Hearing
Loss in Children
Introduction
Prelingual (before language development) hearing loss in children
can be devastating. Without intervention, these children grow up
with delayed speech and language development, poor pronunciation
with social and behavioral deficits. In the worst scenario, the child
lives in a world of silence with no means of communication with those
around him/her, isolated from society. Hence, the main focus in the
management of hearing impaired children is to restore environmental
sound and the ability to discriminate in the hope of developing spontaneous
speech and language so as to allow full integration with society.
There are many causes of hearing loss in children.
The problem can arise from the external ear (microtia, external
ear atresia), middle
ear (otitis media with effusion, ossicular chain fixation or disruption)
or inner ear (congenital). Congenital deafness occurs in about 4
to 5 children per 1000 live births. One of these will have bilateral
(both sides) severe to profound deafness. This is more common than
cleft lip and palate or Down’s syndrome. The principle in the
management is early diagnosis, prompt and adequate amplification
(if required) and intensive auditory-verbal therapy.
Presenting Symptoms
The effect of hearing loss on children depends on the severity of
hearing impairment. Before neonatal screening was available, most
children will present at about 2 years old when the parents become
concern with the lack of speech development. In milder forms of hearing
impairment, children are generally older and can present in the following
scenarios;
With the accessibility of newborn hearing screening, children with
hearing impairment are being detected earlier. Many are referred
to ENT doctors because the hearing screening test failed.
The history that is significant in children presenting soon after
birth include
Examination
A full ENT examination for a suspected hearing loss in a child is
essential. Hearing loss manifest as part of certain syndromes and
characteristic features can be easily identified in some of these
(http://www.tchain.com/otoneurology/disorders/hearing/cong_hearing.html).
The examination should focus on detecting potentially reversible
causes of hearing loss such as impacted wax, microtia, external canal
atresia (no ear canal), perforated eardrum, otitis media (fluid in
the middle ear) and ossicular chain problems. Nasal conditions such
as sinus infections, large adenoids and tonsils can also cause middle
ear disease and hearing loss.
Investigations
The primary aim of investigations is to determine the severity of
hearing loss which can range from mild to profound (Figure 1). The
test used to determine the hearing thresholds in children is partly
dependent on the age of the child. However, the best test for most
children up to age 4 is an Auditory Brainstem Response (ABR, also
known as Brainstem Auditory Evoked Response or BAER). This test requires
the child to be sedated and involves presenting sound in the form
of clicks to the ear which is then picked up by electrodes placed
over the head. The response is seen in the form of 5 waves as the
sound travels from the inner ear to the higher centres (Figure 2).
It gives information on the hearing thresholds within 10dB of the
actual levels.
The ABR is usually complemented with the Steady State Evoked Potentials
(SSEPs) which examines the hearing thresholds of the other frequencies
within a range. Generally, children aged 5 and older can performed
a pure tone audiogram. Other methods of assessing hearing thresholds
include play audiometry and visual reinforcement audiometry.
Tympanograms are used to assess middle ear compliance (Figure 3).
Type A is normal, Type B is found in otitis media, Type C is seen
when the air pressure in the middle ear space is negative in relation
to the atmosphere, Type As is seen when the ossicular chain is stiff
or fixed and Type Ad is found when it is disrupted or broken.
Management
The approach to hearing loss in children is multi-disciplinary and
is tailored to the cause of the hearing loss. When the degree of
hearing loss is severe to profound, a team of audiologists, auditory-verbal
therapists, social worker, counselors and ENT surgeon must work collectively
to bring out the best in the child. Conditions such as otitis media
can be easily overcome through a myringotomy and grommet tube insertion
(figure 4). However, hearing loss originating from the inner ear
cannot be overcome by simple surgery. The approach to inner ear hearing
loss is as follows;
The team in charge of the child must also look into
the home and school environment to ensure maximal sound exposure.
Working closely
with the child’s caregivers and educators is essential in the
successful integration of any hearing impaired child.
Bone-anchored Hearing Aid
If the prescription of an air-conduction hearing aid is not feasible
(as in children without ear canals), bone-conduction or bone-anchored
hearing aids (BAHA, Figure 6) are required. This process requires
implantation of a titanium screw into the skull which subsequently
becomes osseointegrated. The procedure is performed under local
anaesthesia in adults. Children required a GA but can go home the
same day after the procedure. Two weeks later, a hearing device
is then attached to the screw. The hearing device is removable
(for swimming, during sleep). Sound is conducted through the skull
directly to the inner ear, bypassing any obstruction in the external
ear.
http://www.entific.com/aboutBaha.asp
Refer
the child for Auditory-Verbal Therapy (AVT). The principles
of listening and identifying key sounds will be taught to the
child and the caregiver (figure 5). Therapy sessions are initially
conducted
weekly.