Chronic Fatigue Syndrome FAQ: "What is CFS?
Chronic fatigue syndrome (CFS) is an emerging illness characterized by debilitating fatigue (experienced as exhaustion and extremely poor stamina), neurological problems, and a variety of flu-like symptoms. The illness is also known as chronic fatigue immune dysfunction syndrome (CFIDS), and outside of the USA is usually known as myalgic encephalomyelitis (ME). In the past the syndrome has been known as chronic Epstein-Barr virus (CEBV).
The core symptoms include excessive fatigue, general pain, mental fogginess, and often gastro-intestinal problems. Many other symptoms will also be present, however they will typically be different among different patients. These include: fatigue following stressful activities; headaches; sore throat; sleep disorder; abnormal temperature; and others.
The degree of severity can differ widely among patients, and will also vary over time for the same patient. Severity can vary between getting unusually fatigued following stressful events, to being totally bedridden and completely disabled. The symptoms will tend to wax and wane over time. This variation, in addition to the fact that the cause of the disease is not yet known, makes this illness difficult to diagnose.
In addition to the official researchers' definition discussed below, patients and experienced clinicians have noticed symptom patterns that seem prominent in CFS. These are described in question 1.01 above, and also include the observations that cognitive dysfunction often increases over time (over several years), and that brain scans often show that blood flow to the brain is decreased.
CFS is defined somewhat differently by various medical groups in different countries. The 1994 research definition published by the U.S. Centers for Disease Control and Prevention recommends a step-wise approach for identifying CFS cases. The first step is to clinically evaluate the presence of chronic fatigue, i.e. "self-reported persistent or relapsing fatigue lasting 6 or more consecutive months".
Conditions that explain chronic fatigue should exclude a diagnosis of CFS. These are:
- "any active medical condition that may explain the presence of chronic fatigue ..." - any previous condition which might explain fatigue and which has not documentably come to an end; - "any past or current diagnosis of a major depressive disorder with psychotic or melancholic features; bipolar affective disorders; schizophrenia of any subtype; delusional disorders of any subtype; dementias of any subtype; anorexia nervosa; or bulimia"; - substance abuse within 2 years prior to onset; - severe obesity.
The following should not exclude a diagnosis of chronic fatigue:
- conditions which cannot be confirmed by lab tests, "including fibromyalgia, anxiety disorders, somatoform disorders, nonpsychotic or nonmelancholic depression, neurasthenia, and multiple chemical sensitivity disorder"; - any condition which might produce chronic fatigue but which is being sufficiently treated; - any condition which might produce chronic fatigue but whose treatment has already been completed; - any finding which on its own is not sufficient to strongly suggest one of the exclusionary conditions.
After the above criteria are met, the following core criteria for CFS are applied: "A case of the chronic fatigue syndrome is defined by the presence of the following:
1) clinically evaluated, unexplained persistent or relapsing chronic fatigue that is of new or definite onset (has not been lifelong); is not the result of ongoing exertion; is not substantially alleviated by rest; and results in substantial reduction in previous levels of occupational, educational, social or personal activities; and
2) the concurrent occurrence of four or more of the following symptoms, all of which must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue:
- self-reported impairment in short term memory or concentration severe enough to cause substantial reduction in previous levels of occupational, educational, social or personal activities;
- sore throat;
- tender cervical or axillary lymph nodes;
- muscle pain;
- multi-joint pain without joint swelling or redness;
- headaches of a new type, pattern or severity;
- unrefreshing sleep;
- and post exertional malaise lasting more than 24 hours."
The journal citation for the CDC definition article is: Keiji Fukuda, Stephen Straus, Ian Hickie, Michael Sharpe, James Dobbins, Anthony Komaroff, and the International CFS Study Group. "The Chronic Fatigue Syndrome: A Comprehensive Approach to Its Definition and Study". Ann Intern Med. 1994;121:953-959."