[INTEGRATED] NIGHTINGALE RESEARCH CONTINUUM DEFINITION OF 'MYALGIC ENCEPHALOMYELITIS' (IN PROGRESS)
INTEGRATED DEFINITION OF "MYALGIC ENCEPHALOMYELITIS"
Myalgic Encephalomyelitis (also known as "Enteroviral Encephalomyelitis") - M.E.
An integrated physician-facing definition derived from the 2006, 2007, 2011 and 2016 writings of Dr. Byron Hyde, together with his advice to primary-care physicians
PURPOSE OF THIS INTEGRATED DEFINITION
This document integrates Dr. Byron Hyde’s descriptions of Myalgic Encephalomyelitis across his 2006, 2007, 2011 and 2016 writings and his advice to primary-care physicians into a single clinically organized definition.
It is intended to preserve the epidemiological history, infectious onset, neurological disease pattern, enteroviral observations, pathological observations, objective investigations, vascular and physiological abnormalities, and acute and chronic enteroviral investigations described across those sources without repeatedly restating the same observation simply because it occurs in more than one document.
Where the later sources add specificity to an earlier observation, the information is integrated at the point to which it clinically belongs.
The resulting definition describes Myalgic Encephalomyelitis (M.E.), also known in this integrated formulation as Enteroviral Encephalomyelitis, as an acute-onset infectious neurological disease.
It is not defined by the symptom of chronic fatigue and is not treated here as 'synonymous' with Chronic Fatigue Syndrome (CFS), “ME/CFS” or Systemic Exertion Intolerance Disease (SEID).
The separate history and diagnostic architecture of CFS, the subsequent CFS criteria, CCC/“ME/CFS”, ICC, SEID and NICE 2021 ME/CFS are addressed only after the complete M.E./enteroviral disease definition, so that the enteroviral neurological disease is first understood on its own terms.
1. CORE DEFINITION
Myalgic Encephalomyelitis is described by Hyde as an acute-onset neurological disease following an infectious illness.
In the 2006 Little Red Book, Hyde begins his proposed definition with the description:
“A variable and biphasic acute onset disease”
and describes an initial infectious phase followed within a short interval by a second phase characterized by measurable diffuse central nervous system dysfunction.
The disease architecture is therefore fundamentally:
ACUTE INFECTIOUS ILLNESS
↓
BIPHASIC TRANSITION
↓
ACUTE NEUROLOGICAL DISEASE
↓
MEASURABLE CENTRAL NERVOUS SYSTEM DYSFUNCTION
↓
PERSISTENT NEUROLOGICAL AND SYSTEMIC DYSFUNCTION IN THOSE WHO DO NOT RECOVER
In Hyde’s later formulation, the etiological focus becomes increasingly specific to the enterovirus family.
The resulting disease concept is not constructed from prolonged fatigue. It begins with an infectious-neurological event and is investigated through the patient’s onset, neurological findings, physiological abnormalities, functional cerebral abnormalities, vascular abnormalities and virological evidence.
2. A BIPHASIC DISEASE
The distinction between the first infectious phase and the second neurological phase is fundamental.
The first phase may resemble an apparently ordinary infectious illness. It can initially appear influenza-like and may be sufficiently minor that its significance is not recognized at the time.
The second phase represents the development of the neurological disease.
Hyde’s 2006 definition places the transition from the initial infectious illness into the subsequent disease phase within approximately two to seven days.
This distinction is clinically important because the first illness can otherwise be retrospectively dismissed as an inconsequential viral infection while attention is directed only toward the persistent symptoms that follow it.
Hyde’s later advice to physicians also emphasizes that recognition of the two phases may vary with age. The biphasic pattern may be more obvious in children and younger patients, while an adult may not necessarily remember or recognize a relatively minor initial infectious illness once the neurological disease has become established.
Consequently, the initial infectious history should be reconstructed carefully rather than judged solely according to whether the patient remembers a dramatic influenza-like episode.
3. THE ACUTE NEUROLOGICAL TRANSITION
The clinically important event is the appearance of neurological disease following the infectious phase.
This transition can include disturbances involving:
cognition and concentration;
memory;
abstract thought;
motor function;
muscular power;
coordination;
balance;
visual and ocular-motor function;
sensory processing;
pain;
sleep regulation;
autonomic regulation;
vascular regulation;
temperature control;
gastrointestinal function;
and other systems dependent upon central neurological and homeostatic control.
The neurological disease therefore cannot adequately be characterized simply by describing the patient as “fatigued.”
Historical descriptions repeatedly include weakness, loss of muscular power, motor abnormalities, sensory disturbances, coordination abnormalities and other neurological signs.
Hyde’s definition consequently places importance upon measurable neurological and physiological dysfunction, not merely upon the subjective severity of symptoms.
4. EPIDEMIC, ENDEMIC AND SPORADIC DISEASE
The historical disease was observed both in epidemic/endemic settings and subsequently in sporadic cases.
Hyde regarded the epidemic literature as central to understanding the nature of M.E. because it preserved the infectious and neurological characteristics of the disease before later chronic-fatigue terminology was introduced.
By his reconstruction of what was known by 1958, M.E. followed a contagious epidemic and endemic infectious disease and represented a diffuse injury of the central nervous system, with the peripheral nervous system also affected in some cases and other organs and physiological systems sometimes involved.
Hyde considered the precipitating infection probably viral but did not claim that every historical epidemic had been virologically identified.
Rather, he stated that different epidemics appeared to have resulted from different neurotropic infectious agents; some were associated with ECHO viruses, some with other enteroviruses, while most were never virologically categorized.
This distinction is important. The historical evidence should not be rewritten to claim that the same enterovirus was demonstrated in every epidemic.
Hyde’s later argument was that different members of the enterovirus family are capable of producing the neurological disease phenotype.
5. INCUBATION AND EPIDEMIOLOGICAL PATTERN
Hyde gives an approximate incubation period of four to seven days between contact with the infectious illness and appearance of disease.
In epidemic settings, the disease was particularly observed among people living, studying or working in close proximity.
Groups described in the historical material include:
health-care workers;
children and older students in residential schools;
nurses living in nurses’ residences;
hospital populations;
and
students or soldiers living in military barracks.
These clustering patterns formed part of the evidence leading early investigators to regard the disease as infectious rather than as the simultaneous development of an 'unexplained' fatigue syndrome in unrelated individuals.
6. HISTORICAL RELATIONSHIP TO POLIOMYELITIS
The historical development of the M.E. concept cannot be separated from poliomyelitis.
Several of the epidemics subsequently associated with M.E. occurred during the era of epidemic poliomyelitis and produced illnesses sufficiently similar to poliomyelitis to create diagnostic uncertainty while failing to conform to classical paralytic polio.
Hyde emphasizes that patients from these outbreaks could be rejected as not having “true” poliomyelitis despite having a recognizable infectious neurological disease.
He personally states that he examined surviving patients from the Los Angeles epidemic, travelled to Iceland and examined patients associated with the Akureyri epidemic, examined patients associated with the Royal Free Hospital epidemics, and examined Newcastle sporadic illnesses. He regarded these illnesses as the same or closely related disease spectrum that had become known as Myalgic Encephalomyelitis.
The relationship to poliomyelitis is therefore not that M.E. is simply classical poliomyelitis under another name.
Rather, the historical problem concerned a polio-like infectious neurological disease that did not conform to classical paralytic poliomyelitis.
This becomes especially relevant to Hyde’s later emphasis upon non-polio enteroviruses, because polioviruses themselves belong to the enterovirus family and other enteroviruses are capable of neurological disease.
7. LOS ANGELES, 1934 - “ATYPICAL POLIOMYELITIS”
The 1934 Los Angeles outbreak is an important precursor in Hyde’s historical reconstruction.
The outbreak occurred among hospital personnel during the poliomyelitis era and became associated with the concept of “atypical poliomyelitis.”
Hyde gives particular importance to the later investigation of survivors by neurologist and electromyographer Alberto Marinacci.
Marinacci performed electromyographic investigations and reported diffuse peripheral nerve changes.
Hyde emphasizes that these abnormalities were not those of classical poliomyelitis and describes them as different from, although in some respects resembling, a mild Guillain–Barré syndrome.
This observation is significant because it demonstrates that the historical illness was not described solely in terms of subjective exhaustion or cognitive symptoms.
Objective peripheral neurological abnormalities were reported.
The Los Angeles observations therefore contribute to the broader integrated concept of an infectious neurological disease capable of affecting both central and peripheral neurological systems.
8. AKUREYRI, ICELAND
The Akureyri epidemic provides another important part of the historical neurological and enteroviral framework.
The disease appeared in an epidemic infectious setting and was followed in affected individuals by persistent neurological illness.
Hyde discusses three severely affected children who subsequently developed a Parkinson’s-like illness and died. He interprets the reported findings as indicating involvement of the basal ganglia in at least some patients.
This observation becomes relevant to Hyde’s later SPECT findings, in which basal-ganglia hypoperfusion is among the abnormalities he describes in M.E.
Hyde also reports personally seeing two British children with M.E. whose neurological presentation he considered capable of being described as Von Economo encephalitis-like or Parkinson’s-like.
These observations should not be converted into a claim that Parkinsonism is a defining feature of M.E. They demonstrate the range of central neurological involvement described in particularly severe cases.
The Akureyri epidemic also became historically important to the enterovirus hypothesis because of observations surrounding subsequent poliomyelitis exposure and the suggestion that the epidemic illness may have involved an agent related to, but distinct from, classical poliovirus.
That historical inference does not identify one specific enterovirus as the proven cause of every Akureyri case.
9. CUMBERLAND, 1955 - WALLIS’ “ENCEPHALOMYELITIS OF UNKNOWN ORIGIN”
The Cumberland outbreak is particularly important because Wallis left a detailed contemporary clinical description.
Hyde considered Wallis’ account sufficiently characteristic that, although Hyde did not personally examine the Cumberland patients, he regarded the outbreak as part of the M.E. epidemic disease history.
The outbreak began among children at a boarding school in early autumn and subsequently spread to people living in the surrounding area.
The initial illness was frequently interpreted by patients as a chill or influenza-like infection.
The more characteristic neurological disease could follow immediately or emerge several days later.
This again demonstrates the biphasic pattern:
INITIAL INFECTIOUS ILLNESS
↓
NEUROLOGICAL DISEASE
rather than a gradually accumulating fatigue syndrome.
10. WALLIS - EARLY CLINICAL MANIFESTATIONS
The early manifestations recorded by Wallis included a broad neurological and systemic symptom complex.
Patients described excessive tiredness, to the degree that ordinary work became burdensome.
Importantly, they also described difficulty walking because the legs felt as though they had lost power.
The phrase “lost power” is clinically important. It describes a disturbance of muscular or motor function and should not simply be replaced by the generic word “fatigue.”
Other early manifestations included:
unexplained sweating;
difficulty keeping warm;
dizziness;
unsteadiness;
intermittent headaches;
neuralgic pains, particularly around the eye or extending down the neck;
insomnia;
loss of clarity of thought;
impaired concentration;
intermittent aching in the legs and back;
pins and needles in the hands and feet;
and
blurred vision.
This early description already spans motor, sensory, autonomic, cognitive, pain, sleep and visual domains.
11. WALLIS - LATER NEUROLOGICAL SIGNS AND SYMPTOMS
As the illness developed, Wallis recorded a more extensive neurological phenotype.
Paraesthesiae occurred, including burning, prickling or formication that could arise without an external stimulus.
Hyperaesthesia and increased pain sensitivity were described.
There could be impairment or abnormal perception of taste and smell.
Vertigo and blurred vision occurred.
Cognitive and affective manifestations included loss of concentration, poor recent memory, diminished powers of abstract thought, and in some patients depression.
Motor and coordination abnormalities included:
general weakness;
motor dysfunction, generally muscular weakness;
impaired coordination;
unsteadiness;
ataxia;
and a positive Romberg sign.
Wallis gave practical examples of the coordination disorder. Patients could have difficulty:
walking accurately through a doorway;
pouring a cup of tea;
and
handling crockery without breaking it.
Sleep regulation could become disturbed, including inversion of the sleep rhythm.
Visual and ocular abnormalities included:
subjectively impaired visual acuity;
diplopia on upward and lateral gaze;
and
sluggish pupillary reactions to light and accommodation.
Syncope without epileptic evidence was reported.
Tremor occurred in approximately half of the cases described by Wallis and usually disappeared after several months.
These findings describe a changing neurological illness rather than a static fatigue state.
12. WALLIS - CHANGING REFLEXES AND THE NEED FOR REPEATED EXAMINATION
Wallis recorded an especially important longitudinal neurological observation.
Reflexes could be:
normal or decreased initially
and later become:
normal, increased or brisk.
The neurological examination could therefore change as the illness evolved.
This observation has direct clinical implications.
A normal or relatively unrevealing examination at one stage of the illness does not necessarily describe the neurological state at another stage.
The patient should therefore not be dismissed solely because one brief examination fails to reproduce abnormalities documented previously or abnormalities that emerge subsequently.
This historical observation is consistent with Hyde’s later primary-care recommendation for repeat neurological examinations during the course of the acute disease.
13. CUMBERLAND - LIMITED PATHOLOGICAL OBSERVATIONS
Hyde also reports pathological observations from two individuals who had suffered the Cumberland illness and later died.
He describes diffuse micro-haemorrhagic abnormalities associated with small cerebral blood vessels.
In one case, abnormalities were also reported in the basal-ganglia region.
That individual, however, also had Wilson’s disease, creating an important confounding factor.
Hyde himself explicitly cautions that the pathological material was not sufficient or clear enough to establish that the abnormalities had resulted from M.E.
These observations therefore belong in the historical pathological record but must remain appropriately qualified.
They are not evidence of a systematic autopsy series demonstrating identical lesions in all M.E. patients.
