What is Chronic Fatigue Syndrome?

By Cara Lan, N.D.

Myalgic Encephalomyelitis (ME) or Chronic Fatigue Syndrome (CFS) is a complex, chronic, and debilitating illness. For many people it can start with an overt, acute infection such as mononucleosis or other flu-like illness. Symptoms often come on suddenly thereafter. For others, the chronic symptoms begin months or even years after the infection, often during a time of extreme stress, so that the correlation between the flu-like illness and late-onset fatigue is often not obvious.

The medical term “syndrome” implies a collection of symptoms. Such symptoms are often seen together for a particular illness. When diagnosed with a syndrome you may not have every symptom listed, but you will have most of them and need to have the hallmarks of that syndrome. You may have varying degrees of severity of the symptoms listed for that syndrome as well.

The #1, hallmark symptom of ME/CFS is just as the name implies: chronic fatigue. What is not implied in the name are the qualifiers of the fatigue (what differentiates it from other types of fatigue), the severity and debilitating aspect of the fatigue, and the many other symptoms that accompany it.

ME/CFS is comprised of the following collection of symptoms (as listed by the U.S. ME/CFS Clinician Coalition in their 2020 publication)[1]:

Substantial reduction or impairment in the ability to engage in pre-illness activity that persists for 6 months or more and is accompanied by fatigue.
The fatigue is profound, not lifelong, not the result of ongoing exertion, and not alleviated by rest.
Post-exertional malaise (PEM) in which physical or mental activities result in a typically delayed and prolonged exacerbation of symptoms and reduction in functioning. (PEM is the hallmark of ME/CFS and its most distinctive symptom. It is this symptom in particular, that helps to differentiate ME/CFS from other diagnoses of fatigue).
Unrefreshing sleep and a variety of sleep disturbances.
Either cognitive impairment (often referred to as “brain fog”) and/or orthostatic intolerance (the development of symptoms when upright that are alleviated when lying down).
These symptoms must be moderate to severe and present at least 50% of the time.

Other ME/CFS symptoms include:

Muscular weakness and easily fatigued muscles
Muscle soreness long after physical exertion has ended
Widespread pain
Headaches
Visual disturbances
Sensitivities to light, noise, chemicals, foods, and drugs
Flu-like symptoms including chronic sore throat and tender lymph nodes
Susceptibility to infections
Gastrointestinal problems
Genitourinary issues
Respiratory issues such as air hunger
Thermoregulatory issues such as being unable to cool down when hot or warm up when cold
Emotional lability (irritability, depression, weeping, anxiety, overt anger)

As mentioned above post-exertional malaise (PEM) is the hallmark of ME/CFS. It is this symptom that helps to distinguish ME/CFS from other illnesses that cause fatigue. You know you have PEM when any exertion causes a crash in your ability to function or relapse of your chronic symptoms. Those with PEM find that they can no longer tolerate an exercise regimen that previously made them feel energized. Instead, workouts must followed by lots of rest and sleep for days or even weeks afterwards. Many people find that even activities of daily living are too much, as illustrated in Celeste’s story on the previous page. Most, if not all, people living with ME/CFS will modulate the amount of activity they can handle, doing far less than the average person or far less than they used to.

How to assess the severity of ME/CFS:

Eleanor Stein MD, FRCP(C) defines the severity of ME/CFS as the following:

Mild: still able to work or study full time though with effort and rest on weekends
Moderate: able to work or study part time with effort
Severe: unable to work or study and requires assistance to live independently
Extreme: unable to live independently, virtually house and sometimes bed bound[2]

We will examine potential underlying causes of, as well as testing for, ME/CFS on the following page.

[1] ‘Diagnosing and Treating Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)’ by the U.S. ME/CFS Clinician Coalition, Version 2, July 2020.

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