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. 2018 Dec 20;9(1):1.
doi: 10.3390/diagnostics9010001.

Myalgic Encephalomyelitis or What? The International Consensus Criteria

Free PMC article

Myalgic Encephalomyelitis or What? The International Consensus Criteria

Frank Twisk. Diagnostics (Basel). .
Free PMC article


Myalgic encephalomyelitis (ME) is a neuromuscular disease with two distinctive types of symptoms (muscle fatigability or prolonged muscle weakness after minor exertion and symptoms related to neurological disturbance, especially of sensory, cognitive, and autonomic functions) and variable involvement of other bodily systems. Chronic fatigue syndrome (CFS), introduced in 1988 and re-specified in 1994, is defined as (unexplained) chronic fatigue accompanied by at least four out of eight listed (ill-defined) symptoms. Although ME and CFS are two distinct clinical entities (with partial overlap), CFS overshadowed ME for decades. In 2011, a panel of experts recommended abandoning the label CFS and its definition and proposed a new definition of ME: the International Consensus Criteria for ME (ME-ICC). In addition to post-exertional neuroimmune exhaustion (PENE), a mandatory feature, a patient must experience at least three symptoms related to neurological impairments; at least three symptoms related to immune, gastro-intestinal, and genitourinary impairments; and at least one symptom related to energy production or transportation impairments to meet the diagnosis of ME-ICC. A comparison between the original definition of ME and the ME-ICC shows that there are some crucial differences between ME and ME-ICC. Muscle fatigability, or long-lasting post-exertional muscle weakness, is the hallmark feature of ME, while this symptom is facultative for the diagnosis under the ME-ICC. PENE, an abstract notion that is very different from post-exertional muscle weakness, is the hallmark feature of the ME-ICC but is not required for the diagnosis of ME. The diagnosis of ME requires only two type of symptoms (post-exertional muscle weakness and neurological dysfunction), but a patient has to experience at least eight symptoms to meet the diagnosis according to the ME-ICC. Autonomic, sensory, and cognitive dysfunction, mandatory for the diagnosis of ME, are not compulsory to meet the ME-ICC subcriteria for 'neurological impairments'. In conclusion, the diagnostic criteria for ME and of the ME-ICC define two different patient groups. Thus, the definitions of ME and ME-ICC are not interchangeable.

Keywords: chronic fatigue syndrome; diagnosis; muscles; myalgic encephalomyelitis; neurology; symptoms.

Conflict of interest statement

The authors declare no conflict of interest.


Figure 1
Figure 1
Overlap and differences between the case criteria of ME [1,2] and ME-ICC [6]. Note: Surface size does not reflect proportion. The (relative) number of patients in the seven subpopulations, especially the number of patients meeting the diagnosis of ME [1,2] and ME-ICC [6], and the patient subpopulation in the center are yet unknown. Figure 1 illustrates seven relevant patient subpopulations: patients meeting the diagnostic criteria of both ME and ME-ICC (the darkest grey rectangle in the centre), three ME patients subgroups not meeting the diagnosis ME-ICC (dark grey rectangles), and three groups of patients fulfilling the diagnostic criteria of ME-ICC, but not meeting the diagnosis ME (light grey rectangles).

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