Deaf Child

Children with profound (>90 dB loss) or total deafness fail
to develop speech and have often been termed as deaf-mute
or deaf and dumb. However, these children have no defect
in their speech producing apparatus. The main defect is
deafness. They have never heard speech and therefore do
not develop it. In lesser degrees of hearing loss, speech
does develop but is defective. The period from birth to 5
years of life is critical for the development of speech and
language, therefore, there is need for early identification
and of hearing loss and early rehabilitation in
infants and children It was observed that children whose
hearing loss was observed and managed before 6 months
of age had higher scores of vocabulary, better expressive
and comprehensive language skills than those diagnosed
and managed after 6 months of age emphasising the
Importance of ea rly identification and treatment.
Aetiology
Hearing loss in a child may develop from causes before
hirth (prenatal), during birth (perinatal) or thereafter
(postnatal).
A. Prenatal Causes
They may pertain [Q the infant or the mother.
1. Infant factors. An infant may be born with inner ear
anomalies due to genetic or non-genetic causes. Anomalies
may affect inner ear alone (non-syndromic) or may form
art of a syndrome (syndromic).
Anomalies affecting the inner ear may involve only
in the membranous labyrinth or both the membranous and
bony labyrin ths. They include:
i) Sheibe's dysplasia. It is the most common inner ear
anomaly. Bony labyrinth is normal. Superior part of
membranous labyrinth (utricle and semic ircular
ducts) is also normal. Dysplas ia is seen in the
cochlea and saccule; hence also called cochleoso.ccular
dysplasia. It is inherited as an autosomal reces ive
non-syndromic trait
ii) Alexander's dysplasia. it affects only the basal turn of
membranous cochlea. Thus only high frequenc ies
are affected. Residual hearing is present in low frequencies
and can be exploited by amplification
with hearing aids.
iii) Bing-Siebeman dysplasia. There is comple te abse nce
of membranous labyrinth.
iv) Michel aplasia . There is complete absence of bony
and membranous labyr inth. Even the petrous apex
is absent but external and middle car, may be comple
tely unaffected. No hearing ;lids or cochlear
implantation can be used.
(v) Mondini's d)'splasia. O nly basal co il is present or
cochle:1 is 1.5 turns. There is incomplete partition
between the scalae due to absence of osseous sp inal
lamina. Condition is unilate ral or bilateral. This
deformity may be seen in Pend red, Waardenburg,
Branchio-oto-ren al, Treac her-Collins and Wildervanch
syndromes .
(vi) Enlarged vestibular aqueeduc t. Vestibular aqueduct is
enlarged (>2 mm), endolymphatic sac is also enlarged
and can be seen on T2 MRI. It causes early onset sen sorineural
hearing loss which is progressive. Vertigo
may be present. Perilymphatic fistula may occur.
(v i i) Semicircular canal malformations. Both superior and
lateral or only lateral semicircular canal malformations
may be seen. They can be identified on imaging
techniques.
2. Maternal factors
(a) Infections
(b) Drugs during pregnancy
(c) Radiation to mother in the first trim ester
(d) Other factors
(a) Infections. Infections which affect the developing foetus
are toxoplasmosis, rubdla, cytomegalov iruse;; , herpe
type 1 and 2 and syphilis. Remember mnemonic,
TORCHES.(b) Dntgs during pregnancy. Streptomycin, gentamicin ,
robm mycin, amikac in, quinine or chloroquin, when
given to the prcgnanr mother, cross [he placental barrier
and damage the cochlea. TnaLidomide nor only
affects ear hut also causes abnormalities of limbs,
heart, face, lip and palate .
(c) Radiation to mother in the first trimes ter.
(d) Other factors. Nutritional deficiency, diabetes, toxaemia
and thyroid deficiency. Maternal alco holism is
also te ratogenic to tbe developing auditory system.
