What is an encephalopathy?

The decision by researchers on the
American CFS Name Change Advisory Board (meeting in Florida on 12
January 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.

The
reason why 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 (ie encephalitis) and the spinal cord (ie
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 CNS 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.

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 both changes to structure and function.

2
A neurological disorder than can be caused by infections (viral,
bacterial, prion), metabolic or mitochondrial dysfunction, exposure to
toxins (eg drugs, chemicals, pesticides), 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,
dysequilibrium (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 (eg seizures), can also be found in
encephalopathies.

6 Mood disturbances can occur.

7
Abnormalities can be found on neuroimaging, spinal fluid examination
and electroencephalogra ms – depending on the cause of the
encephalopathy.

Examples of well recognised 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.

Dr Charles Shepherd (UK)
[Posted in a personal capacity]