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;
speech that is unclear or unintelligible.
school teachers notice the child having difficulty following instructions or a story
behavioral changes such as irritability, reclusion
social isolation
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
family history of congenital deafness
development of rash and fever during pregnancy (toxoplasmosis, rubella, cytomegalovirus, herpes and syphilis)
birth weight
prematurity (with intensive care stay)
meningitis (infection can spread from the brain directly to the inner ear)
frequent ear infections
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 first step in the management is to adequately amplify the hearing with an aid. The aim is to raise the hearing thresholds into the speech range so that the child will be able to detect environmental sounds. A paediatric audiologist will be able to fit a custom-fitted behind-the-ear (BTE) for the child.
- 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.
- In children with severe to profound hearing loss, regular team assessments are made to determine if the child is progressing well with the use of hearing aids. If the progress slows or become static, candidacy for cochlear implantation is assessed (see Cochlear Implant).
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
