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M.E or CFS ? : Clearing up the Confusion

"In view of more recent research and clinical experience that strongly point to
widespread inflammation and multisystemic neuropathology, it is more appropriate and correct to use the term 'myalgic encephalomyelitis' (ME)
because it indicates an underlying pathophysiology."
Carruthers et al
Journal of Internal Medicine

As the authors of the 2011 Consensus Criteria reiterate: "Using ‘fatigue’ as a name of a disease gives it exclusive emphasis and has been the most confusing and misused criterion.  No other fatiguing disease has ‘chronic fatigue’ attached to its name – e.g. cancer ⁄ chronic fatigue, multiple sclerosis ⁄ chronic fatigue – except ME⁄CFS. Fatigue in other conditions is usually proportional to effort or duration with a quick recovery and will recur to the same extent with the same effort or duration that same or next day."  Not so with M.E.  Many crushing symptoms are exacerbated with the slightest physical or mental exertion, and it takes days or weeks to recover to even the original low functionality - that is, if the exertion was not too far beyond the patient's threshold for recovery, and disease progression continues from a lower activity tolerance threshold.

So, here's why confusion and controversy abound as to whether M.E. and CFS are the same entity:  Words.  Starting in the mid-1980s, different scientific camps and influential government health agencies chose different words (See Definitions) to describe what in most cases was the same illness.  Unfortunately, government bureaucracy and politics has had too much to do with perpetuating this confusion.  They have ignored and even ridiculed expert advice from clinicians and researchers in the field who have attempted to treat patients with this multi-system disease.  But, with little resources and spotty successes, for the most part these clinicians have watched their patients adapt to their circumstances and deteriorate slowly or quickly, depending on the severity or setbacks of the particular case.  As a result, divergent and obscure definitions of what "CFS" really is (or isn't) have intermingled with a distinct disease - M.E. - which is well defined by history, clinical observation and has a clear listing in the International Classification of Diseases (ICD) since 1969.

For more in depth information on the science and politics of ME and CFS, read Osler's Web: Inside the Labyrinth of the Chronic Fatigue Syndrome Epidemic.  (See a brief description of this book on the Links page.)

Also, we attempt to explain the definitional similarities and differences between M.E. and CFS below.  The sidebar to the right offers many excellent resources that will aid in understanding the both the subtle and more obvious distinctions between these illnesses.


ME & CFS Explained

M.E. or cfs ?
Symptoms List
Test Abnormalities
Patient Resources
Doctor Resources

"Myalgic Encephalomyelitis is an acute onset diffuse injury of the brain."
-Dr. Byron Hyde-

"The belief that [ME] CFS is a psychological illness
is the error of our time."
-Dr. Byron Hyde-

Sept 23, 2013
Updated Oct 25, 2013
Open Letter to the Honorable Kathleen Sebelius, U.S. Secretary of Health

2011 Consensus Criteria

 The Nightingale Definition of
Myalgic Encephalomyelitis (M.E.)

Myalgic Encephalomyelitis The Medical Facts
An in-depth description in printable PDF

What is M.E?
by ME Research Group

A Pediatric Case Definition for
Myalgic Encephalomyelitis
and Chronic Fatigue Syndrome

Download a printable PDF version of the 16-page guidebooklet,
What is ME? What is CFS? An Informational Guidebook for Doctors and Patients.

Download the printable pamphlet,
Immune Dysfunction in ME/CFS: A brief overview for patients and families.  (Based on seminars by
Dr. Paul Cheney)

"Though the symptoms of CFS resemble those of ME, the differences are so significant that they would exclude ME patients from the 1988 and 1994 CDC diagnoses of CFS.  The following features of ME separate it from CFS:

●  The epidemic characteristics.

●  The known incubation period.

●  The acute onset.

●  The associated organ pathology, particularly cardiac.

●  Infrequent deaths with pathological CNS changes.

●  Neurological signs in the acute and sometimes chronic phases.

●  The specific involvement of the autonomic nervous system.

●  The frequent subnormal patient temperature.

●  The fact that chronic fatigue is not an essential characteristic of the chronic phase of ME."

