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Chronic Widespread Pain
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Chronic widespread pain presents challenges to patients, clinicians, and researchers in diagnosing and treating its complex manifestations. Chronic widespread pain is a broad category of heterogeneous, centrally mediated pain conditions. While recent advances in understanding centrally mediated pain have improved its mechanistic understanding, consistently applying clinical diagnosis and treatment remains challenging. The unifying theme for these disorders is pain and sensory hyper-responsiveness, which can be identified using sensory testing and is associated with functional neuroimaging changes. Although widespread pain conditions, including fibromyalgia (FM) conditions, have historically struggled for credibility, advances in our mechanistic understanding of these conditions have occurred so rapidly that we can now use this information to better diagnose and treat individuals with chronic pain. FM is a painful condition for a third new descriptor of pain, nociplastic pain, which has been recently adopted by the International Association for the Study of Pain.
Longstanding negative perceptions and beliefs about centrally mediated pain states are likely to interfere with the adoption of standardized treatment protocols. However, some of the objective tests that can be used to identify pathology in these conditions, such as quantitative sensory testing and functional neuroimaging, are not generally available clinically. Despite this, clinicians can use various simple patient-reported outcomes to make inferences regarding underlying pain mechanisms. This chapter summarizes the current status of these chronic widespread pain conditions, focusing on fibromyalgia and its clinical features, epidemiology, pathogenesis, and management.
Fibromyalgia
Evolution of Diagnostic Criteria
One of the more recent developments in understanding fibromyalgia (FM) has been the paradigm shift in evaluating fibromyalgia as a continuum rather than a binary diagnosis. However, the move toward clinical diagnostic criteria and the use of tools such as the current 2011 FM survey criteria have taken a lengthy path to reach our current state. The first American College of Rheumatology (ACR) developed research criteria for the classification of FM syndrome based on the results of a multicenter research study in 1990 ( Table 37.1 ). The scientific community quickly accepted these criteria with a broad application for epidemiologic, biologic, and therapeutic studies. The ACR research classification required only two components for diagnosis: a history of widespread pain (i.e. located in all four quadrants of the body and axial) for at least three months and allodynia in response to digital pressure (defined as pain with 4 kg of pressure) at 11 or more of the 18 anatomically defined tender points ( Table 37.2 ). The research diagnostic criteria demonstrated moderate sensitivity (88.4%) and specificity (81.1%) for FM in control patients. The study design included pain-free individuals and patients with other painful conditions as the control group.
TABLE 37.1
American College of Rheumatology Criteria for Research Classification of Fibromyalgia
| Criterion | Description |
| 1. History | Chronic, widespread (four quadrants) soft tissue pain for three months. |
| 2. Examination | Pain (1+ or greater in severity) induced by 4 kg of digital palpation pressure at 11 of 18 anatomically defined tender points ( Table 37.2 ). |
| 3. 1 and 2 are true | When 1 and 2 are true, sensitivity and specificity for FMS are >80%. |
Adapted from Wolfe F, Smythe HA, Yunus MB, et al. The American College of Rheumatology 1990 criteria for the classification of fibromyalgia report of the multicenter criteria committee. Arthritis Rheum. 1990;33:160–172. FMS , Fibromyalgia syndrome.
TABLE 37.2
Eighteen Anatomically Defined Tender Points in Fibromyalgia Syndrome
| Number | Official American College of Rheumatology Bilateral Tender Point Sites |
| 1, 2 | Occiput—suboccipital muscle insertions |
| 3, 4 | Low cervical—anterior aspects of the C5-7 intertransverse spaces |
| 5, 6 | Trapezius—midpoint of the upper border |
| 7, 8 | Supraspinatus—origins above the scapular spine, near the medial border |
| 9, 10 | Second rib—upper lateral surface of the second costochondral joint |
| 11, 12 | Lateral epicondyle—2 cm distal to the epicondyles |
| 13, 14 | Gluteal—upper outer aspect of the buttock, anterior fold of the muscle |
| 15, 16 | Greater trochanter—posterior to the trochanteric prominence |
| 17, 18 | Knees—medial fat pad, just proximal to the medial condyle |
Adapted from Wolfe F, Smythe HA, Yunus MB, et al. The American College of Rheumatology 1990 criteria for the classification of fibromyalgia report of the multicenter criteria committee. Arthritis Rheum. 1990;33:160–172.
