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Encephalitis Lethargica

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"ENCEPHALITIS LETHARGICA (from Gk. eyx(paXov, a portion of the brain, and XilOapyos, forgetful), a specific infectious disease of the nervous system, of which the most frequent, though by no means invariable, symptom is drowsiness or lethargy, often associated with paralysis of the muscles of the eye, producing diplopia or double vision.

In recent years this disease first appeared in epidemic form in Austria in the winter of 1916, and was described and named by C. von Economo in Vienna in 1917. It reappeared in the following winter, and was recorded in France in March 1918 by A. Netter. In England it was first recorded in April 1918, independently by Wilfred Harris and A. J. Hall. These earlier epidemics were all recognized by the combination of lethargy and diplopia. Subsequently the same seasonal incidence has prevailed, the number of cases diminishing in summer and increasing in winter and spring. In the United States it was reported in March 1919, the epidemic having spread from east to west.

The literature of medicine has been ransacked to ascertain whether or not previous records exist of the occurrence of the characteristic combination of symptoms. In 1890 a small epidemic occurred in North Italy, and later in Austria and other countries, which may be accepted as Encephalitis Lethargica. At the time it was known as Noma. It attracted little attention. The evidence for sporadic cases since then is doubtful.

Previous records are all doubtful. Hippocrates, Sydenham and other less-known authorities have described conditions which may or may not have been Encephalitis Lethargica. Stahl in 1779 recorded more fully an outbreak characterized both by lethargy and diplopia, and with other very suggestive symptoms. Franck in 1837 divided Encephalitis into various types, including a lethargic form which he stated occurred frequently as a result of epidemics of influenza.

sit slzptt Whether or not the observed combinations of symptoms have ever occurred before, the question early arose whether the syndrome should be regarded as a clinical entity or as a special manifestation of some disease previously known in other forms. The three diseases with which its relations have been more particularly considered are botulism, influenza and acute poliomyelitis or Heine-Medin's disease. Botulism results from the consumption of infected meat or other food, usually ham, and is especially characterized by paralysis of the eye muscles. The disease is due to infection with a specific bacterium - the bacillus botulinus. Since the most careful search has invariably failed to detect the presence of this bacillus in Encephalitis Lethargica botulism can be finally excluded. With regard to influenza, the appearance of Encephalitis Lethargica, including Noma as such, has approximately coincided with epidemics of influenza in 1889 and at the present time. On the other hand, there is considerable evidence against their identity. Influenza is highly contagious, while the clinical appearance of Encephalitis Le- thargica occurs in an irregular manner and has not attained any great magnitude as an epidemic. When Encephalitis Lethargica commenced in Austria influenza had not yet appeared. There are also histological differences, since in influenzal encephalitis there is marked oedema of the brain and an absence of the two special characteristics of Encephalitis Le thargica - vascular congestion and infiltration of the perivascular lymph spaces. Pfeiffer's bacillus, the so-called influenza bacillus, is not found in Encephalitis Lethargica.

The relations of Encephalitis Lethargica to Heine-Medin's disease have led to much discussion. Unusual forms unquestionably occur in which the diagnosis is doubtful, both on clinical and pathological grounds, but, considering typical forms, there are striking differences between the two diseases. Heine-Medin's disease particularly attacks persons under 20 years of age, and tends to increase in frequency in summer. The onset of the general symptoms and of the paralysis is acute, the course is brief and the spinal cord is mainly affected. In Encephalitis Lethargica, on the other hand, persons of all ages are liable to attack, and the frequency is greatest in winter and spring. The onset is usually insidious, the course is lengthy, and the mid-brain is especially affected. Histologically there are also important differences. Microscopic haemorrhages are constant in Heine-Medin's disease, while perivascular infiltration is slight, the reverse being true of Encephalitis Lethargica.

Symptoms

Encephalitis Lethargica was primarily recognized by the occurrence of the combination of lethargy and double vision, the latter being due to paralysis of the muscle of the eye. While pathological drowsiness in varying degrees is probably present in 70 to 80 per cent of cases at some stage of their course, further observation has revealed the occurrence of numerous other manifestations. The disease is widespread through the nervous system, and the complexity of the structure of the nervous tissues, together with the high degree of specialization of the functions of its various parts, explains the protean nature of its symptoms. Numerous " types " have been described, but the value of these is slight, as a single patient in the course of a few days often exhibits the characteristics of many such types. The clinical manifestations are probably best classified as Walshe suggested, according to the broad scheme proposed for other nervous diseases many years ago by Hughlings Jackson. In the following description based on this system, " positive " symptoms denote exaltation of function, which may be due either to irritation of nervous tissue or to a loss of the control exercised normally by the higher centres of the brain, while " negative" symptoms denote depression or loss of function principally due to destruction of nervous tissue.

