Terminology Myalgic Encephalomyelitis

The name Myalgic Encephalomyelitis refers to the inflammation of the brain and spinal cord. accompanied by muscle pain.

In 1988 The US Centres for Disease Control (CDC), for reasons best known to them, dismissed fifty years of research and decided to treat the Lake Tahoe outbreak as a new illness, which they christened chronic fatigue syndrome (CFS). CFS is a highly contentious concept to patients and specialists alike. Because of the similarity in terminology, CFS is often confused with “chronic fatigue”. A study found that while most medical trainees consider the symptom complex of CFS to be a serious illness resulting in poor quality of life, the “chronic fatigue syndrome” name may be regarded less seriously than the name “myalgic encephalopathy”. Another study found that nurses and physician assistants viewed a patient’s CFS symptoms as more severe and disabling if they were told the patient had a more medical sounding diagnosis of “chronic neuroendocrineimmune dysfunction syndrome”.

Patients and specialists alike had long lobbied for a name and definition change or reversal of “CFS”. In January 2007 The American “CFS Name Change Advisory Board” consisting of doctors Bateman, Bell, Cheney, Jason, Klimas, Lapp, and Peterson agreed that “CFS downplays the severity of the disease and is hurtful to patients” and publicised their deliberation that CFS should now be termed ME.

Signs and symptoms

The core symptom of ME is muscle fatiguability following minimal exertion, plus delayed recovery of muscle power. Ramsay, a world authority on ME, referred to a diagnostic triad of muscle fatiguability, central nervous system involvement, and impaired circulation. However, ME affects many bodily systems, and other symptoms include: Increased sensitivity to light and sound (photosensitivity, hyperacusis) and general migraine-like sensory intolerance, changes in sensation (hypoesthesia), muscle spasms (myclonus or fasciculation), or difficulty initiating movement (transient paralysis), difficulties with coordination and balance (ataxia), problems in speech and verbalisation (Dysarthria, Dysphasia), visual problems (Nystagmus, blurred vision), acute or chronic pain, difficulty standing (orthostatic intolerance), cardiopulmonary symptoms (palpitations, dysrhythmia and dyspnea), sleep dysregulation (hypersomnia, insomnia, or sleep reversal), gastroenteric difficulties, cognitive impairment, and emotional symptomatology (emotional lability or depression). What differentiates ME from similar conditions is the close link with exertion and the variability, not only from day to day, but from hour to hour.


ME is diagnosed definitively using case history to look for a distinctive pattern and type of symptoms and signs. Diagnosis necessitates involvement of the CNS and musculoskeletal symptomology.

All descriptions of M.E. diagnostic criteria tend to emphasize muscle fatiguability and central nervous system involvement (Myalgic Encephalomyelitis Case Definitions, 2011). The Canadian Consensus Criteria represents international efforts to standardize the diagnosis of ME using clinical data and laboratory data, but are controversial. The list of symptoms is long and there is therefore a danger of misdiagnosis. Research criteria based on Ramsay’s descriptions have been used in various studies (e.g. Costa et al, 1995).

Generally consistent findings of a novel low molecular weight antiviral protein (Rnase-L) have shown promise as a potential diagnostic test for CFS and may be relevant to ME. Another test which may become important in the future is an assay of genes for the immune system and mitochondria, however, these tests are so far seen as discretionary. Without research criteria for ME, it is not possible to confirm that abnormalities found in people with chronic fatigue syndrome are also generalizable to ME.

Differential Diagnosis

The signs and symptoms of ME can be similar to other medical problems, such as multiple sclerosis, Lyme disease, lupus, sarcoidosis, anemia, cancers, and other autoimmune problems. Additional testing may be needed to help distinguish ME from these other problems.