Post-Infectious Encephalomyelitis: Some Aetiological Mechanisms PETER 0
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Postgrad Med J: first published as 10.1136/pgmj.54.637.755 on 1 November 1978. Downloaded from Postgraduate Medical Journal (November 1978) 54, 755-759 Post-infectious encephalomyelitis: some aetiological mechanisms PETER 0. BEHAN M.B., Ch.B., F.R.C.P., F.A.C.P. Department of Neurology, Institute of Neurological Sciences, Southern General Hospital, 1345 Govan Road, Glasgow G51 4TF Summary present with definite neurological deficits, a clear-cut The possibility that acute disseminated encephalo- history of an antecedent infection, and abnormalities myelitis (ADEM) and epidemic myalgic encephalo- of the CSF are readily diagnosed as ADEM. When, myelitis ('epidemic neuromyasthenia') may share a however, psychiatric symptoms predominate and common pathogenesis is examined and many factors neurological features are inconspicuous or absent common to the two diseases are described. It is the disease is rarely if ever diagnosed as ADEM. In suggested that further study of ADEM may help our this paper, the author wishes to stress that far from understanding of epidemic myalgic encephalomyelitis. being rare, psychiatric symptoms, indistinguishable Protected by copyright. from those described in the syndrome of EME, are Acute disseminated encephalomyelitis relatively common in ADEM. It is his contention that Acute disseminated encephalomyelitis (ADEM), EME and ADEM share a common pathogenesis. post-infectious or para-infectious encephalomyelitis, In other publications, the clinical, pathological and is a disease which receives little attention in text immunological features of ADEM are listed in detail books of neurology, gets brief mention in large (Behan and Currie, 1978) so that only a brief books of medicine and is rarely considered in description of these features will be given here. In the text books of psychiatry. Yet it is relatively common, typical case, some days to one week after a viral constituting one third of all cases diagnosed as infection, the patient complains of headache, loss of encephalitis (Scott, 1967) and is often clinically appetite, tiredness, muscle aches, joint pains and indistinguishable from acute multiple sclerosis. often a curious type of 'lumbago'. There is generally Despite the neglect of ADEM, however, a consider- a low grade fever rising to 38°C or more with the able amount of information is available and may onset of neurological signs. In the severe form, help in our understanding of epidemic myalgic the commonest mental change is a depression in the http://pmj.bmj.com/ encephalomyelitis (EME). level of consciousness progressing to stupor and ADEM usually occurs after a banal virus infection sometimes coma. Irritability, hallucinations, dif- (Miller, Stanton and Gibbons, 1956). It may also ficulty in concentration, memory disturbances, develop after vaccination (Spillane and Wells, 1964), Korsakoff's syndrome and acute paranoia have also as an adverse reaction to drugs (Russell, 1937; been noted. When the disease involves the brain Cavanagh, 1953), or rarely, as a complication of rather than the spinal cord, seizures of any type, serum therapy (Csermely, 1950). The disease usually hemiplegias, visual disturbances, choreoathetosis presents within one week of the preceding event but and bilateral optic neuritis have been found. When on September 30, 2021 by guest. may occur at any time up to one month later. In this the spinal cord bears the brunt of the disorder, regard it is important to note that second attacks paraplegia may result. In some cases with spinal may occur after subsequent infections or vaccin- cord involvement, decreased reflexes which may be ations (Holt et al., 1976; Behan, 1977; Callaghan, asymmetrical, mild disturbances of bladder or Feely and Walsh, 1977). rectal sphincters, and muscle fasciculations have It is not well recognized that ADEM has a wide been observed. The patients may complain of a spectrum of clinical presentation. It may present as a wide variety of different forms of paraesthesia: fulminating encephalitis ending fatally after a few often there are unusual chest pains, difficulty with days but at the other end of the spectrum it can be respiration, painful muscles and pain over the an illness which is clinically indistinguishable from vertebral column. EME or the disease described here today as 'epidemic Patients with a similar antecedent viral infection neuromyasthenia' (Table 1). Those cases which to that causing ADEM may present with purely 0032-5473/79/1100-0755$02.00 ©) 1978 The Fellowship of Postgraduate Medicine Postgrad Med J: first published as 10.1136/pgmj.54.637.755 on 1 November 1978. Downloaded from 756 P. 0. Behan TABLE 1. Features of acute disseminated encephalomyelitis (ADEM) and epidemic myalgic encephalomyelitis (EME) contrasted Clinical data ADEM EME Ages affected Not before 2 years Predominantly in All other ages young adults affected Sex Both sexes affected Preponderance of equally females Incubation period 1-3 weeks 1-3 weeks Bacterial studies Negative Negative Virus isolation None None Toxin isolation None None Headache, muscle pains, anorexia, malaise. fever, somnolence + + Stupor, coma, hemiplegia, hemipaesis, seizures, paraplegia + + Choreoathetosis, cranial nerve palsies, optic neuropathy, areflexia, muscle paresis, fasciculations, sensory disturbances, nystagmus, ataxia, diplopia + + Irritability, memory disturbances, hypochondria, severe neurosis + + Personality changes, emotional instability + + Protected by copyright. CSF Protein May be increased May be increased Gammaglobulin May be increased May be increased Cells May be present May be present Sugar Normal Normal Culture Sterile Sterile Blood Leucocytosis may Leucocytosis may occur occur EEG Abnormal May be abnormal EMG Not reported May be abnormal psychiatric manifestations. These may be non- immunization, the case rarely presents to a neuro- specific; they include inability to concentrate, poor logist and the inciting event is often overlooked. memory and poor 'psychic energy' so that any pro- Because of the author's interest in this condition hehttp://pmj.bmj.com/ longed task involving intense concentration is has seen individuals who, following an upper virtually impossible; paranoia and severe hypo- respiratory tract infection, had a plethora of chondriasis have also been noted. Indeed, several of neurotic symptoms. The ADEM would have been these patients bear an obvious resemblance to those overlooked were it not for a little asymmetry of described with encephalitis following rabies im- reflexes, the occasional extensor plantar response and munization; the latter are described thus: 'person- the findling of a mild leucocytosis in the CSF. ality changes were conspicuous and consisted of In ADEM the CSF pressure may be elevated but on September 30, 2021 by guest. deterioration of highly integrated emotional and is usually normal; leucocytosis can occur, with intellectual functions and of constructive conduct' neutrophils in the early stages, but a lymphocytosis (Shiraki and Otani, 1959). In other patients, the is more usual, the cell count varying from a few to psychiatric manifestations are of a purely neurotic several hundred cells. The protein may or may not nature with mild personality changes, the pre- be elevated but it is usually below 100 mg %°. The dominant symptoms being those of hypochondriasis gammaglobulin has been reported to be increased and poor concentration. Detailed neurological in ADEM following anti-rabies vaccination. The examination of such cases often reveals mild cere- EEG is abnormal in most cases, the abnormalities bellar signs or evidence of long tract damage in being those of diffuse slowing in the theta and delta addition. frequencies. Changes in the EEG are helpful in When a patient does develop the purely psy- diagnosis but are most useful in following the chiatric symptoms following a virus infection or an patient's progress. Indeed the patient's condition is Postgrad Med J: first published as 10.1136/pgmj.54.637.755 on 1 November 1978. Downloaded from Post-infectious enicephalomyelitis 757 reflected graphically in the EEG and 'electrical Whilst these rare reports suggest that ADEM is deterioration' is often the first warning of a relapse the result of direct viral invasion of the central (Ziegler, 1966; Durston and Milnes, 1970). nervous system, demonstration of a virus is the Externally the brain appears normal although it exception rather than the rule and in the majority of may show some congestion and swelling in severe cases studied no virus has been isolated. cases. On section it may also appear normal but in A variety of theories have been brought forward severe cases small petechial haemorrhages may be to explain the pathogenesis of ADEM and, of these, observed in the white matter. In the early stages of that of autoimmunity seems to have the most the disease lymphocytes, plasma cells and occasional support. Van Bogaert (1950), in favour of this neutrophil leucocytes are found in the Virchow- hypothesis, cited the frequency of recurring focal Robin spaces. At a later stage there is proliferation infections, skin allergies and joint disease in patients of histiocytic and microglial elements around the and their families. The disorder may follow im- veins, and new reticulin fibres are formed. In a munization and can occur as an adverse reaction to sleeve-like zone of from 1 to 2 mm wide, around certain drugs (Russell, 1937; Cavanagh, 1953). The these small vessels, there is tissue destruction with the latter reaction is regarded