-Dr. Byron Hyde

The Complexities of Diagnosis
Chapter 3 in
Handbook of Chronic Fatigue Syndrome

"...there's one myth left that needs removing. The phrase, "...the chronic
fatigue syndrome, myalgic encephalomyelitis ... " appears to assume that M.E.  is a subset of a number of illnesses, sharing chronic fatigue as a principal symptom, assembled together under the so-called umbrella term Chronic Fatigue
Syndrome. Indeed, many commentators routinely use M.E. and CFS synonymously
and interchangeably. M.E. is neither of these things but a discrete
neurological illness.

The overwhelming exhaustive experience of M.E., disproportionate to energy  expended, is qualitatively and quantitatively different from fatigue as
normally experienced and it is not refreshed by any amount of sleep. In
addition, there is a range of symptoms, including muscle pain and cognitive
dysfunction, not present in mere tiredness.

Persisting using the word "fatigue", which is not a very useful symptom to try to single out any particular illness (because which illness does not have
fatigue associated with it?), is holding back research into the physical cause
of M.E. by bundling different illnesses together, confounding variables and  diluting the reliability of the findings for M.E. sufferers.

I am far from the only person in the global M.E. community appealing for us all to stop using the "F" word.
Dr. John Greensmith

Dr. John Greensmith further explains:  “M.E. is recognised by the World Health Organisation as a neurological illness, for which the physical cause is as yet unknown and is categorised differently from Chronic Fatigue Syndrome.  Bundling them [fatiguing illnesses] all together weakens any research experimental design, dilutes and distorts the findings, making it difficult, if not impossible, to generalise to any one particular illness and, therefore, hampers progress towards finding an appropriate treatment or cure for every one of them, packaged under the controversial umbrella term CFS, not just M.E."

Online Medical Dictionary


"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 of the Nightingale Research Foundation makes the above  very simple yet profound statement in his essay, The Complexities of Diagnosis (Chapter 3 in Handbook of Chronic Fatigue Syndrome).  While just about all patients with M.E. will fit the definition for CFS, not all of those with CFS will fit the definition for M.E.  (But technically, the CDC CFS definition excludes those patients with other serious illnesses that include fatigue as a symptom.  Therefore a patient formally diagnosed with M.E., a serious neurological illness of CNS dysfunction - debilitating fatigue being merely one of MANY disabling symptoms - would be ruled out of the CFS definition.  See Dr. Hyde's comment in sidebar.) If a patient does not fit the definition for M.E. and is given a diagnosis of CFS without further investigation into the cause of the symptoms, it would be tragic if a treatable illness was missed.  And this has happened on numerous occasions (see below for examples).  For a more complete understanding, see the Definitions pages, where the various definitions list diagnostic  requirements.

ME and CFS are described by some as a "medically unexplained" illness with no biomarkers.  Do not accept this; it is far from the truth.  The research cited on our Research pages and other websites, as well as specialized and more in-depth testing as suggested in the Consensus Document (listed on the Test Abnormalities page of this website) and in the Nightingale Definition explain many of the symptoms ME and CFS-labeled patients suffer - tests that, when interpreted together, can give the patient and doctor a more complete picture of what's going on in patients' bodies.  It may also help differentiate whether the patient has M.E., or chronic fatigue arising from some other serious illness that may be treatable.

Descriptions are as individual as the patient

There are as many descriptions of this disease as there are patients, because symptom prominence varies from patient to patient.  But they all will have a common theme: crushing exhaustion that never goes away, no matter how much you rest; that the simplest things most people take for granted physically and mentally now seem like insurmountable tasks.  For example, taking out the trash has become like a march up a mountain, or deciding what you need at the grocery store makes your brain swirl like a page-long physics equation.  And once you have tackled one or two of those chores, you feel an overwhelming compulsion to lie down and rest, even though you know it will do little good.  And usually there is widespread muscle pain that seems to radiate right out of the spine and into the muscles throughout some or all parts of the body.  A severe hangover that never goes away, that varies in intensity day-to-day, even hour-to-hour, is how ME and CFS are often described, or "the flu that never goes away," year after year.  Add to that many of the symptoms on the Symptoms List of this website - some coming and going or waxing and waning, others ever-present, always aggravated by tasks you used to give barely a passing thought to - and you have a person in a state of debility that has been compared by researchers and clinicians to MS, cancer and AIDS.

