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SECTION I — Diseases of Ear
(a) Pure tone audiometry will show sensorineural hear-
ing loss, more marked in high frequencies.
(b) Speech audiometry shows poor speech discrimina-
tion and this is disproportionate to pure tone hearing loss. Roll-over phenomenon, i.e. reduction of discrimination score when loudness is increased beyond
a particular limit is most commonly observed.
(c) Recruitment phenomenon is absent.
(d) Short Increment Sensitivity Index (SISI) test will show
a score of 0–20% in 70–90% of cases.
(e) Threshold tone decay test shows retrocochlear type
of lesion.
2. stapedial reFlex decay test. (see p. 27).
3. Vestibular tests. Caloric test will show diminished
or absent response in 96% of patients. When tumour is
very small, caloric test may be normal.
4. neurological tests. Complete examination of
cranial nerves, cerebellar functions, brainstem signs of
pyramidal and sensory tracts should be done. Fundus is
examined for blurring of disc margins or papilloedema.
Figure 18.1. Inner aspect of lateral end of internal auditory canal
with structures passing through different areas.
5. radiological tests
(a) Plain X-rays (transorbital, Stenver’s, Towne’s and sub-
mentovertical views) give positive findings in 80% of
patients. However, small intracanalicular tumours are
not detected.
(b) Computed tomography (CT) scan. A tumour that pro-
jects even 0.5 cm into the posterior fossa can be detected by a CT scan. If combined with intrathecal
air, even the intrameatal tumour can be detected. CT
scan has replaced earlier methods of pneumoencephalography and myodil meatography.
(c) MRI with gadolinium contrast. It is superior to CT scan
and is the gold standard for diagnosis of acoustic neuroma. Intracanalicular tumour, of even a few millimetres, can be easily diagnosed by this method.
(d) Vertebral angiography. This is helpful to differentiate
acoustic neuroma from other tumours of cerebellopontine angle when doubt exists.
6. eVoked response audiometry (bera). It is very
useful in the diagnosis of retrocochlear lesions. In the
presence of VIIIth nerve tumour, a delay of > 0.2 ms in
wave V between two ears is significant (see p. 28).
7. csF examination. Protein level is raised. Lumbar
puncture is usually avoided.
Important tests for work-up of acoustic neuroma are
given below:
• Pure tone audiometry.
• Speech discrimination score.
• Roll-over curve.
• Stapedial reflex decay.
• Evoked response audiometry.
• MRI with contrast.
Figure 18.2. Acoustic neuroma and its expansion. (A) Intracanalicular. (B) Tumour extending into cerebellopontine angle. (C) Tumour pressing
on CN V. (D) Very large tumour pressing on CN V, IX, X, XI, and brainstem and cerebellum.
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127
DIFFERENTIAL DIAGNOSIS
Acoustic neuroma should be differentiated from the
cochlear pathology (i.e. Ménière’s disease) and other cer-
ebellopontine angle tumours, e.g. meningioma, primary
cholesteatoma and arachnoidal cyst (Table 18.1).
TREATMENT
SURGERY
Surgical removal of the tumour is the treatment of choice.
Surgical approach will depend upon the size of tumour.
The various approaches are:
1. Middle cranial fossa approach.
2. Translabyrinthine approach.
3. Suboccipital (retrosigmoid) approach.
4. Combined translabyrinthine-suboccipital approach.
RADIOTHERAPY
Conventional radiotherapy by external beam has no role in
the treatment of acoustic neuromas due to low tolerance
of the central nervous system to radiation.
TABLE 18.1 TUMOURS OF CEREBELLOPONTINE
ANGLE
• Acousticneuroma
• Meningioma
• Epidermoid(cholesteatoma)
• Arachnoidcyst
• Schwannomaofothercranialnerves(e.g.CNV>VII > IX, X, XI)
• Aneurysm
• Glomustumour
• Metastasis
X-knife or Gamma knife surgery. It is a form of stereotactic radiotherapy where radiation energy is converged on
the tumour, thus minimizing its effect on the surrounding normal tissue. This causes arrest of the growth of the
tumour and also reduction in its size. It can be used in
patients who refuse surgery or have contraindications to
surgery or in those with a residual tumour.
X-knife surgery is done through linear accelerator and
gamma knife through a Cobalt-60 source.
Cyber knife. It is an improvement over the above. It is
totally frameless and more accurate. It uses real-time image guidance technology through computer-controlled
robotics.
