Myalgic Encephalomyelitis or Chronic Fatigue Syndrome is a diagnosis of exclusion – that means there are lots of things for your doctor to rule out before jumping to the conclusion you have ME/CFS.  Just because you’re tired, doesn’t mean you have ME/CFS.  But that said, it can be hard to get doctors to diagnose ME/CFS because historically they have had poor training on ME/CFS.

2015_IOM_report_PEM_chartTo meet the Canadian Consensus Criteria (one of the higher diagnostic thresholds used in the world), you must have something called Post-Exertional Malaise – which is a special kind of non-recovery from using up energy. You must have experienced it consistently for 6 months (or 3 months if a child). PEM has a delayed response. You may feel tired hours or days after your effort, and it may also result in a “dead feeling”, soreness from excess lactic acid in the muscles, and mental decline after exercise.

“There is sufficient evidence that PEM is a primary feature that helps distinguish ME/CFS from other conditions”  Institutes of Medicine

In addition to PEM, you must experience some of the following:

  • Cognitive problems that you didn’t have before you became ill, eg concentration
  • Pain and/or headaches
  • Sleep changes (either too much or too little, or sleep reversal), and it is unrefreshing
  • You are experiencing neuro-sensory changes (eg. sensitivity to light, sound, smells etc)
  • Muscle weakness
  • Flu-like symptoms
  • Gut changes
  • You have to pee more often
  • Rapid heart rate (tachycardia)
  • Body temperature changes (too hot, too cold, unable to tolerate heat or cold)
  • Chemical sensitivity or medication sensitivity
  • Dizzyness
  • Reynauds

If this sounds like you, you may have ME/CFS. See a doctor and ask to be referred to a specialist immediately. Early diagnosis is important.

If you think you have ME/CFS Here’s what you need to know to get started.


The following information is an excerpt from: Carruthers BM, van de Sande MI, De Meirleir KL, Klimas NG, Broderick G, Mitchell T, Staines D, Powles AP, Speight N, Vallings R, Bateman L. Myalgic encephalomyelitis: international consensus criteria. Journal of internal medicine. 2011 Oct 1;270(4):327-38.

Diagnostic Criteria

A patient will meet the criteria for postexertional neuroimmune exhaustion (A), at least one symptom from three neurological impairment categories (B), at least one symptom from three immune/gastro-intestinal/genitourinary impairment categories (C), and at least one symptom from energy metabolism/transport impairments (D).

A. Post-exertional neuroimmune exhaustion sometimes called post-exertional malaise (PEM)

Compulsory. PEN or PEM is a cardinal feature and is a pathological inability to produce sufficient energy on demand with prominent symptoms primarily in the neuroimmune regions. Characteristics are as follows:

  1. Marked, rapid physical and/or cognitive fatigability in response to exertion, which may be minimal such as activities of daily living or simple mental tasks, can be debilitating and cause a relapse.
  2. Post-exertional symptom exacerbation: e.g.acute flu-like symptoms, pain and worsening of other symptoms.
  3. Post-exertional exhaustion may occur immediately after activity or be delayed by hours or days.
  4. Recovery period is prolonged, usually taking 24 h or longer. A relapse can last days, weeks or longer.
  5. Low threshold of physical and mental fatigability (lack of stamina) results in a substantial reduction in pre-illness activity level.

Operational notes: For a diagnosis of ME, symptom severity must result in a significant reduction of a patient’s premorbid activity level.

Severity of ME/CFS

  • Mild: an approximate 50% reduction in pre-illness activity level
  • Moderate: mostly housebound
  • Severe: mostly bedridden
  • Very severe: totally bedridden and need help with basic functions

There may be marked fluctuation of symptom severity and hierarchy from day to day or hour to hour. Consider activity, context and interactive effects.

Recovery time: e.g. Regardless of a patient’s recovery time from reading for ½ hour, it will take much longer to recover from grocery shopping for ½ hour and even longer if repeated the next day – if able. Those who rest before an activity or have adjusted their activity level to their limited energy may have shorter recovery periods than those who do not pace their activities adequately.

Impact: e.g. An outstanding athlete could have a 50% reduction in his/her pre-illness activity level and is still more active than a sedentary person.

B. Neurological impairments in ME/CFS

At least one symptom from three of the following four symptom categories

  1. Neurocognitive impairments  become more pronounced with fatigue.
    1. Difficulty processing information: slowed thought, impaired concentration e.g. confusion, disorientation, cognitive overload, difficulty with making decisionsslowed speech, acquired or exertional dyslexia
    2. Short-term memory loss: e.gdifficulty remembering what one wanted to say, what one was saying, retrieving words, recalling informationpoor working memory
  2. Pain: 
    1. Significant pain can be experienced in muscles, muscle-tendon junctions, joints, abdomen or chest. It is noninflammatory in nature and often migrates. e.g. generalized hyperalgesiawidespread pain (may meet fibromyalgia criteria), myofascial or radiating pain
    2. Headaches: Chronic, generalized headaches often involve aching of the eyes, behind the eyes or back of the head that may be associated with cervical muscle tension; migraine; tension headaches
  3.  Sleep disturbance
    1. a. Disturbed sleep patterns:e.g. insomnia, prolonged sleep including naps, sleeping most of the day and being awake most of the night, frequent awakenings, awaking much earlier than before illness onset, vivid dreams/nightmares
    2. b. Unrefreshed sleep: e.g. awaken feeling exhausted regardless of duration of sleep, day-time sleepiness
  4. Neurosensory, perceptual and motor disturbances
    1. Neurosensory and perceptual: e.ginability to focus vision, sensitivity to light, noise, vibration, odour, taste and touch; impaired depth perception
    2. Motor: e.g. muscle weakness, twitching, poor coordination, feeling unsteady on feet, ataxia


Overload phenomena may be evident when two tasks are performed simultaneously. Abnormal accommodation responses of the pupils are common. 

