eMedicine Specialties > Physical Medicine and Rehabilitation > Muscle Pain Syndromes

Fibromyalgia

Author: Regina P Gilliland, MD, Department of Internal Medicine; Division of Rehab Medicine, Mobile Infirmary Medical Center
Contributor Information and Disclosures

Updated: Aug 13, 2009

Introduction

Background

Fibromyalgia is a complex disorder that was not defined until the late 20th century. It was, however, discovered much earlier, with the condition having been described in medical literature dating as far back as the early 17th century. Many physicians question the existence of fibromyalgia and prefer not to deal with patients who have this complicated disorder. In the past, poor recognition and lack of treatment for fibromyalgia could be explained by a lack of meaningful research. Today, abundant research and medical evidence support the diagnosis of this disease.

Some experts propose that physicians make a paradigm shift in their approach to successfully caring for patients with fibromyalgia. We can no longer rely on the technological advances of science. Even with advanced imaging and laboratory tests, none of the findings confirm the diagnosis of fibromyalgia. A physician skilled in taking a careful history, listening to the patient's concerns, and performing a thorough examination remains the foundation for diagnosing and treating fibromyalgia. The physician must remain a scientist and practice evidence-based medicine without abandoning the Hippocratic principles in the Physician's Oath. We must keep our promises to care for and serve sick and suffering individuals, without prejudicial views.

Definition of fibromyalgia

Fibromyalgia, a common disorder, is a syndrome composed of a specific set of signs and symptoms. Fibromyalgia has long been considered a "wastebasket" diagnosis. However, in 1987, the American Medical Association (AMA) acknowledged fibromyalgia as a true illness and a potential cause of disability. Many well-respected organizations, such as the AMA, the National Institutes of Health (NIH), and the World Health Organization (WHO), have accepted fibromyalgia as a legitimate clinical entity.¹ Fibromyalgia is now recognized as one of many central pain-related syndromes that are common in the general population. Research advances have lead to the conclusion that disturbances within the central nervous system (CNS) known as central sensitization represent the most likely source.²

Patients with fibromyalgia generally see many physicians before receiving a correct diagnosis. Patients may seek medical advice for more than 5 years before a correct diagnosis is made, and more than 50% of patients receive a misdiagnosis and may undergo unnecessary surgery.

Nomenclature

Although the syndrome has been known by other names, the word fibromyalgia was first introduced in 1976. This word is derived from the Latin roots fibro (fibrous tissue), my (muscles), al (pain), and gia (condition of). Fibromyalgia was most commonly known by the misnomer fibrositis, where "itis" implied an inflammatory component. Chaitrow asserts that no inflammatory process has ever been found to be part of this disease.³

Pathophysiology

The sequence of events that causes fibromyalgia remains unknown, but advances and discoveries may help to unravel the mysteries of this disease. Research shows biochemical, metabolic, and immunoregulatory abnormalities associated with fibromyalgia.

Although the pathogenesis of fibromyalgia is not completely understood, the currently known abnormalities substantiate the proposal that fibromyalgia can no longer be considered a subjective pain condition. The biochemical changes seen in the CNS, the low levels of serotonin, the 4-fold increase in nerve growth factor, and the elevated levels of substance P all lead to a whole-body hypersensitivity to pain and suggest that fibromyalgia may be a condition of central sensitization or of abnormal central processing of nociceptive pain input.² Ongoing research will continue to provide a clearer picture of the pathophysiology of this complex syndrome.

Central processes

Clinicians can enhance their approach to diagnosis and treatment by broadening their knowledge of these biochemical and immunoregulatory abnormalities, which may be involved in how nociceptive signals to the CNS are interpreted and how individuals physiologically respond to stress.

Our current understanding of the pathophysiology of fibromyalgia is that the disease is a disorder of central pain processing or a syndrome of central sensitivity. Daniel Clauw, a rheumatologist and fibromyalgia researcher, describes the syndrome as a diffuse problem of sensory volume control that alters the patient's threshold of pain and of other stimuli, such as heat, noise, and strong odors. He also suggests that patients may have hypersensitivity because of neurobiologic changes that affect the perception of nociceptive pain or because of expectancy or hypervigilance, which may be related to psychological factors.⁴

Plasticity in the function of N-methyl-D-aspartate (NMDA) subtype glutamate receptors is necessary for central sensitization to occur. Increased sensitivity of central NMDA receptors were implicated in earlier studies as playing a primary role in fibromyalgia. However, subsequent evidence has suggested that suppression of the normal activity of dopamine-releasing neurons in the limbic system is the primary pathology in fibromyalgia. Increasing evidence indicates that fibromyalgia may represent a dysregulation of dopaminergic neurotransmission.