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TABLE 19.1 SYNDROMES ASSOCIATED WITH HEARING LOSS
Syndrome Features
1. Waardenburg
syndrome
(Figure 19.1)
2. Usher syndrome • Retinitispigmentosa
3. Jervell and LangeNielson syndrome
4. Pendred syndrome • Goitre(nontoxic)usuallyevident
5. Alport syndrome • Hereditaryprogressive
6. Treacher-Collins
syndrome
(mandibulofacial
dysostosis)
7. Crouzon syndrome
(craniofacial
dysostosis)
8. Apert syndrome • Syndactyly
9. Klippel-Feil
syndrome
10. Wildervanck
syndrome
11. Branchio-oto-renal
syndrome
12. Stickler syndrome • Smalljaw
13. Van der Hoeve
syndrome
14. Pierre-Robin
sequence
15. Goldenhar
syndrome (Facioauriculo-vertebral
dysplasia) or (oculoauriculo-vertebral
[OAV] syndrome)
a
• Whiteforelock
• Heterochromiairidis(Figure 19.2)
• Vitiligo
• Dystopiacanthorum
• Nightblindness
• Repeatedsyncopalattacks
• ProlongedQTintervalinECG
before puberty
• Perchloratedischargetestshows
defect in organic binding of iodine
glomerulonephritis
• Cornealdystrophy
• Antimongoloidpalpebralssures
• Colobomaoflowerlid
• Hypoplasiaofmandibleandmalar
bones
• Microtiapinnaandmeatalatresia
• Malformedmalleusandincus(stapes
normal)
• Frogeyes(exophthalmoswith
divergent squint)
• Hypertelorism
• Parrot-beaknose
• Mandibularprognathism
• Prematureclosureofcranialsutures
with mental retardation
• AllotherfeaturesofCrouzon
syndrome
• Shortneck
• Fusedcervicalvertebrae
• Spinabida
• Atresiaofearcanal
• Klippel-Feilsyndrome
• SNHL
• CNVIParalysis
• Branchialstulas/cysts
• Malformedpinnaewithpreauricular
pits or sinuses
• Renalabnormalities
• Cleftpalate(Pierre-Robinsequence)
• Myopia≥ retinal detachment
• Cataract
• Juvenileonsetarthritis
• Osteogenesisimperfectawithhistory
of fractures
• Bluesclera
• Hearingloss(delayedonset)
• Micrognathia
• Glossoptosis
• Cleftpalate
• OftenpartofSticklersyndrome
• Facialasymmetry
• Lowsetears,atresiaofearcanal
• Cardiacabnormalities
• Preauriculartags/pits
• Hemivertebraeincervicalregion
• Epibulbardermoid
• Colobomaofupperlid
Type of hearing
loss
Unilateral or bilateral
SNHL
SNHL Delayed AR
SNHL Congenital AR
SNHL Congenital AR
Progressive SNHL Delayed AD or X-linked
Conductive Congenital AD
Conductive or
mixed
Conductive (Stapes
fixation)
SNHL or mixed Congenital AR
SNHL Congenital X-linked
Conductive or
mixed
Conductive or SNHL Delayed AD
Conductive, SNHL
or mixed (like
otosclerosis)
SNHL Conductive
loss
Mixed or conductive Congenital AD or sporadic Extra
Onset (Congenital/
delayed) Type of inheritance
Congenital AD
Congenital AD
AD
Congenital AD
Delayed AD
AD
chromosome
Multifactorial
(genetic and
environmental)
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TABLE 19.1 SYNDROMES ASSOCIATED WITH HEARING LOSS (CONT.)
Type of hearing
Syndrome Features
16. Down syndrome
(Trisomy 21)
SNHL, sensorineural hearing loss; AD, autosomal dominant; AR, autosomal recessive.
a
It is called a sequence, not a syndrome, because multiple anomalies result in sequence from a single primary abnormality, i.e. micrognathia which leads
to glossoptosis which in turn causes cleft palate.
• Microcephaly
• Mentalretardation/delayed
development
• Shortstature
• Epicanthalfolds
• Stenosisofearcanal
• Highincidenceofserousotitismedia
• Atlanto-axialinstability
loss
Conductive Congenital Extra chromosome
Onset (Congenital/
delayed) Type of inheritance
4. neonatal jaundice. Bilirubin level greater than
20 mg% damages the cochlear nuclei.
5. neonatal meningitis
6. sepsis
Figure 19.1. Waardenburg syndrome. Note white forelock, heterochromia iridis and depigmentation of skin.
7. time spent in neonatal icu
8. ototoxic drugs. used for neonatal meningitis or
septicaemia.
