Tue, 5 Oct 1999 CFS-NEWS Subject: #87 What is ME? -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- 2. What is M.E.? Recent discussions at the Brussels conference and elsewhere have helped to clarify that myalgic encephalomyelitis (M.E.) and CFS are not the same entity. There has been confusion about this, even in Britain where M.E. was first defined and studied under that name. What exactly is M.E.? According to M.E. experts the key difference between M.E. and chronic fatigue syndrome is that M.E. requires the criterion of easy fatiguability following minimal exertion and a delay in recovery of muscle strength. In the CDC definition of CFS this criterion is optional. Several M.E. experts perceive that properly defined M.E. excludes all psychiatric cases, whereas chronic fatigue syndrome as defined by the CDC allows for the inclusion of many psychiatric cases. M.E. has been described several times in medical literature. It was first defined in an editorial published in the Lancet in 1956 which discussed several epidemic outbreaks of prior years. This first description was rather loose and was not very specific. In later years, Acheson, Ramsay, EG Dowsett and others refined the definition of M.E. in various published papers (see the citations below). After Ramsay died in 1990, Dowsett et al. wrote the latest version of the M.E. definition now known as the "London criteria". These have been used in recent papers by Costa (Brainstem perfusion is impaired in patients with CFS, QJM 1995; 88:767-773) and Scholey (A comparison of the cognitive deficits seen in M.E. to Alzheimer's Disease, Proceedings of the British Psychological Society, 1999, January, 12). Below are literature citations for articles that contain definitions of M.E. as they have evolved over the years, followed by the current description of the London criteria. The text of all of these definitions can be seen online at http://www.cais.com/cfs-news/me.htm [In the interests of brevity, I've snipped the list of articles -- if you are interested, go to the above website -- there are a lot of useful links.] Note: in recent years PVFS (postviral fatigue syndrome) has become synonymous with M.E. All three criteria must be present for a diagnosis of ME/PVFS to be made: 1. Exercise-induced fatigue precipitated by trivially small exertion (physical or mental) relative to the patient's previous exercise tolerance. 2. Impairment of short-term memory and loss of powers of concentration, usually coupled with other neurological and psychological disturbances such as emotional lability, nominal dysphasia, disturbed sleep patterns, disequilibrium or tinnitus. 3. Fluctuation of symptoms, usually precipitated by either physical or mental exercise. These symptoms should have been present for at least 6 months and should be ongoing. Although ME/PVFS typically follows an infection, usually a virus illness (which may be subclinical) in a previously fit and active person, it has also been observed to be triggered by other factors such as immunisations, life traumas and exposure to chemicals. Furthermore, in a minority of patients, ME/PVFS has a gradual onset with no apparent triggering factor. For these reasons proof of a preceding viral illness is not a prerequisite for diagnosis. Many symptoms are experienced by people suffering from ME/PVFS and in the right symptomatic context they contribute to the validity of the diagnosis. Nevertheless, not all people suffering from ME/PVFS experience all these symptoms and their absence does not exclude the condition. These can be subdivided into the following two categories: Autonomic: * bouts of inappropriate night or day-time sweating; * Raynaud's phenomenon; postural hypotension; * disturbance of bowel motility manifesting as recurrent diarrhoea or occasionally constipation (these symptoms are frequently indistinguishable from those of irritable bowel syndrome); * photophobia; blurred vision due to disturbed accommodation; * hyperacusis; * frequency of micturition; nocturia. Immunological (Symptoms suggesting persistent viral infection): * episodes of low-grade fever (not exceeding an oral temperature of 38.6C) combined with feeling feverish, (i.e. a down-regulated 'thermostat'); * sore throat which may be persistent or recurrent (i.e. present for at least one week per month); * arthralgia (fixed or migratory) This list is by no means exhaustive. Headaches, nausea and bloating, for instance are common symptoms in many patients but are not sufficiently discriminative because of their widespread occurrence in many other disorders. The curious intolerance to alcohol and hypersensitivity to drugs are highly specific in this context. It should also be emphasised that the symptoms of ME tend to vary capriciously from hour to hour and day to day. Nevertheless it is absolutely characteristic that they tend to be exacerbated by physical or mental exertion and the association should always be sought whilst taking the history. ------------------------------------------------ This description, and that of the previous published versions of the M.E. definition, can be found in: Report from The National Task Force on Chronic Fatigue Syndrome (CFS), Post Viral Fatigue Syndrome (PVFS), Myalgic Encephalomyelitis (ME). Westcare, 1994. Copies of the full report are available from Westcare, 155 Whiteladies Road, Clifton, Bristol BS8 2RF. Tel. 0117-923-9341. Price (U.K.) 9.95 pounds including p&p. The full text of Acheson (1959), Dowsett (1990), Ramsay (1992), and other important papers are included in Byron Hyde's valuable textbook on CFS/ME: Hyde BM, Goldstein JA, Levine P, eds. The Clinical and Scientific Basis of Myalgic Encephalomyelitis / Chronic Fatigue Syndrome. 750 pp. Nightingale Research Foundation, Ottawa 1992. It can be purchased by sending $39 to The Nightingale Research Foundation, 121 Iona St., Ottawa, Ontario, Canada, K1Y 3M1 or use the online order form at http://www.cyberus.ca/~bhyde/night3.html . [Thanks for assistance with this article go to Westcare, the M.E. Association (U.K.), Ellen Goudsmit and Anna-Louise Midsem.]