The tender points in FM are conceptually and anatomically different from the trigger points (TrPs) that define myofascial pain syndrome (MPS). FM tender points are symmetrically distributed throughout the body, whereas TrPs have a more random distribution. In contrast to MPS, these tender points are not limited to muscular locations but also include other soft tissue structures and do not radiate or refer pain to other locations.
The ACR’s original research criteria provided a structure but did not extend to clinical applications. Researchers have developed these criteria to standardize the research identification of FM. The research classification identified 18 anatomically defined tender points ( Table 37.2 ), where patients with FM have allodynia in response to digital pressure. Lacking alternative algorithms for diagnosis, clinicians have appropriated these criteria for clinical practice. Primary care physicians diagnose the majority of FM cases rather than subspecialists. Consequently, many physicians rigidly applied the research criteria or rejected their face validity. Accordingly, few providers consistently identified and applied 4 kg of pressure to all 18 designated areas. They used symptom-based diagnostic criteria that focused on fatigue, cognitive impairment, and somatic symptoms, which were excluded from the original research criteria. Moreover, an additional problem with the criteria is that patients with symptom improvement and examination findings no longer met the research classification.
Twenty years after the initial research classification was developed, the FM research community recognized the growing need for clinical diagnostic criteria that reflect the spectrum of FM and practical components of clinical diagnosis. The objective was to develop a screening tool with wide applicability that could be used to diagnose and assess the severity of FM symptoms. Researchers evaluated patients in whom FM was previously diagnosed using the widespread pain index (WPI) and categorical scales. The new criteria, developed in 2010 and revised in 2011 and 2016, used these categorical scales to assess patients’ cognitive symptoms, unrefreshing sleep, fatigue, and other somatic symptoms. The ACR used these categorical scales to develop a severity scale. Finally, they combined the severity scale with the WPI to stratify disease severity in patients with FM ( Box 37.1 ). The diagnostic criteria for fibromyalgia were initially designed by unblinded rheumatologists for research purposes. With the evolution of diagnostics to extend to clinical space, a large proportion of clinically diagnosed fibromyalgia does not meet the research diagnostic criteria. A critical advance in our understanding of fibromyalgia is the evolution to symptom-based diagnosis and elimination of the tender point criteria, reflecting a shift in thinking about the spectrum of FM symptoms.
• Box 37.1
American College of Rheumatology Preliminary Diagnostic Criteria for Fibromyalgia and Measurement of Symptom Severity
*Somatic symptoms that might be considered are muscle pain, irritable bowel syndrome, fatigue or tiredness, difficulty thinking or remembering, muscle weakness, headache, pain or cramps in the abdomen, numbness or tingling, dizziness, insomnia, depression, constipation, pain in the upper part of the abdomen, nausea, nervousness, chest pain, blurred vision, fever, diarrhea, dry mouth, itching, wheezing, Raynaud’s phenomenon, hives or welts, ringing in the ears, vomiting, heartburn, oral ulcers, loss of or change in taste, seizures, dry eyes, shortness of breath, loss of appetite, rash, sun sensitivity, hearing difficulty, easy bruising, hair loss, frequent urination, painful urination, and bladder spasms.
- 1
Criteria
A patient satisfies the diagnostic criteria for fibromyalgia if the following three conditions are met:
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Widespread pain index (WPI) score >7 and symptom severity (SS) scale score >5 or WPI score of 3 to 6 and SS scale score >9.
- 2
Symptoms present at a similar level for at least three months.
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No disorder present that would otherwise explain the pain.
- 1
- 2
Ascertainment
- 1
WPI: note the number of areas in which the patient experienced pain over the last week. In how many areas has the patient had pain? The score will be between zero and 19.
Shoulder girdle, left hip (buttock, trochanter), left jaw, left upper part of the back
Shoulder girdle, right hip (buttock, trochanter), right jaw, right lower part of the back
Upper part of the arm, left upper part of the leg, left side of the chest, or neck
Upper part of the arm, right upper part of the leg, right side of the abdomen
Left lower part of the arm, left lower part of the leg
Right lower part of the arm, right lower part of the leg
- 2
SS scale score:
Fatigue
Waking unrefreshed
Cognitive symptoms
- 3
For each of the three symptoms above, indicate the level of severity over the past week according to the following scale:
0= No problem
1= Slight or mild problems, generally mild or intermittent
2= Moderate: considerable problems, often present and/or at a moderate level
3= Severe: pervasive, continuous, life-disturbing problems
- 4
Considering somatic symptoms in general, indicate whether the patient has the following*:
0= No symptoms
1= Few symptoms
2= Moderate number of symptoms
3= Great deal of symptoms
- 1
The SS scale score is the sum of the severity of the symptoms (fatigue, waking unrefreshed, cognitive symptoms) and the extent (severity) of somatic symptoms in general. The final score ranged from 0 to 12.
