Chronic Fatigue Syndrome

The definition of chronic fatigue syndrome (CFS) is still under debate. The revised case definition from the U.S. Centers for Disease Control (CDC) permits the diagnosis in patients with a minimum of six months of unexplained fatigue (of new or recent onset) that "is not substantially alleviated by rest and results in substantial reduction in previous activities," and that occurs in concert with four or more commonly encountered symptoms including: "substantial impairment in short-term memory or concentration; sore throat; tender lymph nodes; muscle pain; multi-joint pain without swelling or redness; headaches of a new type, pattern, or severity; unrefreshing sleep; and post-exertional malaise lasting more than 24 hours."