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Full text of "Diseases Of The Nose Throat And Ear"

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CONGENITAL DEAFNESS                             405


In adults, most tests of hearing depend on the active co-operation of the
patient who can tell whether the various test sounds have been heard. In
infants, this is obviously impossible and whether a child has heard a sound
has to be assessed by its reaction to the sound. This examination is time
consuming and requires experience and patience on the part of the examiners.
It is also of the greatest importance that the child should be completely
relaxed in a natural and friendly atmosphere. The room in which the test is
done should be sound-proofed and it should be comfortably furnished with
small tables and chairs and there should be a good selection of toys and
suitable testing apparatus. Time must be allowed for the child to settle in and
to become accustomed to these new surroundings and to those who are
going to carry out the tests. Several visits may be required before rapport is
achieved and the child enjoys his visits to his new friends.


Active co-operation of any kind is not to be expected in most children under
2 years. A newborn baby will respond to loud sounds by a startle reflex.
This has been described as a sort of jerky extension of the spine and limbs,
followed by a quick bowing movement of the arms over the chest, usually
accompanied by a cry. The reflex may be less marked, a blink of the eyelids
or he may simply interrupt what he is doing for a moment. After 6 months
he may turn his head towards the sound. To carry out the test the child is
preferably seated on his mother's knee and his attention held by one examiner
who also observes any responses. A second person makes a variety of noises
out of sight of the child and the first examiner notes any response by the
child. By using sounds of different pitches and loudness an assessment of the
degree of any deafness and the pattern of the loss can be made. Additional
accuracy can be introduced by using a free field audiometer as the sound


After about 2^ years the child can be taught to make some simple movement,
e.g. building up bricks or some other progressive toy, in response to sounds to
which it is known that he responds. At first he is allowed to see the sound
source which could be a xylophone being struck. Once he appears to under-
stand the 'game' the sound is made out of sight and his response to a variety
of sounds can be noted. Once the child has been conditioned in this way
accurate assessment of any hearing loss becomes possible, the most accurate
results being achieved when the child agrees to wear earphones and to respond
to the pure tones of the audiometer.


By 5-7 years of age audiometry is usually possible without preliminary