MYALGIC ENCEPHALOMYELITIS or EPIDEMIC NEUROMYASTHENIA by Dr. Melvin Ramsay
CHAPTER XVII
MYALGIC ENCEPHALOMYELITIS or EPIDEMIC NEUROMYASTHENIA
Taken from 147-152 pages of A. Melvin Ramsay and Ronald T.D. Emond's "Infectious Diseases" (Second Edition) 1978 book.
Synopsis
Myalgic encephalomyelitis or epidemic neuromyasthenia is a condition suggesting a primary infective process for which an aetiological agent has not yet been identified. Epidemics have been reported in various parts of the world since 1934. Approximately two-thirds of the cases show objective evidence of involvement of the central nervous system; tender foci occur in the muscles in rather more than a third of all cases; general asthenia and inability to concentrate are features of most cases and there is usually a prolonged aftermath characterised by emotional lability and fatigue. Relapses are common and may continue to occur over a period of many years. Some patients are left with permanent neurological and psychological sequelae; others recover uneventfully. An abnormal electromyogram may be demonstrated in cases with myalgic foci and abnormal electroencephalograms are found in a large proportion for a considerable period after the onset of the illness. There is no specific therapy.
Aetiology
Although no specific aetiological agent has been found several investigations indicate possible connections with virus infections. During an extensive epidemic of type-1 poliomyelitis in Iceland in 1955 spread of the disease was blocked in the Akureyri district where epidemic neuromyasthenia occurred in 1950 and no evidence of antibody to type-1 poliomyelitis virus was found in any of the children tested. In 1965 Japanese workers isolated a virus from patients with epidemic neuromyasthenia which inhibited the growth of poliovirus; others were successful in isolating a specific virus from patients with subacute myelo-optic neuropathy, a disease with features closely resembling epidemic neuromyasthenia. In Edinburgh in 1970 in 4 cases of epidemic neuromyasthenia a connection with Coxsackie B2 and B5 virus infection was demonstrated and it was suggested that the enteroviral infection had set in train a process of an allergic nature. In both America and Australia an agent transmissible to monkeys produced inflammatory and degenerative changes in the central nervous system corresponding closely to the neurological features of epidemic neuromyasthenia.
During the outbreak among the staff of the Royal Free Hospital, London, in the summer of 1955 intensive bacteriological, serological and virological investigations were carried out. These included throat gargles, nose, throat and post-nasal swabs, blood cultures, faeces and rectal swabs. Inoculations were made into fertile eggs, suckling mice, adult mice, rats, ferrets, guinea pigs, hamsters and rhesus monkeys. Tissue cultures of Hela cells, monkey-kidney, human embryo, human infant kidney and human amnion were also inoculated. No known infectious agent was found and similar investigations carried out by the Public Health Laboratory at Colindale in more recent cases have likewise proved negative. Serological tests were made relating to a variety of viral, protozoal and bacterial infections also with negative results.
Epidemiology
A number of outbreaks in which encephalomyelitis is a prominent feature have been reported from various parts of the world. The disease was first reported in Los Angeles in 1934 when it was assumed to be an aberrant form of poliomyelitis. In 1950 there was an extensive outbreak in Iceland and reports from Australia, New York State and South Africa confirmed its widespread nature. An outbreak of considerable significance was reported from a country practice in Dalston, Cumberland in 1955 shortly before a severe epidemic involving nursing and medical staff in the Royal Free Hospital, London which served to attract a further eponym "Royal Free Disease". The explosive character and size of the outbreak in the Royal Free Hospital created an impression of high infectivity which was further supported by the rapid spread of the disease to other hospitals in the Group (see Fig. 66). A full investigation of water, milk and food failed to give any evidence that these could have been vehicles of transmission. There was no instance of epizootic disease among either experimental or domestic animals which might have affected the human population. An exhaustive enquiry was also made into the possibility of accidental introduction of a neurotoxic substance such as an insecticide but this also proved negative. An outbreak in a teacher’s training college in Newcastle in 1959 was remarkable for the fact that among members of two communities living in the same building there was an attack rate of 40 per cent. in a group of 120 student teachers whereas in an adjacent group of 50 to 60 nuns, most of whom were engaged in teaching or cooking in the college, there was only one case. The disease was prevalent in North London from 1964 to 1967 and the most recent outbreak has occurred in the Hospital for Sick Children in Great Ormond Street.