Serotonin

The most widely acknowledged biochemical abnormality associated with fibromyalgia is abnormally low serotonin levels. Many studies have linked serotonin, a neurotransmitter, to sleep, pain perception, headaches, and mood disorders. Lower-than-normal levels of serotonin have been observed in patients with fibromyalgia. A low platelet serotonin value is believed to be the cause of the low serum levels, which have been correlated with painful symptoms.

Serotonin levels in the CNS are thought to be low because of low levels of tryptophan (amino acid precursor to serotonin) and 5-hydroxyindole acetic acid (metabolic by-product) in the spinal fluid. Investigators have proposed a link between low serotonin levels and symptoms of fibromyalgia.⁵ Moreover, many propose that low serotonin levels may cause fibromyalgia in whole or in part.

Substance P

In support of the idea of a systemic biochemical abnormality in fibromyalgia, investigators from 4 independent studies reported levels of substance P that were 2-3 times higher than normal.⁶

Substance P, the neuropeptide in spinal fluid, is a neurotransmitter that is released when axons are stimulated. Increased levels of substance P increase the sensitivity of nerves to pain or heighten awareness of pain. The elevated levels in the spinal cord cause fairly normal stimuli to result in exaggerated nociception. Some authors believe that neither elevated substance P levels nor low serotonin levels alone can be primary cause. Instead, the dual dysfunction may be responsible for fibromyalgia.

Adenosine triphosphate

Researchers also have found low levels of adenosine triphosphate (ATP) in red blood cells of patients with fibromyalgia. Although the significance is unknown, it has been suggested that low platelet serotonin levels can be explained if platelet ATP levels are also low. ATP is necessary to move and then hold serotonin in platelets.⁷ More investigation into ATP and the link to serotonin is needed.

Dysfunction of the hypothalamic-pituitary-adrenal axis

Some investigators have studied the neuroendocrine aspects of fibromyalgia and have found dysfunction of the hypothalamic-pituitary-adrenal (HPA) axis.⁸ The HPA axis is a critical component of the stress-adaptation response. In a normally functioning system, corticotropin-releasing hormone (CRH) stimulates the anterior pituitary to release adrenocorticotropic hormone (ACTH). ACTH then stimulates the adrenal cortex to produce glucocorticoids, which are powerful mediators of the stress-adaptation response.

Circadian regulation and the stress-induced stimulation of the HPA axis are, in part, regulated by serotonin. Perturbations in serotonin metabolism (as well as premorbid abnormalities of the HPA axis) may explain the abnormalities of the HPA axis in fibromyalgia.

Dysfunction of the HPA axis may exaggerate the effects of abnormal serotonin metabolism. Hypoactivity of the HPA axis may cause low central serotonin levels.

Some authors have noted that 5 main measurable neuroendocrine abnormalities are associated with dysfunction of the HPA axis.⁹ These are as follows:

• Low free cortisol levels in 24-hour urine samples
• Loss of the normal circadian rhythm, with elevated evening cortisol level (when it should be at its lowest level)
• Insulin-induced hypoglycemia associated with an overproduction of pituitary ACTH
• Low levels of growth hormone
• Stimulated ACTH secretion leading to insufficient adrenal release of glucocorticoids

Growth hormone

Growth hormone, produced during delta sleep, is involved in tissue repair. Therefore, disrupted stage 4 (delta) sleep associated with fibromyalgia may account for low levels of growth hormone. Growth hormone stimulates the production of insulinlike growth factor I (IGF-I) in the liver. Some authors have found that most patients with fibromyalgia have low levels of IGF-I and that low levels are specific and sensitive for fibromyalgia.¹⁰

Nerve growth factor

In some studies, nerve growth factor was found to be 4 times higher in the spinal fluid of patients with fibromyalgia than it was in the spinal fluid of individuals without the condition. This factor is important in the pathophysiology of fibromyalgia, because the process enhances the production of substance P in afferent neurons, increasing an individual's sensitivity to or awareness of pain. Nerve growth factor also may play a role in spreading or redistributing perceived pain signals.

