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in tuberculous fluid, which may range from .01 to .2 per cent., and the still larger quantities in other
forms of meningitis.
Evidence cf the presence of dextrose in slight trace is invariable; it also exists in normal cerebrospinal
fluid ; usually, too, in the fluid of tuberculous meningitis, but is absent in other forms of meningitis.
The number of cells (lymphocytes) per c.mm. may show but little increase above the number,.
1-5, normally present, but it is by no means uncommon to find 10 or 20 per c.mm.—i.e., in excess of
the normal limits; occasionally the cell increase may reach 40 or 50, it is rarely as high as 150-200 per
c.mm., in contrast to the well-marked cell increase existing in fluid from tuberculous meningitis, and
ranging from 250 to 1,000 or more per c.mm. with still larger numbers in other forms of meningitis.
The type of cell obtained by centrifugation apart from red corpuscles possibly present is invariably
the small lymphocyte, which may in film preparations from the centrifugalised deposit appear to be
in considerable numbers, occasionally suggesting the possibility of tuberculous meningitis.
The absence of clot formation however, and the failure to find tubercle bacilli by appropriate
staining of the cell film will in the great majority of cases serve to exclude the latter, and the bacteriological
culture of the fluid in encephalitis lethargica proving sterile will exclude also other types of
meningeal infection. It must be said that a report on the cerebro-spinal fluid for purposes of diagnosis
should always be regarded and weighed in conjunction with the clinical features, and that the slight
changes usually found as above described will not serve to distinguish encephalitis lethargica from such
conditions as polioencephalitis, poliomyelitis, neurosyphilis of the brain or spinal cord (in the absence
of the Wassermann test), arterio-sclerosis of cerebral vessels, cerebral softening, cerebral tumour, uraemia,
meningitis, and other conditions associated with cerebral symptoms—e.g., in particular, influenza. With
regard to the diagnosis of encephalitis lethargica and the classification of its various types, a disease so
protean in its clinical aspects and presenting as it does so much diversity in its symptomatology may
necessarily offer very considerable difficulty in diagnosis, the possibilities of which in a doubtful case
are indicated by the variety of the foregoing list of diseases, depending for diagnosis perhaps solely on
elimination by process of exclusion. Attempts at satisfactory classification of a number of cases are
likely to prove both baffling and incomprehensible, unless resting on a scientific basis. The symptomatology
is so varied that, if relied on alone, the grouping becomes intensely complicated with the
numerous permutations and combinations which arise, and it is possible that in ten cases of the disease
no single symptom will be common to all.
Any and every part of the nervous system may be involved, and there is no combination of
symptoms that may not be encountered. In consequence, many cases cannot be placed in any type unless
types are to be multiplied until they cease to have either value or significance. (Walshe. Brain, Vol.
XLlll., Part 3,. Nov., 1920., p. 213). It is, therefore, certain that a clear grasp of the anatomical
distribution of the lesions of encephalitis lethargica is essential both for diagnostic purposes and for
providing the only dependable system of classification. MacNalty has suggested the recognition of a
number of clinical types (vide also Bramwell's contribution in Lancet, 29th May, 1920, p. 1154) under
some of which the 130 cases notified during 1920 are capable of being grouped as follows :—
I. The most common type in which the lesions are situated in the mid-brain—characterised by
fever, lethargy of varying degree in association with weakness of the eye or face muscles—55 cases (16
fatal).
II. Lesions situated in the upper or cortical region of the brain. Lethargy combined with symptoms
of meningeal infection—difficult to distinguish from tuberculous and other forms of meningitis
more particularly the former, influenza, typhoid fever, uraemia,.and cerebral arterio-sclerosis—20 cases
(11 fatal).
III. Type in which fever and lethargy are transitory or inconspicuous, but with pronounced
focal symptoms referable to lesions of the mid-brain, such as paralysis of the ocular and facial muscles
—13 cases (2 fatal).
IV. Ah abortive type in which the symptoms of lethargy, fever and diplopia (double vision)
never well marked, pass off after two or three weeks—6 cases.
V. Type resembling paralysis agitans, with slow defective utterance, mask-like expression,
marked tremors and muscular twitchings (myoclonus), and occasionally choreiform movements, with
onset of fever, lethargy, and diplopia, due to lesion in the pons varolii or lower part of the brain—26 cases
(14 fatal), one case of violent choreiform movements (like St. Vitus' dance) in a girl of 16, who recovered.
VI. Ataxic type—cerebellar in origin—marked by giddiness, staggering and headache, in addition
to lethargy and fever—13 cases (1 fatal).
VII. Type presenting evidence of lesions of the cerebral cortex or part of the motor tract in the
mid-brain, giving rise to hemiplegia or paralysis or Weakness of both arm and leg on one side, or loss of
power in one limb only, with history of fever, lethargy and ocular palsy at the outset—17 (2 fatal).
Walshe has also dwelt on the importance of adopting classification on an anatomical basis,
directing attention to the symptoms which may be ascribed to lesions affect ing the neurones of the three
physiological levels—the upper or cortical, the middle, involving the mid-brain and basal ganglia,
the lower affecting the medulla and spinal ganglia.
In describing cases of myoclonic encephalitis, he attributes the prevailing symptoms of muscular
contraction, which occur in varying degree and distribution, to an irritative or exciting action of the
virus upon the nerve cells of one or other of the three levels. This action of the virus may affect any or
every part of the nervous system from cerebral cortex to spinal roots and thus give rise to the polymorphic
character of the disease in cases showing what may be called irritative symptoms.
On the other hand, in cases showing negative or paralytic symptoms, there is evidence that the
virus has shown a definite and selective action on cells of the basal ganglia and of certain motor nerves
of the brain stem, producing the familiar mid-brain types of the disease with associated lethargy.