Medical Matters > Nomenclature: ME/CFS

ME Essential Autumn 2018


Is there a simple reason why the ME Association also uses the term myalgic encephalopathy instead of myalgic encephalomyelitis?


Many doctors refuse to use the name Myalgic Encephalomyelitis because there is no current clinical evidence (from symptoms or signs) or pathological evidence (from post-mortem or other research) to indicate that people have what doctors and pathologists would regard as an ‘encephalomyelitis' taking place. The term encephalomyelitis refers to the presence of significant and widespread inflammation involving the brain and spinal cord and, while there is some evidence of neuroinflammation (i.e., low level inflammatory changes in some parts of the central nervous system), this is not the same as having an encephalomyelitis.

The ME Association therefore proposed that the name ‘Myalgic Encephalopathy' could be used – as this would be more acceptable to doctors and might help to prevent them from using ‘chronic fatigue syndrome' which has been their preferred alternative (CFS is not a name that we endorse as it doesn't reflect the seriousness of the condition, and is rather like calling dementia, ‘chronic forgetfulness syndrome'). Encephalopathy decribes a serious physical disease process that involves damage to the structure and/or function of the brain. I should also point out that we are not trying to remove myalgic encephalomyelitis from everyday use and I normally use it when talking to the media.

In the World Health Organisation's International Classification of Diseases – which provides a central listing and coding for all known diseases – the parent term for ME/CFS is ‘Post-Viral Fatigue Syndrome', and that it also recognises ‘myalgic encephalomyelitis' and indexes to ‘chronic fatigue syndrome'.

In light of the 2021 NICE Clinical Guideline the abbreviated ‘ME/CFS' is now more likely to used in the NHS as the clinical recommendations are implemented and become more widely known. This situation is unlikely to change until research can accurately determine what causes the condition and it is accepted by the medical profession.

However, SNOMED-CT – the electronic diagnostic coding system used by the NHS – is employing ‘chronic fatigue syndrome (disorder)' as its parent term. It recognises other names for the condition – though not as codable terms – and correctly codes it under ‘diseases of the nervous system' i.e., neurological. But there is a pressing need to change the parent term at least to ME/CFS. It also fails to recognise or code Post-Viral Fatigue Syndrome which is something else it should do to comply with the World Health Organisation's International Classification of Diseases version 11.

These codes are applied to all patient medical records so it is important that they are correct. It would also enable the NHS to provide more accurate data relating to e.g., ME/CFS prevalence – something it has consistently failed to be able to do. We will continue with our efforts to try and get SNOMED-CT to more accurately reflect the condition as we understand it.

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Information provided by The ME Association should not be construed as medical advice. Don't assume any new or worsened symptoms are simply the result of having ME/CFS or Long Covid. We recommend that any information you deem relevant is discussed with your NHS GP as soon as possible. It is important that you seek personalised medical advice from the GP who is in charge of your care and who knows you well.

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