Annals ofthe Rheumatic Diseases 1996; 55: 497-501 497 REVIEW: PAIN Series editor: Bruce L Kidd Ann Rheum Dis: first published as 10.1136/ard.55.8.497 on 1 August 1996. Downloaded from Chronic pain syndromes Simon Carette Chronic pain has traditionally been defined as with widespread pain and tender points.3 This pain lasting more than three to six months. growing interest in studying fibromyalgia in Many conditions in rheumatology can produce recent years is reflected by the number ofindex chronic pain. These include diseases such as entries extracted from Index Medicus, which rheumatoid arthritis and osteoarthritis. Pain in have increased from 37 in 1974 to more than these conditions can usually be attributed to 500 since 1990. specific pathological mechanisms such as By contrast with the other chronic pain syn- inflammatory synovitis or joint destruction. dromes related to the musculoskeletal system, Effective treatment modalities are available to fibromyalgia is the only one for which validated relieve some, if not most, of the pain in these classification criteria have been proposed.4 situations. Thus, a patient with widespread pain as defined Over the past two decades or so, more by pain affecting the axis and the right and left attention has been given to previously existing sides of the body, above and below the waist, conditions, now redefined as syndromes, that and in whom tenderness can be shown on produce chronic musculoskeletal pain but in digital palpation of at least 1 1 of 18 pre- which the underlying pathophysiological determined sites can be classified as having mechanisms responsible for the pain have not fibromyalgia. Based on these criteria, 3 4% of been elucidated. These conditions have been women and 0 5% of men in the general arbitrarily divided into those causing diffuse population ofWichita, KS, USA were found to versus regional pain. Fibromyalgia is by far the be affected.5 The prevalence increased with most common chronic diffuse musculoskeletal age, with highest values attained between 60 pain syndrome seen by rheumatologists. Myo- and 79 years. Seventy six per cent of affected fascial pain syndromes (MPS) and repetitive patients had seen a physician in the preceding strain syndromes (RSS) represent examples of six months; two thirds took some form of pain chronic regional pain syndromes. These diffuse medication and 19-7% had applied for, and and regional pain syndromes have many 7-3% had received, disability benefits. Fibro- features in common including the absence of myalgia accounts for as many as 20% to 25% http://ard.bmj.com/ an identifiable organic cause, behavioural of new referrals to rheumatologists, ranking maladaptations to pain, and much overlap in second after osteoarthritis.6 symptoms and signs (table). The purpose of The aetiology of fibromyalgia is basically this article is to review some of the recent unknown. The finding that it occurs at least 10 concepts and controversies related to these times more often in women than men is still three syndromes. unexplained.7 No genetic predisposition has been documented.8 Whereas it has been on September 27, 2021 by guest. Protected copyright. suggested that fibromyalgia may in some cases Fibromyalgia arise after trauma, surgery, or a medical illness, The syndrome that we now call fibromyalgia such associations do not prove causality.9 has been known for a long time. The asso- Despite intensive research, the pathogenesis ciation of diffuse musculoskeletal pain, sleep is not understood.'0 No specific abnormalities disturbances, and exhaustion can be traced to have been found in the tender muscles of biblical times.' Various names have been used patients with fibromyalgia by light microscopy, over the centuries to describe this association histochemistry, or electron microscopy." The of symptoms as new explanations for their possibility that fibromyalgia could result from cause were proposed.2 A renewed interest in defects in muscle energy metabolism was this condition followed the description by suggested by studies in which local hypoxia'2 Moldofsky and Smythe of distinct electro- and reduced high energy phosphate concen- encephalographic sleep anomalies in patients trations were demonstrated at sites of muscle tenderness.'3 A recent study with phosphorus Department of magnetic resonance spectroscopy reinforced Medicine, Laval Comparison offibromyalgia (FM), myofascialpain University, Ste-Foy, syndrome (MPS), and repetitive strain syndrome (RSS) this hypothesis by documenting a higher rate Quebec, Canada of phosphodiester resonance among the S Carette Vaiable FM MPS RSS patients with fibromyalgia than among healthy Correspondence to: Pain Diffuse Regional Regional subjects.'4 However, another study using the Dr S Carette, Physical