OUTBREAK OF ACUTE ENCEPHALOMYELITIS IN ROYAL FREE HOSPITAL GROUP JUNE-NOVEMBER, 1955
Pathology
As the disease is rarely fatal very little is known regarding the pathology. No specific changes have been observed in the very limited material available for histological examination.
Clinical Course
Initial clinical features take the form of an upper respiratory tract infection with sore throat, conjunctival irritation and a dry cough, or of a gastro-intestinal disturbance with nausea, diarrhoea and abdominal cramps, while general lassitude, headache, pain in the limbs, dizziness and vertigo are fairly constant symptoms. Pyrexia is invariably low grade and seldom exceeds 38.0°C. The posterior cervical glands are usually enlarged and tender while extremely tender foci in muscles, particularly the trapezius and the gastrocnemii, are a feature of about 40 per cent of cases.
The full clinical features fall into three broad categories:
1. Those affecting the mental state with difficulty in concentration and impairment of memory, vivid dreams and emotional lability as the most constant.
2. Those arising from involvement of the autonomic nervous system, abnormal coldness of the extremities, sweating, profound pallor (especially of the face), constipation, bladder disturbances and orthostatic tachycardia being the most outstanding.
3. Those indicative of involvement of the central nervous system. Muscle weakness is the most constant finding; this may affect muscle groups in one or more limbs or there may be profound weakness in the whole skeletal system. In contrast to poliomyelitis, the weakness, though often severe, is seldom complete and wasting is never a feature. But fatiguability is without doubt the most striking phenomenon of this disease. Pain is the commonest sensory manifestation and is usually felt diffusely throughout weak limbs and associated with marked muscle tenderness. Sensory loss is usually maximal peripherally and its distribution frequently coincides with the motor weakness. Cutaneous sensory loss is more prominent than loss of joint or vibration sense. Cutaneous hyperaesthesia is common and often severe.
Very wide variation in clinical presentation is encountered in different epidemics and Parish has suggested that these fall into three groups:
Group 1 epidemics occurring concurrently with outbreak of anterior poliomyelitis in which neurological changes are found in the majority of cases but reticulo-endothelial involvement is minimal.
Group 2 an intermediate group not associated with outbreaks of poliomyelitis but with clinical features resembling Group 1. "Royal Free Disease" and the Dalston epidemic in which neurological changes were noted in 20 per cent. and reticulo-endothelial disorders were common fall into this category.
Group 3 epidemics with the basic features of the illness-malaise, headache, aching limbs, upper respiratory and gastro-intestinal disturbances, the characteristic fatiguability and prolonged convalescence in patients subject to relapses-but no direct evidence of involvement of the central nervous system.
The mildest cases become symptom-free within a month and are able to return to work but there is a marked tendency to relapse if physical activity is resumed too rapidly during convalescence. In more protracted cases the duration depends on the severity and extent of the nervous system manifestations. Relapses occurring after long periods of good health may be the result of reinfection or of a state of immunological insufficiency.
The features which are constant and which colour the aftermath are (a) proneness to tire readily and (b) emotional lability. Those with paresis find that the affected muscles become progressively more fatigued as the day wears on: patients who report themselves fit on rising in the morning may be prostrate within a very short period of time and even young people are forced to retire to bed by mid-afternoon. Many patients suffer from psychological symptoms usually of a depressive nature. Some are fully aware of a change in personality; for example, a person of previously equable temperament may become irascible and subject to violent outbursts of temper. Some report sexual frigidity, some that obstinate constipation has replaced a previously normal bowel habit; others find they have frequency of micturition but urine examination proves negative and the condition clears with the termination of the episode. Many complain of circulatory changes with constant coldness or even numbness in the extremities. All have difficulty in concentrating for any length of time and it is noticeable that both school children and medical students suffer from impaired mental capacity for some weeks or months. Many find that they are prone to drop articles or fumble quite simple manoeuvres. Some have terrifying nightmares and in many a typical "functional overlay" develops; if seen for the first time at this stage there is the tragic possibility of misdiagnosis of “hysteria” which has unfortunately been increased as a result of the McEvedy and Beard hypothesis that this is the sole explanation of the condition.
