Our Goals • Site Map


HomeM.E. or CFS ?DefinitionsThe ResearchLinks


Definitions Overview

"...The failure to agree on firm diagnostic criteria has distorted the data base for epidemiological and other research, thus denying recognition of the unique epidemiological pattern of myalgic encephalomyelitis."
-Dr. A. Melvin Ramsay-

    MYALGIC (muscle pain)
+ ENCEPHALO (relating to the brain)
+ MYEL (relating to the spinal cord)
+ ITIS (inflammation)
(brain and spinal cord inflammation with muscle pain)


***UPDATE - October 2012***
This new definition (ICC) published July 2011provides the foundation for a new set of clinical and research criteria,

Myalgic Encephalomyelitis: International Consensus Criteria, for both adult and pediatric cases.

In 2012, its authors provided a condensed version to offer as Physician's Guidelines (ICC Primer):
Myalgic Encephalomyelitis, Adult & Paediatric, International Consensus Primer for Medical Practitioners.

(We will continue to provide access to our other Definitions pages for comparison and historic reference.)

At the heart of confusion between ME and CFS lie the research and clinical definitions.  One of our goals in establishing NAME-US.org is to present a clear understanding of the differences between Myalgic Encephalomyelitis and the many illnesses that can fall under the CFS umbrella. It is important to also note that a doctor uses a clinical definition to diagnose patients, while a researcher uses a research definition to select subjects for research studies.  While both types of definitions can appear to be similar at first glance, there can be differences, and it is in the details and vague areas that problems arise.

As stated in our Goals, we support and advocate for the international implementation of the most current and comprehensive clinical definition, Myalgic Encephalomyelitis/Chronic Fatigue Syndrome:  Clinical Working Case Definition, Diagnostic and Treatment Protocols; A Consensus Document, produced by an eleven-member international ME/CFS Expert Consensus panel selected by Health Canada, and published in 2003.  This definition places post-exertional  worsening of symptoms and prolonged recovery time after even minor exertion, and neurological/cognitive manifestations as major criteria in procuring a diagnosis.  We also support The Nightingale Definition of Myalgic Encephalomyelitis (M.E.), which states, "...there is always a measurable and persistent diffuse vascular injury of the Central Nervous System in both the acute and chronic phases. Primary M.E. is associated with immune and other pathologies."

Conversely, the US Centers for Disease Control CDC (Fukuda) definition for CFS places emphasis on fatigue, with neurological signs being minor and optional.

Unfortunately, the most current research definition used internationally dates back to 1994 (CDC, Fukuda), which is a "CFS" definition that broadens the research subjects to include patients that may not necessarily fit the current and past definitions for ME.  The practice of using the CFS (Fukuda) research definition (and its predecessor, the Holmes definition) has flooded the research subject pool with many "fatiguing illnesses" that  do not necessarily fit the past and current definitions for the neurologically defined disease, ME.   This has only served to dilute and muddy research results into a turbid confusion of mixed results.  This also does a disservice to those patients who do not fit into the category of  the historic ME definitions, the 2003 Consensus Document for ME/CFS and The Nightingale Definition of Myalgic Encephalomyelitis (M.E.) by pooling them all under an umbrella of "fatigue", rather than searching into the specifics that distinguish them from each other.  (See Dr. John Greensmith's comment on the NAME-US Hompage.)

Thus, we also support and advocate for the adaptation of the 2003 Consensus Document for ME/CFS and the 2006 Nightingale Definition to an international research definition, basing future research on the disruption of the central nervous system so prevalent in this disease, rather than on degrees or variations of "fatigue," which is merely one of many symptoms in this disease.  Fatigue is also a prevalent symptom in many other diseases and illnesses, as well as a normal physiological state.

The links at the top of the right sidebar of this page provide an overview of the various definitions, and hopefully a better understanding of our goal to refine and consolidate what has been learned in close to a century about ME.

Dr. E.G. Dowsett
A Rose By Any Other Name

"Historical Background:  The earliest definitions were brief but succinct, based on clinical observation and accompanied by a checklist of symptoms.  Wallis (1955) provided a concise list with appropriate variations for children and adolescents, while Ramsay (1956) introduced the descriptive term (Myalgic Encephalomyelitis), which has stood the test of time over half a century in the UK, Europe, Canada and Austrialasia."

"Fatigue States:  These definitions first arose in the USA following the 1984 Lake Tahoe epidemic (which was misattributed to a Herpes virus infection).  Both the earliest definition (Holmes et al, 1988) and its revision (Fukuda, 1994) elevated tonsillitis, glandular enlargement and fatigue to unreal importance, while overlooking the characteristic encephalitic features of the genuine illness [M.E.]."

