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poliomyelitis, the disease which produces the flaccid paralysis of the extremities,
commonly known as "infantile paralysis." The prefix folio stands for grey, the
inflammation in this disease attacking a horn of the crescent of the grey mass of
nerve cells making up the centre of the spinal cord.
As will be shown later, some of the symptoms of these diseases are due to the
general action of the poison or toxin of the disease and the fever which accompanies
their production, and others depend entirely on the part of the nervous system which
chances to be affected.
The term "lethargica" was added on account of the stupor which is a feature
in many cases, so much so that in popular language the condition is often called
"sleepy sickness." This popular name has led to considerable public confusion
between "encephalitis lethargica" and the tropical African disease "sleeping
sickness" or "negro lethargy," which is an entirely different illness due to infection
by an animal organism introduced into the blood by the bite of the tsetse fly.
The two diseases, however, have this in common—that the lethargy is in either case
due to the morbid processes affecting the same part of the brain stem, thus illustrating
the point made previously, that certain symptoms are due to the site of the inflammation
quite apart from the cause of the inflammation. The exact causal agent
in encephalitis lethargica is as yet unknown, although it can be shown that the
disease can be transmitted from one animal to another and is possibly conveyed by
the nasal secretions.
Recent
history of
encephalitis
lethargica.
The first cases of an obscure nervous disorder, not recognised as belonging to
any of the ordinary categories, occurred behind the French lines on the Yerdun
front in 1915-16, and were studied in various military neurological clinics, but
attracted little attention. Later in 1916-17, cases occurred in Vienna, presenting
the now well-known features of stupor and diplopia (double vision), and from that
time onward attention began to be paid to the supposed new disease. In Great
Britain cases were noted at the end of 1917, in which the most constant symptom was
a rapid onset of languor or drowsiness, with moderate fever, often muscular tremors,
a dropping of the eyelids, termed ptosis, and a weakness of the muscles of the face,
giving rise to a mask-like expression. Death occurred in a large number of the cases
from a progressive paralysis of the muscles concerned in swallowing and breathing,
so that the patients were literally drowned in their own secretions. In those who
recovered, the duration of the illness varied from a few days to six weeks or longer.
As similar symptoms had been noted in certain cases of poisoning by infected food,
the condition was at first suspected to be due to a particular variety of food poisoning
known as botulism. Considerable attention was directed to this so-called new disorder.
Researches were instigated and memoranda prepared by the medical officers of
the then Local Government Board. In London, the Council circulated an explanatory
memorandum of the Local Government Board, and placed the services of medical
officers of the public health department at the disposal of practitioners for the purpose
of consultation. The whole subject was fully reported upon to the Public Health
Committee, and reports thereon will be found in the annual reports of the county
medical officer of health. It was soon found that the disease could not be due to
food poisoning, and for a time it was thought to be a cerebral form of acute poliomyelitis,
though later it was regarded as a separate disease. Since 1918, practically
all parts of the world have been affected. For a time, however, attention was largely
diverted from its consideration, owing to the world-wide outbreak of influenza which
started in the early summer of 1918. The prevalence of encephalitis still continues,
though perhaps the recent cases have been rather less severe than in earlier years.
General
description.
The disease attacks both sexes equally and affects all ages, though there are
proportionally rather more cases in the earlier decades of life. The earlier stages
of the disease may last for a few days or extend to a fortnight. During this period
there is general lassitude, headache, occasional vomiting or diarrhcea, with soreness