14. THE HISTORICAL DISEASE CONCEPT BY THE LATE 1950's
Bringing the early epidemic observations together, Hyde characterizes the historical disease as:
a disease following a contagious epidemic or endemic infectious illness;
a diffuse central nervous system injury, with peripheral nervous-system involvement in some patients;
a disease in which other organs and physiological systems could also become involved;
an illness following an infection that appeared probably viral;
and
a disease in which different epidemics could have different neurotropic infectious causes.
Some epidemics were associated with ECHO viruses and some with other enteroviruses, while most were never virologically categorized.
The historical definition therefore does not depend upon retrospective proof that every epidemic was caused by one identical virus.
It establishes the clinical and epidemiological framework from which Hyde’s later, more specifically enteroviral, definition developed.
15. ROYAL FREE HOSPITAL AND THE FORMAL M.E. DISEASE CONCEPT
The Royal Free Hospital outbreak of 1955 occupies an important position in the development of the disease concept that subsequently became known as Myalgic Encephalomyelitis.
Hyde places the Royal Free experience within the same historical sequence as Los Angeles, Akureyri, Cumberland and the later sporadic illnesses he examined.
The importance of this history is not simply that groups of patients developed prolonged symptoms after an infection. The historical disease being described was an acute infectious neurological illness, with evidence pointing toward involvement of the central nervous system and, in some patients, the peripheral nervous system and other physiological systems.
Hyde states that he personally examined patients associated with the Royal Free epidemics and regarded them as belonging to the same or closely related disease spectrum as the other epidemic and sporadic cases he investigated. In his historical synthesis he explicitly regarded these outbreaks as cases of Myalgic Encephalomyelitis.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
The Royal Free history therefore belongs within the development of the infectious-neurological M.E. disease concept, rather than being retrospectively defined merely by the presence of 'chronic fatigue'.
16. NEWCASTLE AND THE TRANSITION FROM EPIDEMIC TO SPORADIC DISEASE
Hyde also refers to Newcastle sporadic illnesses among the patients he personally examined.
This is important because the recognition of M.E. was not intended to depend upon the patient having been part of a conspicuous institutional epidemic.
The epidemic outbreaks helped reveal the disease because clustering made the infectious event visible. A clinically similar disease could nevertheless occur sporadically, without an obvious recognized outbreak surrounding the individual patient.
Thus, absence of a known epidemic exposure does not, within Hyde's model, convert an otherwise characteristic acute infectious neurological illness into CFS.
The disease concept progresses from:
EPIDEMIC INFECTIOUS NEUROLOGICAL DISEASE
to recognition of:
ENDEMIC AND SPORADIC INFECTIOUS NEUROLOGICAL DISEASE.
Hyde's historical statement is that many of the epidemic and sporadic illnesses he examined were the same or similar and that patients had sometimes been rejected because their disease was not classical poliomyelitis.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
17. WHY THE 'POLIOMYELITIS' COMPARISON MATTERS?
The historical comparison with poliomyelitis has several components and should not be reduced to the claim that M.E. is classical paralytic polio.
First, the early outbreaks occurred in the poliomyelitis era and could clinically resemble poliomyelitis.
Second, some patients demonstrated neurological abnormalities despite failing to satisfy the expected pattern of classical paralytic poliomyelitis.
Third, polioviruses belong to the enterovirus family.
Fourth, Hyde's later work increasingly focused upon other members of that same enterovirus family.
Fifth, some non-polio enteroviruses are themselves capable of producing serious central nervous system disease and flaccid motor syndromes.
The historical term “atypical poliomyelitis” therefore reflects the clinical problem encountered by physicians observing a polio-like epidemic neurological illness that did not behave exactly like classical poliomyelitis.
Within the integrated definition, the poliomyelitis comparison is principally virological, neurological, pathological and historical.
18. PATHOLOGICAL COMPARISON WITH POLIOMYELITIS
Hyde's 2006 discussion contains another observation that he considered important to the distinction between the two diseases.
He reports preserved cerebral tissue from a woman known to Dr. John Richardson as having typical M.E. According to Hyde, Dr. James Mowbray demonstrated an autoimmune inflammatory injury at the capillary level of the brain and basement membrane, the interface separating the capillaries from neurons and other brain tissue.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
Hyde describes this as anatomically analogous in its juxtaposition to inflammatory injury in poliomyelitis, but emphasizes a different principal location:
M.E. - brain
compared with
classical poliomyelitis - principally spinal cord, while acknowledging that 'poliovirus' can also injure subcortical brain structures.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
Hyde additionally reports that the spine of another UK M.E. patient had subsequently been examined and that an inflammatory process had also been found.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
These observations form part of Hyde's pathological argument for retaining 'encephalitis/encephalomyelitis' terminology rather than replacing it with the 'nonspecific' term 'encephalopathy'.
They must nevertheless be interpreted according to their evidentiary scale: they are individual reported pathological observations, not a large systematic neuropathological series demonstrating an identical lesion in every patient.
19. THE CAPILLARY / BASEMENT-MEMBRANE CONCEPT
Hyde's interpretation of the reported brain pathology is particularly vascular.
He describes the inflammatory injury as occurring at the capillary and basement-membrane interface within the brain.
In the Little Red Book he consequently characterizes the disease as a diffuse inflammatory injury involving the capillaries at the level of the brain's basement membrane.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
This concept later connects with Hyde's broader emphasis upon:
cerebral vascular dysfunction
regional cerebral hypoperfusion
SPECT abnormalities
and
systemic vascular abnormalities.
Those later physiological findings do not themselves prove the same microscopic lesion in every patient. They represent different levels of evidence that Hyde integrates into a vascular-neurological model.
20. INVESTIGATE AND SUBTYPE THE PATIENT
Hyde's response to the heterogeneity of neurological and systemic findings is not to discard the disease concept.
He argues instead for 'intensive investigation' and 'subtyping' according to the abnormalities actually demonstrated in the individual patient.
In the 2006 discussion, after describing the pathological material, he calls for physicians to return to:
investigating the patients
segregating them into sub-type injuries
and
working on treatment.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
This principle is fundamental to the integrated definition.
M.E. is not being defined as a requirement that every patient demonstrate every abnormality ever reported in the disease.
Rather:
the acute disease has a common infectious-neurological architecture, while the anatomical and physiological injuries demonstrated in individual patients may differ.
21. DIFFERENT NEUROTROPIC INFECTIONS IN THE HISTORICAL EPIDEMICS
Hyde's historical analysis explicitly cautions against assuming that every M.E. epidemic was caused by one identical infectious agent.
His 2006 summary states that M.E. followed an infection that was probably viral in nature, but that different epidemics appeared to have resulted from different neurotropic diseases.
He states:
some were definitely ECHO
and
some were other enteroviruses
while
most were never categorized.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
This is important for the integrated enteroviral definition.
The 'enterovirus hypothesis' is not dependent upon finding a single universal “M.E. virus.”
The later Hyde model instead proposes that multiple 'enteroviruses' can produce the disease.
22. THE 100-PATIENT OBSERVATION - 'ACUTE' VERSUS 'GRADUAL ONSET'
Hyde's own clinical investigation provides an important bridge between the historical epidemic observations and his later distinction between M.E. and CFS.
He describes a group of:
100 patients
divided into:
40 acute-onset cases
and
60 gradual-onset cases.
In this group, Hyde reports:
no suggestion of 'enteroviruses' among the 60 gradual-onset cases
while
10 of the 40 'acute-onset' cases had recoverable 'enteroviruses'.
Of those ten enterovirus-associated acute-onset cases:
2 followed transfusion
and
8 followed infection.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
The observation is important, but so is its limitation.
Hyde explicitly states:
“The cause in 90% of the cases remained a mystery.”
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
Therefore this particular study does not establish enterovirus in every 'acute-onset' patient.
What it demonstrates within Hyde's work is that acute and gradual onset were clinically meaningful variables, and that the recoverable enteroviruses in this group occurred within the acute-onset population rather than the gradual-onset population.
The detailed implications for Hyde's proposed 'gradual-onset' CFS population will be retained for the 'separate' CFS section at the end of this integrated definition.
23. ACUTE ONSET AS AN ETIOLOGICAL CLUE
Hyde's emphasis upon acute onset is therefore not simply a descriptive preference.
In his framework, onset contains etiological information.
A 'sudden' infectious disease followed by 'neurological deterioration' raises a different diagnostic question from a 'slowly developing illness' characterized principally by 'progressive fatigue'.
The physician should therefore establish:
What happened immediately before the illness?
Was there a recognizable infectious disease?
Was the onset 'abrupt' or 'gradual'?
Was there a biphasic transition?
When did neurological manifestations begin?
Which neurological manifestations were present during the acute phase?
Were samples collected during the acute infection?
Were other people ill at the same time?
Was the patient part of an institutional, family, school, hospital or community cluster?
These questions can contain information that is permanently lost if the history is reduced years later to:
“When did the fatigue begin?”
24. WHY FAILURE TO RECOVER AN 'ENTEROVIRUS' DOES NOT IDENTIFY THE ORIGINAL CAUSE?
Hyde repeatedly emphasizes the historical difficulty of recovering enteroviruses from patients.
This problem is not unique to M.E.
He uses poliomyelitis as an important comparison: even in recognized poliomyelitis, recovery of the causative virus from a living patient could be difficult depending upon timing, specimen and disease stage.
Enteroviral investigation therefore has a substantial temporal component.
A negative investigation performed long after the original infectious disease cannot reconstruct specimens that were never obtained during the acute phase.
Consequently:
failure to identify an enterovirus years later does not establish what caused the original acute neurological illness.
Conversely:
an acute infectious onset alone does not prove enterovirus.
The correct approach within Hyde's model is to seek virological evidence as early as possible, while simultaneously establishing the neurological disease objectively.
25. THE ENTEROVIRUS FAMILY
Hyde's later etiological model focuses upon the enterovirus family rather than a single viral subtype.
His discussions encompass:
polioviruses
Coxsackie A viruses
Coxsackie B viruses
ECHO viruses
and
other numbered non-polio enteroviruses.
This family-level approach is essential because different enteroviruses can have different tissue tropisms and neurological expressions.
It also provides the biological context for the historical relationship between classical poliomyelitis, non-polio enteroviral neurological disease and the disease Hyde identifies as M.E.
26. POLIOVIRUS AND NON-POLIO ENTEROVIRUSES
Hyde's 2016 discussion emphasizes the relationship between polioviruses and other enteroviruses while also attempting to distinguish their characteristic neurological patterns.
In Hyde's proposed model, classical poliovirus disease has a particular tendency toward severe involvement of the spinal cord and brainstem, producing the familiar paralytic poliomyelitis phenotype.
By contrast, the enteroviral disease he identifies with M.E. is described as having prominent involvement of the upper central nervous system/brain, although this distinction is not absolute.
This is Hyde's anatomical model, rather than a rule that a non-polio enterovirus cannot affect the spinal cord or that poliovirus cannot affect the brain.
Indeed, Hyde explicitly recognizes exceptions to such a simple division.
27. NON-POLIO ENTEROVIRUSES CAN PRODUCE FLACCID PARALYSIS
Hyde specifically notes that non-polio enteroviruses can produce flaccid paralysis simulating poliomyelitis.
The examples identified in the 2016 material are:
EV-68
and
EV-71.
This point is important because it prevents the enteroviral M.E. model from being artificially restricted to the cerebral cortex.
A non-polio enteroviral neurological disease can extend into structures responsible for lower-motor-neuron and flaccid motor function.
Where such structures are affected, the phenotype may overlap with an:
ENTEROVIRAL POLIOMYELITIS-LIKE SYNDROME
or
ACUTE FLACCID MOTOR / MYELITIC SYNDROME.
The precise anatomical diagnosis should depend upon the structures demonstrated as involved in the individual patient.
28. ANATOMICAL CONTINUUM OF ENTEROVIRAL CNS DISEASE
This allows the source material to be integrated anatomically without pretending that every patient has an identical distribution of CNS injury.
Depending upon the structures involved, enteroviral neurological disease can overlap with:
ENTEROVIRAL MENINGITIS
where the meninges are principally involved;
ENTEROVIRAL MENINGOENCEPHALITIS
where meningeal and cerebral involvement coexist;
ENTEROVIRAL ENCEPHALITIS
where brain parenchymal involvement predominates;
ENTEROVIRAL BRAINSTEM ENCEPHALITIS / RHOMBENCEPHALITIS
where brainstem structures are significantly involved;
ENTEROVIRAL LIMBIC ENCEPHALITIS
where limbic structures are significantly involved;
ENTEROVIRAL ENCEPHALOMYELITIS
where brain and spinal-cord involvement coexist;
ENTEROVIRAL MENINGOENCEPHALOMYELITIS
where meninges, brain and spinal cord are involved;
and
ENTEROVIRAL POLIOMYELITIS-LIKE / ACUTE FLACCID MOTOR DISEASE
where spinal motor/anterior-horn or related lower-motor-neuron structures are significantly involved.
This is an anatomical integration of the disease spectrum. It should not be attributed to Hyde as though he wrote this exact classification as a single list.
Its purpose is to make the neurological relationships intelligible to a physician while preserving the different anatomical manifestations discussed in the source material.
29. THE BRAIN INJURY IS NOT REQUIRED TO BE ANATOMICALLY IDENTICAL IN EVERY PATIENT
Hyde's model repeatedly emphasizes variation in the distribution of neurological injury.
One patient may demonstrate more prominent:
cortical dysfunction
while another may demonstrate:
basal-ganglia dysfunction
motor-cortex dysfunction
brainstem manifestations
autonomic dysfunction
spinal or peripheral motor abnormalities
or a combination of these.
Therefore the disease should not be reduced to one obligatory focal brain lesion.
