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Note: This commentary is reproduced with permission from the website of the UK-based ME Association. Dr. Shepherd posted it in his personal capacity, and not as the association's honorary medical advisor.
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The decision by researchers on the American CFS Name Change Advisory Board (at their meeting in Florida on January 12, 2007) to agree that a new name should be adopted for Chronic Fatigue Syndrome (CFS) is obviously very welcome. At the same time, they have expressed support for the use of the term ME as myalgic encephalopathy (as this is "diagnostically accurate") rather than myalgic encephalomyelitis. This decision has once again opened up the debate over what is the most appropriate term to use to describe the clinical, examination, and pathological features of this illness.

What’s the Point of the Debate?

The reason so many clinicians and researchers now either refuse - or are extremely reluctant to use - the term ME as myalgic encephalomyelitis is due to the continuing lack of evidence to demonstrate that the principal pathological feature is a widespread inflammatory change taking place within the brain (i.e., encephalitis) and the spinal cord (i.e., myelitis).

And while there is undoubtedly some evidence of past or present inflammatory changes within the central nervous system taking place in some people with ME/CFS (mainly in research-defined CFS cases), this is not the sort of evidence that would confirm a diagnosis of encephalomyelitis to a neurologist.

Evidence of past or present inflammation within the central nervous system can have a number of explanations - and care needs to be taken to avoid drawing conclusions from existing research material (the results of neuroimaging studies in people with research-defined CFS in particular) that cannot be justified on scientific grounds.

Adopting this approach is also likely to be counter-productive when it comes to challenging medical opinion on the issue of nomenclature.

Consequently, some doctors, including myself, have proposed that the term encephalopathy should replace encephalomyelitis as the ‘E’ in ME, on the grounds that encephalopathy is a far more appropriate description of the neurological symptoms, signs, and investigative abnormalities that have been described in the literature.

Encephalopathy is also a term that doctors cannot simply dismiss on the grounds that it is pathologically inaccurate in relation to ME (or research-defined cases of CFS).

There does, however, continue to be considerable confusion over what an encephalopathy is - with some people claiming, quite wrongly, that it is a psychiatric diagnosis rather than a medical diagnosis.

Key Features of an Encephalopathy

To provide some clarification, the key features of an encephalopathy (all of which are consistent with ME/research-defined CFS) are listed below:

1. A significant and sometimes diffuse disorder of the brain that can involve changes to both structure and function.

2. A neurological disorder than can be caused by infections (viral, bacterial, prion), metabolic or mitochondrial dysfunction, exposure to toxins (such as drugs, chemicals, pesticides), or lack of oxygen or blood supply to the brain.

3. A disorder that commonly produces serious disturbances in cognitive function - involving memory, concentration, etc.

4. Other neurological symptoms that can be found in an encephalopathy include myoclonus (twitching of muscles or muscle groups), nystagmus (involuntary eye movements), tremor, muscle atrophy and weakness, disequilibrium (and unsteady gait), paraesthesiae (sensory disturbances), hypothalamic dysfunction, orthostatic intolerance, and postural hypotension.

5. More serious neurological symptoms, as described in section 4.2.1.2 of the Chief Medical Officer's report (such as seizures), can also be found in encephalopathies.

6. Mood disturbances can occur.

7. And abnormalities can be found on neuroimaging, spinal fluid examination, and electroencephalograms - depending on the cause of the encephalopathy.

A Few Examples of Encephalopathies

Examples of well recognized neurological encephalopathies include:

• Bovine spongiform encephalopathy ('mad cow disease')
• Coxsackie virus encephalopathy
• HIV encephalopathy (and AIDS dementia complex)
• Hepatitis C encephalopathy
• Liver (cirrhotic) encephalopathy
• Lyme disease encephalopathy
• Mycoplasma encephalopathy
• Sarcoid encephalopathy
• Wernicke's (thiamine deficiency) encephalopathy.

This is an important debate and I am pleased that it is now taking place in America as well as here in the UK.