Medscape Medical News article, by Miriam Tucker, November 04, 2016: Post exertion ‘Crash,’ not Fatigue per se, Marks Syndrome

Article extract:

The name “chronic fatigue syndrome” is being phased out not just because it is viewed as trivializing a condition that renders many patients completely or nearly bedbound but also because it gives the misleading impression that the illness is characterized simply by prolonged unexplained fatigue.

In fact, ME/CFS is characterized by multiple heterogeneous symptoms, with PEM, often described as a “crash” or a significant worsening of already-present symptoms, being a near-universal experience.

“Many studies show that physical exertion can help with insomnia in healthy people, and even people with other medical conditions such as depression, anxiety, or even heart failure. But in ME/CFS patients, physical exertion exacerbates their symptoms,” conference cochair Lily Chu, MD, from Stanford University, Palo Alto, California, told Medscape Medical News.

“The way these patients present is very different from healthy people or people with other medical conditions.”

Indeed, recent diagnostic criteria for the illness, including the February 2015 Institute of Medicine report, require PEM among other symptoms to make the diagnosis of ME or ME/CFS as opposed to older definitions of CFS. However, the Centers for Disease Control and Prevention continues to endorse a 1994 CFS definition that lists PEM as an optional criterion, but does not make it mandatory for the diagnosis.

What Is PEM?

At the IACFSME conference, Dr Chu presented findings from her group’s study of 150 patients diagnosed with the 1994 criteria who completed a survey about their symptoms after physical or cognitive exertion or emotional distress.

The majority (89%) reported experiencing PEM after both types of triggers, but 10% reported no effect after emotional distress, whereas overall physical exertion elicited significantly more symptoms than did emotional distress (seven vs five; P < .001).

Although fatigue was the most commonly exacerbated symptom, more than 30% of patients also reported cognitive difficulties, sleep disturbance, headache, muscle pain, and influenza-like feelings. Some also reported gastrointestinal, orthostatic, and mood-related exacerbations.

Timing and duration of symptoms varied among respondents and per respondent, but 11% reported a consistent post trigger delay of at least 24 hours, whereas 23% said that their symptoms typically lasted for 3 or more days.

 “PEM consists of more than just fatigue and pain. It’s an exacerbation of multiple symptoms, some of which are atypically associated with exertion,” Dr Chu told Medscape Medical News.

She added, “PEM can be difficult for clinicians and patients to identify. We suggest patients keep a diary for a week or two, documenting symptoms and activity so we can look at and see relationship of activity and timing, duration, and intensity of symptoms.”

Read full article, including overview of other biological studies into PEM [you will need to register with Medscape]