Prevalence Estimates
FM has been found in all ethnic groups studied to date; it is not limited to affluent or industrialized nations. With prevalence estimates ranging from 2% to almost 12% in the general population, it must be viewed as a common medical condition. , Its prevalence increases with age, most dramatically in women, with a peak in the fifth to seventh decade (7.4% to 10%). Using the original 1990 criteria, including tender points, women were four to seven times more likely to be affected than men of similar age. This was another unintended consequence of the 1990 ACR criteria, by using the same tenderness threshold in men and women, even though we now understand that women are substantially more tender than men, which overestimates the prevalence of FM in men. Using the newer criteria, the ratio was closer to a 2:1 female:male ratio. In contrast, the sex distribution of childhood FM is almost equal (until puberty, girls have similar levels of tenderness relative to boys). Many children outgrow their symptoms. Fibromyalgia the incidence of fibromyalgia is poorly characterized, but risk factors for its development may include obesity, lack of physical activity, poor life/job satisfaction, physical trauma, a febrile illness, or a family history of FM; these factors may not be mutually exclusive.
Clinical Features
The proposed clinical flow would stratify these patients for improved management ( Box 37.2 ). The clinical manifestations of FM typically involve much more than pain, and in fact, these non-pain symptoms are often the key to differentiating the nociplastic pain of FM from nociceptive or neuropathic pain.
• Box 37.2
Proposed Plan for Screening and Comprehensive Care of Patients With Fibromyalgia
- 1
Phase 1: Pain Screening and Primary Care
Phase 1 involves a simple screening questionnaire in which the receptionist for a primary care health professional (primary care physician [PCP], chiropractor, nurse practitioner, physician assistant, general practitioner, general internist) would give every patient entering the waiting room until all the primary care professionals’ regular patients had been assessed ( Fig. 37.2 ). After that, it may be administered only to new patients. When the PCP reviews the form of a patient with pain (question 1 answered “yes”), a decision about the symptom’s distribution would be made (localized pain, regional pain, widespread pain). A second decision would be to initiate care for the patient’s symptoms or refer the patient for further care of this problem.
- 2
Phase 2: Comorbidity Screening and Secondary Care
Based on the findings on the screening material, a patient identified as having widespread pain would be examined by the PCP or referral physician to make the diagnosis (fibromyalgia [FM] if it applies). The next stage would be screening for comorbid conditions by a well informed and willing PCP or consultant (rheumatologist, neurologist, pain specialist, internist, physiatrist). The patient began an exercise program and counseling with a professional specifically trained to provide advanced care for FM. Problems found in counseling (e.g. marital, financial, and psychiatric) would spin off to an experienced specialist (e.g. counselor, psychologist, psychiatrist, disability advisor, financial counselor).
- 3
Phase 3: Comorbidity Screening and Tertiary Care
Based on the second line screening for comorbid conditions, care would begin for additional diagnoses. This phase may invoke referral to tertiary subspecialty care (e.g. cardiologists, gastroenterologists, neurologists, neurosurgeons, physical therapists, psychiatrists, physiatrists, obstetrician-gynecologists, urologists). This care should be integrated with follow up by primary care resources.
- 4
Phase 4: Long-Term Primary Care and Follow Up Assessment
Primary or secondary healthcare professionals will continue to monitor the patient over time and assess the status of care for pain and comorbid conditions. There would be monitoring for side effects to medications and new problems intruding on the continuity of the FM that might or might not be related to it. In this phase, it is important not to assume that every new symptom in a patient with FM is a component of FM. Healthcare providers need to know what is and is not expected with FM.