Genetic predisposition

Increasing evidence suggests that genetic and environmental factors play a role in the etiopathology of fibromyalgia. The most probable mode of inheritance is polygenic. According to Olson, early results of studies involving more than 140 families may confirm that the genes associated with serotonin play a role in fibromyalgia.¹¹ Some evidence indicates that the etiology of fibromyalgia may involve polymorphisms of genes in the serotonergic, catecholaminergic, and dopaminergic systems.¹² Future genetic studies are needed in the fields of fibromyalgia and related conditions.

Some investigators suggest that the genetic predisposition manifests when the person reaches a critical age or when he/she sustains an external insult, such as trauma or illness.

Frequency

United States

Conservative estimates suggest that at any given time, 2% of the general population meet the criteria for the diagnosis of fibromyalgia; this percentage, which includes children, translates into 3.4% of women and 0.5% of men.

As a result, fibromyalgia the second most common disorder that rheumatologists encounter. Physicians may find that approximately 8% of their patients have fibromyalgia. In a rheumatology and physiatry practice, however, as many as 15% of evaluated patients have fibromyalgia. This incidence implies that 1 of every 10 patients evaluated in a medical practice has fibromyalgia.

International

Cases of fibromyalgia have been reported by researchers from around the world.

Mortality/Morbidity

The social, emotional, economic, and functional effects of fibromyalgia on an individual's life have been compared with those of rheumatoid arthritis. Research indicates that the socioeconomic impact of fibromyalgia includes the following¹³ :

• Approximately one third of patients with fibromyalgia reportedly modify their work to keep their job. Some patients shorten their workday and/or workweek, and many persons with fibromyalgia change to a job that is less physically and mentally taxing than their previous one. Patients have also reported an inability to achieve career or educational advancement, and some have reported career loss. Such changes often lead to a decreased income and increased financial burdens.
• One study on patient perspectives confirmed that fibromyalgia has a significant negative impact on the quality of social and economic functions in patients' lives.
• One report suggested that approximately 15% of the people with fibromyalgia are receiving disability benefits. Disability rates as high as 44% are reported.
• It has been estimated that overall, fibromyalgia costs the American economy over $9 billion annually.

Race

Fibromyalgia exhibits no race predilection. Researchers have reported the condition in all ethnic groups and cultures.

Sex

Fibromyalgia is 4-7 times more common in women than in men. No universally accepted explanation exists for this predilection, since differences between boys and girls are hardly recognized.

Age

Fibromyalgia can occur in individuals of all ages. Symptoms usually arise in persons aged 20-55 years, but the condition may be diagnosed in childhood.

Clinical

History

Although insurance reimbursement and other aspects of the medical infrastructure are often barriers to giving patients the necessary examination time, a thorough and detailed history saves time in the long run, reduces the potential for litigation, helps to prevent incorrect diagnosis, and eliminates inappropriate or unnecessary treatments. Without a thorough history, it is impossible to develop a complete list of comorbid illnesses, with the inevitable result that treatment is incomplete and often inappropriate. Patients with fibromyalgia do significantly better when they receive a comprehensive, individualized treatment regimen than when they do not, and a thorough history is the first step toward developing that regimen.

Start the evaluation by identifying the chief complaint, which usually is pain. However, avoid treating patients based on the chief complaint alone. Premature treatment may lead to symptom chasing and ineffective treatment. Patients with fibromyalgia experience changes in symptoms from day to day, a feature that may not reflect the global nature of their disorder. This waxing and waning or fluctuating pattern of symptoms is common in fibromyalgia.

Next, expand on the chief complaint by asking specific questions about the patient's pain. Question the patient about the distribution of pain (eg, ask whether the pain is regional or generalized). Ask about the duration and onset of the pain. Patients can usually remember a sudden onset of pain. If the pain began gradually, determining the exact time of onset is difficult. Inquire about aggravating and alleviating factors. Record the description or characteristics of the pain (eg, ask whether the pain is migratory, burning, tender, sore, aching, sharp, or radiating).

Question the patient about his/her sleep habits and environment. If possible, ask the patient's sleeping partner if the patient snores or kicks while asleep. Inquire as to how long it takes for the patient to fall asleep and how many times he/she awakens. Ask patient how he/she feels in the morning.