C. POSTNATAL CAUSES
1. genetic. Though deafness is genetic, it manifests later
in childhood or adult life. Deafness may occur alone as in
familial progressive sensorineural deafness or in association
with certain syndromes, e.g. Alport, Klippel-Feil, Hurler, etc.
2. nongenetic. They are essentially same as in adults
and include:
(a) Viral infections (measles, mumps, varicella, influen-
za), meningitis and encephalitis.
(b) Secretory otitis media.
(c) Ototoxic drugs.
(d) Trauma, e.g. fractures of temporal bone, middle ear
surgery or perilymph leak.
(e) Noise-induced deafness.
EVALUATION OF A DEAF CHILD
Figure 19.2. Heterochromia iridis. Iris showing different colours.
FINDING THE CAUSE
This may require a detailed history of prenatal, perinatal or
postnatal causes, family history, physical examination and
certain investigations depending on the cause suspected.
1. Suspicion of hearing loss. Hearing loss is suspected if
(i) the child sleeps through loud noises unperturbed or
fails to startle to loud sounds, (ii) fails to develop speech
at 1–2 years. A partially hearing child may have a de-
fective speech and perform poorly in school and be la-
belled mentally retarded. It is essential that all children
at risk for hearing loss should be screened and followed.
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TABLE 19.2 METHODS OF HEARING ASSESSMENT
IN INFANTS AND CHILDREN
• Neonatalscreeningprocedures
• ABR/OAEs
• Arousal test
• Auditory response cradle
• Behaviourobservationaudiometry
• Moro’s reflex
• Cochleopalpebral reflex
• Cessation reflex
• Distractiontechniques(6–18months)
• Conditioningtechniques(7months–2years)
• Visual reinforcement audiometry
• Play audiometry (2–5 years)
• Objectivetests
• ABR
• Otoacoustic emissions
• Impedance audiometry
2. Risk factors for hearing loss in children (Recommendations of Joint Committee on Infant Hearing—
updated to 1994).
(a) Family history of hearing loss.
(b) Prenatal infections (TORCHES).
(c) Craniofacial anomalies including those of pinna
and ear canal.
(d) Birth weight less than 1500 g (3.3 lbs).
(e) Hyperbilirubinaemia requiring exchange transfusion.
(f) Ototoxic medications included but not limited
to aminoglycosides used in multiple courses or in
combination with loop diuretics.
(g) Bacterial meningitis.
(h) 1Apgar score of 0–4 at 1 min or 0–6 at 5 min.
(i) Mechanical ventilation for 5 days or longer.
(j) Stigmata or other findings associated with a
syndrome known to include sensorineural and/or
conductive hearing loss.
ASSESSMENT OF HEARING IN INFANTS
AND CHILDREN
Assessment of auditory function in neonates, infants and
children demands special techniques. They are grouped
under the following heads (Table 19.2):
1. screening procedures. They are employed to test
hearing in “high-risk” infants and are based on infant’s
behavioural response to the sound signal. It is now observed that 95% of children with one or more risk factors
have normal hearing. On the contrary, 50% of children
with sensorineural hearing loss had no risk factor. This
leads to a programme of universal neonatal screening for
early detection.
Two important tests are to study otoacoustic emissions
(OAEs) and auditory brainstem responses (ABR).
(a) OAEs are generated at outer hair cells and can be
picked up from the external ear as the energy produced by them travels in reverse direction from outer
hair cells → ossicles → tympanic membrane → ear
canal where it is picked up. OAEs are absent if outer
hair cells in the cochlea are nonfunctional or there is
middle ear effusion or canal debris due to meconium
which may persist for 3–4 days. They are normal even
when VIIIth nerve is nonfunctional. Thus can be used
in the diagnosis of neuropathy of VIIIth nerve.
(b) ABRs are generated in response to sound stimulus pre-
sented to the ear and picked up from the scalp. With
a response of 30–35 dB nHL, the infant who passes
the test and the hearing is considered normal. Infants
who fail these tests are followed up with repeat tests.
Arousal test. A high-frequency narrow band noise is
presented for 2 s to the infant when he is in light sleep. A
normal hearing infant can be aroused twice when three
such stimuli are presented to him.
Auditory 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 respiration) in
response to auditory stimulation are monitored by transducers. It can screen babies with moderate, severe or profound hearing loss.
2. behaViour obserVation audiometry. Auditory sig-
nal 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
consists of sudden movement of limbs and extension of
head in response to sound of 80–90 dB. In cochleopalpebral
reflex, the 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.