B. Perinatal Causes
They relate to causes during birth or in early neonatal
period. They are:
1. Anoxia. It damages the cocnlear nuclei and causes
haemorrhage into the ear. Placenta praevia, pro longed
labo ur, co rd round the neck and prolapsed cord can a ll
cause foetal anoxia.
2 . Prematurity and low birth weight. Born befote
term o r with birth we ight less tnan 1500 g.
3. Birth inj uries, e .g. forceps delivery. They may
calise intrac ranial haemo rrhage with extra vasation of
bluod into the inner ear.
4. Neonatal jaundice. Bilirubin level greater than
20 mg% damages the cochlear nucle i.
5. Neonatal meningitis.
6. Sepsis.
7. Time spent in neonatallCU.
8. Ototoxic drugs used for neonatal meningitis or
septicaemia.
C. Postnatal Causes
1. Genetic. Though deafness is genetic it manifes ts
later in childhood ot adult life. Deafness may occur a lone
as in familial progressive sensorineural deafness or in assoc iation
with certain syndromes, e.g. Alport's, Klippel-Feil,
Hurler, etc.
2. N on-genetic. They are essenrially same as in adults
and include:
(i) Vira l infections (measles, mumps, varicella,
influenza ), meningitis and encephalitis.
(ii) Secretory otitis media.
(iii) Ototoxic drugs.
(iv) Trauma, e .g. fractures of tempo ral bone, middle ear
surgery or perilymph leak.
(v) Noise-induced deafness .
EVALUATION OF A DEAF CHILD
Finding the Cause
This may require a detailed history of prenata l, perinaea I or
pos tnatal causes, fa mily history, physical examination and
certa in investigations depending on the causc suspected.
Suspicion of hearing loss. Hearing loss is suspected if
(i) the child sleeps th rough loud noises unperturbed or
fails to startle to loud sound, (il) fails to develop speech
at 1-2 years. A partially hearing child may have a defective
speech and perform poorly in school and be labelled
mentally retarded. lr is essential that all children at risk
for hear ing loss should be screened and followed.
Risk factors for hearing loss in children (Recommendations
of }ointCommittee on Infant H earing-updated
to 1994). .
(i) Family histo ry of hearing loss .
(ii) Pren atal infections (TORCHES).
(iii) Craniofacial anomalies includi ng those of pinna
and ear canal.
(iv) Birth weight less than 1500 g (3.3 lbs).
(v) Hyper bili rubinaemia requi ring exchange transfusion.
(vi) Ototoxic med ications included but not limited to
aminoglycosides used in multi ple courses or in
combination with loop diuretics.
(vii) Bac terial meningitis.
(viii) '"Apgar score of 0-4 at 1 minute or 0-6 at 5 minutes.
(ix) Mechanical ventilation for 5 days or lo nger.
(xl Stigmata or other findings assoc iated with a sy ndrome
known to include sensorineural and/or conducti
ve hearing loss.
Assessment of Hearing in Infants and
Children
Assessment of audi to ry function in neonates, infants and
children demands special techniques. They are grouped
under the following heads (Table 19.2):
(a) Screening procedures. They are employed to test
h earing in "high risk" infa nts and are based on infant's
behav ioural response to the sound signal.
Arousal test. A high frequency narrow band noise is
presented for 2 seconds to the infant when he is in lighr
sleep. A normal hea ring infant can be aroused twice
when three such stimuli are presented to him.
Auditor)' response cradle is a screening device for newborns,
where baby is placed in a cradle and his behaviour
(trunk and limb movement, head jerk and respira tion) in
response to auditory stimu la tion are monitored by transducers.
It can screen babies with moderate, severe or profound
hearing loss.