Pellegrino and the present author suggest that physicians obtain information about the patient's diet, particularly about the individual's caffeine and carbohydrate intake.^14,15

The history should include any symptoms that may indicate the presence of 1 or more coexisting conditions (see Associated conditions, below). Information on medications, exercise, and fatigue is also important. List any allergies and perpetuating factors. (See Clinical presentation, below.)

The patient's history of pain can be summarized as follows:

• Widespread pain
  • Right and left sides of the body
  • Above and below the waist
  • Along the axial skeleton
• Duration of pain
  • Constant
  • More than 3 months

Diagnostic criteria

Before 1990, no guidelines for evaluating and diagnosing fibromyalgia existed, and for a long time, no medical or imaging tests were available to definitely diagnose the condition. However, a blood test involving antipolymer antibodies has been developed. Approximately 50% of patients with fibromyalgia have these antibodies. This blood test provides objective evidence for the identification of a subgroup of people with fibromyalgia. Routine laboratory tests and radiography can help to evaluate suspected coexisting conditions or to rule out other possible diseases.

To reduce misdiagnosis and confusion, the American College of Rheumatology (ACR) recognized the need to establish a clear definition and guidelines. They sponsored a multicenter study to develop these criteria. In 1992, at the Second World Congress on Myofascial Pain and Fibromyalgia, the diagnostic criteria for fibromyalgia were expanded and refined.

The diagnostic criteria include 2 basic requirements. The first is the presence of pain in all 4 quadrants of the body, as well as in the axial skeleton on a more or less continuous basis for at least 3 months. The pain often is described as widespread or global.

The second criterion is the presence of at least 11 of 18 anatomically specific tender points (see Physical, below). A tender point hurts only at the area where pressure (enough to cause the examiner's nail bed to blanch, or about 4 kg) is applied, and there is no referred pain. An instrument known as a dolorimeter can be used to apply exactly 4 kg of pressure over the tender points during the examination. The 18 possible tender points exist as 9 pairs. Tender points may be found in any palpable muscle, but 18 sites are consistently present in patients with fibromyalgia and are used for diagnosis. The ACR criteria describe 4 pairs of tender points on the anterior of the body and 5 pairs on the posterior of the body.¹⁶

Clinical presentation

Before receiving a correct diagnosis, the typical patient with fibromyalgia has seen an average of 15 physicians and has had the condition for approximately 5 years. Many cases are misdiagnosed, and many patients endure costly treatments that provide little benefit. At some point, most patients have been told that nothing is medically wrong with them and that the condition is imagined. Therefore, many patients become frustrated and skeptical. Although most patients are relieved when a correct diagnosis is finally made, the patient may need to be convinced that the clinician actually knows what is wrong and that a treatment plan has been formulated.

Most patients with fibromyalgia are female and do not appear chronically ill, although they may look fatigued or agitated. Their chief complaint is often "I hurt all over all the time." The quality of their constant pain is described as burning, aching, and soreness. They may feel as if they are bruised all over, even though there are no physical signs of this. Although the pain is constant, the location migrates and the intensity varies. Many patients may complain of only a single painful area, such as the low back or neck.

A careful history reveals that the individual's pain is global, not focal, in its distribution. Patients may initially complain of pain at 1 site because they are primarily concerned about their worst pain. Because many patients do not understand that their symptoms are connected, they provide a fragmented history. The physician must ask the right questions to develop a complete understanding of the patient's distribution of pain.

Patients generally do not tell the physician that they have a sleeping disorder. Again, a carefully taken history reveals unrefreshing sleep in about 65% of patients and morning fatigue in about 80%. Patients awaken as tired as they were before sleeping. Most patients awaken frequently throughout the night, and some have difficulty falling asleep. They finally fall asleep in the early morning hours, describing this as their best sleep. Many patients fall asleep immediately, deny sleep onset problems, and report only infrequent awakenings. Sleep onset this rapid is abnormal and should not be overlooked.¹⁷

Most patients complain of morning stiffness of variable duration. Question the patient's sleeping partner about leg movements. Approximately 20% of persons with fibromyalgia have concomitant restless legs syndrome, which may lead the physician to choose or add medications other than antidepressants.