3. distraction techniques. are used in children
6–7 months old. The child at this age turns his head to
locate the 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 one side to see if the child tries to locate it. Sounds
used are high frequency rattle (8 kHz), low-frequency
hum, whispered sound as “S, S, S”, xylophone, warbled
tones or narrow band noise (500–4000 Hz).
4. conditioning techniques
(a) Visual reinforcement audiometry (VRA). It is a condition-
ing technique in which child is trained to look for an
auditory stimulus by turning his head. This behaviour
is reinforced by a flashing light or an animated toy.
This test helps to determine the hearing threshold using standard audiometric techniques. The auditory
stimulus is delivered by headphones or better still by
insert earphones which are accepted better and are
also light weight. Test is well-suited between the developmental age of 6 months to 2 years.
(b) Play audiometry. The child is conditioned to perform
an act such as placing a marble in a box, putting a ring
on a post or putting a plastic block in a bucket each
time he hears a sound signal. Each correct performance
of the act is reinforced with praise, encouragement or
reward. Ear specific thresholds can be determined by
standard audiometric techniques. This test can be used
in children with developmental age of 2–4 or 5 years.
(c) Speech audiometry. The child is asked to repeat the
names of certain objects or to point them out on the
pictures. The voice can be gradually lowered. In this
way, hearing level and speech discrimination can be
Chapter 19 — The Deaf Child
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133
tested. The test can also be used to examine the child’s
expressive ability when he is asked to name the toys
like horse, duck or objects like cup, plate, etc.
5. objectiVe tests
(a) Evoked response audiometry.
(i) Electrocochleography. It can measure auditory sen-
sitivity to within 20 dB. But it is an invasive procedure requiring placement of electrodes through
the tympanic membrane.
(ii) Auditory brainstem response. It is not a direct test
of hearing but correlates highly with the puretone thresholds. Identifiable waveforms in ABR
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 less than 40 dB 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.
(b) Otoacoustic emissions (see p. 29). Transient evoked
emissions (TEOAEs) are absent in ears where hearing loss exceeds 30 dB. Distortion product emissions
(DPOAEs) are absent when hearing loss exceeds 50 dB.
(c) Impedance audiometry. Normally, stapedius muscle
contracts reflexly 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 pro-
grammes and in hearing evaluation in infants and children.
MANAGEMENT
It is essential to know the degree and type of hearing loss,
and other associated handicaps such as blindness or mental retardation and whether hearing loss is prelingual (before development of speech) or postlingual. 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 that their child is deaf. They should
be dealt with sympathetically, so as to accept the child.
They should be told of child’s disability and how to
care for it. Habilitation of the deaf demands a lot from
parents: care and periodic replacement of hearing aid,
change of ear-moulds as child grows, follow-up visits for
re-evaluation, education at home and the selection of
vocation.
2. hearing aids. Most deaf children have a small but
useful portion of residual hearing which can be exploited
by amplification of sound. Hearing aids should be prescribed as early as possible. If necessary, binaural aids, one
for each ear, can be used. Hearing aids help to develop
lip-reading also.
3. cochlear implants (see p. 138)
4. deVelopment oF speech and language. Communi-
cation is a two way process, depending 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 faculty is poor or
totally absent (Figure 19.3). Thus, for proper communication, there is need either to improve hearing through amplification of the residual hearing or cochlear implants;
and in the absence of the feasibility of developing the auditory faculty, one has to develop visual or tactile means
of communication.
(a) Auditory-oral communication. This is the 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 postlingually
Figure 19.3. The faculties of a hearing-impaired person which can be utilized for receptive and expressive skills in communication.
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SECTION I — Diseases of Ear
deaf. Hearing aids are provided to augment auditory
reception. At the same time, training is also imparted
in speech reading, i.e. to read movements of lips, face,
and natural gestures of hand and body. Expressive
skill is encouraged through oral speech.
(b) Manual communication. It makes use of the sign lan-
guage or finger-spelling method but has the disadvan-
tage that abstract ideas are difficult to express and
general public does not understand it.
(c) Total communication. It uses all modalities of sensory
input, i.e. auditory, visual, tactile and kinaesthetic.
Such children are taught to develop oral speech, lipreading and sign language. All children with prelingual severe to profound deafness, should undergo
training in this form of communication. Vibrotactile
aids are useful for those who are totally deaf and also
blind. These aids are attached to the child’s hand or
sternum and the vibrations of speech are perceived
through tactile sensation.