Tender points Trigger points Tender points Centre Hospitalier de examination same technique showed no difference in any of l'Universite Laval, 2705 Fatigue +++ ++ ++ the measures of muscle energy metabolism in Boulevard Laurier, Ste-Foy, Sleep disturbance +++ ++ ++ PQ, Canada G1V 4G2. Psychological +++ ++ ++ patients with fibromyalgia compared with distress controls carefully matched for their level of Accepted for publication Unknown Unknown 28 December 1995 Pathophysiology Unknown aerobic fitness.'5 498 Carette The role of disturbed sleep in the aetiology unconditional believers in the specificity of the or perpetuation of symptoms of fibromyalgia condition.3" Using modifications of previously has been studied extensively in the past 20 published criteria, fibromyalgia was found in Ann Rheum Dis: first published as 10.1136/ard.55.8.497 on 1 August 1996. Downloaded from years.'6 The documentation of ao wave in- only 0.75% of the Finish population.36 In this trusion into stages 3 and 4 of the non-rapid eye study, fibromyalgia was associated with a high movement sleep (NREM) was initially thought risk ofmental disorder and all subjects fulfilling to be specific for the syndrome especially after the criteria for fibromyalgia also fulfilled the symptoms of fibromyalgia were reproduced criteria for at least one other musculoskeletal experimentally in healthy sedentary volunteers disorder. This led the authors to conclude that with artificial sleep manipulation.'7 However, there was little epidemiological support for the recent studies have shown that these electro- concept of fibromyalgia as being a distinct encephalographic sleep anomalies lack both disorder. The specificity of tender points has sensitivity'8 and specificity.'9-20 also been questioned.37 In a cross sectional Several investigators have suggested the study conducted in two general practices in possibility that neuroendocrine abnormalities north west England, 40% of patients with such as a deficiency in serotonin23-25 and chronic widespread pain had tender point hyothalamic-pituitary axis perturbations26 27 counts of 11 or more. However, 19% of could be implicated in the syndrome. These patients with regional pain and 5% with no findings need to be confirmed in studies using pain also had as many tender points. Whereas controls matched for pain and sleep the presence of tender points was related to disturbances rather than normal subjects. So complaints of pain, they were also indepen- far, two studies have shown higher concen- dently associated with depression, fatigue, and trations of substance P in the cerebrospinal poor sleep, suggesting that tender points are a fluid of patients with fibromyalgia than in measure ofgeneral distress rather than markers normal controls.28 29 However, the significance of a distinct disease entity. of this potentially interesting finding was At this time, I think that recognising the dampened when an inverse relation was found physical and psychological suffering of patients between the substance P concentrations and with these symptoms is really what matters, the severity of pain which was the opposite of whether we call their condition "fibromyalgia" that expected if substance P was a key factor or "chronic diffuse pain syndrome". So far, all in the pathophysiology of the syndrome.29 reports from tertiary referral centres that have It is well accepted that pain perception can looked at the prognosis of these patients be influenced by multiple factors including indicate that symptoms and signs tend to past experiences, culture, personality, and a persist with time in the vast majority.38-4' The host of psychosocial factors. Patients with outcome in patients from community based fibromyalgia and their family members have practices may be better.42 Tricyclic agents43-47 been shown to have had a greater history of and aerobic exercises48 49 are the therapeutic depression.30 One recent study showed that modalities that have been most extensively http://ard.bmj.com/ previous sexual abuse, physical abuse, and studied. Both produce short term benefit in a drug abuse were higher in patients with fibro- small percentage of patients. By contrast, non- myalgia compared with control patients with steroidal anti-inflammatory drugs44 50 and rheumatic disease.3' These findings are in corticosteroids5' are ineffective. Behaviour contrast with another study in which the preva- modification approaches have a lot of appeal as lence and type of sexual abuse were not differ- their primary objective is to de-emphasise the ent between women with fibromyalgia and pain focus in favour of active patient partici- community controls.33 However, the abused pation towards increased function and return on September 27, 2021 by guest. Protected