The common concept is an acute infectious neurological disease with measurable CNS dysfunction, with the anatomical expression established through the patient's history, serial neurological examination and appropriate investigations.
30. THE RUCHILL HOSPITAL ENTEROVIRUS INVESTIGATIONS
Hyde's later enteroviral model draws heavily upon longitudinal investigations associated with Ruchill Hospital in Glasgow.
In his 2016 account, Hyde describes work beginning around 1984 and continuing into the 1990's.
He states that the Nightingale Research Foundation obtained quarterly blood specimens from more than:
70 disabled post-infectious M.E. patients
together with approximately:
30 controls.
These samples were investigated at Ruchill by D. N. Galbraith and Carron Nairn, in the laboratory associated with Eleanor Bell.
The longitudinal design is important.
Rather than depending upon one isolated blood specimen, patients were sampled repeatedly over time.
31. WHY LONGITUDINAL SAMPLING MATTERS?
Enteroviral evidence may vary according to:
stage of infection
specimen type
timing of collection
and
the laboratory method used.
Repeated sampling can therefore provide information that a single late specimen may fail to capture.
Within Hyde's argument, the Ruchill work was particularly important because it investigated post-infectious patients longitudinally and attempted to characterize the 'enteroviruses' associated with them rather than simply reporting an undifferentiated positive/negative result.
32. ENTEROVIRUS SUBTYPES AND PHYLOGENETIC DIVERSITY
Hyde reports that the Ruchill investigations were able to identify a significant number of enterovirus subtypes in samples associated with 20 Canadian and American M.E. patients.
The phylogenetic material reproduced in the 2016 definition includes reference viruses and branches involving:
ECHO 3
ECHO 4
ECHO 7
ECHO 9
ECHO 11
ECHO 20
Coxsackie A9
Coxsackie A31
Coxsackie A34
Coxsackie B1
Coxsackie B4/B4A
Coxsackie B5
together with other enteroviruses represented within the comparison.
Polioviruses are also represented within the phylogenetic material.
Hyde's conclusion from this work is:
“many different enteroviruses are capable of causing M.E.”
This is Hyde's interpretation of the investigations and should be identified as such rather than silently converted into an independently established universal proposition.
33. THE “ECHO-21 LIKE ENTEROVIRUS”
Hyde's 2016 material additionally identifies an:
“ECHO-21 Like Enterovirus.”
In discussing the phylogenetic figure, he describes many of the enterovirus-positive M.E. cases represented there as occupying what he regarded as a newly discovered branch of the enteroviral tree.
This observation is relevant because Hyde's model is not restricted to the standard proposition:
one named Coxsackie virus = M.E.
Instead, his later formulation treats M.E. as a neurological disease that may be produced by different enteroviruses.
The ECHO-21-like material belongs within that broader enteroviral diversity argument.
It is not proposed as a compulsory viral subtype that must be demonstrated in every patient.
34. ACUTE ENTEROVIRUS IDENTIFICATION IN HYDE'S PATIENTS
Hyde's 2016 definition additionally states that acute enterovirus identification in the M.E. patients he discusses had been made through:
the Government of Ontario Health Services
and
D. N. Galbraith and Carron Nairn, previously of Ruchill Hospital, Glasgow.
� The Nightingale Research Foundation Definition (2016).pdf
This acute evidence becomes important when considered alongside Hyde's later discussion of chronic enteroviral evidence in gastric tissue.
The two observations concern different stages and different specimens:
ACUTE DISEASE → attempts to identify the infecting enterovirus
versus
ESTABLISHED/CHRONIC DISEASE → investigation for evidence of persistent enterovirus.
They should therefore not be treated as interchangeable tests.
35. THE CENTRAL ENTEROVIRAL PROPOSITION
The enteroviral evidence integrated thus far produces the following source-derived progression:
Historical epidemics were infectious and neurological.
↓
Some historical outbreaks were associated with ECHO or other enteroviruses, while many were never virologically categorized.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
↓
Hyde's 100-patient observation recovered enteroviruses from a subset of 'acute-onset' patients but not from his 'gradual-onset' group.
� A new and simple definition of Myalgic Encephalomyelitis and a new simple definition of Chronic Fatigue Syndrome (The Little Red Book) (2006).pdf
↓
Longitudinal Ruchill investigations contributed further enteroviral evidence and subtype/phylogenetic information.
↓
Hyde's later definition argues that multiple different enteroviruses can cause the M.E. disease phenotype.
↓
Later tissue investigations are incorporated into Hyde's argument for persistent enteroviral involvement in established disease.
The next clinical question is therefore not merely whether “an enterovirus test” was positive or negative.
It is:
which specimen was tested, at what stage of illness, using which method, and what form of enteroviral evidence was actually being sought?
That question leads directly into the complete acute and chronic enterovirus investigation framework, which must be integrated alongside Hyde's neurological, SPECT, vascular and pathological investigations rather than treated as a single laboratory test.
36. ENTEROVIRAL INVESTIGATION IS STAGE-DEPENDENT
Hyde's enteroviral investigation cannot be reduced to a single laboratory test.
The appropriate investigation depends upon when in the disease course the patient is examined, what biological material remains available, and what type of enteroviral evidence is being sought.
The integrated investigative model therefore separates:
A. THE ACUTE INFECTIOUS / NEUROLOGICAL PHASE
from
B. THE ESTABLISHED OR CHRONIC NEUROLOGICAL PHASE.
During the acute illness, the objective is to investigate the infectious agent as close as possible to the disease onset, while simultaneously documenting the neurological disease.
During established disease, the diagnostic opportunity has changed. Acute specimens may no longer be available, and the physician may instead have to consider serological evidence, previous laboratory records, archived specimens, tissue evidence and persistent objective neurological abnormalities.
A negative late investigation therefore cannot be interpreted as though it were an acute specimen collected during the original infection.
37. HYDE'S SIX ENTEROVIRAL TESTING APPROACHES
Hyde's 2016 definition contains a specific section on Enteroviral (EV) Testing.
He identifies six approaches:
1. Rising titres to specific enteroviruses at disease onset
2. Mowbray/Yousef monoclonal-antibody testing
3. Bell ELISA antibody testing for enterovirus
4. Chia gastric-mucosa testing
5. Various stool tests for enterovirus
6. PCR testing.
These methods investigate different forms of evidence.
They should therefore not be collapsed into the question:
“Was the patient tested for enterovirus?”
A physician instead needs to establish:
what test was performed;
which specimen was examined;
when it was collected in relation to onset;
whether the investigation concerned acute infection, antibody response, viral nucleic acid or tissue evidence;
and
whether repeat specimens were obtained.
38. ENTEROVIRUS TITRES AT ONSET
The first approach Hyde identifies is the demonstration of rising titres to specific enteroviruses at the onset of the disease.
The significance lies in change over time rather than treating one isolated antibody measurement as automatically establishing causation.
This makes timing important.
If a physician first sees the patient during the acute illness, appropriate samples should be obtained while the opportunity exists.
If the patient is first investigated months or years after onset, the diagnostic question is different and the absence of a contemporaneous rising titre cannot retrospectively recreate an acute serological series that was never collected.
Hyde's primary-care advice consequently places particular emphasis upon investigating the patient at or close to onset.
39. THE ANTIBODY RESPONSE DURING THE EARLY MONTHS
Hyde does not regard the opportunity for antibody investigation as disappearing immediately after the acute illness.
In his advice to primary-care physicians, he states that when the patient is encountered during the chronic second phase, enteroviral antibody investigation may remain worthwhile during the first several months and, in some patients, for approximately the first year.
He describes the antibody response as relatively slow.
This creates a practical distinction:
ACUTE ONSET
→ obtain appropriate acute virological material and serial samples wherever possible;
EARLY ESTABLISHED DISEASE
→ antibody investigation may still provide useful information;
LATE ESTABLISHED DISEASE
→ acute serology becomes progressively less capable of reconstructing what occurred at onset, increasing the relevance of historical records, archived samples, tissue investigation and persistent neurological abnormalities.
40. MOWBRAY / YOUSEF MONOCLONAL-ANTIBODY TESTING
Hyde separately lists Mowbray/Yousef monoclonal-antibody testing among the methods used in the investigation of enterovirus.
This belongs to the historical laboratory evidence incorporated into Hyde's enteroviral model.
It should be preserved as a distinct methodology rather than being incorrectly rewritten as PCR or ordinary enterovirus serology.
The fact that Hyde lists several different methods reflects an important feature of his approach:
no single historical enterovirus assay encompasses all of the forms of evidence that were investigated.
41. BELL ELISA ENTEROVIRUS ANTIBODY TESTING
Hyde separately identifies Bell ELISA antibody testing for enterovirus.
This connects with the work associated with Eleanor Bell and Ruchill Hospital, already described in the longitudinal enterovirus section.
Again, antibody evidence is not equivalent to:
viral isolation
PCR evidence
or
viral protein demonstrated in tissue.
Each result has to be interpreted according to the method actually used.
42. STOOL INVESTIGATION
Hyde includes various stool tests for enterovirus among his six investigative approaches.
Stool is particularly relevant to enteroviruses because these viruses can involve and be shed through the gastrointestinal tract.
In the acute investigation, Hyde's physician guidance includes obtaining stool for enterovirology.
The clinical value of a stool specimen is consequently dependent upon timing, laboratory methodology and the particular enterovirus involved.
A stool test obtained during or close to an acute enteroviral disease does not answer the same question as a stool test performed years into an established neurological illness.
43. PCR
Hyde lists PCR testing as another distinct enteroviral investigative approach.
PCR seeks evidence of viral nucleic acid and must therefore be distinguished from:
antibody titres
ELISA antibody investigation
monoclonal-antibody methods
and
tissue immunohistochemical evidence.
The specimen tested is critical.
A negative PCR result from one specimen at one stage of disease cannot automatically be generalized to every anatomical compartment or to the original acute infection.
Equally, PCR positivity must be interpreted according to the specimen, timing and clinical context.
The integrated definition therefore does not designate a single negative late PCR as a universal exclusion test for the historical acute disease.
44. GASTRIC-MUCOSAL INVESTIGATION - JOHN CHIA
Hyde's later enteroviral formulation incorporates the work of Dr. John Chia concerning evidence of enterovirus in gastric mucosa.
This is particularly relevant to patients who are no longer in the acute infectious phase.
Hyde draws attention to an important practical point: patients who previously underwent gastroscopy/endoscopy with gastric biopsy may already have tissue preserved by the pathology department.
Such biopsy material may have been embedded in paraffin blocks and retained after the original gastrointestinal investigation.
It may therefore be possible to return to the original pathology material and obtain unstained sections for appropriate enteroviral investigation rather than subjecting the patient automatically to another invasive procedure.
This creates an additional historical diagnostic resource:
previously collected tissue may contain information relevant to an infectious disease that was not being investigated when the biopsy was originally taken.
45. THE 20-PATIENT GASTRIC-TISSUE OBSERVATION
Hyde reports a specific observation involving 20 of his M.E. patients whose gastric tissue was investigated by Chia.
In Hyde's account, chronic enteroviral evidence was demonstrated in the gastric-mucosal material from all 20 patients in that particular group.
Hyde contrasts this with comparator gastric material supplied through Memeo and Timpanaro, in which he reports that enterovirus evidence was not demonstrated.
This observation needs to be represented exactly at its evidentiary scale.
It is:
a reported finding in a particular group of 20 Hyde patients whose tissue was investigated
and not:
a requirement that every person with M.E. must have a positive gastric biopsy.
Nor does a positive gastric-tissue result by itself specify the precise anatomical distribution of the patient's neurological injury.
The neurological disease and the virological evidence remain related but distinct components of the investigation.
46. LINKING ACUTE AND CHRONIC ENTEROVIRAL EVIDENCE
Hyde considered the gastric findings especially important because some of the patients had also had enterovirus identified during the acute illness through the Ontario Government Health Services and/or the Ruchill-associated investigations of Galbraith and Nairn.
In Hyde's interpretation, this creates a possible longitudinal relationship:
ACUTE ENTEROVIRAL DISEASE
↓
ACUTE NEUROLOGICAL ILLNESS
↓
PERSISTENT NEUROLOGICAL DISEASE
↓
LATER ENTEROVIRAL EVIDENCE IN GASTRIC TISSUE.
This relationship forms part of Hyde's argument for persistent enteroviral involvement.
It should nevertheless be described as Hyde's interpretation of the evidence rather than as proof that an identical mechanism has been demonstrated in every patient.
47. ENTEROVIRAL PERSISTENCE AND THE DIAGNOSTIC MODEL
Hyde's later definition therefore moves beyond the simple question of whether a patient once had an acute viral infection.
The model asks whether an enterovirus:
initiated the acute disease
and whether:
evidence of that enteroviral infection can persist or subsequently be demonstrated in tissue.
This is conceptually different from saying that every patient with chronic neurological symptoms necessarily has freely circulating virus detectable in blood.
Persistence may have to be investigated using the appropriate tissue and methodology.
The diagnostic model consequently distinguishes:
acute enterovirus detection
from
evidence compatible with persistent enteroviral infection.
48. ENTEROVIRUS AND LOCALIZED MYOSITIS
Hyde's enteroviral discussion is not restricted to the central nervous system or gastrointestinal tissue.
He cites the work of Leonard C. Archard in relation to enteroviral infection and muscle and states:
“EV infection causing localized myositis has also been demonstrated.”
This provides another potential anatomical component of enteroviral disease.
It is important, however, not to use this observation to collapse all muscular dysfunction in M.E. into viral myositis.
Hyde's own model contains several possible contributors to motor and muscular disability, including:
central motor dysfunction
cerebral hypoperfusion
spinal/peripheral neurological dysfunction
vascular abnormalities
and
localized muscular pathology.
The patient's actual mechanism therefore requires investigation.
