Winfried Häuser1,2 & Mary-Ann Fitzcharles3,4 1 Department Internal Medicine I and Interdisciplinary Center of Pan Medicine, Klinikum Saarbrücken, Germany 2 Department of Psychosomatic Medicine and Psychotherapy, Technische Universität München, Germany 3 Division of Rheumatology, McGill University Health Centre, Montréal, Québec, Canada 4 Alan Edwards Pain Management Unit, McGill University Health Center, Montréal, Québec, Canada Musculoskeletal pain is the most prevalent pain type occurring in the general population and in the clinical setting. Musculoskeletal pain can be classified as localized (a single pain site), regional (several pain sites in one body region) or widespread. There has been debate over the years regarding the best criteria to identify widespread or multisite pain, such as the requirement of a minimum of four of five pain regions [1] or more recently at least six of nine body sites [2]. Other than disease localized to the joints or soft tissues around the joints, most musculoskeletal pain syndromes are not associated with any specific organ pathology. The two most common musculoskeletal pain conditions are: (a) myofascial pain syndrome (MPS), a non‐specific local and regional chronic musculoskeletal pain condition; and (b) fibromyalgia syndrome (FMS), characterized by chronic widespread pain and associated with other symptoms such as fatigue, sleep disturbance, cognitive difficulties amongst others. MPS and FMS can be overlapping disorders. The exact underlying pathogenic mechanisms of both MPS and FMS are currently not fully clarified. There is considerable evidence pointing to the role of central sensitization in FMS, but peripheral pain generators may also be operative in perpetuating ongoing pain in a subgroup of patients. Some authors have even suggested that FMS pain may at least be partially initiated by pain arising from trigger points (TrPs). In contrast, MPS is believed to originate at the motor endplate of muscle, with some studies reporting histological, biochemical and electromyographic abnormalities [3]. Recommendations for the management of FMS are derived from the updated interdisciplinary German guideline on the classification, pathophysiology and management of FMS [4] and on the updated recommendations of the European League Against Rheumatism [EULAR] [5]. There are no current guidelines for the management of MPS, with recommendations based on a selective literature search in PubMed using the terms “myofascial pain syndrome” AND “systematic review”. Criteria for FMS must be viewed as classification criteria, used to identify homogenous patient groups for study, or diagnostic criteria that can be much more appropriately applied to an individual patient in the clinical setting. Classification criteria for FMS were first developed by the American College of Rheumatology (ACR) in 1990 and defined FMS as chronic (>3 months) widespread pain (including pain on both sides of the body, above and below the waist, and axial pain) and tenderness on manual palpation in at least 11 out of 18 defined tender points [6]. FMS is not a distinct nosological entity and the clinical presentation of patients is heterogenous. It is now recognized that FMS presents as a spectrum of symptoms along a continuum, with variable expression in severity at different time points. FMS should therefore not be ruled as a binary condition as either present or absent, but rather as a condition with mild, moderate or severe expression at a specific time. Within this context FMS can be conceptualized as a cluster of symptoms which are somatic (mainly pain and physical fatigue) and psychological (mainly sleeping and cognitive problems) within a continuum of distress. The heterogeneity of FMS is further exemplified by the fact that patients have differences in their ability to use coping strategies to deal with psychosocial stressors, and manifest differing mental and somatic comorbidities. There are also differences in the impact of FMS on level of function such as ability to work [7]. MPS is characterized by the presence of TrPs, but there is no consensus on the essential diagnostic criteria for diagnosing a TrP. An expert panel has provided the following definitions: a) TrPs are identified when stimulation reproduces any symptom experienced by the patient (e.g. pain, tenderness, paraesthesia), either partially or completely, whereby the symptom is recognized as a familiar experience by the patient, even though it may not be present at the moment of the examination. b) Latent TrPs are identified when stimulation fails to reproduce any symptom experienced by a subject (symptomatic or asymptomatic) and the subject does not recognize the elicited symptom as familiar [8]. Active TrP are classified as those that cause spontaneous pain, whereas latent TrP have all the same clinical features without being responsible for the pain complaint [9]. Active myofascial TrPs may have a role in patients with FMS, tension headache, neck and low back pain, temporomandibular disorders, extremity pain (shoulder, hip, limb), abdominal, thoracic and pelvic/urogenital pain syndromes [9]. Tender point (TP) examination is no longer required for recent diagnostic criteria of FMS [2, 16, 17]. The main difference between TPs and TrPs is that TPs can only be defined in terms of their localization, whereas TrPs can be found upon palpation which may cause a specific referred pain pattern. A systematic review reported a prevalence of FMS in the general population to be 1.8% (95% confidence interval 1.7 to 1.9). The sex ratio for females vs. males is 