Sleep disturbances are typically expressed by prolonged sleep, sometimes extreme, in the acute phase and often evolve into marked sleep reversal in the chronic stage.

Motor disturbances may not be evident in mild or moderate cases but abnormal tandem gait and positive Romberg test may be observed in severe cases.

C. Immune, gastro-intestinal and genito-urinary impairments in ME/CFS

At least one symptom from three of the following five symptom categories:

  1. Flu-like symptoms may be recurrent or chronic and typically activate or worsen with exertion. e.g. sore throat, sinusitis, cervical and/or axillary lymph nodes may enlarge or be tender on palpitation
  2. Susceptibility to viral infections with prolonged recovery periods
  3. Gastro-intestinal tract: e.g. nausea, abdominal pain, bloating, irritable bowel syndrome
  4. Genitourinary: e.g. urinary urgency or frequency, nocturia
  5. Sensitivities to food, medications, odours or chemicals

Notes: Sore throat, tender lymph nodes, and flu-like symptoms obviously are not specific to ME but their activation in reaction to exertion is abnormal. The throat may feel sore, dry and scratchy. Faucial injection and crimson crescents may be seen in the tonsillar fossae, which are an indication of immune activation.

D. Energy production/transportation impairments in ME/CFS

At least one symptom

  1. Cardiovascular: e.g. inability to tolerate an upright position – orthostatic intolerance, neurally mediated hypotension, postural orthostatic tachycardia syndromepalpitations with or without cardiac arrhythmias, light-headedness/dizziness
  2. Respiratory: e.g. air hunger, laboured breathing, fatigue of chest wall muscles
  3. Loss of thermostatic stability: e.g. subnormal body temperature, marked diurnal fluctuations; sweating episodes, recurrent feelings of feverishness with or without low grade fever, cold extremities
  4. Intolerance of extremes of temperature

Notes: Orthostatic intolerance may be delayed by several minutes. Patients who have orthostatic intolerance may exhibit mottling of extremities, extreme pallor or Raynaud’s Phenomenon. In the chronic phase, moons of finger nails may recede.

Paediatric considerations when Diagnosing ME/CFS

Symptoms may progress more slowly in children than in teenagers or adults. In addition to post-exertional neuro immune exhaustion, the most prominent symptoms tend to be neurological: headaches, cognitive impairments, and sleep disturbances.

  1. Headaches: Severe or chronic headaches are often debilitating. Migraine may be accompanied by a rapid drop in temperature, shaking, vomiting, diarrhoea and severe weakness.
  2. Neurocognitive impairments: Difficulty focusing eyes and reading are common. Children may become dyslexic, which may only be evident when fatigued. Slow processing of information makes it difficult to follow auditory instructions or take notes. All cognitive impairments worsen with physical or mental exertion. Young people will not be able to maintain a full school programme.
  3. Pain may seem erratic and migrate quickly. Joint hypermobility is common.

Notes: Fluctuation and severity hierarchy of numerous prominent symptoms tend to vary more rapidly and dramatically than in adults.

Classification of ME/CFS

Myalgic encephalomyelitis

Atypical myalgic encephalomyelitis: meets criteria for post-exertional neuroimmune exhaustion but has a limit of two less than required of the remaining criterial symptoms. Pain or sleep disturbance may be absent in rare cases.


Co-Morbid Entities for ME/CFS:

The following conditions are frequently experienced by people with ME/CFS and do not preclude the diagnosis of ME/CFS: Fibromyalgia Syndrome (FMS), Myofascial Pain Syndrome (MPS), Temporomandibular Joint Syndrome (TMJ), Irritable Bowel Syndrome (IBS), Interstitial Cystitis, Irritable Bladder Syndrome, Raynaud’s Phenomenon, Prolapsed Mitral Valve, Depression, Migraine, Allergies, Multiple Chemical Sensitivities (MCS), Hashimoto’s thyroiditis, Sicca Syndrome, etc. Such co-morbid entities may occur in the setting of ME/CFS. Others such as IBS may precede the development of ME/CFS by many years, but then become associated with it. The same holds true for migraines and depression.  Their association is thus looser than between the symptoms within the syndrome. ME/CFS and FMS often closely connect and should be considered to be overlap syndromes.

Idiopathic Chronic Fatigue:

If the patient has unexplained prolonged fatigue (6 months or more) but has insufficient symptoms to meet the criteria for ME/CFS, it should be classified as idiopathic chronic fatigue.