The most important manifestation in FM and nociplastic pain is that pain is more widespread and more severe than expected. In the new FM criteria, the widespread nature of pain is assessed by asking individuals if they have pain in 19 different bodily regions; this is scored from zero to 19 depending on how man sites are involved. The comorbid symptoms that are most commonly seen and thus are scored from zero (not present) to three (severe) within the Symptom Severity Index in the new FM criteria are difficulty with sleep, memory, and fatigue, and headaches, irritable bowel syndrome symptoms, and depression are also assessed in this measure and are given one point each toward the total score on this measure. Another set of symptoms that are becoming increasingly understood with a better understanding of the pathophysiology of these conditions is sensory hyper-responsiveness. Individuals with FM are just as sensitive to the loudness of noises or brightness of lights as they are to painful stimuli, and these symptoms of sensory hyper-responsiveness throughout the body (leading to symptoms such as urinary frequency, dry eyes) can be very helpful in identifying this type of pain.
Cognitive Dysfunction
Ranging from difficulty concentrating when reading a book to short-term memory deficits, people with FM frequently complain of diminished cognitive function. Research has suggested that FM patients perform poorly on a range of cognitive tasks and exhibit premature cognitive aging, with the main evidence of abnormality being derived from distraction or multitasking experiments.
Insomnia
Most patients with FM experience chronic insomnia. Some have difficulty falling asleep (initial insomnia), but most awaken feeling distressingly alert after only a few hours of sleep (mid-insomnia) and are then unable to sleep soundly again until it is almost morning (terminal insomnia). People with FM typically awaken in the morning feel painfully stiff, cognitively sluggish, and unrefreshed by their sleep.
Stiffness
The morning stiffness experienced by most FM patients is lengthy and severe compared with other mechanisms for morning stiffness. The typical stiffness of osteoarthritis usually lasts 5 to 15 min, whereas that of patients with inflammatory rheumatoid arthritis is 30 min to 2 h. By comparison, the stiffness of FM patients typically lasts from 45 min to 4 h. The best clinical correlate with morning stiffness in FM is pain; therefore patients have challenges distinguishing these constructs from their experiences.
Fatigue
Approximately 80% of FM patients complain of fatigue. Consequently, a large proportion of individuals who meet the criteria for FM also meet the criteria for chronic fatigue syndrome. The differential diagnosis of fatigue is difficult because it must include various sleep disorders, chronic infections, autoimmune disorders, psychiatric comorbidities, and neoplasia. Fatigue may also result from residual levels of prescribed medication, such as tricyclic anti-depressant drugs or other neuropathic medications often used to treat insomnia associated with FM.
Constellations of Previously Diagnosed Comorbid Pain Conditions
There are two sets of comorbid conditions typically seen in association with FM or nociplastic pain: other Chronic Overlapping Pain Conditions (COPCs), that are also predominantly nociplastic pain (e.g. irritable bowel syndrome or tension headache); and other pain conditions that have a different primary pain mechanism (nociceptive or neuropathic pain) wherein nociplastic pain is superimposed. The former category had previously been called primary FM, and the latter category secondary FM or central sensitization.
It may be very important to differentiate primary from secondary FM because, in secondary FM or central sensitization, ongoing nociceptive input or neuropathic damage may be partially driving or maintaining the central sensitization. In these individuals, more aggressively treating the underlying problem might help improve the FM or nociplastic pain, whereas that would not be expected in primary FM, which seems to be more of a top-down brain disorder that typically begins early in life.
Chronic Overlapping Pain Conditions
COPCs appear to be system-based expressions of central sensitization, , reflecting a range of severities and present on functional neuroimaging and quantitative sensory testing. , An alternate term previously used was sensory sensitivity symptoms. The spectrum of centrally mediated painful conditions includes headache, facial pain, temporomandibular disorders (TMD), irritable bowel syndrome, dyspepsia, interstitial cystitis, painful bladder syndrome, vulvodynia, endometriosis, and female urethral syndrome. These disorders may have specialist involvement of neurology, dentistry, gastroenterology, urology, or gynecology with a primary diagnosis of one of these centrally sensitizing spectrum conditions.
Neurologic/Dental Sensitization
People with coexisting headaches, facial pain, and TMD may cycle between specialist providers in neurology, dentistry, and pain, but the shared sensitization appears to be consistent across the diagnoses. Headache demonstrates overlapping sensitization through shared pathways and treatment responses. ,
Gastrointestinal Sensitization
Irritable bowel syndrome (IBS) and benign dyspepsia are common gastrointestinal conditions that occur in 30% to 50% of patients with FM. A feature common to both FM and IBS may be central sensitization and underlying neuroplastic alterations. These conditions may be synergistic with respect to patients’ perceptions of their illness and have a modulating effect on clinical outcomes.
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