2–21: 1. Most patients with FMS are in the age range of 40–60 years, but FMS can also be diagnosed in children, adolescents and the elderly [10]. There are no data on the prevalence and sex ratio of MPS in representative samples of the general population. In clinical samples MPS is most common in women and those of middle age. It is plausible that there will be clinical overlap of FMS and MPS in some patients, but due to inconsistencies in diagnostic criteria for FMS and MPS, there are no reliable data on the overlap. It has been estimated that 18‐40% of patients diagnosed with MPS also met the ACR 1990 classification criteria for FMS, and up to 75% of patients with FMS could be diagnosed with MPS [11]. Longitudinal studies of FMS have demonstrated that symptoms persist in nearly all patients. Some patients do adapt sufficiently to ongoing symptoms and the associated limitations and indeed report a better long‐term satisfaction with their health status. FMS is not associated with a reduced life expectancy overall [12]. There are no longitudinal outcome studies for MPS. It has been observed in the clinical setting that some patients with MPS might remit spontaneously or resolve with appropriate correction of predisposing factors and therapy. MPS that has been present for longer than 6 months or has followed a chronic relapsing course tends to be continuous. Localized myofascial pain can spread and evolve to regional chronic pain or to chronic widespread pain (CWP) and/or FMS [9]. A pain diagram can be helpful to identify patients pain location in FMS, but it is not uncommon for patients to report “pain all over.” Some key points to consider when taking the history from a patient suspected of having FMS include the following: It can be expected that the physical examination will be within normal limits for the age of the patient for most patients with FMS. Some may demonstrate mild pressure allodynia on palpation of muscles, and in a third of patients there is a report of dysesthesia on light touch. Tender point examination is not required by the new diagnostic criteria (see below). Irrespective of whether a tender point examination is performed, a complete physical examination including musculoskeletal and neurological examination is required to ensure that no underlying condition can be masquerading as CWP in the context of FMS [13]. The following routine blood tests are recommended for the initial evaluation of patients with CWP to screen for somatic diseases which might mimic or contribute to CWP and fatigue: Unnecessary laboratory and radiographic studies are strongly discouraged (e.g. testing for rheumatoid factor or antinuclear antibodies without clinical justification [14]. Chronic pain of various degrees is a common symptom of patients presenting to internal medicine and neurologists. Physicians must be aware that many medical conditions can present with diffuse body pain and masquerade as FMS. Early inflammatory rheumatic diseases, endocrine diseases, malignancies, myopathies and polyneuropathies might cause or contribute to CWP and fatigue [13]. With the recognition that localized areas of pain, such as osteoarthritis of a knee, may act as a peripheral pain generator, attention should be paid to this localized pain, in the hopes that there could be attenuation of the widespread pain. In contrast, comorbid FMS in well‐defined and controlled somatic diseases such as inflammatory rheumatic diseases will require treatments focused toward FMS rather than changes in treatments for the underlying primary disease [15]. Medications should always be remembered as a potential cause of widespread body pain that can be confused with FMS. These include lipid lowering agents in the category of statins, aromatase inhibitors, bisphosphonates and paradoxically – even opioids that can induce a hyperalgesic syndrome [13]. Table 30.1 The 2010 ACR preliminary and 2016 Revisions to the 2010/2011 fibromyalgia diagnostic criteria and the AAPT diagnostic criteria
Chapter 30
Fibromyalgia syndrome and myofascial pain syndromes
Introduction
Definitions
Prevalence
Course and prognosis
Diagnosis of fibromyalgia syndrome
History
Physical examination
Blood tests and diagnostic imaging
Differential diagnosis
Criteria (reference)
Diagnostic items
Comments
ACR 2010 preliminary diagnostic criteria [16]
Widespread pain and substantial somatic symptoms
Symptoms present for ≥3 months
No other disorder that could explain the pain
Pain is scored by the physician according to the number of affected areas, widespread pain index (WPI) (score: 0–19) and symptom severity (SSS) measured in four domains of fatigue, unrefreshing sleep, cognitive and somatic symptoms with ranges from no problem (0) to severe symptoms (3)(score: 0–12). Total score: is the sum of WPI and SSS 0–31;
Criteria are met if WPI is 3‐6 and SSS ≥9 or of WPI is ≥7 and SSS is ≥5
2016 Revisions to the 2010/2011 fibromyalgia diagnostic criteria [17]
Modified version of research (survey/2011 criteria (entirely self‐reported assessment of symptoms)
Widespread Pain Index (WPI) is scored by the patient according to the number of affected areas (total score: 0–19). The SSS is modified to include headaches, pain or cramps in the lower abdomen and depression (score: 0–12). Total score is the sum of WPI and SSS: 0–31 (see Table 30.2)
Criteria are met if WPI 4‐6 and SSS ≥9 or of WPI is ≥7 and SSS is ≥5 and there is generalized pain sites in at least four of five body regions (four quadrants and axial) except the face and the abdomenRelated posts:
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