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The
diagnosis of ME
CFS(ME)
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CFS(ME)
and Fibromyalgia
The
clinical picture of CFS(ME)
Chronic fatigue syndrome (CFS) is the term used to describe a number of disorders characterised by disabling, ongoing fatigue. Although the nomenclature for these conditions is comparatively new, the disorders themselves are not. Indeed, references to illnesses closely resembling CFS have been documented in the British literature since 1750 (Bakheit 1993) . Some cases of CFS are closely associated with and may represent psychiatric disorders (David 1991, Hickie et al 1995, Wessely 1994) . Others have been linked with infections such as glandular fever and Lyme disease (Bruce-Jones et al 1994, Coyle et al 1994) and exposure to toxins (Behan and Haniffah 1994, Chester and Levine 1994). However, since the 1980s, much of the attention has focused on a mysterious illness known as myalgic encephalomyelitis (ME) or post-viral fatigue syndrome (PVFS).
In the US, the Holmes et al definition of CFS (1988) tends to cover many patients with ME; more recent criteria (e.g. Fukuda et al 1994, Sharpe et al 1991) select a much more heterogeneous population.
There are a number of definitions and guidelines which have been formulated for the diagnosis of ME. For clinical purposes, some specialists use the definition suggested by Ramsay (1988) and Dowsett (Dowsett et al 1990 and Dowsett and Welsby 1992). This recognises both acute onset cases which follow an infection and the cases which develop more gradually.
The cardinal features of ME as described in Dowsett and Welsby (1992) and Macintyre (1992) are considered to be:
For research purposes, ME specialists have devised what have become known as the ‘London criteria’ (National Task Force Report 1994). These require the presence of fatiguability following minor exertion, evidence of central nervous involvement and the marked fluctuation of symptoms. Furthermore, the symptoms should have lasted at least six months and must be ongoing.
The emphasis on both fatiguability and central nervous system involvement means that the criteria for ME are consistent with the guidelines for PVFS formulated by Ho-Yen (1993) and the case definitions of CFS developed by Australian researchers (Lloyd et al 1990) and Walsh and Cunha (1993). They are also similar to the definitions of PVFS adopted by Behan and his colleagues (Behan and Bakheit 1991) and Weir (1991) .
The criteria for ME differ from the American and Oxford definitions for CFS in three ways. Firstly, the latter do not require evidence of central nervous system dysfunction. Secondly, they do not include any references to the fluctuation of symptoms or the close links between symptoms and exertion. Thirdly, the older CDC criteria place a much greater emphasis on infection-related symptoms such as mild fever, sore throat and tender glands compared to the definitions of ME (Hyde et al 1992) .
The view that ME may not be identical to all cases covered by the term CFS led the National Task Force on CFS, PVFS and ME, an independent body of experts which was set up to advise the British Department of Health, to describe the various disorders as the "chronic fatigue syndromes". They also chose to distinguish between specific subgroups, for instance, giving the name CFS(ME) to cases of CFS who also met the criteria for ME. In line with their approach and similar suggestions by Wilson et al (1994) and Schluederberg et al (1992), this classification will also be adopted here to denote cases diagnosed as either ME or PVFS.
Since the introduction of the term CFS, many researchers have expressed concern about the growing emphasis on the symptom of fatigue (e.g. Hyde et al 1992) . For instance, it has been pointed out that tiredness is a common complaint among the general population (Cathebras et al 1992, Popay 1992), and associated with a variety of disparate causes (Cope et al 1994, Pawlikowska et al 1994) . Indeed, as recent studies have shown, most patients who seek help for chronic fatigue do not fulfil the criteria for CFS(ME) or strictly-defined CFS1 (Wessely et al 1995, Wilson et al 1994) . For example, in one study of 611 people attending their general practitioners, 70 (11.5%) reported experiencing fatigue for three months or more (David et al 1990) . Of these, only one person (1.4%) was thought to have CFS(ME) .
These results are consistent with those of Elnicki et al (1992) who identified only one case (2%) of CFS among 52 patients with chronic fatigue. Similarly, a study of 135 patients complaining of fatigue for one month revealed that only six (4.4%) met the CDC criteria for CFS (Manu et al 1988) . It is possible therefore, that factors which are of aetiological and therapeutic significance for most patients presenting with unexplained fatigue may not be relevant to people with either CFS or subgroups such as CFS(ME) . Until more is known about the differences between chronic fatigue and CFS, generalising findings from one sample to another may lead to an inaccurate interpretation of the data and possibly to inappropriate advice and an exacerbation of symptoms (cf. Wessely et al 1995).
Unfortunately, researchers do not always distinguish between subgroups of patients with chronic fatigue (e.g. Pawlikowska et al 1994) . Moreover, where subgroups are identified, it is not always clear whether the diagnosis was made by clinicians using accepted definitions. For instance, MacDonald et al (1993) noted that 4 (23.5%) of their CFS patients thought that they had CFS(ME) . However, these researchers did not state how this diagnosis had been made.
A number of features can be used to distinguish CFS(ME) from other fatigue-related disorders. One is the nature of the fatigue. For example, Durndell (1989) reported that a group of students with CFS(ME) were able to differentiate between their fatigue and the normal tiredness which might follow an activity such as a sporting event. According to Durndell: "the latter was described as pulsating, exhilarating and pleasant, whilst the former was described as overwhelmingly negative, draining, like flu and being ill".