The patients report their fatigue is second only to pain. The fatigue is worse in the morning and early evening. By 10 or 11 o'clock in the morning, the fatigue subsides somewhat. Several investigators, including the present author, have found that poor sleep, physical activity, and diet can worsen the patient's fatigue.

Patients may not admit to feeling depressed or anxious; therefore, the physician must inquire about these conditions. The source of the patient's emotional stress may be multifactorial.

Approximately 50% of patients with fibromyalgia present with complaints of tissues feeling swollen and of numbness and tingling in the extremities. These symptoms generally are more common in the upper extremities than in the lower ones. Objective swelling, sensory changes, and other neurologic findings are usually absent.

Some investigators list many other common complaints, including chronic headaches and tenderness of the scalp to the touch. Complaints of chest pain, shortness of breath, and palpitations are common. Serious cardiac problems should be considered and may require extensive evaluation. Many symptoms in patients with fibromyalgia are related to mitral valve prolapse syndrome.

Approximately 40% of patients with fibromyalgia describe having alternating bouts of diarrhea and constipation, and also experience bloating, cramping, and an increased urge to defecate. These symptoms are most likely related to irritable bowel syndrome. Some patients also may complain of symptoms that include urgency, frequency, and a sense of incomplete voiding. Pelvic pain and dysmenorrhea may be present as well.

Associated conditions

Several medical conditions and diseases frequently occur with fibromyalgia. In 1984, Yunus used a Venn diagram to depict the interrelationships of these syndromes. He proposed that the syndromes are interconnected, similar, and overlapping, with a probable common pathophysiologic mechanism.^18,19 Ironically, they have been described as functional syndromes. This is a misnomer, because their pathophysiology is based on the dysfunction of the neuroendocrine system. Central sensitization is likely the common pathophysiologic pathway.

These coexisting conditions can aggravate and perpetuate the patient's symptoms. If unrecognized, the physician might inadvertently prescribe an ineffective or even harmful treatment regimen, leading to costly and unnecessary testing.

The conditions most commonly associated with fibromyalgia include the following:

• Irritable bowel syndrome
• Tension/migraine headaches
• Dysmenorrhea
• Nondermatomal paresthesia
• Temporomandibular joint syndrome
• Mitral valve prolapse
• Interstitial cystitis, vulvodynia
• Female urethral syndrome
• Vulvar vestibulitis
• Hypermobility syndrome
• Restless legs syndrome
• Allergy
• Multiple chemical sensitivity syndrome
• Enthesopathies
• Vestibular disorders
• Esophageal dysmotility
• Ocular disturbances
• Anxiety disorders
• Pulmonary symptoms
• Raynaud phenomenon
• Thyroid dysfunction
• Lyme disease
• Silicone breast implant syndrome
• Rheumatoid arthritis
• Systemic lupus erythematosus
• Sjögren syndrome
• Infections
• Osteoarthritis
• Chronic fatigue syndrome
• Carpal tunnel syndrome
• Hyperventilation
• Premenstrual syndrome (PMS)
• Depression (see Depression, below)
• Myofascial pain syndrome (see Myofascial pain syndrome, below)
• Cognitive dysfunction (see Cognitive dysfunction, below)
• Sleep disorders^17,20
  • Sleep is not a state of massive system shutdown. On the contrary, the brain is active during sleep, constantly communicating with the body. Many neurohormones, antibodies, and other molecules are synthesized during sleep; therefore, when sleep is disrupted, biochemical abnormalities can occur, leading to multisystem disturbances.
  • Sleep studies have shown that patients with fibromyalgia have disordered sleep physiology. Most of these patients experience unrefreshing sleep, with morning fatigue.
  • To understand abnormal sleep architecture, it is essential to know the basics of normal sleep. Sleep can be divided into 2 main parts: nonrapid eye movement (NREM) and rapid eye movement (REM), which alternate cyclically through the night, always starting with NREM sleep. In each successive cycle through the night, NREM sleep decreases, and REM sleep increases. Each cycle, NREM plus REM, lasts about 90 minutes.
  • NREM is divided into 4 stages: stage 1 is initial drowsiness; stage 2, light sleep; and stages 3 and 4, progressively deeper levels of sleep. In stages 3 and 4, an electroencephalogram (EEG) will show delta waves, which are high-amplitude (>75 mV) waves that move slowly (0.5-2 Hz). Much of the body's regulatory work, as well as the synthesis of many substances (eg, antibodies, growth hormone, other neurochemicals), occurs during NREM sleep.
  • REM sleep has a low-voltage, mixed-frequency pattern on EEGs and is considered dream sleep. In this stage, the body has a complete loss of muscle tone, known as flaccid paralysis, and it cannot move. During this part of sleep, consolidation of memories may occur, but disagreement still exists as to what takes place with regard to memory during REM sleep. Some investigators have found that during waking hours, the brain generates alpha waves with a frequency of 7.5-11 Hz.
  • Sleep dysfunction is considered an integral feature of fibromyalgia. About 70% of patients recognize a connection with poor sleep and increased pain, along with feeling unrefreshed, fatigued, and emotionally distressed. Several studies have linked abnormal sleep with these symptoms.
  • Researchers have studied fibromyalgia and sleep, confirming the disordered sleep physiology in fibromyalgia. This abnormality has been identified as a sleep anomaly of alpha-wave intrusion, which occurs during NREM stage 4 sleep. This intrusion into deep sleep causes the patient to awaken or to be aroused to a lighter level of sleep.
  • Some investigators describe the altered sleep physiology and somatic symptoms as a nonrestorative sleep syndrome. This dysfunction is believed to be linked to the numerous metabolic disturbances associated with fibromyalgia, including abnormal levels of neurotransmitters (serotonin, substance P) and neuroendocrine and immune substances (growth hormone, cortisol, interleukin-1). These metabolic imbalances are thought to be responsible—through impairment of tissue repair and disturbance of the immunoregulatory role of sleep—for the increased symptoms associated with this sleep disorder of alpha-wave intrusion.
  • Most alpha-wave intrusions occur during the first few hours of sleep, decreasing throughout the night to normal levels by early morning. This hypothesis has been well correlated with patients' frequent reporting that their best sleep is obtained in the early morning hours, just before arising.
• Depression²¹
  • Depression in fibromyalgia is a controversial topic. In support of the contention that fibromyalgia is not a psychiatric illness, some authors believe that the symptoms of fibromyalgia are not connected with psychological factors. Others have determined that fibromyalgia is not a psychiatric disorder. The depression associated with fibromyalgia is believed to result from pain, sleep deprivation, and dysfunction.
  • Depression in fibromyalgia may be treated with a regimen that includes nonpharmaceutical therapies. Treating depression alone does not cure fibromyalgia. Antidepressants may help, but the clinician also should address other symptoms, such as fatigue or pain. Modifying diet and practicing good sleep hygiene are crucial. Starting a rehabilitation exercise program is important. Behavioral modification techniques and stress management may also be used.
• Myofascial pain syndrome^1,22,23,24
  • Fibromyalgia and myofascial pain syndrome may coexist, creating a complex clinical picture. However, fibromyalgia and myofascial pain syndrome are not the same condition. Some authors assert that fibromyalgia and myofascial pain syndrome can each magnify and perpetuate the symptoms of the other.
  • Fibromyalgia is a generalized amplification of pain or a hypersensitivity condition associated with tender points in the muscles. These points are exquisitely tender and painful to compression where pressure is applied; the pain is not referred to distant areas.
  • Narrowly defined, myofascial pain syndrome is a disorder of trigger points. Similar to tender points, trigger points are discreet areas in muscle tissue and/or its associated fascia that are exquisitely tender to compression; however, pain occurs at the site of the applied pressure and also at a distant site (zone of pain referral). Trigger points are found in taut bands (firm, elongated bands) in muscle fibers and are associated with the local twitch response. This response is an involuntary, transient contraction of the taut bands and can be elicited by snapping or pinching the band.
  • Several differences have been noted between fibromyalgia and myofascial pain syndrome; the table below lists a few of these differences. A more detailed review of the similarities and differences in the 2 syndromes is found in Acupuncture, Trigger Points, and Musculoskeletal Pain: a Scientific Approach to Acupuncture for Use by Doctors and Physiotherapists in the Diagnosis and Management of Myofascial Trigger Point Pain (2nd ed, 1993), by Baldry, a leading British physician and acupuncturist.²⁵