(b) Behaviour observation audiometry. Auditory signal
presented to an infant produces a change in behaviour,
e.g. alerting, cessation of an activity, widening of eyes or
facial grimacing. Moro's reflex is one of them and co nsist,
of sudden movement of limbs and extension of head in
*Developed by Virgin i~ Apgar, an anaesrhesiologi s(. lr rakes nore of
five irems: hean rarc, respiratory ('ffun, muscle [One, reflex irrirabilir\'
and colour; noted ar 1 and 5 mInutes afrer birth . Low score is ° and
highesr 10, ie. 2 marks for each item.
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Table 19.2 Methods of hearing assessment In
infants a nd children
A. Neonatal screening procedures
• Arousal test
• Auditory response cradle
• ABR/OAE's
B. Behaviour observation audiometry
• Moro's reflex
• Cochleopalpebral reflex
• Cessation reflex
C. Distraction techniques
D. Conditioning techniques
• Visual reinforcement audiometry
• Play audiometry
E. Objective tes ts
• ABR
• Otoacoustic emissions
• Impedance audiometry
response to sound of 80-90 dB. In cochleopalpebral reflex,
fhe child responds by a blink to a loud sound. In cessation
reflex, an infant stops activity or starts crying in response
to a sound of 90 dB.
(c) Distraction techniques are used in children 6-7
months old. The child at this age turns his head to locate
he source of sound . In this test, the child is seated in his
mother's lap, an assistant distracts the child's attention
while the examiner produces a sound from behind or from
me side to see if the child tries to locate it. Sounds used
'U high frequency rattle (8 kHz), low frequency hum,
r hispered sound as "S, S, S", xylophone, warbled tones or
n::mow band noise (500-4000 Hz).
(d) Conditioning techniques
Visual reinfOTcement audiometry (VRA). It is a condi-
Ioning technique in which child is trained to look for an
JLlditory stimu lus by turning his head. This behaviour is
"t:inforced by a flashing light or an animated toy. This
-cst helps to determine the hearing threshold using stanrd
audiometric techniques. The auditory stimulus is
Je livered by headphones or better st ill by insert earones
which are accepted better and are also light
"eight. Test is well suited between the developmental
.!e of 5 months to 2 yea rs.
Play audiometry. The child is conditioned to perform
act such as placing a marble in a box, putting a ring
'11 a post or putting a plastic block in a bucket each time
. hears a sound signal. Each correct performance of the
c t is reinforced with praise, encouragement or reward.
::: r specific thresholds can be determined by standard
diometric techniques. This test can be used in children
ith developmental age of 2-4 or 5 years.
peech audiometry. The child is asked to rereat the
Jmes of certain objects or to point them out on the picres.
The voice can be gradually lowered. In this way,
THE DEAF CHILD
hearing level and speech discrimination can be tested.
The test can also be used to examine the child's expressi
ve ability when he is asked to name the toys like horse,
duck or objects like cup, plate, etc.
(e) Objective tests
(i) Evoked response audiometry.
Electrocochleography. It can measure auditory sensitivity
to within 20 dB. But it is an invasive procedure.
Auditory brainstem response. It is not a direct test of
hearing but correlates highly with the pure-tone thresholds.
Identifiab le waveforms in ABRs are generally present
10-20 dB above behavioural threshold. ABR
provides an ear specific information as sound stimulus can
be presented to each ear separately by headphones or ear
inserts. It is an objective test and can be done under sedation
as the latter has no effect on ABR. ABR is used both
as a screening test and as a definitive hearing assessment
test in children. In a screening test, a response to a click
stimulus of 40 nHL or less is the criterion of passing the
test. To find hearing threshold in an infant, ABR tracing
is obtained first at higher sound stimulus and then gradually
lowered till wave V is just identifiable but repeatable.
(ii) Otoacoustic emissions (see page 29) . Transient evoked
emissions (TEOAE's) are absent in ears where hearing
loss exceeds 30 dB. Distortion product emissions
(DPOAE's) are absent when hearing loss exceeds 50 dB.