49. THE NEUROLOGICAL DIAGNOSIS CANNOT DEPEND UPON VIROLOGY ALONE
Although enteroviruses become central to Hyde's later etiological formulation, his definition does not reduce M.E. to a laboratory result in isolation.
The disease remains fundamentally neurological.
The physician must establish:
the nature of the onset
the infectious history
the biphasic development
the neurological manifestations
objective CNS dysfunction
the anatomical distribution of neurological abnormalities
and the available virological evidence.
This distinction prevents two opposite diagnostic errors:
ERROR 1: diagnosing an enteroviral neurological disease solely because an enterovirus-related laboratory result exists, without demonstrating a compatible neurological illness;
ERROR 2: ignoring an acute infectious neurological disease because an enterovirus was not recovered from a late or inappropriate specimen.
50. REPEATED NEUROLOGICAL EXAMINATION
Hyde's advice to primary-care physicians emphasizes repeated neurological examination.
This is consistent with the historical Wallis observations already integrated, where neurological signs - including reflex abnormalities - changed during the disease.
The neurological examination should therefore consider, according to the patient's presentation:
cranial-nerve function
ocular movements
pupillary responses
motor power
muscle tone
deep-tendon reflexes
plantar responses
coordination
gait
Romberg testing
sensory abnormalities
tremor
balance
cognitive function
and other relevant neurological signs.
The purpose is not to require every listed abnormality.
It is to localize and document the neurological disease actually present in the individual patient.
51. COGNITIVE AND NEUROPSYCHOLOGICAL DYSFUNCTION
Hyde's neurological model includes measurable abnormalities of higher cerebral function.
Historical descriptions already include:
loss of concentration
poor recent memory
impaired abstract thought
and
loss of clarity of thought.
Hyde's later definition includes measurable neuropsychological abnormalities among the supportive objective findings that can occur.
These abnormalities should be distinguished from the nonspecific statement that a patient has “brain fog.”
A physician-facing definition should instead ask:
Which cognitive domain is impaired?
Can the impairment be demonstrated?
Does it fluctuate with disease activity?
Does intellectual activity worsen neurological function?
Does the pattern correspond with other objective CNS abnormalities?
52. FUNCTIONAL CEREBRAL IMAGING - WHY HYDE EMPHASIZES SPECT?
Hyde places substantial diagnostic importance upon brain SPECT because it assesses cerebral perfusion rather than simply gross structural anatomy.
This is a different diagnostic question from conventional CT or MRI.
A structurally unremarkable scan does not necessarily demonstrate normal cerebral perfusion or normal neurological function.
Hyde's physician guidance therefore includes functional cerebral investigation rather than treating normal conventional structural imaging as proof that the brain is functioning normally.
53. THE SEGAMI SPECT METHOD
Hyde particularly emphasizes the Segami method of SPECT analysis.
His physician advice distinguishes the Segami approach from a conventional visual interpretation of SPECT images.
The purpose is to identify and quantify regional cerebral perfusion abnormalities that may otherwise be underestimated or missed.
Within Hyde's diagnostic model, the question is therefore not simply:
“Was a SPECT scan performed?”
but:
what method was used, how was the scan analyzed, and were regional perfusion abnormalities quantitatively assessed?
This methodological distinction is important to understanding why Hyde places more weight on some SPECT investigations than others.
54. SPECT AND THE “TESTABLE BRAIN CHANGE”
Hyde's 2007 Nightingale definition makes the concept of a testable brain change central to his attempt to define M.E. objectively.
The disease is therefore not defined simply by the patient's report of neurological symptoms.
Hyde seeks objective evidence that the CNS has changed following the acute disease.
SPECT is one of the principal methods he uses for this purpose.
Other neurological investigations remain important, but functional cerebral perfusion abnormalities occupy a particularly prominent place in his later definition.
55. REGIONAL 'CEREBRAL HYPOPERFUSION'
Hyde describes regional 'cerebral hypoperfusion' rather than requiring one identical perfusion defect in every patient.
Regions discussed across the material include:
temporal regions
cingulate regions
motor cortex
basal ganglia
and other cortical/subcortical areas depending upon the individual patient.
The distribution therefore contributes to neurological localization and patient subtyping.
A basal-ganglia abnormality, for example, may have different clinical implications from predominant motor-cortex or temporal-region dysfunction.
56. BASAL-GANGLIA HYPOPERFUSION
Hyde includes basal-ganglia hypoperfusion on SPECT among the supportive laboratory findings in his 2016 definition.
This finding has historical resonance with the Akureyri material and Hyde's descriptions of Parkinsonian/Von-Economo-like neurological manifestations in particularly severe cases.
It should not, however, be converted into a requirement that every patient demonstrate basal-ganglia hypoperfusion.
Hyde explicitly describes the 2016 laboratory findings in this category as not invariably present and not essential to his laboratory diagnosis.
The correct formulation is therefore:
basal-ganglia hypoperfusion can support and anatomically characterize the neurological disease where demonstrated.
57. MOTOR-CORTEX HYPOPERFUSION
Hyde also discusses motor-cortex hypoperfusion in relation to motor and muscular dysfunction.
This is particularly relevant to the historical complaint that the patient's limbs may feel as though they have lost power.
Within Hyde's model, abnormal muscular performance can therefore have a central neurological component.
This prevents the patient's physical deterioration from automatically being interpreted as ordinary deconditioning or subjective tiredness.
At the same time, the existence of central motor dysfunction does not exclude simultaneous peripheral or muscular pathology.
58. PHYSICAL ACTIVITY CAN WORSEN 'CEREBRAL HYPOPERFUSION'
Hyde reports repeated SPECT observations in which physical activity was followed by greater 'cerebral hypoperfusion'.
This is important because it provides an objective physiological correlate for deterioration following exertion in at least some of the patients he investigated.
The sequence becomes:
PHYSICAL ACTIVITY
↓
WORSENING CEREBRAL PERFUSION
↓
WORSENING NEUROLOGICAL FUNCTION
↓
PROLONGED RECOVERY TOWARD THE PATIENT'S PREVIOUS BASELINE.
This should not be reduced to the generic statement that “exercise makes the patient tired.”
59. 'INTELLECTUAL ACTIVITY' CAN ALSO WORSEN 'CEREBRAL FUNCTION'
Hyde's observations are not confined to physical exertion.
He also describes deterioration associated with intellectual activity.
This is clinically important because it suggests that the relevant stressor can be increased central nervous system demand, not simply skeletal-muscle work.
A patient may therefore deteriorate following:
sustained reading
complex conversation
problem solving
concentration
or other cognitively demanding activity,
even when little physical exercise has occurred.
This provides a neurological rationale within Hyde's model for separating central functional deterioration from ordinary muscular fatigue.
60. DELAYED DETERIORATION AFTER ACTIVITY
Hyde's 2016 material describes the 'cerebral hypoperfusion' as potentially becoming more severe approximately:
24-48 hours after significant activity.
This delayed deterioration is important.
The patient's condition immediately after activity may therefore fail to represent the maximum physiological consequence of that activity.
A clinical assessment confined to the immediate post-activity period can miss the delayed component.
61. PROLONGED RESTORATION OF FUNCTION
Hyde additionally reports that recovery of 'cerebral perfusion' toward the patient's previous 'abnormal baseline' can require:
approximately one week or longer.
Thus, the activity-related phenomenon in Hyde's model is not simply:
activity → transient tiredness → rapid recovery.
It can instead be:
activity
↓
delayed neurological/physiological deterioration
↓
prolonged loss of function
↓
slow restoration toward the previous baseline.
The previous baseline itself may remain abnormal.
62. ABNORMAL 'MUSCLE FATIGABILITY' AND 'LOSS OF MUSCLE POWER'
The historical M.E. literature repeatedly emphasizes abnormal 'muscle fatigability' and prolonged 'restoration of muscle power' following exertion.
This needs to be distinguished from a 'nonspecific' feeling of fatigue.
Clinically, the phenomenon concerns what the muscle or motor system can do after activity, not simply how tired the patient feels.
It may manifest as:
reduced muscular power
difficulty repeating previously possible movement
limb weakness
impaired walking
loss of motor endurance
and
prolonged restoration of function.
In an individual patient, the mechanism may involve central motor dysfunction, peripheral neurological dysfunction, vascular abnormalities, muscle pathology, or more than one of these.
63. POST-EXERTIONAL 'MOTOR WEAKNESS' IS 'NOT SYNONYMOUS' WITH “MALAISE”
For clinical precision, 'post-exertional loss of muscle power' should not automatically be replaced by the broader term 'post-exertional malaise'.
“Malaise” describes a subjective state of illness.
'Motor weakness' or 'loss of muscle power' describes 'impaired function'.
The distinction matters when reconstructing the historical M.E. phenotype because the earlier descriptions include; paresis, weakness, abnormal muscle fatigability and prolonged restoration of muscular power.
A physician should therefore document the actual motor phenomenon rather than translating every exertional abnormality into one later symptom label.
64. THE NEUROLOGICAL AND MUSCULAR COMPONENTS CAN OVERLAP
The integrated disease model consequently permits several overlapping mechanisms:
CEREBRAL / MOTOR-CORTEX DYSFUNCTION
↓
impaired central motor output
SPINAL OR LOWER-MOTOR-NEURON INVOLVEMENT
↓
weakness, paresis or flaccid motor abnormalities
PERIPHERAL NERVOUS-SYSTEM INVOLVEMENT
↓
weakness and sensory/motor abnormalities
MUSCLE INVOLVEMENT
↓
myalgia, localized myositis or impaired muscle performance
VASCULAR / PERFUSION ABNORMALITIES
↓
impaired physiological support of neurological and muscular function.
The physician's task is therefore to localize and characterize the dysfunction, not merely record “fatigue.”
65. STRUCTURAL NEUROIMAGING - MRI AND MRA
Hyde's primary-care advice includes:
MRI and MRA using an MS protocol.
The purpose includes investigating structural and vascular neurological disease and assisting differential diagnosis.
MRI and MRA therefore occupy a different role from SPECT:
MRI/MRA
→ structural and vascular investigation;
SPECT
→ functional cerebral perfusion investigation.
A patient may have important functional cerebral abnormalities without a conventional structural scan showing an equivalent lesion.
Conversely, a structural abnormality may identify an alternative or additional neurological diagnosis that requires its own management.
66. CT DOES NOT ANSWER THE SAME QUESTION
Hyde's physician material is particularly dismissive of relying upon routine CT brain scanning for the disease process he is attempting to demonstrate.
The underlying diagnostic principle is more important than the rhetoric:
a test should be selected according to the pathology or physiological abnormality being investigated.
A conventional CT scan cannot substitute for:
MRI/MRA where structural or vascular neurological detail is required
or
functional cerebral perfusion imaging where that is the question being investigated.
67. LUMBAR PUNCTURE AND CEREBROSPINAL FLUID
Hyde's acute physician pathway includes lumbar puncture and CSF investigation.
This is clinically consistent with an acute disease being considered within the encephalitic/encephalomyelitic spectrum.
Across the supplied Hyde material, possible CSF abnormalities include:
mildly increased CSF pressure
oligoclonal bands
and
leukocytosis during the earlier illness.
Enteroviral investigation may also be relevant according to disease stage and available methodology.
These abnormalities are not presented as universally present.
Indeed, Hyde's 2016 definition explicitly places several of these CSF findings among abnormalities that may occur but are not invariably present and are not essential to his laboratory diagnosis.
68. ABSENCE OF ONE CSF ABNORMALITY DOES NOT DEFINE THE WHOLE DISEASE
Because the reported CSF abnormalities are variable, the integrated definition does not require:
oligoclonal bands in every patient
or
persistent CSF leukocytosis in every chronic case.
Timing is again important.
An inflammatory CSF abnormality present during the acute neurological illness may no longer be detectable years later.
The CSF result must therefore be interpreted in relation to:
the stage of disease
the neurological presentation
the tests actually performed
and
the other objective findings.
69. NEUROPSYCHOLOGICAL TESTING
Hyde includes measurable neuropsychological abnormalities among the supportive objective findings in his later definition.
Formal neuropsychological investigation can help characterize:
attention
processing efficiency
memory
executive/abstract function
and other cognitive domains affected in an individual patient.
Again, this is not a requirement that every patient demonstrate one identical psychometric profile.
The purpose is objective characterization of the neurological dysfunction.
70. THE OBJECTIVE NEUROLOGICAL INVESTIGATION AS A WHOLE
The neurological component of the integrated definition should therefore be investigated through a combination appropriate to the individual patient:
detailed history of the acute infectious and neurological onset
serial neurological examination
MRI/MRA where indicated
functional cerebral imaging/SPECT within Hyde's proposed approach
lumbar puncture and CSF investigation where clinically indicated
neuropsychological assessment where appropriate
motor/peripheral neurological investigation where indicated
and
virological investigation appropriate to the disease stage.
No single test should be detached from the clinical disease and treated as the whole definition.
The purpose of the investigation is to demonstrate, localize and characterize the neurological disease process.
71. FROM NEUROLOGICAL INJURY TO SYSTEMIC PHYSIOLOGICAL DYSFUNCTION
Hyde's definition does not end with the brain scan.
His later writings describe abnormalities involving vascular regulation, circulating blood volume, cardiovascular function, autonomic regulation, endocrine systems, sleep physiology, immune function and gastrointestinal tissues.
These observations are important because the patient can present with widespread physiological consequences despite the disease being conceptualized principally as an infectious neurological disorder.
The next part of the integrated definition therefore addresses those vascular, autonomic, cardiovascular, endocrine, gastrointestinal, immune and systemic abnormalities, while preserving Hyde's distinction between findings he regarded as central and findings he explicitly described as supportive or variable.
72. VASCULAR DYSFUNCTION AS PART OF HYDE'S DISEASE MODEL
Hyde's later formulation of M.E. does not treat the neurological abnormalities as isolated from the vascular system.
