Fibromyalgia is a chronic condition that affects about 2% of the U.S. population. Most patients are women. The initial presentation of this painful condition occurs between approximately 30 and 40 years of age, but the distribution is variable between the age of onset and diagnosis because most patients tend to cope with the pain rather than pursue the necessary medical attention.
Fibromylagia is characterized by a variety of nonspecific symptoms, such as diffuse soft-tissue pain, fatigue, morning stiffness, and nonrestorative sleep (when a person awakens without feeling refreshed). Less common symptoms include migraine headache, irritable bowel syndrome, restless legs syndrome, myofascial pain, subjective swelling, and major depression. All of these symptoms are usually determined by various circumstances, including stress, physical activity, sleep abnormalities, and the weather.
With no established laboratory tests to diagnose fibromyalgia, the diagnosis usually is based on standards of exclusion. Palpation of specific sites (“tender points”) during a physical assessment aids in guiding practitioners in arriving at the diagnosis. These 18 diagnostic points produce a considerable amount of generally localized pain that does not radiate when pressure is applied. The sites are as follows:
For a diagnosis of fibromyalgia to be confirmed, certain criteria established by the American College of Rheumatology must be met. Fibromylagia is defined as pain and tenderness existing for at least three months and manifested in 11 of 18 tender points upon palpation after a force of 4 kg is applied. The pain must be located on bilateral sites of the body, above and below the midsection, and within the axial skeleton. Patients describe the pain as being more severe than that experienced with rheumatoid arthritis and osteoarthritis. Muscle cramping, aching, and stiffness limit everyday functions as well as the sleep patterns of affected individuals.
The pathophysiology of fibromyalgia remains a mystery, but many speculations and hypotheses abound in the literature. Many agree that a viral infection, toxin exposure, or some type of trauma might be a cause. Impaired functioning of the hypothalamic-pituitary axis and changes in certain neuro-transmitters, such as serotonin, epinephrine, substance P, and ,/V-methyl-D-aspartate, correlate with pathophysiological hypotheses.
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Serotonin, a key neurotransmitter, is implicated in the origin of fibromyalgia because it is responsible for part of the sleep cycle, pain thresholds, depression, anxiety, and other psychiatric disorders. Decreased serum concentrations of serotonin and an increased density of serotonin receptors, located on circulating platelets, are characteristic. These factors have been associated with the common symptoms of the condition. For example, low serum concentrations of serotonin have been associated with a decreased pain threshold because serotonin regulates pain perception in both the central nervous system and the periphery and modulates the function of substance P (which is involved primarily in pain transmission).
Fibromyalgia also produces sleep abnormalities caused by impaired serotonergic neurotransmission within the brain and spinal cord. Sleep abnormalities have also been associated with restless legs syndrome and nocturnal muscle spasms. As the quality of sleep is affected, patients are more prone to experiencing the symptoms of fatigue and irritability. These neurotransmitter mechanisms play a role in the increased pain, poor quality of sleep, and possibly even mood disorders in affected patients.