Apr 17, 2011
An in-depth report on the causes, diagnosis, treatment, and prevention of fibromyalgia.
Fibromyalgia is sometimes categorized as primary or secondary. In primary fibromyalgia (also called idiopathic fibromyalgia) the causes are not known, and in secondary fibromyalgia the causes can be identified. Primary fibromyalgia is the more common form.
Many experts believe that fibromyalgia is not a disease but rather a chronic pain condition brought on by a constellation of dysfunctional biologic responses to stress. Such individuals are thought to be more susceptible to stress because of traumatic personal histories, genetic factors, or both. Physical injuries, emotional trauma, or viral infections, such as Epstein-Barr, may act as triggers for the onset of the disorder, but none have proven to be a cause of primary fibromyalgia.
Chronic Sleep Disturbance
Sleep disturbances are common in fibromyalgia. Pain is certainly a factor. In addition, fibromyalgia patients have more sleep disturbances than others. Specifically, both adult and young patients have a higher than average incidence of a sleep disorder called periodic limb movement disorder (PLMD), (formerly known as nocturnal myoclonus). In this condition, the leg muscles involuntarily contract every 20 to 40 seconds during sleep, occasionally arousing the patient, who, however, is usually unaware of the cause of the interruption.
Some experts believe that fibromyalgia does not lead to poor sleeping patterns, but that sleep disturbances come first, precipitating many cases of fibromyalgia pain. In one study, healthy volunteers reported fibromyalgia-like pain after they had been subjected to disrupted deep sleep. Disturbed sleep appears to trigger factors in the immune system that cause inflammation, pain, fatigue, and a decreased pain threshold. The June 2004 journal of Rheumatology found that in fibromyalgia patients, the cyclic alternating (sleep) pattern, or CAP, was significantly increased compared to controls. The increase CAP produced significant sleep impairment, which in turn correlated strongly to symptom severity. (Previous studies have also suggested that CAP may be related to PLMD.) A second study, reported in the May 1, 2004, issue of Sleep, found that sleep-disordered breathing, specifically inspiratory airflow limitation, is common in women with fibromyalgia. Other biologic measures of troubled sleep, however, such as levels of the hormone melatonin, which helps to regulate circadian rhythms and the sleep-wake cycle, appear to be normal in most fibromyalgia sufferers.
Brain Chemicals and Hormonal Abnormalities
Studies of hormonal, metabolic, and brain chemical activity in fibromyalgia patients have shown a number of abnormalities. Alterations appear to occur with a number of brain chemicals, although no consistent pattern has emerged that fits most patients. Some experts believe that such abnormal deviations are a result of the effects of pain and stress on the central nervous system and are not a cause of fibromyalgia.
Serotonin. Of particular interest to researchers is serotonin, an important nervous system chemical messenger (neurotransmitter) found in the brain, gut, and other areas. Serotonin plays important roles in feelings of well being, modulating pain, and promoting deep sleep. Serotonin abnormalities have been linked to many disorders, including depression, migraines, and irritable bowel syndrome. And lower levels have also been noted in some patients with fibromyalgia.
Stress Hormones. Researchers have also noted abnormalities in the hormone system known as the hypothalamus-pituitary-adrenal gland (HPA) axis, which controls important functions, including sleep, response to stress, and depression. Alterations in the HPA axis appear to produce lower levels of norepinephrine and cortisol, which are important stress hormones. (In depression, stress hormones are higher than normal.) Deficiencies produce impaired and weaker responses to psychological or physical stresses (such infection or exercise).
The hypothalamus is a highly complex structure in the brain that regulates many important brain chemicals. Malfunction of this area of the brain may give rise to cluster headaches.
Click the icon to see an image of the adrenal glands.
Low Growth Hormone Levels. Some studies have reported low levels of insulin-like growth factor-1 (IGF, also called somatomedin C) in about a third of fibromyalgia patients. IGF is a hormone that is controlled by adult growth hormone and promotes bone and muscle growth. Low levels are associated with impaired thinking, lack of energy, muscle weakness, and intolerance to cold. In a 2003 study, however, there was no association between IGF levels and fibromyalgia. Researchers in the study noted that lower levels of IGF also occur with aging and obesity, which must be factored in when studying its role in fibromyalgia. Nevertheless, severe growth hormone deficiency, which may be treatable, has been observed in a subset of fibromyalgia patients.