Many scientists would describe ME or CFS in less personal, more technical terms. Words like "post-exertional malaise" and "neurocognitive impairment" sound fairly important, but simply do not convey what the patient is really experiencing.  But the clinicians and researchers who have collectively worked with thousands of ME and CFS-labeled patients know that, "There is no word in the the English lexicon that describes the lack of stamina, the paucity of energy, the absolute malaise and turpitude that accompanies this illness." (-Dr. Charles Lapp-)

Then what's the difference between M.E. and CFS?

Still confused?  You're not alone!  The short answer is that in many cases (possibly most cases) ME and CFS are the same disease with different names.  Often patients are incorrectly diagnosed, depending on the physician's knowledge of the differing clinical definitions, and there are very few physicians that have the knowledge, or take the time to differentiate the patient's diagnosis.  SO...

...M.E. experts from the U.K., U.S., Canada, Australia and many other countries who have studied this disease have stated that it's the definitions that determine the diagnosis.  The current Consensus Document and most M.E. definitions (Ramsay, Dowsett and historic) require the major criteria of severe muscle fatigue following minimal exertion with prolonged recovery time, and neurological disturbances, especially autonomic, cognitive and sensory functions, and variable involvement of cardiac and other systems, with a prolonged relapsing course.  This is a very specific list of criteria, and a major point to note is that the CNS (central nervous system) dysfunction of M.E. can be measured.  (See below.)

Alternately, CFS definitions present the major criterion of fatigue that lasts 6 months and reduces the level of function by at least 50%.  Post-exertional malaise and neurological abnormalities are considered minor and optional criteria.  So this broad definition could encompass any of many illnesses in which fatigue plays a role.  Fatigue is not only a symptom of numerous illnesses, but it is something experienced by normal, healthy people.  And there are no reliable objective ways to measure fatigue.

"The primary diagnostic criterion for M.E. is acquired CNS change.  We have excellent tools for measuring these physiological and neuropsychological changes: SPECT, xenon SPECT, PET and neuropsychological testing. 
CFS patients may not have any of these findings...."

Dr. Byron Hyde, author of the Nightingale Definition of M.E. states that, "I do not describe a patient as having M.E. unless there is an abnormal SPECT.  If the SPECT is normal, I often repeat it along with xenon SPECT.  If the brain scans remain normal, I conclude that it is unlikely to be M.E.  I then refer to the patient as a CFS patient and search for other causes of the fatigue syndrome."  (See examples of SPECT, xenon SPECT and other neuroimages of ME and CFS patients on the Neurology Research page.)

Dr. Hyde has described patients that have come to him with a "CFS" or psychiatric diagnosis that he has investigated more thoroughly.  Some he has diagnosed with M.E. after thorough interview, including determining acute or gradual onset, neurological, cardiac and other screening.  But in many others he has found underlying, treatable causes for their debilitating fatigue.  Some examples he gives are:

1) One man came to him diagnosed as a psychiatric patient which Dr. Hyde initially agreed with, due to the man's obvious irrational behavior during Dr. Hyde's interview with him.  The man said he slept a lot, was still tired after sleeping and felt he had "chronic fatigue syndrome," since he met the CDC CFS case definition criteria.  Dr. Hyde simply listened to the man and observed his behavior over the course of two hours.  He gave the man a  requisition for a few tests which within days revealed he was severely diabetic with extreme hyperlipidemia (high cholesterol/triglycierides, etc.). Within weeks of beginning treatment, the man was behaving rationally, and it was further determined he had had a recent myocardial infarction (heart attack).

2) A woman from the U.S. who had been diagnosed with "CFS" by several ME/CFS physicians came to Dr. Hyde with significant brain dysfunction and overwhelming fatigue.  He had Doppler tests done on her the same day that found "80% obstruction of both internal carotids, and complete obstruction of the basilar artery feeding the brain."  Internists, neurologists and ME/CFS specialists in the U.S. had all missed the obvious.  "The obstruction in one of the arteries was removed and she improved."

Drs. Hyde, Dowsett and others state that doctors should also take a complete patient history to determine other significant factors that distinguish M.E. from CFS and other fatiguing illnesses.  (See sidebar)


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