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150
a quarter of the whole. About half a century ago, it was asserted by the investigators
of that time that the proportion of congenital to acquired cases was greater, but
Mygind, when he published his survey of the statistics of all countries in 1894, prophesied
that in course of time better knowledge and superior methods of investigation
would show that the congenital cases formed far less than instead of more than
half of the total number. True Hereditary Deafness was proved in 83 cases, 20.54
per cent. of all the congenital cases.
Of Sporadic Deaf Birth there were 305 examples, 75.49 per cent. of the congenital
cases. This group is always unsatisfactory, because at present the absolute knowledge
of their causation is practically nil. Kerr Love, before the war, sought to
show that a certain percentage could be referred with certainty to Congenital Syphilis,
and there is no doubt that this is so. Unfortunately, however, the Wassermann
test, upon which he based his argument, has been shown recently by McDonagh
and others to be untrustworthy. Indeed, McDonagh has pointed out that it may
be positive in some cases of chronic intestinal intoxication from which all possibility
of syphilis can be conclusively excluded. During the past 2 years the conviction
has grown that intestinal intoxication plays a very definite and important part in
the production of deafness, and since the condition is demonstrably hereditary and
its signs have been noted in an appreciable number of congenitally deaf chilldren,
both of the sporadic and hereditary types and also in their parents. In this fact
may lie the elucidation of a considerable proportion of the cases which have so long
baffled otologists. The lesion is probably cortical, but until a number of investigations
into the histology of the cortex and of the big ganglia of deaf-mute brains have
been made, the hypothesis here suggested must rest upon clinical grounds only.
The observations presented to the International Congress of Otology, at Copenhagen
in 1928 (Yearsley), suggest that there is a connection between certain cases of congenital
deafness and that hereditary condition which manifesting itself after birth
goes under the unsatisfactory name of "otosclerosis."
Among the Congenital cases, the rare condition of deafness in Congenital Cerebellar
Ataxy is represented by 1 case.
Acquired Cases.—These cases numbered 1,117 or 72.7 per cent. of the whole.
They may be grouped into three primary groups of which the proportions are
as follows:—
1. Diseases of the Nervous System 119 10.6 per cent.
2. Infectious and Infective Diseases 316 28.3 „
3. Primary Ear Disease and Injuries 682 61.15 „
The first of these groups, that of Diseases of the Nervous System, is occupied
almost entirely by cases of meningitis. There were, during the past 10 years, 2 cases
of deafness due to Hydrocephalus and 1 due to Infantile General Paralysis. The
primary causes of the meningitis cases are indicated in the general analysis
(page 84) and, as is usual in all statistics of this nature, the greatest number comes
under the head of "causes unknown." There is need for an investigation into the
etiology of these cases, with a view to better classification and prevention.
Of the Infectious Fevers, measles and scarlet fever are responsible for the
greatest number of cases, the former being slightly in excess. Diphtheria is less in
evidence than it used to be. The other Infective Diseases are made up largely of
pneumonia and congenital syphilis. The incidence of the latter during the past
10 years has been:—11-12-9-7-6-9-5-7-3-1. These figures appear to suggest that
the improved methods of dealing with Syphilis are yielding good results.
The cases of Acquired Deafness due to Primary Ear Disease always form the
largest group. The figures given speak for themseves. Otosclerosis occupies about
0.9 per cent. only, the great bulk consisting of middle ear suppuration, middle ear
catarrh, and their results. The vast majority of these cases are the result of tonsils
and adenoids.