His model repeatedly connects neurological dysfunction with abnormalities of cerebral and systemic circulation.
This is consistent with several different observations already established in this integrated definition:
the limited historical micro-haemorrhagic observations around small cerebral vessels;
the reported capillary/basement-membrane inflammatory injury;
regional cerebral hypoperfusion demonstrated by SPECT;
activity-associated worsening of cerebral perfusion;
and
abnormalities of circulating blood volume and cardiovascular function described in later patients.
These findings should not be collapsed into a claim that one vascular lesion has been demonstrated universally.
They represent different observations that Hyde incorporates into a broader neurological-vascular disease model.
73. CEREBRAL PERFUSION IS FUNCTIONALLY IMPORTANT
Within this model, cerebral blood flow is not simply an incidental imaging measurement.
Reduced perfusion of a neurological region may affect the function dependent upon that region.
Consequently, the anatomical distribution of hypoperfusion may help explain why individual patients have different combinations of:
cognitive dysfunction;
motor dysfunction;
coordination abnormalities;
sensory abnormalities;
autonomic abnormalities;
and
other neurological manifestations.
This is one reason Hyde places emphasis upon regional, rather than merely global, cerebral perfusion.
74. SYSTEMIC VASCULAR INVOLVEMENT
Hyde's 2007 Nightingale definition extends the vascular concept beyond the brain.
His model includes the possibility of peripheral vascular dysfunction and abnormalities in the distribution and regulation of blood flow.
A physician should therefore not assume that symptoms involving:
cold extremities;
changes in skin colour;
temperature dysregulation;
orthostatic symptoms;
weakness when upright;
presyncope;
or
activity-related deterioration
necessarily arise from one mechanism.
The relevant question is whether there is demonstrable vascular, autonomic, cardiac or neurological dysfunction, individually or in combination.
75. REDUCED CIRCULATING BLOOD VOLUME
Hyde's 2016 definition lists reduced circulating blood volume among the objective abnormalities that may be found.
Importantly, Hyde places this within a group of findings that are not invariably present and are not essential to his laboratory diagnosis.
Reduced blood volume should therefore be understood as:
a potentially measurable physiological abnormality in a subgroup of patients
rather than:
a mandatory defining criterion for every case of M.E.
Where demonstrated, however, it may be relevant to:
orthostatic intolerance;
reduced cerebral perfusion;
exercise intolerance;
cardiovascular compensation;
and
the patient's ability to remain upright or physically active.
76. AUTONOMIC NERVOUS-SYSTEM DYSFUNCTION
The autonomic nervous system regulates functions that ordinarily occur without conscious control, including:
heart rate;
blood-pressure regulation;
vascular tone;
temperature regulation;
sweating;
gastrointestinal motility;
bladder function;
and numerous other homeostatic processes.
Autonomic manifestations therefore fit naturally within a disease capable of producing widespread central neurological dysfunction.
The historical descriptions already contain manifestations compatible with autonomic disturbance, including:
unexplained sweating;
difficulty maintaining warmth;
dizziness;
syncope;
and disturbances involving gastrointestinal and other physiological functions.
These should be documented as the specific abnormalities present rather than grouped indiscriminately under “fatigue.”
77. ORTHOSTATIC DYSFUNCTION
A patient with neurological/autonomic and circulatory dysfunction may experience deterioration when upright.
Clinically relevant manifestations can include:
dizziness
light-headedness
weakness
visual disturbance
palpitations
presyncope
syncope
and deterioration in cognitive or neurological function while upright.
Where such symptoms are prominent, objective autonomic and cardiovascular assessment may be appropriate.
The purpose is to identify the physiological abnormality rather than assume that difficulty standing is simply a manifestation of general tiredness.
78. TEMPERATURE AND SWEATING ABNORMALITIES
Temperature dysregulation appears repeatedly in the historical neurological descriptions.
Wallis recorded:
unexplained sweating
and
difficulty keeping warm.
Within an integrated neurological model, these manifestations can be clinically relevant because thermoregulation and sweating depend substantially upon autonomic and central regulatory systems.
A physician should therefore record:
episodes of excessive sweating;
abnormally cold extremities;
difficulty maintaining body temperature;
subjective feverishness;
objective fever where present;
and
abnormal temperature fluctuations.
These findings should not themselves be treated as proof of enterovirus.
They contribute to characterization of the neurological/autonomic phenotype.
79. CARDIOVASCULAR INVESTIGATION
Hyde's disease model also includes cardiovascular abnormalities.
These are clinically important because cardiac dysfunction, vascular dysfunction, blood-volume abnormalities and autonomic dysfunction can produce overlapping symptoms.
Consequently, complaints such as:
palpitations
chest discomfort
exercise intolerance
orthostatic weakness
breathlessness
presyncope
and
reduced physical capacity
should not automatically be assigned to the neurological disease without appropriate investigation.
The patient should be assessed for specific cardiovascular disease as well as physiological abnormalities associated with the M.E. phenotype.
This reflects Hyde's broader principle:
investigate abnormalities rather than explain everything by a syndrome label.
80. CARDIOVASCULAR EXERCISE DYSFUNCTION
Hyde's 2016 definition includes cardiovascular exercise dysfunction among the supportive laboratory findings that may occur.
As with reduced blood volume, Hyde does not make this abnormality mandatory.
It can nevertheless provide objective evidence that the patient's impaired response to physical activity is physiological rather than simply a subjective perception of exertion.
Cardiovascular exercise investigation should be interpreted separately from:
motor weakness
muscle fatigability
cerebral hypoperfusion
and
autonomic/orthostatic dysfunction.
These phenomena may coexist, but they are not synonymous.
81. DIFFERENT FORMS OF 'EXERTIONAL DYSFUNCTION' MUST 'NOT' BE 'CONFLATED'
This distinction is particularly important in a physician-facing definition.
A patient can deteriorate after activity through several potentially overlapping mechanisms:
CENTRAL NEUROLOGICAL DETERIORATION
→ worsening cognitive, sensory, motor or other cerebral function;
CEREBRAL PERFUSION DETERIORATION
→ increased regional hypoperfusion;
MOTOR DYSFUNCTION
→ reduced muscular power or impaired motor control;
MUSCLE FATIGABILITY
→ abnormal inability to reproduce muscular work with prolonged restoration;
CARDIOVASCULAR EXERCISE DYSFUNCTION
→ abnormal physiological response to exertion;
ORTHOSTATIC/AUTONOMIC DYSFUNCTION
→ inability to maintain normal function while upright;
and potentially
LOCAL MUSCLE DISEASE
→ including the enteroviral myositis observation cited by Hyde.
A single umbrella expression such as “exercise intolerance” does not distinguish these mechanisms.
82. MOTOR DYSFUNCTION
Motor dysfunction is an important component of the historical disease.
Manifestations described across the source material include:
generalized weakness;
loss of muscular power;
difficulty walking;
paresis;
impaired coordination;
ataxia;
tremor;
abnormal muscle fatigability;
and, in the broader non-polio enteroviral neurological spectrum,
flaccid weakness or paralysis.
These manifestations require neurological localization.
A physician should consider whether the abnormality principally reflects:
brain/motor-cortex dysfunction;
brainstem disease;
spinal-cord/anterior-horn involvement;
peripheral nerve disease;
neuromuscular dysfunction;
muscle pathology;
or a combination.
83. THE ENTEROVIRAL POLIOMYELITIS-LIKE OVERLAP
Where non-polio enteroviral disease produces significant involvement of spinal motor/anterior-horn or related lower-motor-neuron structures, the clinical phenotype can overlap with a poliomyelitis-like syndrome.
Hyde's 2016 discussion explicitly acknowledges non-polio enteroviruses capable of producing flaccid paralysis simulating polio, including EV-68 and EV-71.
This observation is important to the integrated definition because encephalomyelitis itself permits involvement of both:
brain
and
spinal cord.
Therefore a patient with enteroviral encephalomyelitis need not have a purely cerebral phenotype.
Where spinal motor structures are significantly affected, findings may include:
limb weakness;
asymmetric paresis;
reduced muscle power;
altered reflexes;
muscle wasting where denervation is substantial or prolonged;
and other anterior-horn/lower-motor-neuron features.
These findings warrant appropriate neurological investigation rather than being relabelled as 'generalized fatigue'.
84. BRAINSTEM INVOLVEMENT
Enteroviral neurological disease can also involve the brainstem.
In an anatomically integrated framework, clinically significant brainstem disease can potentially disturb:
cranial-nerve function;
ocular movements;
facial motor function;
speech;
swallowing;
balance;
autonomic regulation;
respiratory control;
and other functions dependent upon medullary, pontine or midbrain structures.
Where this pattern is demonstrated, terminology such as:
brainstem encephalitis
or
rhombencephalitis
may anatomically overlap with the broader diagnosis of 'enteroviral encephalomyelitis'.
This is an anatomical integration; it should not be represented as though Hyde prescribed one 'mandatory' brainstem syndrome for all M.E. patients.
85. CRANIAL-NERVE AND BULBAR MANIFESTATIONS
Historical ocular abnormalities already described include:
diplopia
and
abnormal pupillary responses.
Where brainstem or cranial-nerve involvement is present, additional neurological manifestations can include disturbances of:
eye movement;
facial movement;
articulation;
swallowing;
and related bulbar functions.
Such findings should prompt appropriate neurological localization.
Significant dysarthria, dysphagia, respiratory compromise or progressive cranial-nerve dysfunction cannot safely be treated as merely manifestations of 'chronic fatigue'.
86. MENINGITIC, ENCEPHALITIC AND MYELITIC OVERLAP
The integrated anatomical terminology should follow the structures involved:
MENINGITIS
→ principally meningeal inflammation;
ENCEPHALITIS
→ brain parenchymal involvement;
MYELITIS
→ spinal-cord involvement;
MENINGOENCEPHALITIS
→ meninges and brain;
ENCEPHALOMYELITIS
→ brain and spinal cord;
MENINGOENCEPHALOMYELITIS
→ meninges, brain and spinal cord.
These terms can therefore overlap clinically in an enteroviral neurological disease depending upon the anatomical distribution.
This provides a more precise physician-facing framework than treating all neurological presentations as one undifferentiated symptom syndrome.
87. SENSORY DYSFUNCTION
Sensory abnormalities are prominent in the historical clinical descriptions.
Wallis recorded:
paraesthesiae;
pins and needles;
hyperaesthesia;
neuralgic pain;
altered taste and smell;
visual disturbance;
and other sensory phenomena.
These findings again support a neurological disease model.
The physician should document:
the sensory modality involved;
the anatomical distribution;
whether abnormalities are focal, asymmetric or generalized;
whether there are objective sensory signs;
and
whether the pattern suggests central, spinal, peripheral or mixed involvement.
88. PAIN
Pain in this disease construct can arise through different mechanisms and should not be treated as one nonspecific symptom.
The historical descriptions include:
neuralgic pain;
pain around the eye;
neck pain;
leg and back aching;
myalgia;
and
sensory hypersensitivity.
Potential mechanisms can therefore include:
central neurological pain processing;
peripheral nerve involvement;
muscle disease;
inflammatory processes;
and other pathology requiring appropriate differential investigation.
89. GASTROINTESTINAL DYSFUNCTION
Gastrointestinal involvement occupies two distinct positions in Hyde's later model.
First, gastrointestinal symptoms can occur as part of the systemic/autonomic disease phenotype.
Second, gastrointestinal tissue becomes important in the investigation of persistent enteroviral evidence, particularly through the gastric-mucosal work associated with John Chia.
These two concepts must not be confused.
GASTROINTESTINAL SYMPTOMS DO NOT THEMSELVES PROVE ENTEROVIRAL PERSISTENCE.
Conversely, enteroviral evidence in gastric tissue does not mean that the patient's only pathology is gastrointestinal.
90. NEUROGASTROENTEROLOGICAL INVOLVEMENT
Where autonomic or neurological control of the gastrointestinal tract is affected, the patient can develop abnormalities of:
motility;
gastric emptying;
intestinal propulsion;
bowel function;
nausea;
abdominal discomfort;
and nutritional intake.
Severe gastrointestinal dysmotility requires specific investigation.
Conditions such as 'gastroparesis' or 'paralytic ileus', where clinically suspected or demonstrated, are specific gastrointestinal/neurological diagnoses and should be managed accordingly rather than being treated as generic “ME/CFS symptoms.”
These particular diagnostic labels are part of the anatomical clinical integration, not claims that Hyde states every M.E. patient develops gastroparesis or ileus.
91. ENDOCRINE AND NEUROENDOCRINE ABNORMALITIES
Hyde also investigates endocrine dysfunction, particularly abnormalities involving the pituitary-thyroid system.
His approach again illustrates the principle that a multisystem presentation should be investigated rather than assumed to represent one unexplained symptom complex.
Endocrine assessment discussed in the material includes:
TSH;
free T3;
free T4;
thyroid/microsomal antibodies;
parathyroid hormone;
calcium;
and
phosphorus.
These tests help characterize endocrine abnormalities and identify alternative or additional disease.
92. SERIAL THYROID ULTRASOUND
Hyde gives particular attention to thyroid ultrasound.
He argues that anatomical thyroid abnormalities may develop before conventional biochemical thyroid testing necessarily becomes abnormal.
Consequently, he advocates serial thyroid ultrasound in the relevant clinical context rather than assuming that one normal serum TSH permanently excludes evolving thyroid pathology.
This is Hyde's proposed investigative approach.
It should be distinguished from a universally accepted diagnostic requirement for M.E.
The broader clinical principle is nevertheless clear:
objective abnormalities in another organ system should be investigated and characterized rather than attributed automatically to the M.E. label.
93. IMMUNOLOGICAL INJURY
Hyde's 2007 formulation refers to an infectious and immunological injury.
