteria for restless legs syndrome and sleep-disordered breathing; frank sleep apnea can also be present. Cognitive complaints are characterized as slowness in processing, difficulties with attention or concentration, problems with word retrieval, and short-term memory loss. Studies have demonstrated altered cognitive function in these domains in patients with FM, though speed of processing is age-appropriate. Symptoms of anxiety and depression are common, and the lifetime prevalence of mood disorders in patients with FM approaches 80%. Although depression is neither necessary nor sufficient for the diagnosis of FM, it is important to screen for major depressive disorders by querying for depressed mood and anhedonia. Analysis of genetic factors that are likely to predispose to FM reveals shared neurobiologic pathways with mood disorders, providing the basis for comorbidity.
Because FM can overlap in presentation with other chronic pain conditions, review of systems often reveals headaches, facial/jaw pain, regional myofascial pain particularly involving the neck or back, and arthritis. Visceral pain complaints involving the gastrointestinal tract, bladder, and pelvic or perineal region are also often present. Patients may or may not meet defined criteria for specific syndromes. It is important for patients to understand that there may be shared pathways that mediate symptoms and that using treatment strategies effective for one condition may help with global symptom management.
FM is often comorbid with chronic musculoskeletal, infectious, ...