(iii) Impedance aud.iometry. Normally, stapedius muscle
contracts reflex I y in response to a sound of 70-100 dB HL
and this reflex can be recorded. Absence of acoustic
reflex indicates middle ear disorder, retrocochlear hearing
loss or severe to profound SNHL. Used with behaviour
audiometry, acoustic reflexes are useful component to
cross-check. Absence of acoustic reflex, but a normal
tympanometry with parental concern for hearing loss suggests
possibility of SNHL of severe to profound degree.
Absence of acoustic reflex but an abnormal tympanogram
generally indicates conductive loss. Since ABR and
OAEs provide more information, use of acoustic reflexes
in assessment of paediatric testing has declined.
OAEs and ABR have been used both in screening
programmes and in hearing evalua tion in infants and
children.
Management
It is essential to know the degree and type of hearing loss,
and other Clssociated handicaps such as blindness or mental
retardation and whether hearing loss is pre-lingual (before
development of speech) or post-lingual. Aetiology of
hearing loss remains obscure in about half the cases.
Aims of habilitation of any hearing-impaired child are
development of speech and language, adjustment in society
and useful employment in a vocation.
1. Parental guidance. It is a great emotional shock
for parents to learn thar their child is deaf. They should
be dealt with sympathetically, so as to accept the child. They shou ld be told of child's disability and how to care
for it. Hab ilitation of the deaf demands a lot from pa rents:
care and periodic replacement of hearing aid , change of
ear moulds as child grows, follow up visits for reevaluation,
educa tion at home and the selection of vocatio n.
2. Hearing aids. Most deaf chi ldren have a small but
usefu l port ion of residual hearing which can be exp lo ited
by amplification of sound. Hearing a ids should be presc
ribed as early as possible. If necessary, binaural aids, one
for each ear, can be used. Hearing aids help to develop
lip-read ing also.
3. Development of speech and language. Communication
is a two way process, derending on the receptive
and expressive skills. Reception of information is through
visual, auditory or tactile faculties while expression is
through oral or written speech or the manual sign language
. In the hearing-impaired, auditory fac ulty is poor or
to tally absent (Fig. 19.2). Thus, for proper communication,
there is need either to improve hear ing through amplification
of the residual hearing or cochlear implants; and in the
absence of feasibilit y of developing the aud itory facu lty,
to de velop visual or tac tile means of commun ication.
(a) Auditor)'.oral communication. This is lhe method
used by a normal person and is the best way of communication.
In the deaf, it can be used in those with moderate
to severe hearing Loss or those who are
post-lingually deaf. Hearing aids are prov ided to augment
aud itory reception. At the same time, training is a lso
imparted in speech reading, i.e. to read movements of
lips, face, and natural gestures of hand and body.
Expressi ve skill is encouraged through ora l speech.
(b) Manual communication. It makes use of the sign
language or finger·sp el!ing method but has the disadvantage
that abstract ideas are difficu lt to express and general
public does not understand it.
(c) Total communication It uses all modalities of sensor\'
input, i.e. auditory, visual, tac tile and kinaesthetic. Such
children are taught to develop oral speech, lip-reading
and sign language. All children with pre-lingual severe
to profound deafness , should undergo training in thi
form of communication. Vibrotactile aids are useful for
those who are to ta lly deaf and a lso blind. These aids are
attached to the child 's hand or sternum and the vibrations
of speech are perceived th rough tac tile sensa tion.
4. Education of the deaf. There are residential and
day schools for the deaf. Some deaf children with moderate
hearing loss can be integrated into schools for the
normal children with preferential seating in the c lass.
Radio hearing aids have revolutionised education ot
the deaf. In this dev ice, the microphone and transmitter
are worn by the teacher and the receiver and amplifier by
the child. With this sys tem, the child can hear th
teacher's voice better, without being disturbed by environmental
noises.
5. Vocational guidance. The deaf are sincere and
good wo rkers. Given the opportunity, commensurate
with their abil Lt y, they can be usefully employed in several
vocat ions.