This introduces an immune component into the pathophysiological model without making an unspecified immune abnormality synonymous with M.E.
The distinction is important:
ENTEROVIRAL EVIDENCE
concerns the proposed infectious agent;
whereas
IMMUNOLOGICAL ABNORMALITY
concerns the host response or immune dysfunction.
One does not automatically establish the other.
94. NATURAL-KILLER-CELL ABNORMALITIES
Hyde's 2016 supportive laboratory findings include:
reduced natural-killer-cell numbers and/or activity, particularly during the earlier weeks of disease.
Once again, Hyde explicitly places this among findings that are not invariably present and are not essential to his laboratory diagnosis.
It should therefore be recorded as:
a potentially supportive immune abnormality
rather than:
a mandatory diagnostic biomarker.
95. SLEEP PHYSIOLOGY
Sleep disturbance appears both in the historical clinical descriptions and in Hyde's later objective investigations.
Wallis described disturbances including insomnia and inversion of the sleep rhythm.
Hyde's later material additionally refers to objective sleep-study abnormalities, particularly:
reduced or absent stage 3 sleep
during the earlier years of disease.
This is another finding Hyde categorizes as supportive rather than obligatory.
The sleep disturbance should therefore be considered part of the neurological/physiological phenotype where present, rather than used as a stand-alone definition of the disease.
96. THE SUPPORTIVE FINDINGS MUST REMAIN SUPPORTIVE
Hyde's 2016 definition is particularly useful because it prevents several objective abnormalities from being converted improperly into compulsory criteria.
The findings he discusses as potentially supportive include:
CSF oligoclonal bands;
mildly increased CSF pressure;
early CSF leukocytosis;
basal-ganglia hypoperfusion;
measurable neuropsychological abnormalities;
reduced circulating blood volume;
reduced natural-killer-cell number/activity;
cardiovascular exercise dysfunction;
and
abnormal sleep studies, including reduced or absent stage 3 sleep.
Hyde expressly says findings in this category are not always present and are not essential to his laboratory diagnosis.
Therefore:
their presence can characterize or support the individual disease phenotype;
but
their absence cannot simply be converted into an automatic exclusion rule that Hyde himself did not establish.
97. THE MULTISYSTEM FINDINGS DO NOT MAKE THE DISEASE A SYMPTOM COLLECTION
The presence of neurological, vascular, autonomic, cardiac, endocrine, gastrointestinal, muscular, immune and sleep abnormalities might superficially make the disease appear to be an unrelated collection of symptoms.
That is not how Hyde constructs it.
His model begins with:
an acute infectious disease
followed by:
a neurological disease with measurable CNS dysfunction
and then investigates the individual distribution and consequences of that injury.
The systemic manifestations are therefore investigated anatomically and physiologically rather than simply counted toward a symptom score.
98. OBJECTIVE ABNORMALITIES SHOULD BE SUBTYPED
The appropriate physician-facing approach is consequently:
identify the neurological disease;
localize the neurological abnormalities;
investigate the proposed infectious cause;
identify vascular/autonomic abnormalities;
investigate cardiovascular dysfunction;
investigate motor, peripheral-nerve and muscle disease where indicated;
investigate gastrointestinal dysfunction and available tissue where relevant;
investigate endocrine abnormalities;
characterize cognitive dysfunction;
and
record supportive immune, CSF, sleep and physiological findings.
The result is an individual disease profile, not merely a count of symptoms.
99. THE PRIMARY-CARE PHYSICIAN'S CRITICAL OPPORTUNITY
The primary-care physician may be the first doctor to see the patient during the period when the infectious agent is most accessible to investigation.
This creates a diagnostic opportunity that may never recur.
If an acute infectious illness is followed by significant neurological manifestations, the physician should not wait months to determine whether the patient eventually satisfies a chronic-fatigue case definition.
Hyde's physician guidance instead treats the acute disease as requiring hospital investigation.
The objective at this stage is to:
recognize the neurological disease;
exclude other urgent neurological causes;
obtain time-sensitive infectious/virological specimens;
investigate CSF where appropriate;
document neurological abnormalities;
and
establish a baseline against which subsequent changes can be assessed.
100. IMMEDIATE HOSPITALIZATION IN HYDE'S PHYSICIAN GUIDANCE
Hyde's advice to primary-care physicians is explicit that the patient with the acute-onset case of M.E. he describes should be immediately hospitalized.
This recommendation follows from his conception of the disease as an acute neurological illness requiring investigation, rather than a condition to be diagnosed retrospectively after months of unexplained fatigue.
This is Hyde's clinical recommendation in the source material.
It should not be represented as though it were the wording of a current NICE emergency protocol.
Nevertheless, within the integrated Hyde definition, it establishes an essential distinction:
THE ACUTE M.E./ENTEROVIRAL ENCEPHALOMYELITIS PATHWAY BEGINS DURING THE NEUROLOGICAL ILLNESS - NOT SIX MONTHS LATER.
101. THE ACUTE HOSPITAL INVESTIGATION - LUMBAR PUNCTURE
Hyde's acute pathway includes lumbar puncture.
The CSF should be investigated according to the acute neurological presentation.
Within the source material, this can include evaluation for:
cellular inflammatory abnormalities;
CSF pressure abnormalities;
oligoclonal bands;
and
appropriate enteroviral investigation where available and clinically relevant.
The broader purpose is to investigate an acute encephalitic/encephalomyelitic disease, not simply to confirm a chronic symptom syndrome.
102. ACUTE ENTEROVIRAL SAMPLING
Hyde's physician guidance includes collecting material for enterovirological investigation during the acute disease.
The source material identifies:
enterovirus titres;
oropharyngeal swab;
stool;
and
blood for enterovirology.
The objective is to obtain specimens while the infectious event is still relatively recent.
Where possible, serial samples may provide information that a single specimen cannot.
The physician should document:
date of symptom onset;
date of neurological deterioration;
date and type of each specimen;
laboratory methodology;
and
the actual enterovirus identified or antibody response demonstrated.
103. VIROLOGIST INVOLVEMENT
Hyde's physician advice specifically includes consultation with a virologist.
His objective is not merely to establish the generic proposition that the patient once had “a virus.”
He advocates attempting to recover and identify/subtype the enterovirus.
This distinction matters because his later work proposes that multiple different enteroviruses can produce the disease.
Accurate virological characterization therefore contributes to:
individual diagnosis;
epidemiological investigation;
recognition of clusters;
and
research into whether different enteroviruses produce different neurological phenotypes.
104. NEUROLOGICAL REASSESSMENT DURING HOSPITALIZATION
Because neurological findings can evolve, Hyde advocates repeated neurological examination.
This is particularly important in light of the historical Wallis observation that reflexes could change from normal or decreased earlier in disease to normal, increased or brisk later.
Serial examination may also document the appearance, progression or resolution of:
motor weakness;
cranial-nerve abnormalities;
coordination abnormalities;
sensory signs;
tremor;
gait disturbance;
cognitive abnormalities;
and
autonomic manifestations.
A single normal examination should therefore not automatically erase a documented evolving neurological history.
105. MRI/MRA IN THE ACUTE WORK-UP
Hyde's primary-care guidance calls for:
MRI/MRA using an MS protocol.
This serves several purposes:
investigation of structural CNS abnormalities;
investigation of vascular abnormalities;
assessment for other encephalitic or demyelinating disease;
and
differential diagnosis of other neurological conditions capable of explaining the presentation.
The MRI/MRA component therefore complements rather than replaces:
CSF investigation
SPECT
serial neurological examination
and
virological investigation.
106. SPECT DURING THE ACUTE AND CHRONIC DISEASE
Hyde's physician guidance also includes brain SPECT, particularly using the Segami analytical approach discussed earlier.
He states that SPECT abnormalities can be more severe at onset, while remaining demonstrable during established disease.
This makes functional cerebral imaging potentially useful at more than one disease stage:
ACUTE DISEASE
→ characterize severe functional cerebral abnormalities;
CHRONIC/ESTABLISHED DISEASE
→ demonstrate persistent functional CNS abnormalities where they remain.
Longitudinal imaging may additionally provide information about change over time.
107. THE CHRONIC SECOND PHASE - INVESTIGATION STILL MATTERS
Hyde explicitly addresses the common situation in which the physician first encounters the patient only after the acute infectious period has passed.
His position is that it remains worthwhile to investigate.
The loss of the ideal acute virological window does not justify abandoning neurological or infectious investigation and substituting a chronic-fatigue label.
Instead, the physician should reconstruct:
the original infectious illness;
the biphasic transition;
the neurological manifestations at onset;
any investigations performed at the time;
any stored blood, CSF or tissue specimens;
previous imaging;
the subsequent neurological course;
and
the current objective abnormalities.
108. EARLY CHRONIC ENTEROVIRAL ANTIBODY INVESTIGATION
During the earlier chronic phase, Hyde considers enteroviral antibody investigation potentially worthwhile.
His physician guidance describes the antibody response as slow and indicates that useful investigation may remain possible during the first several months, and in some cases for approximately the first year.
This is not equivalent to saying that one late antibody titre proves the original cause.
The result must be interpreted alongside:
the onset history
serial measurements where available
the clinical neurological disease
and
other virological evidence.
109. ARCHIVED GASTRIC BIOPSY MATERIAL IN ESTABLISHED DISEASE
Where a patient with established disease previously underwent endoscopy and gastric biopsy, Hyde's later approach suggests determining whether the pathology department retains the paraffin block.
If retained, unstained sections may potentially be obtained for appropriate enteroviral investigation.
This is clinically useful because the original biopsy may have been taken for an entirely different gastrointestinal reason.
The tissue can therefore potentially be revisited without automatically requiring another invasive procedure.
Hyde's incorporation of the Chia work makes this one of the important chronic-phase enteroviral investigations in his later definition.
110. DO NOT CONFUSE A NEGATIVE LATE TEST WITH A NEGATIVE ACUTE INVESTIGATION
This principle now becomes central to interpreting the complete testing framework.
Consider two patients:
PATIENT A
has stool, throat, blood and appropriate acute neurological/CSF specimens obtained during the infectious-neurological illness;
PATIENT B
first receives one blood PCR years after onset.
These are not equivalent investigations.
Therefore the statement:
“enterovirus testing was negative”
is clinically inadequate without specifying:
specimen;
method;
timing;
number of samples;
and
disease stage.
This is one of the most important practical consequences of integrating Hyde's acute and chronic testing material.
111. THE COMPLETE HYDE INVESTIGATIVE LOGIC
The diagnostic sequence developed across the 2006, 2007, 2016 and physician-advice material can now be expressed methodically:
1. ESTABLISH THE ONSET
Acute or gradual?
Infectious or non-infectious?
Biphasic or not?
Epidemic/clustered or sporadic?
↓
2. IDENTIFY THE NEUROLOGICAL DISEASE
Brain?
Brainstem?
Spinal cord?
Cranial nerves?
Peripheral nervous system?
Motor system?
Autonomic system?
Mixed involvement?
↓
3. INVESTIGATE THE ACUTE INFECTION
Appropriate blood, throat/oropharyngeal, stool, serological and other enterovirological investigation according to timing and laboratory availability.
↓
4. INVESTIGATE THE CNS
Serial neurological examination, CSF, MRI/MRA, functional cerebral imaging/SPECT and neuropsychological investigation where appropriate.
↓
5. INVESTIGATE THE PHYSIOLOGICAL CONSEQUENCES
Vascular, autonomic, cardiovascular, blood-volume, motor, muscular, endocrine, gastrointestinal, immune and sleep abnormalities as clinically indicated.
↓
6. IF THE ACUTE WINDOW HAS PASSED
Reconstruct previous results and investigate persistent objective abnormalities, antibody evidence where temporally useful, archived specimens and tissue evidence where appropriate.
↓
7. SUBTYPE THE PATIENT ACCORDING TO THE DISEASE ACTUALLY DEMONSTRATED.
This final step is fundamental to Hyde's approach.
112. THE DIAGNOSIS IS NOT “EVERY TEST MUST BE POSITIVE”
Hyde's material does not support constructing an artificial checklist requiring:
positive enterovirus PCR + positive gastric biopsy + abnormal SPECT + oligoclonal bands + reduced blood volume + NK-cell abnormality + abnormal sleep study
in every patient.
He explicitly identifies several of these abnormalities as variable and non-essential.
Nor were all of these investigations available to patients in the historical epidemics.
The integrated definition therefore requires the physician to distinguish:
core disease architecture
from
etiological evidence
from
objective neurological characterization
from
supportive/subtyping abnormalities.
113. CORE DISEASE ARCHITECTURE
In the integrated Hyde framework developed thus far, the core architecture is:
an acute infectious illness
followed by
a biphasic transition into neurological disease
with
measurable central nervous system dysfunction
and, in those who remain ill,
persistent neurological and physiological disability.
Hyde's later etiological formulation places enteroviruses at the centre of this disease model.
The precise enterovirus and the anatomical distribution of neurological injury can differ between patients.
114. ETIOLOGICAL EVIDENCE
Evidence relevant to the enteroviral etiology can include, depending upon disease stage and available material:
rising specific enterovirus titres;
Mowbray/Yousef monoclonal-antibody testing;
Bell ELISA enterovirus antibody investigation;
stool enterovirus investigation;
PCR;
acute blood/oropharyngeal and other appropriate virological specimens;
historical viral isolation/subtyping;
longitudinal Ruchill-type investigation;
and
gastric-mucosal/tissue investigation of persistent enteroviral evidence.
These results require interpretation according to the method used and the disease stage.
115. OBJECTIVE NEUROLOGICAL CHARACTERIZATION
The neurological disease can be characterized through:
serial clinical neurological examination;
CSF investigation;
MRI/MRA;
functional cerebral imaging/SPECT;
neuropsychological investigation;
motor/peripheral neurological studies where indicated;
and other investigations directed by the patient's neurological phenotype.
