Chronic Fatigue Syndrome: Cause Unknown, Diagnosis Difficult

Chronic fatigue syndrome, or CFS, is a complex disorder characterized by weakness and a profound fatigue that is not improved by bed rest. The illness can be worsened by physical or mental activity. People with CFS most often function at a much lower level of activity than they were able to before the illness began. In addition to these features, patients report various nonspecific symptoms, including weakness, muscle pain, impaired memory and/or mental concentration, insomnia, and fatigue lasting more than 24 hours after exertion.

In some cases, CFS can persist for years. The cause of CFS has not been identified and no specific diagnostic tests are available. Moreover, since many illnesses have extreme fatigue as a symptom, care must be taken to rule out other known and often treatable conditions before a diagnosis of CFS is made.

Definition of CFS
There has been much debate about how best to define CFS. In general, in order to receive a diagnosis of chronic fatigue syndrome, a patient must satisfy two criteria:

1. Have severe chronic fatigue of six months or longer, with other known medical conditions ruled out by clinical diagnosis, and
2. Have four or more of the following symptoms at the same time: significant trouble with short-term memory or concentration, sore throat, tender lymph nodes, muscle pain, pain in several joints without swelling or redness, headaches of a new type, pattern or severity, unrefreshing sleep, and malaise (symptoms such as discomfort, weakness, or nausea) lasting more than 24 hours after activity.

The symptoms must have continued or recurred during six or more months of illness in a row and must not have started before the fatigue.

Other Commonly Observed Symptoms in CFS
In addition to the primary defining symptoms of CFS, a number of other symptoms have been reported by some CFS patients. The frequencies of occurrence of these symptoms vary from 20% to 50% among CFS patients. They include abdominal pain, alcohol intolerance, bloating, chest pain, chronic cough, diarrhea, dizziness, dry eyes or mouth, earaches, irregular heartbeat, jaw pain, morning stiffness, nausea, night sweats, psychological problems (depression, irritability, anxiety, panic attacks), shortness of breath, skin sensations, tingling sensations, and weight loss.

Clinical Course of CFS
It is vital to understand the clinical course of CFS. This knowledge is required to simplify communication between physicians and patients, to evaluate possible new treatments, and to address insurance and disability issues. The clinical course of CFS varies considerably among persons who have the disorder; the actual percentage of patients who recover is unknown, and even the definition of what should be considered recovery is subject to debate.

Some patients recover to the point that they can resume work and other activities, but continue to experience various or periodic CFS symptoms. Some patients recover completely with time, and some grow progressively worse. CFS often follows a cyclical course, alternating between periods of illness and relative well being. Recovery is defined by the patient and may not reflect complete symptom-free recovery. The Centers for Disease Control and Prevention (CDC) continues to monitor patients enrolled in a four-city surveillance study conducted by the CDC from 1989 to 1993.

About 50% of those patients reported "recovery," and most recovered within the first 5 years after the illness began. No characteristics were identified that made one patient more likely to recover than another. At the start of the illness, the most commonly reported CFS symptoms were sore throat, fever, muscle pain, and muscle weakness. As the illness progressed, muscle pain and forgetfulness increased and the reporting of depression decreased.

Other Conditions Can Cause Fatigue
There are many clinically defined, frequently treatable illnesses that can result in fatigue. These include hypothyroidism, sleep apnea and narcolepsy, major depressive disorders, chronic mononucleosis, bipolar affective disorders, schizophrenia, eating disorders, cancer, autoimmune disease, most hormonal disorders, subacute infections, obesity, alcohol or substance abuse, and reactions to prescribed medications. Diagnosis of any of these conditions would rule out a diagnosis of CFS, unless this other condition has already been treated and no longer explains the fatigue and other symptoms.

Similar Medical Conditions
In addition to illnesses that cause fatigue, a number of other conditions have been described that have a group of symptoms to CFS. Although these illnesses might have a primary symptom other than fatigue, chronic fatigue is commonly associated with all of them. These include fibromyalgia syndrome, myalgic encephalomyelitis, neurasthenia, multiple chemical sensitivities, and chronic mononucleosis.

Treatment of Chronic Fatigue Syndrome
A variety of therapeutic approaches have been described as helping patients with chronic fatigue syndrome. Since no cause for CFS has been identified, treatment programs are directed at relief of symptoms, with the goal of the patient regaining some level the function and well-being they had before becoming ill.

Decisions about treatment for CFS or any chronically fatiguing illness should only be made with the help of a health care provider. Currently, most health care providers with experience in treating persons with CFS use some combination of:

• Physical activities: light exercise, stretching, or yoga; or therapies such as massage or acupuncture
• Education: learning how to adjust activities and behaviors that could make the illness worse
• Medications: Pharmacologic therapy is directed toward the relief of specific symptoms experienced by the individual patient. The usual treatment strategy is to begin with very low doses and to gradually increase dosage as necessary and as tolerated. These might include drugs to ease pain, reduce fatigue, relieve depression, improve sleep, and treat anxiety.

Although many experimental drugs and treatments have been promoted for improvement of CFS symptoms, in fact none have been proven to be effective. Some are useless and others can be dangerous. They should be avoided until research has validated their claims.

In addition, a variety of dietary supplements and herbal preparations are claimed to have potential benefits for CFS patients. With few exceptions, the effectiveness of these remedies for treating CFS has not been evaluated in controlled trials. Contrary to common belief, the "natural" origin of a product does not ensure safety. Dietary supplements and herbal preparations can have potentially serious side effects and some can interfere or interact with prescription medications. CFS patients should seek the advice of their health care provider before using any unprescribed remedy.

Researchers continue to work on the complex issues of chronic fatigue syndrome and its treatment, with the hope of one day finding out how it is caused and how to treat or even cure this complicated and difficult illness.

The information in this article has been made available by the CDC/National Center for Infectious Diseases.

Each year, Medical College of Wisconsin physicians care for more than 180,000 patients, representing nearly 500,000 patient visits. Medical College physicians practice at Children's Hospital of Wisconsin, Froedtert Memorial Lutheran Hospital, the Milwaukee VA Medical Center, and many other hospitals and clinics in Milwaukee and southeastern Wisconsin.