A. General Symptoms Due to Toxic Infection

These include weakness, headache, often occipital with some stiffness of the neck, shivering, vertigo, muscular pains and vomiting or other gastro-intestinal disturbances. The pulse may be rapid and eruptions, usually resembling measles, occasionally occur. The temperature is variable, and it has no characteristic course. It often rises after some days from lot ° to 105° F. for a short period, but may be more prolonged, or pyrexia may be absent throughout.

B. Nervous Symptoms

These are general and focal, the latter being due to affection of highly specialized portions of the brain.

(I) General Nervous Symptoms. - Positive symptoms are delirium, mania, restlessness and various degrees of excitement, while the more common negative manifestation is the characteristic lethargy, in all grades from simple apathy to complete coma. Innumerable degrees occur of these two extremes, or even combinations. The } 1. v 4st;, t, patient may slowly drift into a somnolent state or may not uncommonly combine somnolence by day with insomnia or restlessness by night. Rarely an attack commences suddenly with the wildest delirium or mania.

(II) Focal Nervous Symptoms. - The positive symptoms include the following (1) Convulsions, which are occasionally generalized, resembling the epileptiform fit.

(2) Involuntary movements. These may develop during the attack or several months later in the course of convalescence. Numerous forms occur. The " myoclonic " type is characterized by short, rapid, rhythmic contractions of muscles, especially affecting the abdominal muscles and also the diaphragm, but the entire musculature or any group of muscles, or even a part of a single muscle may be affected. The contractions are 30 or 40 to the minute. Epidemic hiccough is possibly a variety of this type. Tremors, choreiform, athetoid and other movements of muscles may develop after the attack, some causing coarse spontaneous movements of lar e amplitude.

3) Rigidity. This group includes the "Parkinsonian mask " and catalepsy, the latter being a condition of rigidity in which the limbs are retained for long periods in the position in which they are placed by an observer. The Parkinsonian mask, an expressionless facies, is common, and combined with rigidity produces the appearance of acute paralysis agitans, or Parkinson's disease.

(4) Muscular pains. These may be severe.

The negative symptoms are represented by paralyses. The commonest of these is the characteristic affection of the muscles of the eye, especially those innervated by the third pair of cranial nerves. The principal clinical symptoms are ptosis or drooping of the eyelids, double vision and paralysis of the muscles of accommodation. The pupils are often unequal and their reaction altered, the most common change being loss of reaction to accommodation while still reacting to light; but in rare instances the Argyle-Robertson reaction may be present. Optic neuritis is extremely rare, and never advanced. Less common are affections of the remaining cranial nerves, producing facial paralysis, difficulty in swallowing or in production of speech, etc. No portion of the nervous system is immune, and instances occur with paralysis of limbs and other parts, producing monoplegia, hemiplegia, diplegia, or aphasia. The sensory system is much less frequently affected. The deep reflexes are commonly but not invariably absent.

Morbid Anatomy

The small vessels of the brain and meninges are dilated, the congestion often being visible both to the eye and under the microscope, but the most characteristic change is infiltration with small round cells of the perivascular lymph spaces, surrounding the capillaries. Other less constant and less conspicuous changes include degeneration of the nerve cells and destruction of neurons, proliferation of the mesoblastic cells lining the vessel walls and of the glial cells, and the occasional occurrence of haemorrhages and of thrombosis of veins. The lesions are most common in the mid-brain and basal ganglia, but any portion of the nervous system or meninges may be affected.

Prognosis

Excluding mild and abortive cases, and the so-called formes frustes, the mortality is about 33 per cent. Including all cases it is under 20%, but the exact figure is doubtful. Deaths usually occur within three weeks from onset. The duration may be many weeks or even months. Alteration of the mental functions may be prolonged, and paralyses, aphasia and other changes have persisted long enough in some instances to be regarded as permanent, but when recovery takes place, it usually becomes complete.

Treatment

This is on the general lines of treatment of acute febrile disease. Hexamine is usually administered. Netter strongly advocates the production of a local abscess by the injection of turpentine, 1-2 cc., into the thigh, but the value of this is not yet confirmed. (H. L. T.)