The anatomical diagnosis can consequently range across overlapping:
meningitic
encephalitic
brainstem/rhombencephalitic
limbic
myelitic
meningoencephalomyelitic
and
poliomyelitis-like/flaccid motor
patterns where clinically demonstrated.
116. SUPPORTIVE AND SUBTYPING ABNORMALITIES
Additional objective abnormalities may characterize important subgroups, including:
regional cerebral hypoperfusion;
basal-ganglia abnormalities;
motor-cortex abnormalities;
reduced circulating blood volume;
cardiovascular exercise dysfunction;
autonomic/orthostatic abnormalities;
neuropsychological abnormalities;
NK-cell abnormalities;
sleep-study abnormalities;
endocrine/thyroid abnormalities;
gastrointestinal abnormalities;
peripheral neurological abnormalities;
and
muscular abnormalities.
The presence or absence of these findings helps define the individual disease phenotype.
117. THE CLINICAL MEANING OF “ENCEPHALOMYELITIS”
In this integrated formulation, the term encephalomyelitis is being used anatomically:
ENCEPHALO-
refers to the brain;
-MYELITIS
refers to inflammatory disease involving the spinal cord.
The clinical spectrum can therefore include differing proportions of:
cerebral disease
brainstem disease
and
spinal-cord disease.
Where meningeal involvement also occurs, meningoencephalomyelitis may be the more anatomically descriptive term.
Where spinal motor/anterior-horn injury dominates, the presentation may overlap with a non-polio enteroviral poliomyelitis-like syndrome.
This anatomical terminology is used to clarify the integrated disease model; it should follow demonstrated clinical anatomy rather than be assigned indiscriminately.
118. MYALGIC ENCEPHALOMYELITIS AS ENTEROVIRAL ENCEPHALOMYELITIS - INTEGRATED CLINICAL FORMULATION
The material integrated to this point can therefore be brought into a single physician-facing formulation:
Myalgic Encephalomyelitis (also known as Enteroviral Encephalomyelitis) is an acute-onset, biphasic infectious neurological disease described historically in epidemic, endemic and sporadic forms. An initial infectious illness is followed by a neurological phase characterized by measurable central nervous system dysfunction. The neurological injury may involve cerebral, brainstem, spinal, central motor, peripheral neurological, autonomic and related systems in differing combinations.
Historical and later investigations led Hyde increasingly toward the enterovirus family as the principal etiological focus. His later model incorporates Coxsackie, ECHO and other non-polio enteroviruses rather than proposing one universal M.E. virus, and recognizes that non-polio enteroviruses can also produce severe spinal motor disease and flaccid paralysis.
The anatomical phenotype can therefore overlap with enteroviral meningitis, meningoencephalitis, encephalitis, brainstem encephalitis/rhombencephalitis, limbic encephalitis, encephalomyelitis, meningoencephalomyelitis and, where spinal motor/anterior-horn structures are involved, an enteroviral poliomyelitis-like/flaccid motor syndrome.
The disease is investigated through the onset history, repeated neurological examination, appropriate acute and chronic enterovirology, cerebrospinal-fluid investigation, structural and functional neurological imaging, neuropsychological investigation and phenotype-directed vascular, autonomic, cardiovascular, motor, muscular, gastrointestinal, endocrine, immune and other physiological investigations.
Individual abnormalities are used to characterize and subtype the patient. Findings that Hyde himself describes as variable or supportive are not converted into mandatory diagnostic requirements.
119. THE NEXT NECESSARY DISTINCTION
Having defined the M.E./Enteroviral Encephalomyelitis disease construct first, the separate question can now be addressed:
What is Chronic Fatigue Syndrome, and why does Hyde argue that it should not be used as a synonym for this disease?
This distinction must begin with Hyde's own gradual-onset CFS examples from the Little Red Book, including the extensive list of missed or insufficiently investigated diseases that he says can produce a CFS presentation.
Only after that should the chronology proceed through:
Holmes 1988
↓
Fukuda 1994
↓
CCC 2003 / “ME/CFS”
↓
Hyde's explicit M.E.–CFS separation
↓
ICC 2011
↓
IOM/SEID 2015
↓
NICE 2021 ME/CFS
↓
the exclusion of established M.E./Enteroviral Encephalomyelitis from SEID and NICE ME/CFS where the specific neurological/infectious disease explains the presentation
↓
**and the requirement, within this integrated framework, for a separate acute/emergency M.E./Enteroviral Encephalomyelitis pathway.**
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120. CHRONIC FATIGUE SYNDROME MUST BE CONSIDERED SEPARATELY
The preceding sections have deliberately defined Myalgic Encephalomyelitis / Enteroviral Encephalomyelitis first, without using Chronic Fatigue Syndrome as its organizing framework.
The distinction is necessary because Hyde's Little Red Book gives CFS a fundamentally different diagnostic construction.
In Hyde's proposed CFS criteria, the starting point is:
“A gradual onset fatigue syndrome”
which he states is usually due to a missed major disease.
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This differs fundamentally from his M.E. construction:
M.E.
→ acute infectious onset
→ biphasic transition
→ neurological disease
→ measurable CNS dysfunction
→ etiological and anatomical investigation
compared with Hyde's proposed:
CFS
→ gradual-onset fatigue syndrome
→ investigate for a major diagnosis that has been missed.
The two concepts therefore should not simply be made synonymous within an integration of Hyde's definitions.
121. HYDE'S COMPLETE “MISSED MAJOR DISEASE” FRAMEWORK
Hyde does not leave “missed major disease” as an abstract statement.
His Little Red Book identifies a broad series of diagnostic categories that he believes can be overlooked in a patient given a CFS diagnosis.
They include:
missed cardiac disease;
missed malignancy;
missed vascular disease;
missed brain disease, including vascular or space-occupying lesions;
missed test-positive rheumatological disease;
missed test-negative rheumatological disease;
missed endocrine disease;
missed physiological disease;
missed genetic disease;
missed chronic infectious disease;
missed pharmacologically or immunization-induced disease;
missed social disease;
missed drug-use disease or habituation;
missed dietary-dysfunction disease;
and
missed psychiatric disease.
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This complete list is important because Hyde's argument is not simply:
“CFS patients are actually M.E. patients.”
His argument is the opposite.
A person presenting with a gradual-onset fatigue syndrome may have any of a wide range of underlying diseases, and the physician's responsibility is to find the diagnosis producing the fatigue syndrome.
122. THE GRADUAL-ONSET GROUP
This interpretation connects directly with Hyde's previously discussed 100-patient observation.
Hyde divided those patients into:
40 acute-onset patients
and
60 gradual-onset patients.
Recoverable enteroviruses were found in a subset of the acute-onset group, whereas Hyde reported no suggestion of enteroviruses in the 60 gradual-onset patients in that particular investigation.
This did not establish the cause of every acute case; Hyde explicitly acknowledged that the cause remained unknown in most of the patients.
But it contributed to his insistence that acute and gradual onset should not be casually combined into one disease population.
123. “FATIGUE” IS A PRESENTATION, NOT AN ETIOLOGICAL DIAGNOSIS
The clinical logic underlying Hyde's CFS argument is that fatigue is nonspecific.
A patient can experience severe fatigue because of:
cardiac disease
malignancy
vascular disease
neurological disease
rheumatological disease
endocrine disease
chronic infection
genetic/metabolic disease
medication or drug effects
nutritional disease
psychiatric disease
or numerous other pathological processes.
Consequently:
THE PRESENCE OF CHRONIC FATIGUE DOES NOT IDENTIFY ITS CAUSE.
A fatigue syndrome should therefore trigger diagnostic investigation rather than terminate it.
124. WHY THIS MATTERS FOR M.E.?
Within Hyde's framework, an individual who has already demonstrated an acute infectious neurological disease with objective CNS abnormalities should not have that specific disease displaced merely because the individual later develops chronic fatigue.
The hierarchy should instead be:
SPECIFIC ESTABLISHED DISEASE
↓
explains the patient's manifestations
rather than:
NONSPECIFIC FATIGUE SYNDROME
↓
replacing the established disease.
This principle is particularly important where the patient has evidence of:
encephalitis
meningoencephalitis
rhombencephalitis
encephalomyelitis
meningoencephalomyelitis
or
enteroviral poliomyelitis-like disease.
Such diagnoses identify neurological pathology more specifically than the descriptive statement that the patient experiences chronic fatigue.
125. HOLMES 1988 - THE FORMAL CDC CFS CASE DEFINITION
Chronic Fatigue Syndrome was formally defined by the US Centers for Disease Control in the Holmes et al. 1988 case definition.
This represents a different historical and diagnostic pathway from the epidemic M.E. literature discussed earlier.
The Holmes definition was constructed around chronic or relapsing debilitating fatigue, accompanied by additional symptom and physical criteria and subject to exclusionary conditions.
It was therefore a case definition based upon a clinical syndrome and exclusion process, rather than an etiological definition identifying a particular infectious agent or a specific encephalomyelitic lesion.
This distinction must be retained even though some people satisfying a CFS definition may have experienced an infectious onset.
A case definition can select patients sharing specified manifestations without demonstrating that every selected patient has one underlying disease.
126. HOLMES CFS AND ENTEROVIRAL NEUROLOGICAL DISEASE
A patient with a diagnosed disease capable of explaining the fatigue presentation should not be reduced to unexplained CFS merely because fatigue is present.
This is the general diagnostic logic of an exclusion-based syndrome definition.
Thus, where a patient has an established:
enteroviral encephalitis
enteroviral meningoencephalitis
enteroviral encephalomyelitis
or another specific neurological disease explaining the presentation,
the physician has moved from an unexplained syndrome to a specific explanatory diagnosis.
This distinction should not be confused with saying that enteroviruses could never be found among people recruited under CFS terminology. The issue is whether a specific disease has actually been demonstrated and explains the presentation.
127. FUKUDA 1994 - BROADENING/REVISING THE "CFS RESEARCH" CONSTRUCTION
The CDC subsequently revised its CFS case definition in 1994, producing the Fukuda definition.
Fukuda requires clinically evaluated, unexplained, persistent or relapsing chronic fatigue of new or definite onset, producing substantial reduction in previous activity, together with a required number of additional symptoms.
The accompanying symptom group includes manifestations such as:
impaired memory or concentration;
sore throat;
tender lymph nodes;
muscle pain;
multi-joint pain;
headache;
unrefreshing sleep;
and
post-exertional malaise.
Importantly, the Fukuda definition remains centered upon unexplained chronic fatigue plus symptom criteria and exclusions.
It does not require demonstration of:
enterovirus;
encephalitis;
encephalomyelitis;
CSF inflammation;
abnormal cerebral perfusion;
or another specific neurological lesion.
A systematic review found that Fukuda became the most frequently cited CFS/ME case definition in research, and also found meaningful differences in which populations were selected by different definitions.
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128. HOLMES AND FUKUDA DO NOT SELECT IDENTICAL POPULATIONS
The change from Holmes to Fukuda was not simply a change in spelling or disease name.
Different case definitions select different patient populations.
Studies comparing definitions have found different prevalence estimates and only partial overlap between populations satisfying different criteria.
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This is important to the integrated definition because research performed in a population selected by one CFS criterion cannot automatically be assumed to characterize:
all other CFS criteria
or
Hyde-defined M.E./Enteroviral Encephalomyelitis.
The population-selection method has to be stated.
129. THE 2003 CANADIAN CONSENSUS CRITERIA - “ME/CFS”
The Canadian Consensus Criteria (CCC) used the combined terminology ME/CFS and required a substantially more complex symptom pattern than Fukuda.
The CCC requires manifestations involving:
fatigue;
post-exertional malaise and/or fatigue;
sleep dysfunction;
pain;
neurological/cognitive manifestations;
and manifestations drawn from autonomic, neuroendocrine and immune categories.
This produces a more symptomatically specified population than Fukuda.
However, the CCC remains a clinical criteria-based construction.
It does not require demonstration of the specific infectious-neurological disease architecture that Hyde uses to define M.E.
The IOM's later comparative review confirms that the CCC, Fukuda and ICC impose materially different symptom requirements.
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130. WHY THE COMBINED TERM “ME/CFS” CREATES A NOSOLOGICAL PROBLEM IN THE HYDE FRAMEWORK?
Within Hyde's disease model, combining the names does not demonstrate that the underlying definitions identify the same disease.
The two historical constructions begin from different premises:
M.E.
→ epidemic/infectious neurological disease
→ acute onset
→ CNS dysfunction
→ objective investigation
→ later enteroviral etiological model
whereas:
CFS
→ chronic fatigue syndrome
→ symptom/case-definition requirements
→ exclusion of alternative explanatory disease.
Calling a criteria set “ME/CFS” therefore does not itself establish biological equivalence between the historical M.E. disease construct and populations previously selected under CFS definitions.
131. HYDE'S EXPLICIT 2006 SEPARATION
Hyde makes his intended separation particularly clear at the end of the Little Red Book.
He states that his proposed M.E. criteria:
restore M.E. to a CNS disease entity
and distinguish it from what he describes as the CDC's CFS collection of disease entities.
He emphasizes:
acute onset for M.E.
and places his proposed CFS construction in:
gradual-onset missed major diagnosis.
� Invest in ME +1
Whatever one concludes about Hyde's proposed nosology, this distinction must be preserved accurately when integrating Hyde's own definitions.
It would be source-inaccurate to rewrite Hyde as defining M.E. and CFS as interchangeable names for one disease.
132. THE NIGHTINGALE DEFINITION 2007
Hyde's 2007 Nightingale Definition of M.E. continued this attempt to distinguish M.E. from CFS through objective disease characteristics.
A later systematic review catalogued the Nightingale Definition of ME (2007/Hyde) separately from CDC CFS definitions, NICE criteria, CCC-derived definitions and ICC.