Diagnosis
Since the disease is so very protean in it's manifestations it may masquerade as influenza, respiratory catarrh, tonsillitis, gastroenteritis, rheumatism or as some transient virus infection.
Fig. 72. Electromyographs from case of myalgic encephalomyelitis. The upper tracing from the left tibialis anterior muscle is abnormal showing grouping of large polyphasic motor-unit potentials. The lower tracing from the right tibialis anterior muscle is normal. (Calibration 500 and 100 μV at 50 cycles per sec.)
While there may be a functional prolongation of the disease the original attack is an undoubted organic entity. Bacteriological, serological and virological investigations all prove negative as does examination of the cerebrospinal fluid. Although the white blood cell count is usually consistent with that found in virus infections, haematological examination is really of no diagnostic value. Anaemia is not a feature of the disease and the erythrocyte sedimentation rate is either normal or slightly raised.
Extensive electromyographic surveys among patients affected by epidemic neuromyasthenia in the Los Angeles area (including patients with residual paralysis from the 1934 outbreak as well as recent cases) and in the Royal Free outbreak showed complex polyphasic activity, scattered fibrillation and reduction of normal interference pattern while in some American epidemics a considerable increase in creatinuria and in the creatine-creatinine ratio was noted during the acute stage of the illness. These findings are suggestive of, and consistent with, a prolonged metabolic disorder affecting cellular energy systems.
Non-specific electroencephalographic abnormalities have also been reported.
Treatment
It is important to advise rest during the acute phase of the disease or during relapses. Patients require sympathy, understanding and reassurance and must be encouraged to accept the limitations imposed upon them and to "come to terms" with the disease. Admonitions to "snap out of it" are totally misplaced. While further search for an infective agent is clearly essential a study of the cellular energy systems is likely to prove productive.
SELECTED READING
Albrecht, R. M.; Oliver, V. L.; Poskanzer, D. C. (1964). “Epidemic Neuromyasthenia: Outbreak in a Convent in New York State.” JAMA, 187:904–907 - JAMA full text and PubMed.
Innes, S. G. B. (1970). “Encephalomyelitis resembling benign myalgic encephalomyelitis.” The Lancet, 1:969-971 - Lancet page and PubMed.
Inoue, Y. K.; Mishibe, Y. (1973). The Lancet, 1:776 - I couldn’t locate a digitized copy or PubMed record for this specific item; it may be a brief correspondence. A library search (print index for The Lancet 1973, vol. 1, p. 776) or interlibrary loan will likely be needed.
Parish, J. G. (1974). “Epidemic neuromyasthenia: a reappraisal.” IRCS Journal of International Research Communications (Medical Science), 2:22-26 - This journal (ISSN 0300-5577) is sparsely digitized; I couldn’t find a stable online copy, but multiple sources confirm the citation details.
Royal Free Hospital Staff (1957). “An Outbreak of Encephalomyelitis in the Royal Free Hospital Group, London, in 1955.” Br. Med. J., 2:895–904 - BMJ landing page, free PMC full text, and PubMed.
Wallis, A. L. (1955). “An unusual epidemic.” The Lancet, 2:1091 (letter) - Issue table of contents showing p.1091; additional bibliographies note related letters at 1955;2:290 and 1956;2:146.
Wallis, A. L. (1957) "Investigation into an unusual disease seen in epidemic and sporadic form in a general practice in Cumberland in 1955 & subsequent years" M.D. Thesis, University of Edinburgh - Open-access thesis in the Edinburgh Research Archive (PDF).
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