5. education oF the deaF. There are residential and day
schools for the hearing impaired. Some children with moderate hearing loss can be integrated into schools for the normal hearing children with preferential seating in the class.
Radio hearing aids have revolutionized education of
the deaf. In this device, the microphone and transmitter
are worn by the teacher and the receiver and amplifier
by the child. With this system, the child can hear the
teacher’s voice better, without being disturbed by environmental noises.
6. Vocational guidance. The deaf are sincere and good
workers. Given the opportunity, commensurate with their
ability, they can be usefully employed in several vocations.
Chapter 20
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Rehabilitation of the Hearing Impaired
All hearing-impaired individuals need some sort of aural rehabilitation for communication. The various means
available to them are:
1. Instrumental devices
(a) Hearing aids
(i) Conventional hearing aids
(ii) Bone-anchored hearing aids
(iii) Implantable hearing aids (vibrant soundbridge)
(b) Implants
(i) Cochlear implants
(ii) Auditory brainstem implants
(c) Assistive devices for the deaf
2. Training
(a) Speech (lip) reading
(b) Auditory training
(c) Speech conservation
I. INSTRUMENTAL DEVICES
A. HEARING AIDS
Conventional Hearing Aids
A hearing aid is a device to amplify sounds reaching the
ear. Essentially, it consists of three parts: (i) a microphone,
which picks up sounds and converts them into electrical impulses, (ii) an amplifier, which magnifies electrical
impulses and (iii) a receiver, which converts electrical impulses back to sound. This amplified sound is then carried
through the earmould to the tympanic membrane.
types oF hearing aids
air conDuction hearing aiD. In this, the amplified
sound is transmitted via the ear canal to the tympanic
membrane.
Bone conDuction hearing aiD. Instead of a receiver,
it has a bone vibrator which snugly fits on the mastoid
and directly stimulates the cochlea. This type of aid is
especially useful in persons with actively draining ears,
otitis externa or atresia of the ear canal when ear inserts
cannot be worn.
Most of the aids are air conduction type. They can be:
1. Body-worn types. Most common type (Figure 20.1A );
microphone and amplifier along with the battery are
in one case worn at the chest level while receiver is
situated at the ear level. This type of aid allows high
degree of amplification with minimal feedback. It is
useful in severely deaf persons or children with congenital deafness.
2. Behind-the-ear (BTE) types. Here microphone, amplifier, receiver and battery are all in one unit which
is worn behind the ear. It is coupled to the ear canal
with a tubing and an earmould. It is useful for slight
to moderate cases of hearing loss particularly the high
frequency ones.
3. Spectacle types. It is a modification of the “behindthe-ear” type and the unit is housed in the auricular
part of the spectacle frame. It is useful to persons who
need both eye glasses for vision and a hearing aid. It is
not very popular now.
4. In-the-ear (ITE) types. The entire hearing aid is
housed in an earmould which can be worn in the ear.
It is useful for mild to moderate hearing losses with flat
configuration. They are very popular because of their
cosmetic appeal.
5. Canal types (ITC and CIC). The hearing aid is so small
that the entire aid can be worn in the ear canal without projecting into the concha. For using this aid, it is
required that the ear canal should be large and wide,
and patient should have the dexterity to manipulate
the minute controls in the aid. It is useful for mild
to moderate cases of hearing loss of high frequency
(1–4 kHz).
Two types are available: in the canal (ITC) and another
still smaller and invisible type, completely in the canal
(CIC).
indications For hearing aid. Any individual who has
a hearing problem that cannot be helped by medical or
surgical means is a candidate for hearing aid.
1. Sensorineural hearing loss, which interferes with dayto-day activities of a person. Hearing aid may not suit
all such persons because of the intolerable distortion of
sound in some, particularly in those with recruitment.
2. Deaf children should be fitted with hearing aid as early as possible for development of speech and learning.
In severely deaf children, binaural aids (one for each
ear and individually fitted) are more useful. Training
in lip reading is given simultaneously.
3. Conductive deafness. Most of such persons can be
helped by surgery but hearing aid is prescribed when
surgery is refused or not feasible or has failed.
Fitting a hearing aid. While fitting a hearing aid,
consideration is given to:
1. Degree of hearing loss.
2. Configuration of hearing loss (type of frequencies affected).
3. Type of hearing loss (conductive or sensorineural).
4. Presence of recruitment.
5. Uncomfortable loudness level.
6. Age and dexterity of patient.
7. Condition of the outer and middle ear.
8. Cosmetic acceptance of the aid.
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