Historical context
Although the term “chronic fatigue syndrome” is a relatively new diagnostic label, similar syndromes have been described in the past. In the late nineteenth century, a syndrome was described which was characterised by severe fatigue, exacerbated by exertion and accompanied by other symptoms including poor concentration, irritability and muscle pain. This was known as “neurasthenia”, a condition of uncertain cause that at the time was commonly attributed to “the stresses of modern life on the human nervous system” [9].
In the 20th Century, the diagnosis of neurasthenia declined and eventually fell out of common use. It is possible that the incidence of these symptoms in the population also declined. However, it seems more likely that patients with similar symptoms were given alternative diagnoses. These included diagnoses that suggested aetiological agents or specific disease processes such as chronic brucellosis, chronic Epstein-Barr virus and myalgic encephalomyelitis (ME), as well as the psychiatric diagnoses of depression and anxiety.
The term “myalgic encephalomyelitis” (ME) was first used in 1956 after an outbreak of illness among nursing and medical staff at the Royal Free Hospital in London. The cause of this outbreak remains uncertain. The term implies a pathological process of inflammation of the brain and spinal cord which, to date, has not been shown to be present in individuals with CFS. However, the term “ME” is still often used, mainly by patients, as synonymous with CFS and patient organisations are increasingly using the term “myalgic encephalopathy”.
In the past 20 years, the medical profession has increasingly come to believe that the symptoms of individuals with CFS are not readily explained either by recognisable organic disease or by depression and anxiety. The term “medically unexplained” has been used to address the lack of a clearly understood aetiology [10]. Other medical conditions that have been categorised in this group include fibromyalgia, irritable bowel syndrome and chronic pain syndromes.
Although chronic pain syndromes are characterised by pain, fibromyalgia by tender points and irritable bowel syndrome by altered bowel function, these syndromes are all accompanied by the symptom of fatigue. It has also been observed that an individual with one of the foregoing conditions is more likely than average to suffer from another in the group. This has led to the proposal that they share a common pathophysiology and are best grouped together [11].
Before a diagnosis of CFS is made, it is important that other medical conditions are excluded. These include conditions such as thyroid disorders and anaemia, which typically can present with tiredness. Other less common conditions that also cause fatigue, such as sleep apnoea and coeliac disease, may need to be considered. The initial investigations in individuals presenting with fatigue are likely to be undertaken by their general practitioner, with referral on to secondary care at a later stage, if appropriate.
