Homo sapiens stands apart with a highly developed
system of communication. Any impairment
that interferes with our ability to communicate threatens our integration in
society. Childhood hearing loss is taken
seriously by all and significant resources are expended in prevention,
detection and management.
Childhood hearing loss not only affects speech and language
development but also cognitive; social and emotional development.
The challenge of early detection and intervention in severe and
profound sensorineural hearing loss has to be balanced with a more expectant
and conservative approach in the commonest type of childhood hearing loss from
otitis media with effusion.
Technological advances have improved early detection and paediatric
cochlear implantation is nothing short of a miracle. Working with hearing
impaired children requires a team approach and good communication with
community workers and schools.
Screening only those children with selected risk factors is
inefficient as 95% of children with one or more risk factor will have normal
hearing. Conversely, half of children
eventually shown to have sensorineural hearing loss will have no risk factors. This realisation has prompted a progressive
change to Universal Neonatal Hearing Screening. This has been shown to increase
detection rates and decrease the age of detection with benefits in speech and
language development.
Ideally, screening protocols should only pass neonates with normal
hearing accepting that some who fail may eventually also be shown to have
normal hearing after subsequent testing. The tests should be relatively cheap
and require minimal training. Most
programmes are based on a mixture of otoacoustic emissions (OAE) and brain stem
evoked responses (BSER), either using both or a 2 tier system with initial
screening with OAE. Support and information must be given to parents who have
failed a screening test as they wait anxiously for the next level test.
OAE are acoustic responses of the cochlear to auditory stimulation.
They are present in neonates with normal hearing so long as the external and
middle ear are also normal. Middle ear effusions or canal debris can affect the
results as can testing in a noisy environment. OAE test outer hair cell
function so rare abnormalities of the inner hair cell or auditory nerve will be
missed.
BSER are responses to auditory stimulation recorded from scalp
electrodes. The stimulus is a non frequency specific click. Automated detection algorithms are used in
screening to give a pass/fail equivalent to about 30-35 dB nHL.
Early detection of hearing loss is useless without prompt further
assessment, confirmation of loss and most importantly, early provision of hearing
aids. Alongside early aiding, support, information and counselling is needed
for the family.
Neonates who fail screening and have a genuine hearing loss confirmed,
warrant further investigation. This includes
those who have survived prematurity, as prematurity without significant hypoxic
episodes or ototoxicity does not itself seem to cause deafness. Investigations
will include blood tests as well as an ECG and genetic testing. Protocols are evolving which rely more
heavily on genetic testing as this becomes more widely available. Connexin 26 mutations are the commonest cause
of non syndromic deafness accounting for 50% of all autosomal recessive
non-syndromic hearing loss in Caucasians.
Despite universal neonatal hearing screening it is important to test
the hearing of children at older ages as well. This will pick up those who have
progressive or acquired nerve deafness as well as the common condition of glue
ear. Some children will be identified at screening while other children will
present to their GP with a suspected hearing loss.
Children from 6 months to 18 months can be tested by distraction
testing. Here they sit on their mother’s
knee and their attention is on a visual stimulus in front of them. This
stimulus is withdrawn leaving them in a state optimised to receive an auditory
stimulus from the side which prompts a head turning response. Properly
conducted with an experienced team in a sound proofed room this can give accurate
frequency specific information for each ear separately. A development is to
reward an appropriate head turn with a visual “treat” such as a moving
toy. This is visually reinforced
audiometry.
Older children from 2 ½ to 3 years onward can perform conditioned
audiometry. They are taught to respond
to sounds by performing a task such as putting men in a boat. Once the game is established the amplitude is
reduced to threshold and different frequencies tested. In the youngest this may have to be free field
but once headphones are tolerated each ear can be tested accurately. Older children can respond with a button as
in adult testing.
Impedance testing is often used in general practice and school as it
is quick and objective but it does not test hearing. It tests the ability of
the middle ear to absorb sound at different ear canal pressures. It can show
the presence of middle ear effusions as well as perforated or hypermobile
tympanic membranes.
Middle ear effusions are common in children and can be
asymptomatic. Effusions can however be
associated with frequent recurrent ear infections and/or with significant
hearing loss and with subsequent speech, social and educational delay. It is clear that glue ear is not a discrete
condition with a simple management plan that fits all. As it is common and
self-limiting, the initial approach to investigation and intervention should be
conservative and should generally include a period of “watchful waiting”.
The history is important to asses the impact of the condition in the
individual child. A typical presentation
with hearing loss would include inattention, variable response to commands,
high volume levels for television and poor articulation. The level of competing noise at school or in
the home is important as it affects the child’s ability to cope with a hearing
loss. Speech delay is assessed in young children by vocabulary, articulation
and the development of language as evidenced by the number of 2 to 3 word
utterances. In older children, articulation is the key area affected by hearing
loss in glue ear. Frustration is a common finding in younger children with
speech delay secondary to glue ear with consequent poor behaviour at nursery.
In children with ear infections associated with glue ear the age of
the first infection is a good prognostic indicator of future troubles. It is important to try to decide if the ears
return to normal in between infections “discrete infections” , whether the
infection recurs after a short course of antibiotics “inadequately treated
infections” or if separate infections are occurring on a background of
quiescent glue ear “recurrent infections”.
A history of snoring and mouth breathing may suggest associated adenoid
hypertrophy.
Examination of the ear may show a dull grey, plum or yellow membrane.
Fluid levels and bubbles show that at least some air is present in the middle
ear. Balance and gait may be
affected. Simple conversational test in
the office are useful as a guide and to help parents understand the level of
hearing loss from glue ear.