Abnormal Pain Perception and Substance P. Some studies have suggested that fibromyalgia may involve overactivity in the parts of the central nervous system that process pain (called the nocioceptive system). Brain scans of fibromyalgia patients have, in fact, suggested abnormalities in pain processing centers. Of particular interest is research that has detected up to three times the normal level of substance P in the cerebrospinal fluid of fibromyalgia patients. Substance P is a neurotransmitter associated with increased pain perception.
Some research suggests that fibromyalgia patients may suffer from a state called generalized hypervigilance, which is an amplification of sensation. People with this condition are oversensitive to external stimulation and are preoccupied with the sensation of pain. For example, one study compared patients with fibromyalgia, rheumatoid arthritis, and those without chronic pain. They were surveyed to assess their response to pain and noise. Of the three groups, the fibromyalgia patients were least tolerant of and most attentive to such stimuli. A 2001 analysis of studies on fibromyalgia, however, found no strong support for the hypervigilance theory.
Fibromyalgia has some symptoms that resemble a number of rheumatic illnesses, including rheumatoid arthritis and lupus (systemic lupus erythematosus). These are autoimmune diseases, in which a defective immune system produces factors known as autoantibodies, which mistakenly attack proteins in the body's own healthy tissue and produce inflammation and damage. The pain in fibromyalgia, however, does not appear to be due to autoimmune factors, and there is little evidence to support a role for an inflammatory response in fibromyalgia.
Psychological and Social Effects
Although not primary causes, psychological and social factors may contribute to fibromyalgia in three ways:
They could make individuals susceptible to fibromyalgia.
They may play some role in triggering the onset of the condition.
They may help perpetuate it.
Studies have reported a greater incidence of severe experiences of victimization from emotional and physical abuse in patients with fibromyalgia than in the general population. Most often the abuse originated from family or partners. This suggests that post-traumatic stress disorder (PTSD) or chronic stress may play a strong role in the development of fibromyalgia in some patients. PTSD is an anxiety disorder that is a reaction to a specific traumatic event. Symptoms of this condition, which can occur for years after the traumatic event, include emotional withdrawal, hopelessness, irritability, mood swings, sleep problems, inability to concentrate, and an excessive startle response to noise. There is some evidence that PTSD actually results in changes in the brain, possibly from long-term overexposure to stress hormones.
Some research has detected muscle defects in fibromyalgia patients, which can be classified as follows:
Biochemical abnormalities. For example, one study reported that fibromyalgia patients had lower levels of the muscle-cell chemicals phosphocreatine and adenosine triphosphate (ATP). Such chemicals regulate the ebb and flow of calcium in muscle cells, an important component in their ability to contract and relax. If ATP levels are low, calcium is not "pushed back" into the cells and the muscle remains contracted.
Structural and blood flow abnormalities. Some researchers have observed overly thickened capillaries (tiny blood vessels) in the muscles of fibromyalgia patients, which could produce lower levels of certain compounds essential for muscle function as well as reduce the flow of oxygen-rich blood to these tissues.
Functional abnormalities. The pain and stress of the disease itself may impair muscle function.
The observed biochemical and structural defects could derive from defective signals in the brain, including hormones produced in the hypothalamus and pituitary that influence the production of stress hormones in the adrenal glands, which sit atop the kidneys. Defects in the hypothalamus-pituitary-adrenal gland (HPA) axis have been reported in fibromyalgia patients.
Causes of Secondary Fibromyalgia
Secondary fibromyalgia has the characteristic symptoms of fibromyalgia but unlike primary fibromyalgia, a specific cause can be identified. Possible causes include the following:
Physical injury. In one study, for example, secondary fibromyalgia developed in over 20% of patients who had neck injuries. The symptoms are identical to those of primary fibromyalgia but are harder to treat. Another study reported a high incidence of fibromyalgia in workers complaining of repetitive stress injuries, although it is not clear which condition caused the other.
Lyme Disease. According to one study, between 10% and 25% of patients with Lyme disease subsequently developed fibromyalgia, which did not respond to the standard Lyme treatment consisting of antibiotics.
Hepatitis C. Hepatitis C may prove to be a trigger for some cases of fibromyalgia.
Endometriosis. According to a 2001 study, about 31% of women with the painful condition known as endometriosis go on to develop fibromyalgia or chronic fatigue syndrome, a related illness.
Silicone breast implants. A limited but worrisome 2002 study reported that when silicone breast implants ruptured and the silicon leaked outside the scar around the implant, women were 2.8 times more likely to have fibromyalgia than those whose implants remained intact. (They did not appear to have a higher risk for connective tissue or autoimmune diseases.) Further follow-up is called for.