View report page

21
(b) The anatomical location of the mischief. If the stress of the attack falls upon the cells
in the grey matter of the anterior horns of the spinal cord, the case is one of poliomyelitis ; if
the nuclei of the cranial nerves are involved it is polioencephalitis or encephalitis lethargica;
if the meninges of the brain and cord are affected it is cerebro-spinal meningitis.
Upon this general scheme there are superimposed the following further qualifications. Drowsiness
is held to imply encephalitis lethargica; retraction of the head, cerebro-spinal meningitis; and
when lumbar puncture is practised the physical characters and bacteriological findings in the fluid are
held to differentiate between cerebro-spinal meningitis and the other two categories of the disease. The
strict bacteriological tests for identification of the meningococcus are so rarely complied with that this
criterion alone does not often determine the diagnosis.
As a result of reviewing some hundreds of the cases assigned to the three categories of disease
the suspicion already entertained has been strengthened, that in most of the cases one common influence
was at work, operating here upon one and there upon another portion of the central nervous system;
here in an infant, there in a young child, or again in a young adult or older person. It may therefore
be suggested that had the point of attack of the mischief been, say, the respiratory mucous membrane
instead of the cerebro-spinal system, a parallel state of things would have resulted if some hundreds of
"common colds" had been notified in part as affections of the anterior fauces, in part as affections of the
pharynx, tonsils and eustachian tubes, etc., and finally in part as affections of the larynx or lungs.
The following report on encephalitis lethargica in London during 1920 has been prepared by
Dr. J. G. Forbes:—
Dr. J. G.
Forbes'
Heport on
Encephalitis
Ltthargica.
During 1920, 149 cases of encephalitis lethargica were notified as occurring within the Administrative
County of London; in 19 of these cases the diagnosis was not confirmed. The actual number
of cases of the disease was, therefore, 130, of which 48 proved fatal, or close on 37 per cent.
Seasonal incidence showed distinct waves of greatest prevalence during the summer and winter
months, the crest of each wave being attained in June and December with 22 and 27 cases respectively,
and the trough in April and October with 4 and 3 cases. This incidence may be compared with that of
the three previous years which provide the following figures :—
Year.
No. of cases.
Mortality per cent.
Seasonal prevalence.
1919* London 85 48.3 Dec.-Feb.
England and Wales (including London) 538 54.6 Dec.-Feb.
1920 London 130 36.9 Dec.-Jan.
June-July
England and Wales (including London) 914 —Dec.-March
May-July
* Encephalitis lethargica was made notifiable as from 1st January, 1919.
The monthly incidence, of cases, together with the number of deaths (in brackets) was as follows:—
January 19 (7); February, 6 (3); March, 8 (4); April, 4 (2); May, 10 (4); June, 22 (7); July, 15 (6);
August, 4 (1); September, 6 (2); October, 3 (0); November, 6 (3); December, 27 (9).
The maximum and minimum incidence of each wave, therefore, occurred at intervals of exactly
six months. The number of cases and mortality rate of the disease for each month do not appear in
direct ratio to each other, the months of lowest case incidence providing the highest mortality rate,
as is indicated by the bracketed figures of fatal cases in the above list for each month,
The distribution between the two sexes falls about equally—viz., males, 69 (24 fatal); females, 61
(24 fatal). The age incidence is shown in the following table. The number of cases proving fatal is
noted in brackets :—
No. of cases. No. of cases.
Under 5 years 5 (3) 30-40 years 24 (6)
5-10 years 12 (4) 40-50 „ 13 (7)
10-20 „ 38(10) 50-60 „ 10(5)
20-30 „ 19 (6) Over 60 years 9 (7)
The disease therefore appeared most prevalent among those in the second decade of life, whilst
the mortality was highest in the later decades, particularly over the age of 60.

Examination of the cerebro-spinal fluid is often of much value as an aid to the diagnosis of
encephalitis lethargica, and without this necessary investigation it may be impossible to distinguish the
meningitic type of the disease from tuberculous meningitis, cerebro-spinal and other forms of meningitis,
particularly in children, if reliance is placed solely on clinical evidence. The fluid obtained by lumbar
puncture in encephalitis lethargica is occasionally under pressure and increased in amount, is usually
clear and colourless and showing but little change from the normal; it may be blood-tinged and exceptionally
yields any visible cell deposit on centrifugation apart from traces of blood. Very rarely is there
evidence of fibrinous coagulum, in fine particles, but not in the delicate pellicle of clot so familiar in
the slightly turbid fluid from tuberculous meningitis. The definite trace of protein generally present
in amounts which may not be capable of measurement, and from .005 to .01 per cent, of albumen, serve
to distinguish from the normal faint trace of globulin, and from the larger amounts of albumin present