Age appropriate audiometry is important though levels will fluctuate
as glue ear is a seasonally fluctuant condition. The pattern seen on
typmanometry affects the likelihood of an effusion being present. The flat line “B” type trace has a 80%
likelihood of effusion whilst the “normal” “A” trace has less than 5% chance of
an effusion.
Treatment is expectant, medical or surgical. A period of 3 months “watchful waiting” is
recommended. If presentation is delayed this period may have elapsed by the
time of presentation. During the waiting
period cows protein free diets can be tried as can homeopathic remedies. There is no evidence to support cranial
osteopathy for glue ear. Medical treatment is either antibiotics or
steroids. Long courses of low dose broad
spectrum antibiotics (such as Co-Amoxiclav) have a small, medium length benefit
in clearing effusions but are particularly useful in controlling the infections
in recurrent acute otitis media with effusion.
Oral steroids are effective and there may also be a small benefit from
nasal inhaled steroids. Medically it
would seem reasonable to offer antibiotics if glue ear is associated with
infections and to try inhaled steroids if there is a history of allergy.
Surgical drainage of middle ear effusions alone gives a short lived
benefit with re-accumulation of fluid in most cases within 6 weeks. Laser myringotomy under local anaesthesia is
not practical in most children. Surgical
treatment for most children consists of drainage followed by placement of a
ventilation tube which typically will last up to a year. After this time there is little long term
benefit of ventilation tubes unless tubes that are designed to stay longer are
used. These typically have a higher chance of being complicated by a
perforation.
Many protocols have been developed to decide which children with glue
ear should be offered tubes. A moderate
hearing loss of over 30dB is a fair consensus but the effect of the loss on the
child and in particular speech delay is a factor. Educational difficulties and behavioural
problems from frustration with poor speech all need to be put into a balanced
decision with parental guidance. Parents
need to be offered alternatives including no treatment or amplification. They need to realise that the tubes are
designed to be extruded and that a proportion of children may need a further
set of tubes.
The majority of children suffer few complications from tube insertion
other than occasional discharge and minor tympanosclerosis of the membrane
which does not affect the hearing. Major
anaesthetic complications in children undergoing tube insertion alone have not
been reported.
Discharge that persists should be sent for culture and oral treatment
started. If the organism is not readily treatable orally, antibiotic ear drops
need to be used. Some are ototoxic
though it is unclear if this is a theoretical or genuine but very rare
risk. Topical ciprofloxacillin available
as eye drops is safe and effective for pseudomonas.
There is no clear evidence to stop children swimming which is an
important life skill and part of school life for many. A few children have repeated episodes of
discharge and this group should probably wear silicone or customised ear plugs,
drying the canal after swimming with a hair dryer if practical.
Children with tubes need a follow up to check normalisation of the
audiogram and further checks until the tube has extruded to identify rare
sequelae such as cholesteatoma and perforation.
Adenoidectomy helps resolution of glue ear even if the adenoids are
not enlarged and there are no symptoms of obstruction. Combining adenoidectomy with tube insertion
offers the medium term benefit of ventilation tubes with the longer term
benefit of adenoidectomy. Newer
techniques such as suction diathermy avoid bleeding and have a very low
recurrence rate. There remains the small risk of hypernasality which may be an
expression of a submucous cleft palate.
Conductive deafness in the absence of perforation or effusion is due
to ossicular fixation or discontinuity.
Both are rare in non-syndromic children.
Children with Treacher-Collins, Aperts, Crouzons, CHARGE Down’s and
hemifacial microsomia. In some the outer
ear and pinna are unaffected but in other there is a variable degree of canal
stenosis or atresia and microtia.
These aids stimulate the intact cochlear by bone conduction, bypassing
any cause of conductive deafness and avoiding the problems of bone conducting
aids of the “
In some children, hearing loss is so severe that they derive little
benefit from conventional hearing aids.
This group can be helped by direct stimulation of the auditory nerve
with a multi-channel implanted wire within the cochlea. Sound is picked up externally
by a microphone and amplified, filtered and coded in the external speech
processor. The coded signal is then relayed to an implanted device by an
external coil held in place with a magnet. The internal device deciphers the
coded signal and separates it into the different channels of the wire within
the cochlea. The signal is based on
speech but is not just an amplified and filtered speech signal. Different strategies have been developed to
code the signal which is presented to the channels of the implant which
represent regions of the cochlea. Even
adults, who lose hearing but already have speech, take time to interpret the
coded signal. Children implanted very
early, before they have developed speech, tend to do very well because of the
tremendous plasticity of the brain at that early stage. At present the lower age of implantation in
congenital deafness is about a year. Below this it is difficult to establish
hearing levels and to have an effective trial of hearing aids. In a situation
which mirrors the gradual provision of bilateral hearing aids, the provision of
bilateral cochlear implants is becoming more common. As the technology improves and surgery
becomes ever more routine the level of hearing loss that justifies a cochlear
implant is gradually reducing so that now children are implanted who could gain benefit from conventional
aids but who will gain more benefit
from an implant
Any child with a persistent hearing loss benefits from experienced
professional support in the educational environment to ensure that teachers are
aware of the extent of the loss and how best to overcome it. FM signals from a
teachers microphone received by the child’s hearing aid give clear sound
without the amplified background noise which bedevils conventional hearing aid
use.
The future is very bright for hearing impaired children with
technology improving conventional aids and cochlear implants. In time it may be possible to regenerate lost
hair cells to improve hearing in a truly remarkable and physiological way.
1. Hemifacial microsomia
2. Stickler syndrome
3. Congenital cytomegalo virus
4. Usher syndrome
5. Branchio-oto-renal syndrome
6. Pendred syndrome
7. CHARGE Association
8. Neurofibromatosis type II
9. Mitochondrial disorders
10.
Waardenburg
syndrome
http://www.biomedsci.creighton.edu/faculty/he.html
to see outer hair cell responding to music