A second difference between CFS(ME) and other disorders relates to the marked fluctuations in symptoms and signs (e.g. Durndell 1989, Patarca et al 1993, Ramsay 1988) . The presence of the latter can be used to differentiate CFS(ME) from the condition colloquially referred to as ‘tired-all-the-time’ or TATT (Dowsett and Welsby 1991) . A third feature which may distinguish CFS(ME) from other conditions is the characteristic link between exertional and fatigue. Research has shown that this is far less pronounced in psychiatric disorders such as depression (White et al 1995) . A diagnosis of depression is further supported by the presence of anhedonia, apathy, reduced feelings of self-worth, suicidal ideation, delusions and psychomotor retardation, all of which are less common in CFS(ME) (Calabrese et al 1992) .
Another disorder which may be confused with CFS is hyper-ventilation or effort syndrome (Nixon 1993) . However, while overbreathing has been documented in some patients with CFS, research to date has not found this to be a common problem in the patient group as a whole (Riley et al 1990, Saisch et al 1994) .
Since a number of conditions now referred to as CFS are clearly different from the disorder described in 1988 (cf. Price et al 1992), some American specialists have referred to the more severe condition as CFS with encephalopathy or chronic fatigue immune dysfunction syndrome (Bell 1991, Peterson et al 1992, Pross 1992, Suhadolnik et al 1992) .
CFS(ME) patients may report areas of muscle tenderness similar to those documented in fibromyalgia. However, the latter more often has a gradual onset, morning stiffness is a more prominent symptom, fatigue tends to be worse early in the day, and there are generally fewer signs of ongoing infection (Calabrese et al 1992, Yunus 1994) . Fibromyalgia is also more common than CFS, affecting an estimated 2-4% of the population at large (Wolfe 1993) . While further clarification is clearly required, the consensus of opinion seems to be that the two conditions share certain similarities, but that they are not one and the same (Ho-Yen 1994, Norregaard et al 1993, Wysenbeek et al 1991) .
The illness seen nowadays tends to start as an unremarkable viral infection, with myalgia, lymphadenopathy and in some cases, a gastro-intestinal or respiratory upset (Shepherd 1992) . However, instead of recovering, patients begin to experience profound fatigue following activities which were previously completed without difficulty. Also typical is a prolonged delay in the restoration of muscle power (Ramsay 1988) .
The fatigue, which some have likened to that reported by people with multiple sclerosis (Behan and Bakheit 1991), is invariably accompanied by other complaints. For instance, many patients report a flu-like malaise, general weakness and neurological symptoms such as disequilibrium and vertigo (Dowsett et al 1990, Murdoch 1987, Shepherd 1992) .
The involvement of the autonomic nervous system may lead to frequency of micturition, night sweats, palpitations and disturbances in thermoregulatory control e.g. feeling weak after a hot bath (Macintyre 1992, Ramsay 1988, Shepherd 1992) . Patients may also experience sensory disturbances such as paraesthesia, tinnitus and hyperacusis as well as visual abnormalities such as photophobia (Potaznick and Kozol 1992), sluggish accommodation (Hyde and Jain 1992) and/or increased sensitivity to certain patterns (Smith 1991) . At the same time, problems with co-ordination may lead to falls, while clumsiness can make it harder to complete fine motor tasks.
Neuropsychological symptoms associated with CFS(ME) include headaches and cognitive problems such as loss of short-term memory, an inability to concentrate and difficulty in finding the right word (Fleming 1994) . In addition, many patients become emotionally labile, and some also begin to experience panic attacks, depression (Macintyre 1992, Shepherd 1992) and sleep disorders (Krupp et al 1993, Whelton et al 1992) .
Aside from the fatiguability, the muscle weakness and apparent central nervous system dysfunction, there may also be symptoms associated with impaired circulation. This manifests itself in cold extremities, low temperatures and a sudden facial pallor (Ramsay 1983). Other symptoms commonly reported by patients with CFS(ME) include gastro-intestinal disturbances such as recurring nausea and abdominal pain, and the development of adverse reactions to alcohol, foods and chemicals (Hobbs et al 1989, Innes 1970, Smith 1989) .
All these symptoms show a marked diurnal and cyclical variability in their intensity, and although it is not always possible to identify a specific cause for the exacerbations, reports suggest that the condition may worsen as a result of over-exertion, concurrent infections, changes in the weather, and in some cases, by ‘stress’ (Dowsett et al 1990, Komaroff 1994).
Unfortunately, since the adoption of the term CFS, less attention has been paid to some of the features and symptoms of CFS(ME), e.g. the fluctuations and the presence of neurological complaints. For instance, David and Wessely (1993) summarised the illness as "characterised by a main complaint of fatigue, both mental and physical, with other somatic symptoms and mental phenomena like worry and depression present" . This is consistent with other descriptions of CFS and although it is recognised that space often prohibits a fuller discussion, the emphasis on fatigue may have limited many clinicians’ understanding of CFS(ME) . It may also undermine the diagnostic process, since there is still no laboratory test for CFS(ME), and physicians have little to guide them except their knowledge of symptomatology (Holmes et al 1988, Weir, 1991) .
1 Strictly-defined CFS refers to cases which fulfil the Australian criteria, or early versions of the CDC criteria (1988, 1992) .
Copyright Dr. EM. Goudsmit 1996.
Chartered Health Psychologist/Archivist, London.
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