Open table in new window

• Cognitive dysfunction²⁶
  • Cognitive function can be considered the ability to think, reason, image, remember, or learn words. The available research on cognition in fibromyalgia suggests that cognitive actions are faulty. This impact on cognition may cause some patients with fibromyalgia the most disability.
  • The euphemism "fibro-fog" is often used to describe the memory problems and unclear thinking (cognitive dysfunction) that occur in patients with fibromyalgia. Decades of research have shown elucidated several memory systems: short term, working, episodic, semantic (predominantly verbal memory), and procedural (memory for different skills).
  • Symptoms include confusion and forgetfulness, an inability to concentrate and recall simple words and numbers, and the transposition of words and numbers. Cognitive functions are often so impaired that patients cannot perform the activities of daily living (ADL), getting lost in familiar places or losing the ability to communicate effectively. Patients who work may fear losing their job, and many pediatric patients drop out of school because of their inability to complete their schoolwork.
  • Advances in noninvasive technology have made it possible to visualize the brain. Various modalities, such as single-photon emission computed tomography (SPECT) scanning, have helped to define some of the abnormalities linked to the cognitive dysfunction. SPECT shows decreased blood flow in the right and left caudate nuclei and thalami. Functional magnetic resonance imaging (fMRI) can show brain activity by depicting increased blood flow to areas actively engaged in a task. Increased blood flow, and hence increased oxygenation, has different magnetic properties. These properties can be detected and measured using fMRI.
  • CNS imbalances have been linked to cognitive dysfunction. Abnormal levels of such neurotransmitters as substance P, serotonin, dopamine, norepinephrine, and epinephrine may cause cognitive dysfunction. Neuroendocrine imbalance of the HPA axis may play a role in fibro-fog.
  • Another possible cause of cognitive dysfunction is the distracting quality of pain in fibromyalgia. Cognitive performance of patients with fibromyalgia is correlated with their reported level of pain. Researchers are looking at tissue volumes in areas of the brain (hippocampus) that may be damaged by the effects of stress hormones. Others studies have implicated yeast overload, water retention, and glial cell abnormalities as causes of cognitive dysfunction in fibromyalgia.
  • One study showed that the working memory and episodic memory scores of patients with fibromyalgia were similar to those of healthy control subjects who were 20 years older. Patients were matched for age and education.
  • In another study, brain fMRI was performed while participants were shown a string of 3 or 4 letters. These letters were presented in jumbled, nonalphabetical order and then in a maintenance condition in which they were alphabetized. The participants were asked to mentally organize the letters into alphabetical order and then press one key if they were in the correct order or another key if they were not. Patients with fibromyalgia performed almost as well as controls, but more of their brain areas were activated during the memory task than were activated in the controls, because the task was harder for the patients to perform. This finding was consistent with the results found in adults who were older than the patients.
  • Additional research is needed to determine the brain systems involved, why patients have cognitive problems, and what to do about these problems.

Physical

The goal of the physical examination is to confirm the diagnosis, rule out concomitant systemic diseases, and recognize common coexisting conditions.

The physical examination can be quickly summarized as follows:

• Palpate the muscles by using 4 kg of pressure.
• To meet the diagnostic criteria, pain must occur in 11 of 18 paired tender points.
• The tender-point examination should be performed first during the physical examination, because a number of factors may influence the sensitivity of the tender points during the examination.

The diagnostic criteria include 2 basic requirements. The first diagnostic criterion is the presence of pain in all 4 quadrants of the body and in the axial skeleton on a more or less continuous basis for at least 3 months. The pain often is described as widespread or global. The second diagnostic criterion is, as mentioned above, the presence of at least 11 of 18 anatomically specific tender points. A tender point hurts only at the area where pressure (enough to cause the examiner's nail bed to blanch, or about 4 kg) is applied, and the patient has no referred pain.²⁷ Additional examination details are as follows:

• Procedure for the tender-point examination - The thumb pad of the examiner's dominant hand is used to apply pressure to the evaluation sites during the tender-point examination. This allows the examiner to use important tactile cues and is as reliable as the use of a dolorimeter. (A dolorimeter can be used to apply exactly 4 kg of pressure over the tender points during the examination.) Because the sequence in which the sites are examined may influence the patient's responses, a standardized procedure for evaluating the tender points enhances interobserver reproducibility and reliability in reporting the findings.¹⁶
  • First, visually locate the evaluation site.
  • Then, with the thumb pad, press perpendicularly into the evaluation site for 4 seconds.
  • Press the site only once to avoid sensitization.
  • Four kilograms of pressure should be applied to the site; this is enough force to blanch the examiner's nail bed.
  • Have the patient wear a standard gown to allow for easy access to the evaluation sites.
  • Always examine the 18 diagnostic sites and 3 control sites (sites 1, 16, and 17; see Site locations, below) in the designated order. The 3 control points should be palpated and recorded to provide baseline documentation of the patient's pain perception.
  • Examine the right site and then the corresponding left site.
  • The patient should sit on the examination table for the evaluation of the first 17 sites. The individual should lie on his/her side contralateral to the site for the testing of sites 18 and 19, and should lie on his/her back for the evaluation of sites 20 and 21.
  • Other tender points may be present and also should be recorded, but they are not necessary for diagnosis. Some patients may present with fewer than 11 tender points. Experts contend that fibromyalgia can be diagnosed with as few as 8 or 9 tender points if the patient has other symptoms, such as sleep problems, fatigue, and any of the characteristic coexisting conditions.
  • The patient should respond with a "yes" or "no" if he/she has any pain at the site being examined. If the patient's response is "yes," have the individual rate the pain on a scale of 0 (no pain) to 10 (worst pain), and record each response.
  • The patient's position during examination, the amount of force applied at the evaluation site, the number of times the evaluation site is palpated, and the method of applying force (dolorimeter vs finger pad) may influence tender-point sensitivity.
• Site locations - The 18 possible tender points exist as 9 pairs. Tender points may be found in any palpable muscle, but 18 sites are consistently present in patients with fibromyalgia and are used for diagnosis. The ACR criteria describe 4 pairs of tender points on the anterior of the body and 5 pairs on the posterior of the body.²⁸
  • 1, control site - Forehead
  • 2 and 3 diagnostic sites - Occiput at the nuchal ridge
  • 4 and 5 diagnostic sites - Trapezius
  • 6 and 7 diagnostic sites - Supraspinatus
  • 8 and 9 diagnostic sites - Gluteal
  • 10 and 11 diagnostic sites - Low cervical
  • 12 and 13 diagnostic sites - Second rib
  • 14 and 15 diagnostic sites - Lateral epicondyle
  • 16, control site - Distal middle third of the right forearm
  • 17, control site - Nail of the left thumb
  • 18 and 19 diagnostic sites - Greater trochanter
  • 20 and 21 diagnostic sites - Medial knee
• The 1990 ACR criteria for the location of tender points are as follows:
  • Anterior body - Bilateral
    • At the fifth through seventh intertransverse spaces of the cervical spine
    • In the pectoral muscle, at the second costochondral junctions
    • Approximately 3 finger breadths (2 cm) below the lateral epicondyle
    • At the medial fat pad, proximal to the joint line
  • Posterior body - Bilateral
    • At the upper border of the shoulder in the trapezius muscle, midway from the neck to the shoulder joint
    • At the craniomedial border of the scapula, at the origin of the supraspinatus
    • In the upper outer quadrant of the gluteus medius
    • Just posterior to the prominence of the greater trochanter at the piriformis insertion
• Other evaluations - After completing the tender-point examination, the physician should include neurologic, joint, and musculoskeletal evaluations. Note the presence of swelling, deformities, and erythema. Examine the patient's gait, joint range of motion (ROM), and posture for structural asymmetry and skeletal deficiencies. Palpate the soft issues for tone or spasm. Check for taut bands, twitch responses, and trigger points; their presence signals the coexistence of a myofascial pain syndrome.

Causes

No cause for fibromyalgia has been accepted universally, although many theories have been proposed. Some authors suggest that an inheritance factor may be involved.

• The frequent comorbidity of fibromyalgia with mood disorders suggests a major role for the stress response and for neuroendocrine abnormalities.
• Fibromyalgia is associated with polymorphisms in the catechol-O-methyltransferase enzyme that inactivates catecholamines and the serotonin transporter gene.⁵
• Basal and stimulated activity of several neuroendocrine axes are altered, and dysfunction of the autonomic nervous system is demonstrated in fibromyalgia.
• Psychosocial factors contribute to the expression of fibromyalgia.

The question remains as to whether these abnormalities are causes or effects of fibromyalgia. Ongoing research may soon provide the answer.

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