Chronic fatigue syndrome

General introduction
Chronic fatigue syndrome is a devastating and complex disorder. People with chronic fatigue syndrome have overwhelming fatigue and a host of other symptoms that are not improved by bed rest and that can get worse after physical activity or mental exertion. They often function at a substantially lower level of activity than they were capable of before they became ill.

Besides severe fatigue, other symptoms include muscle pain, impaired memory or mental concentration, insomnia, and post-exertion malaise lasting more than 24 hours. In some cases, chronic fatigue syndrome can persist for years.

Researchers have not yet identified what causes chronic fatigue syndrome, and there are no tests to diagnose chronic fatigue syndrome. Moreover, because many illnesses have fatigue as a symptom, doctors need to take care to rule out other conditions, which may be treatable.

Definition
There are several case definitions for chronic fatigue syndrome and all require fatigue as one of the symptoms. CDC uses the 1994 chronic fatigue syndrome case definition, which requires meeting three criteria:

(1) The individual has had severe chronic fatigue for 6 or more consecutive months and the fatigue is not due to ongoing exertion or other medical conditions associated with fatigue (these other conditions need to be ruled out by a doctor after diagnostic tests have been conducted)
(2) The fatigue significantly interferes with daily activities and work
(3) The individual concurrently has four or more of the following eight symptoms:

• post-exertion malaise lasting more than 24 hours
• unrefreshing sleep
• significant impairment of short-term memory or concentration
• muscle pain
• pain in the joints without swelling or redness
• headaches of a new type, pattern, or severity
• tender lymph nodes in the neck or armpit
• a sore throat that is frequent or recurring

These symptoms should have persisted or recurred during 6 or more consecutive months of illness, and they cannot have first appeared before the fatigue.

Causes of chronic fatigue syndrome
Despite a vigorous search, scientists have not yet identified what causes chronic fatigue syndrome. While a single cause for chronic fatigue syndrome may yet be identified, another possibility is that chronic fatigue syndrome has multiple triggers. Some of the possible causes of chronic fatigue syndrome might be:
• infections
• immune dysfunction
• abnormally low blood pressure that can cause fainting (neurally mediated hypotension)
• nutritional deficiency
• stress that activates the axis where the hypothalamus, pituitary, and adrenal glands interact (the HPA axis)

Symptoms of chronic fatigue syndrome
The primary symptom of chronic fatigue syndrome is unexplained, severe fatigue lasting at least 6 months that is not improved by bed rest and that can get worse after physical activity or mental exertion. Individuals with chronic fatigue syndrome experience a fatigue so strong that their activity levels and stamina decline dramatically. However, fatigue is not the only symptom, and for some patients may not be the symptom that bothers them the most.

As stated in the 1994 case definition, the fatigue of chronic fatigue syndrome is accompanied by at least four of eight characteristic symptoms lasting at least 6 months. These symptoms include:
• post-exertion malaise lasting more than 24 hours
• unrefreshing sleep
• significant impairment of short-term memory or concentration
• muscle pain
• pain in the joints without swelling or redness
• headaches of a new type, pattern, or severity
• tender lymph nodes in the neck or armpit
• a sore throat that is frequent or recurring

The symptoms listed above are the symptoms used to diagnose this illness. However, many patients with chronic fatigue syndrome may experience other symptoms, including irritable bowel, depression or other psychological problems, chills and night sweats, visual disturbances, brain fog, difficulty maintaining upright position, dizziness, balance problems, fainting, and allergies or sensitivities to foods, odors, chemicals, medications, or noise.

Diagnosis of chronic fatigue syndrome
Because there is no blood test, brain scan, or other lab test to diagnose chronic fatigue syndrome, it is a diagnosis that can only be made after ruling out other possible illnesses. A doctor will first take a detailed patient history and then will conduct a thorough physical and mental health exam. Next, a series of laboratory screening tests will be ordered to help identify or rule out other possible causes of symptoms. There may also be additional tests to follow up on results of these tests. If a patient has had severe fatigue for 6 months or longer but does not does not have at least four of the eight symptoms of chronic fatigue syndrome (and thus, does not meet the criteria for a chronic fatigue syndrome diagnosis), the doctor may make a diagnosis of idiopathic fatigue (fatigue with an unknown cause). As a practical matter, patients with idiopathic fatigue are managed like chronic fatigue syndrome patients.

A clinician should consider a diagnosis of chronic fatigue syndrome if these three criteria are met:
(1) The individual has unexplained, persistent fatigue for 6 months or longer that is not due to ongoing exertion, is not substantially relieved by rest, has begun recently (is not lifelong)
(2) The fatigue significantly interferes with daily activities and work
(3) The individual has had four or more of the following eight symptoms:

• post-exertion malaise lasting more than 24 hours
• unrefreshing sleep
• significant impairment of short-term memory or concentration
• muscle pain
• pain in the joints without swelling or redness
• a sore throat that is frequent or recurring
• tender lymph nodes in the neck or armpit
• headaches of a new type, pattern, or severity

Treatment of chronic fatigue syndrome
Managing chronic fatigue syndrome can be as complex as the illness itself. There is no cure, no prescription drugs have been developed specifically for chronic fatigue syndrome, and symptoms can vary a lot over time. Thus, people with chronic fatigue syndrome should closely monitor their health and let their doctor know of any changes; and doctors' should regularly monitor their patients' conditions and change treatment strategies, as needed.

A team approach that involves doctors and patients is one key to managing chronic fatigue syndrome. Patients benefit when they can work in collaboration with a team of doctors and other health care practitioners, who might include rehabilitation specialists, mental health professionals, and physical or exercise therapists. Together, they can create an individualized treatment program that best meets the needs of the patient with chronic fatigue syndrome. This program should be based on a combination of therapies that address symptoms, coping techniques, and managing normal daily activities.

This information was developed by the Centers for Disease Control and Prevention.

Centers for Disease Control and Prevention. Basic Facts. Available at: https://www.cdc.gov/cfs/general/index.html. Last accessed April 30, 2013.

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