Hearing loss in children


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Hearing is one of the five classical senses, the others being sight, smell, touch and taste. Each sense modality is a means for our brain to detect light and sound waves, as well as molecules floating in air, fluid or hard objects, in order to enable the brain to understand where we stand in our world.

In popular imagination, sight is often rated above hearing in order of importance, but as many people can attest to, having one or both ears not hearing pro- perly can be a real pain.

In children, optimal hearing is essential for acquiring language and proper pronunciation of words.

From kindergarten onwards, the ability to hear well allows smooth interaction between the child and her peers and teachers, which is important to achieve learning milestones.

Occasionally, deaf mute young adults can be seen in public, recognisable from the rapid gesticulations that represent sign language and their very spontaneous laughter.

Deaf mutes have become less common compared to two generations ago, as medical science has managed to control infect-ions of the womb and infancy that lead to severe and profound deafness.

However, mild to moderate hearing impairment is still common in children – still a disadvantage, but certainly not a hindrance to learning.

There are many people holding on to normal jobs and going to university with mild to moderate hearing impairment.

An explanation of the auditory pathway is helpful to understand hearing and the lack thereof.

The pinna, or outer shell, of the ear acts as a funnel to channel sound waves in the air into the ear canal, which hits the eardrum. The vibrations of air molecules are converted into movements of the eardrum.

In turn, this moves the ossicles of the middle ear – a chain of little bones consisting of the malleus, incus and stapes, connected via joints – not unlike the hip, knee and ankle joints, albeit tiny versions.

Ultimately, the bony movements move the oval window membrane of the cochlea.

Any disturbances in the ear canal, eardrum or ossicles result in conductive hearing loss, which is connected to the carriage of sound to the oval window.

The vibrations of the oval window membrane are transmitted into the cochlear fluids, ultimately moving the hair cells within the cochlea. Different frequencies of sound are served by dedicated hair cells, very much like the piano keyboard – from one end for high pitch noises to another for low pitch ones.

The hair cells generate electrical impulses that travel along the auditory nerve to parts of the brain, and finally to the auditory cortex of the temporal lobe that processes sound stimuli.

Abnormalities of the inner ear and the brain result in sensorineural hearing loss, or nerve deafness.

I shall focus on conductive hearing loss in children, especially a couple of common causes.

Wax impaction

The commonest cause of hearing loss, at least in the context of Malaysia, both in children and adults, is hardened ear wax blocking the ear canal.

Ear wax, or cerumen, is composed of keratin (“dead skin”) and sebum (the natural oil of the skin). There are various consistencies of wax, from the dry, hard type to the oily, soft type.

It is said that one type predominates in certain racial groups, but I have seen both dry and oily types in all races in Malaysia.

Ear wax is constantly made, by continuous keratin shedding, and a natural “conveyor belt” exists to bring it out of the ear canal – a self-cleaning system that only very rarely breaks down.

The term ‘cerumen’ has a neutral scientific tone, but when referred to in our vernacular languages, does have connotations of being unclean (e.g. tahi telinga), which explains the favourite Malaysian pastime of “ear-digging”.

Therefore, it is common in our culture to remove wax as much as possible.

Many parents engage in regular wax cleaning sessions with their children, with all manner of tools designed to remove wax, including hooked tips, scoops, spiral corkscrews and suction tips, none of which is truly effective.

The commonest method employed at home is with the ubiquitous cotton bud. There is usually variable success in the amount removed.

Otolaryngologists would mostly counsel against the use of cotton buds, mainly because, as explained before, wax comes out of the ear canal spontaneously.

In fact, the cotton bud mostly pushes lumps of wax deeper into the ear canal, against the natural outflow, making wax impaction a mainly self-inflicted problem, resulting in reduced hearing, and occasionally, pain.

However, in certain cases, cleaning with cotton buds may be permissible, especially if the wax consistency is the soft, oily type, which would allow adherence to the cotton tip, and the child has a wide ear canal.

In children, the ear canal is usually narrow, which means it becomes totally blocked much sooner, compared to a wider adult ear canal.

Glue ear and grommets

Middle ear infection in children is a common occurrence, inevitable with every upper respiratory tract infection, viral or bacterial. Viral infection often clears up in a few days, but some may progress to bacterial infection.

In contemporary medical practice, antibiotics are often given, leading to a quick resolution of the middle ear infection.

Regardless of viral or bacterial, or whether antibiotics are given, in all cases of middle ear infection, there will be a time when the whole middle ear space is filled with mucous or pus.

The mucous, which is sticky like glue (thus the term ‘glue ear’), will mostly disappear within a month, with only a tiny minority dragging on longer.

In the context of Malaysia, with our warm, tropical weather, middle ear infect-ions are not as common as in winter climates, and probably resolve faster too.

Glue ear, or known by its medical synonyms of serous otitis media, otitis media with effusion and middle ear effusion, is only significant when there is pain or hearing impairment.

The degree of hearing impairment in glue ear is never worse than mild. In other words, the child can still hear, but may not respond in the first instance, may ask others to repeat themselves, or have the television turned on louder than usual.

There are a few treatment options available to manage glue ear. Most commonly, waiting with awareness of the child’s hearing impairment and adjustments to accommodate will be fine.

After all, the hearing impairment is temporary and self-resolving in most cases.

Antibiotics and nasal decongestants may also be tried, as it makes sense that hastening recovery of the nasal problem will also hasten that of the middle ear.

Another common suggestion in the ma- nagement of glue ear is the insertion of ventilation tubes, otherwise known as grommets. These are plastic silicone tubes placed in an artificial perforation that allow mucous to drain out and air to enter the middle ear. This restores the middle ear’s normal air space, thereby making hearing near normal again.

Put another way, one loses 1% of hearing with a grommet, but glue ear results in 20% hearing loss. It is reasonable to consider grommet insertion when glue ear has persisted beyond one to two months, i.e. when the glue ear has not disappeared by itself after a few weeks.

However, there are disadvantages to grommets. It requires a general anaesthetic before insertion in children, which carries its own inherent risks.

Once a grommet is inserted, it does not spontaneously come out, or extrude, for six to twelve months. It may leave a permanent hole in the eardrum after extrusion.

The biggest problem is the entry of swimming pool or bath water into the middle ear, which may lead to infection and weeks of troublesome pus and mucous discharge.

This means that every bath time necessitates plugging the ear canals to avoid water entry.

Swimming and playing in pools is a favourite activity of children in Malaysia, which means children with grommets have to wear earplugs and caps to prevent water entry into the ear.

Grommets are a good means of overcoming problems of hearing impairment, but in return, minor inconveniences of constant ear canal plugging have to be tolerated.

As they say in the real estate business, buyer beware!


This article is courtesy of the Malaysian Association of Paediatric Surgery. For further information, e-mail starhealth@thestar.com.my. The information provided is for educational and communication purposes only and it should not be construed as personal medical advice. Information published in this article is not intended to replace, supplant or augment a consultation with a health professional regard-ing the reader’s own medical care. The Star disclaims all responsibility for any losses, damage to property or personal injury suffered directly or indirectly from reliance on such information.

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Hearing loss in children

   

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