Myalgic Encephalomyelitis (previously called Chronic Fatigue Syndrome) is an acquired complex disorder characterized by a variety of symptoms and physical findings potentially affecting multiple systems of the body. Many cases are preceded by a viral infection, usually a flu-like or upper respiratory illness, although ME can also be preceded by a non-viral illness or other trauma. Onset is usually rapid but gradual onsets are also reported. Affected individuals do not recover from the infection and instead experience a wide variety of symptoms including an inability to produce sufficient energy to meet daily demands. Marked fatigue and weakness, sickness, cognitive dysfunction and symptom flare-up follows physical and cognitive exertion. Additional symptoms that may occur include headaches, pain, muscle weakness, neck pain, vision abnormalities (such as blurred vision), a sensation of tingling, burning or numbness of the extremities, bladder and bowel dysfunction, and sleep dysfunction. Cardiovascular abnormalities have also been reported. Myalgic encephalomyelitis is a chronic and disabling disorder. Severe cases often leave affected individuals bedridden or housebound.
Also called “core” symptoms, three primary symptoms are required for diagnosis:
- Greatly lowered ability to do activities that were usual before the illness. This drop in activity level occurs along with fatigue and must last six months or longer. People with ME/CFS have fatigue that is very different from just being tired. The fatigue of ME/CFS:
- Can be severe.
- Is not a result of unusually difficult activity.
- Is not relieved by sleep or rest.
- Was not a problem before becoming ill (not life-long).
- Worsening of ME/CFS symptoms after physical or mental activity that would not have caused a problem before illness. This is known as post-exertional malaise (PEM). People with ME/CFS often describe this experience as a “crash,” “relapse,” or “collapse.” During PEM, any ME/CFS symptoms may get worse or first appear, including difficulty thinking, problems sleeping, sore throat, headaches, feeling dizzy, or severe tiredness. It may take days, weeks, or longer to recover from a crash. Sometimes patients may be house-bound or even completely bed-bound during crashes. People with ME/CFS may not be able to predict what will cause a crash or how long it will last. As examples:
- Attending a child’s school event may leave someone house-bound for a couple of days and not able to do needed tasks, like laundry.
- Shopping at the grocery store may cause a physical crash that requires a nap in the car before driving home or a call for a ride home.
- Taking a shower may leave someone with ME/CFS bed-bound and unable to do anything for days.
- Keeping up with work may lead to spending evenings and weekends recovering from the effort.
- Sleep problems. People with ME/CFS may not feel better or less tired, even after a full night of sleep. Some people with ME/CFS may have problems falling asleep or staying asleep.
In addition to these core symptoms, one of the following two symptoms is required for diagnosis:
- Problems with thinking and memory. Most people with ME/CFS have trouble thinking quickly, remembering things, and paying attention to details. Patients often say they have “brain fog” to describe this problem because they feel “stuck in a fog” and not able to think clearly.
- Worsening of symptoms while standing or sitting upright. This is called orthostatic intolerance. People with ME/CFS may be lightheaded, dizzy, weak, or faint while standing or sitting up. They may have vision changes like blurring or seeing spots.
Other Common Symptoms
Many but not all people with ME/CFS have other symptoms.
Pain is very common in people with ME/CFS. The type of pain, where it occurs, and how bad it is varies a lot. The pain people with ME/CFS feel is not caused by an injury. The most common types of pain in ME/CFS are:
- Muscle pain and aches
- Joint pain without swelling or redness
- Headaches, either new or worsening
Some people with ME/CFS may also have:
- Tender lymph nodes in the neck or armpits
- A sore throat that happens often
- Digestive issues, like irritable bowel syndrome
- Chills and night sweats
- Allergies and sensitivities to foods, odors, chemicals, or noise