"Clinical descriptions of diseases have a way of protecting those of us
who are doctors from the intensity of suffering our patients actually experience.
I have always wished that doctors could learn about disease directly from patients...."
-Dr. David S. Bell-

The specificity of the CDC-1994 criteria for chronic fatigue syndrome: comparison of health status in three groups of patients who fulfill the criteria.
Authors: Kennedy G, Abbot NC, Spence V, Underwood C and Belch JJF
Institution: Vascular Diseases Research Unit, Department of Medicine, University of Dundee  "Conclusions: Differences in simple, easily performed clinical outcome measurements can be observed between groups of patients, all of whom fulfill the CDC-1994 criteria for CFS. It is likely that their response to treatment may also vary. The specificity of the CFS case definition should be improved to define more homogeneous groups of patients for the purposes of treatment and research."  Read full abstract and comment.

See the results of 3 research articles by Dr. Leonard Jason comparing patients using various definitions for ME and CFS.

"Many patients with a diagnosis of CFS today have non-diagnosed major diseases.  These patients warp any statistical or scientific examination of the CFS patient.  Most of the patients I have seen from Canada, the United States, or from the United Kingdom with gradual onset CFS illness have non-diagnosed major medical illness or anomaly."
-Dr. Byron Hyde-


March 2014
Bold Evidence that US Health Officials have worked to make ME & cfs "Evaporate"

See the complete commentary by Craig Maupin: CDC AND NIH Officials Discussed "Desirable Outcome" of Seeing A Distinct Illness "Evaporate”

Dr. Stephen E. Straus to Dr. Keiji Fukuda: “I predict that… the notion of a discrete form of fatiguing illness will evaporate. We would, then, be left with Chronic Fatigue that can be distinguished as Idiopathic or Secondary to an identifiable medical or psychiatric disorder. I consider this a desirable outcome.” “I commend you again on your efforts to forge an international consensus that has scientific merit and is politically acceptable.”



Definitions Overview
ICC - Consensus Criteria
Canadian Consensus
Dr. Byron Hyde
Historic ME
Dr. A. Melvin Ramsay
Dr. E.G. Dowsett
Prof. Malcolm Hooper
ME/cfs Australia
Pediatric ME & cfs

Immune Abnormalities in Patients Meeting New Diagnostic Criteria for Chronic Fatigue Syndrome / Myalgic Encephalomyelitis

From Dr. Spence's  lecture,
ME/CFS: A research and clinical conundrum

"As you can see, the [CDC] definition relies on 'fatigue' as its major criterion. For that reason, many patients who fall under this diagnostic label hate the name — they call it the F-word — since, for many of them, 'fatigue' per se is not the major problem, and does not best represent how they would explain their condition. Thus, this CDC-1994 definition is now widely recognised to have a number of limitations...it makes no attempt to differentiate patients on the basis of severity of illness or level of functional disability.
Indeed, there is a growing realisation that the current CDC-1994-defined 'CFS' term is an impossibly inclusive diagnostic construct, begging Simon Loblay (1995) to ask the ontological question: 'Is CFS a recognisable disease entity with a unique pathophysiology, or is it a ragbag of common non-specific symptoms with many causes, mistakenly labelled as a syndrome?'"

"The definitions of myalgic encephalomyelitis and chronic fatigue syndrome describe what may have been the same disease, but the differing definitions have caused confusion."
-Dr. Byron Hyde-
Clinical and Scientific Basis of M.E./CFS

"...two major errors are responsible for the present confusion surrounding the case definition, aetiology and diagnosis of M.E.  First, there has been a failure to distinguish the syndrome from post-viral debility following Epstein-Barr mononucleosis, influenza and other common fevers.  Compared to M.E., these lack the dramatic effect of exercise upon muscle function, the multi-system involvement, diurnal variability of symptoms and prolonged relapsing course.  Second, there has been a failure to recognize the unique epidemiological pattern of M.E."
-Dr. E.G. Dowsett-
Clinical and Scientific Basis of M.E./CFS

"Recommendation 10: We would encourage the classification of CFS as a 'Nervous System Disease,' as worded in the ICD-10 G93.3"
From the 6th meeting of the
CFSAC in 2005

See a summary of CFS and ME definitions here.

"When these sort of neurological symptoms and/or signs occur, it is always important to exclude the possibility of the cause being another neurological disorder. One such condition is Hashimoto's encephalopathy. This very interesting case involved a 14-year-old girl whose initial (mis)diagnosis had been severe CFS, along with neurological features (including hand tremor, jerking leg movements and blurred vision) and a number of thyroid function test anomalies consistent with an autoimmune thyroiditis (as occurs in Hashimoto's encephalopathy)."
Dr. Derek Enlander's

"Where the one essential characteristic of M.E. is acquired CNS [central nervous system] dysfunction,
that of CFS is primarily chronic fatigue."
-Dr. Byron Hyde-

Online Medical Dictionary


Home • ME & cfs Explained • Definitions • The Research • About Us


© 2006-15 National Alliance for Myalgic Encephalomyelitis
All rights reserved