� PubMed Central (PMC)
The definition's emphasis upon:
acute onset;
measurable neurological dysfunction;
vascular dysfunction;
functional cerebral abnormalities;
and
infectious/enteroviral investigation
has already been integrated into the preceding sections rather than repeated here.
Its significance in this section is nosological:
Hyde continued to construct M.E. as a definable neurological disease rather than as another name for the CDC chronic-fatigue syndrome.
133. ICC 2011 - ANOTHER DISTINCT CRITERIA CONSTRUCTION
The International Consensus Criteria (ICC) were published in 2011 under the name Myalgic Encephalomyelitis.
ICC replaced the central CFS emphasis upon fatigue with post-exertional neuroimmune exhaustion (PENE) and required manifestations across neurological, immune/gastrointestinal/genitourinary, and energy-production/transport categories.
This creates another distinct criteria-selected population.
It should not automatically be equated with the Hyde/Nightingale definition simply because both use the name M.E.
The definitions have different architecture and requirements. The IOM's comparative review likewise treats ME-ICC as a separate criteria set from CCC, Fukuda and NICE.
� NCBI
134. A SPECIFIC EXPLANATORY NEUROLOGICAL DIAGNOSIS TAKES PRECEDENCE
The clinically important principle remains:
criteria should not displace an established explanatory diagnosis.
If appropriate investigation demonstrates that a patient's presentation is explained by a specific neurological infectious disease - for example, enteroviral encephalomyelitis - that disease should be recorded and treated as the specific diagnosis.
The patient may phenotypically satisfy many symptoms contained in CCC, ICC, Fukuda or another case definition.
Symptomatic overlap does not make the diagnoses biologically identical.
This is particularly important because symptoms such as:
weakness
cognitive impairment
sleep disturbance
autonomic dysfunction
pain
and
activity-related deterioration
occur in numerous neurological and systemic diseases.
135. IOM 2015 - SYSTEMIC EXERTION INTOLERANCE DISEASE (SEID)
In 2015, the US Institute of Medicine proposed new diagnostic criteria and the name:
Systemic Exertion Intolerance Disease (SEID).
The report was explicitly commissioned to address the illness being discussed under ME/CFS terminology and proposed replacing that terminology with SEID.
� NCBI
Its diagnostic architecture centers upon:
substantial impairment in previous activity accompanied by fatigue;
post-exertional malaise;
unrefreshing sleep;
and at least one of:
cognitive impairment
or
orthostatic intolerance.
The IOM report regarded SEID as a medical illness, not a psychiatric diagnosis.
� NCBI
This is therefore another symptom/clinical-criteria construction and is not an enterovirus-specific definition of encephalomyelitis.
136. SEID DOES NOT REQUIRE DEMONSTRATION OF "ENTEROVIRAL ENCEPHALOMYELITIS"
The SEID criteria do not require:
acute enterovirus identification;
CSF evidence of enteroviral CNS infection;
encephalitis;
myelitis;
SPECT evidence of the abnormalities Hyde describes;
gastric-tissue enteroviral evidence;
or
the acute biphasic neurological onset required by Hyde's M.E. construction.
Consequently, satisfying SEID criteria does not by itself establish Hyde-defined M.E./Enteroviral Encephalomyelitis.
Conversely, a patient with a specific diagnosed neurological disease should be clinically managed according to that established disease rather than having the specific diagnosis replaced merely because the patient also satisfies a symptom algorithm.
137. NICE 2021 ME/CFS
NICE published NG206, “Myalgic encephalomyelitis (or encephalopathy)/chronic fatigue syndrome: diagnosis and management,” on 29 October 2021. NICE states that it covers children, young people and adults diagnosed within its ME/CFS framework.
� Nice
NICE currently states that there is no diagnostic test for ME/CFS and that the diagnosis is made clinically.
� Nice
NICE requires four principal symptom domains:
debilitating fatigue worsened by activity;
post-exertional malaise;
unrefreshing sleep or sleep disturbance;
and
cognitive difficulties.
� Nice
For diagnosis, the symptoms must have persisted for 3 months and must not be explained by another condition.
� Nice
NICE therefore uses a clinical symptom-based framework together with investigation for alternative explanatory diagnoses.
138. NICE ITSELF REQUIRES INVESTIGATION OF ALTERNATIVE EXPLANATORY DISEASE
This point needs to be stated precisely.
NICE does not say that every patient experiencing its four symptom domains automatically has ME/CFS.
NICE instructs clinicians to perform:
medical assessment;
physical examination;
and
investigations to exclude other diagnoses.
� Nice
NICE's evidence review explicitly recognizes that people can be wrongly diagnosed with ME/CFS and consequently fail to receive appropriate treatment for another disease. It therefore emphasizes careful consideration of differential diagnoses and continued investigation when new findings suggest another explanation.
� NCBI
This distinction is directly relevant to the integrated definition.
139. WHAT “EXCLUDED” MEANS IN THIS INTEGRATED FRAMEWORK?
The exclusion statement should therefore be formulated clinically rather than ambiguously:
IF A SPECIFIC DIAGNOSED ENTEROVIRAL ENCEPHALOMYELITIS EXPLAINS THE PATIENT'S PRESENTATION, THAT PATIENT DOES NOT HAVE AN UNEXPLAINED PRESENTATION FOR WHICH SEID OR NICE ME/CFS SHOULD REPLACE THE SPECIFIC NEUROLOGICAL DIAGNOSIS.
For NICE specifically, this follows from its requirement that the diagnostic symptom complex not be explained by another condition.
� Nice
This does not mean NICE explicitly publishes the sentence “Hyde M.E. is excluded.”
Rather, it is the diagnostic consequence within this integrated framework of establishing an explanatory neurological disease.
That distinction is important for a document intended for physicians.
140. SYMPTOMATIC OVERLAP DOES NOT OVERRIDE THE SPECIFIC DIAGNOSIS
An individual with enteroviral encephalomyelitis may also experience:
profound activity limitation;
post-exertional deterioration;
sleep disturbance;
cognitive dysfunction;
orthostatic intolerance;
pain;
and
autonomic dysfunction.
Those manifestations can overlap substantially with modern ME/CFS criteria.
But symptom overlap does not logically require replacement of:
ENTEROVIRAL ENCEPHALOMYELITIS
with:
ME/CFS.
The appropriate diagnostic question is:
HAS A MORE SPECIFIC DISEASE BEEN ESTABLISHED THAT EXPLAINS THE PRESENTATION?
If it has, the specific disease remains clinically relevant.
141. CFS AS “MISDIAGNOSIS” - THE PRECISE HYDE FORMULATION
Within Hyde's Little Red Book framework, his proposed gradual-onset CFS population is approached as a population in whom a major diagnosis has often been missed.
Therefore, for purposes of accurately integrating Hyde's position:
CFS is not used here as an alternative name for M.E.
Rather, a CFS label should prompt renewed investigation for an explanatory diagnosis, including the broad categories Hyde lists:
cardiac
malignant
vascular
neurological
rheumatological
endocrine
physiological
genetic
infectious
pharmacological
nutritional
psychiatric
and other disease.
Hyde summarizes his own proposed CFS criteria as placing the condition where he believed many physicians effectively left it: a gradual-onset missed major diagnosis.
� Invest in ME +1
This is Hyde's proposed interpretation, not a statement that contemporary medicine has established every person currently diagnosed with CFS or ME/CFS as misdiagnosed.
142. THE DEFINITIONS SHOULD NOT BE RETROSPECTIVELY COLLAPSED
The chronology can therefore be represented without conflation:
HISTORICAL EPIDEMIC M.E.
→ infectious neurological disease described before CFS
HOLMES CFS - 1988
→ chronic-fatigue case definition with exclusions
FUKUDA CFS - 1994
→ revised chronic-fatigue research case definition
CCC - 2003
→ more restrictive multisystem criteria using combined ME/CFS terminology
HYDE / NIGHTINGALE - 2006–2007
→ explicit attempt to restore M.E. as an acute-onset objectively demonstrable CNS disease and separate it from CFS
ICC - 2011
→ consensus criteria using the name M.E. and PENE-centered criteria
IOM/SEID - 2015
→ new clinical diagnostic criteria and proposed replacement name for the population discussed as ME/CFS
HYDE - 2016
→ further development of his M.E. definition, including the extensive enteroviral material integrated earlier
NICE NG206 - 2021
→ clinical ME/CFS diagnosis based upon specified symptoms persisting for the required duration and not explained by another condition.
� Nice +2
These definitions overlap symptomatically but are not interchangeable research instruments and do not necessarily select identical populations.
143. WHY THIS MATTERS TO A DOCTOR?
A physician faced with a patient who has:
documented acute enteroviral infection
followed by
acute encephalitic/encephalomyelitic neurological disease
with
objective CNS abnormalities
should investigate and manage that neurological disease on its own terms.
The subsequent development of chronic:
weakness
abnormal muscle fatigability
cognitive impairment
autonomic dysfunction
sleep disturbance
pain
or
activity-related deterioration
does not erase the original neurological diagnosis.
Equally, a patient presenting only with unexplained chronic fatigue should not automatically be assigned an enteroviral encephalomyelitis diagnosis without evidence supporting the infectious-neurological disease.
The two diagnostic errors run in opposite directions.
144. THE NEED FOR AN ACUTE NEUROLOGICAL PATHWAY
This distinction leads to the final practical consequence of the integrated definition.
A patient presenting during an acute infectious illness followed by significant new neurological dysfunction should not be made to wait until the duration requirements of a chronic symptom-defined diagnosis have elapsed before the acute neurological disease is investigated.
Hyde's own primary-care advice advocates immediate hospitalization for the acute-onset M.E. case he describes and investigation including lumbar puncture, virology, serial neurological assessment and neurological imaging.
Modern emergency evaluation should, of course, be determined by the patient's actual acute neurological presentation and contemporary clinical standards.
The fundamental diagnostic principle remains:
ACUTE ENCEPHALITIC, MYELITIC, MENINGITIC, BRAINSTEM OR FLACCID-PARALYSIS FEATURES REQUIRE ACUTE NEUROLOGICAL ASSESSMENT - THEY SHOULD NOT BE DEFERRED INTO A LATER CHRONIC-FATIGUE DIAGNOSTIC PROCESS.
145. SEPARATE PATHWAYS
The integrated model therefore requires two conceptually separate routes:
PATHWAY A - ACUTE INFECTIOUS NEUROLOGICAL DISEASE
Acute infection
↓
neurological deterioration
↓
urgent neurological assessment
↓
CSF/appropriate infectious investigation
↓
MRI/MRA and other indicated imaging
↓
appropriate enterovirology
↓
repeated neurological examination
↓
anatomical diagnosis and disease-specific management.
PATHWAY B - UNEXPLAINED CHRONIC FATIGUE / (ME/CFS) - TYPE PRESENTATION
Persistent symptom complex
↓
comprehensive history and examination
↓
investigation for explanatory disease
↓
application of the relevant clinical criteria only when the presentation remains appropriately unexplained.
The existence of Pathway B must never become a reason to bypass Pathway A.
146. FINAL INTEGRATED DIAGNOSTIC STATEMENT
Myalgic Encephalomyelitis, described in this integrated Hyde-derived formulation as Enteroviral Encephalomyelitis, is treated as an acute-onset infectious neurological disease rather than as a synonym for Chronic Fatigue Syndrome. Its historical description derives from epidemic, endemic and sporadic neurological disease; Hyde's later etiological formulation increasingly focuses upon the enterovirus family.
The disease is characterized through its infectious and biphasic onset, neurological manifestations and objectively investigated CNS dysfunction. Depending upon anatomical involvement, the clinical disease can overlap with enteroviral meningitis, meningoencephalitis, encephalitis, brainstem encephalitis/rhombencephalitis, limbic encephalitis, encephalomyelitis, meningoencephalomyelitis and non-polio enteroviral poliomyelitis-like/flaccid motor disease.
Enteroviral investigation is stage-dependent. Acute investigation and later investigation of possible persistent infection answer different questions and cannot be treated as interchangeable. Hyde's material incorporates rising enterovirus titres, historical monoclonal-antibody methods, Bell ELISA testing, stool investigation, PCR, acute enterovirological sampling, longitudinal Ruchill investigations and Chia's gastric-mucosal work.
Neurological characterization may include repeated neurological examination, CSF investigation, MRI/MRA, functional cerebral imaging/SPECT, neuropsychological assessment and phenotype-directed motor, peripheral neurological and other investigations. Vascular, autonomic, cardiovascular, blood-volume, muscular, gastrointestinal, endocrine, immune and sleep abnormalities can further characterize individual patients; abnormalities that Hyde explicitly describes as variable remain supportive rather than compulsory.
Chronic Fatigue Syndrome follows a different definitional history beginning with the CDC Holmes criteria in 1988 and subsequently including Fukuda and other CFS constructions. Hyde's own proposed CFS formulation in the 2006 Little Red Book instead treats gradual-onset chronic fatigue as a signal to search extensively for missed major disease. CCC, ICC, SEID and NICE ME/CFS are later criteria constructions with differing requirements and should not retrospectively be assumed to define the identical patient population merely because terminology overlaps.
Where a specific enteroviral neurological disease has been demonstrated and explains the patient's presentation, the specific neurological diagnosis should remain the diagnosis rather than being displaced by a nonspecific symptom-defined label. Conversely, unexplained fatigue or fulfilment of symptom criteria alone does not establish enteroviral encephalomyelitis.
The practical consequence is a dedicated acute neurological pathway: a patient developing significant neurological abnormalities during or immediately following an infectious illness requires timely investigation of the acute neurological disease. The diagnostic opportunity for CSF, virological specimens, serial examination and acute imaging should not be lost while waiting to determine whether the patient will later satisfy the duration requirements of a chronic symptom-defined diagnosis.
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