Hearing and deafness
Hearing loss is common and can affect people of any age. It is thought that half the general population above the age of 60 have some hearing loss. Children are the next most common group to be affected, usually due to fluid or infection in the middle ear but also due to congenital problems or viral illness during early childhood. Hearing loss can interfere with normal communication with others on a daily basis.
How do you hear?
We are able to hear because sounds enter the ear canal and pass along it to the eardrum. The sounds cause vibrations first of the eardrum and then of the little bones, called ossicles, which bridge the gap between the drum and the cochlea (part of the inner ear).
In the cochlea the vibrations are translated into electrical signals which are passed on to the brain along the acoustic, or auditory, nerve.
Types of deafness
A problem of transmission (or conduction) of sound waves through the ear canal and middle ear is referred to as a conductive hearing loss. A problem with the translation of the sound waves into an electrical signal by the inner ear or the onward passage of those electrical impulses via the nerves to the brain is referred to as a sensorineural hearing loss.
A conductive hearing loss occurs when there is a failure of the conversion of sound waves into movements by the eardrum and the little bones of the middle ear. This can occur either because the sound waves are not reaching the eardrum, for example because of wax blocking the ear canal, or because the vibrating mechanisms of the eardrum or ossicles are not working properly, for example because of current or previous infections.
There are a great number of causes of conductive hearing loss including blockage by wax, infection, a collection of fluid, trauma or fixation of the ossicles in the middle ear (which is called otosclerosis). Fortunately, they can often be treated and hearing in the infected ear can be corrected or improved.
A sensorineural hearing loss is due to a problem of the inner ear or of the nerve that carries the signal from the inner ear to the hearing centres in the brain. Again there are many causes, the most common being that of hearing loss in old age (presbyacusis), which usually affects both ears to a similar degree and can be associated with noises in the ear (tinnitus). Other common conditions which affect the inner ear are infections (particularly by viruses), trauma, the side effects from certain medication and congenital causes.
While some inner ear problems are reversible, generally speaking the hearing loss is irreversible (i.e. permanent). Extremely rarely, but more seriously, the hearing loss may be due to a growth, otherwise known as a tumor, on the hearing nerve in the brain.
The main difficulty with sensorineural hearing loss is an inability to hear adequately in conversations, especially when there is background noise. Many people complain that they can hear the sounds of a conversation, but cannot discriminate exactly what is being said. It can lead to immense frustration and feelings of isolation.
Although frequent in older people, it is not uncommon for people to notice problems with speech discrimination whilst they are in their 30s or even earlier, especially if they have had regular exposure to loud noise, for example by going clubbing.
Whilst there is no absolute cure for a sensorineural hearing loss, hearing aids help to amplify or increase the sounds that are transmitted to the inner ear and so partially overcome the hearing loss. The technology in hearing aids is continuing to improve and they can work very well for many people.
Diagnosis
You should always see your doctor urgently if you have a sudden hearing loss, as sometimes treatment for sudden deafness should be started within 48 hours of its onset.
If you notice a hearing loss only in one ear, you should see your doctor, who will probably refer you on to an ENT specialist or an audiological physician.
Hearing aids
A hearing aid is a device that is used to increase the loudness of the sound reaching the ear of a person with a hearing difficulty. Modern hearing aids consist of three basic electronic components: a microphone, an amplifier and a loudspeaker.
The most common types of hearing aids are those that are worn in or behind the ear, but there are others, such as implantable hearing aids, which can be used in certain situations
Externally worn hearing aids
The most commonly used type of aid is the behind-the-ear hearing aid, where all the electronic components are contained in a skin-colored plastic case that sits behind the ear.
Cosmetically more popular is the in-the-ear hearing aid, which is a smaller, more compact device worn in the ear canal, but it is inappropriate for people with severe deafness because it is not powerful enough to compensate for their hearing loss. It is not suitable for those with some loss of manual dexterity, because the control switches are quite small.
Even smaller is the completely-in-the-canal hearing aid, which is virtually invisible when worn. Again, because of its small size, its casing is too small to be able to hold a very powerful amplifier and so it is only useful for mild hearing losses.
People with a conductive hearing loss may benefit from a device which is held in place behind the ear with a headband or ‘alice band’. This is known as a bone conduction hearing aid.
People tend to benefit from this type of hearing aid if they have problems in the ear canal or middle ear, for example because of recurrent ear infections, previous surgery, or anatomical abnormalities such that they are unable to wear conventional hearing aids. Bone conduction aids can work very well, but can be quite bulky and obvious, and a more sophisticated type of bone conduction aid has been developed.
Analogue and digital hearing aids
There has been a lot written in the media recently about digital hearing aids. The ‘digital’ part of the hearing aid implies that these types of aids are more sensitive and better at restoring hearing than the older type of aids, and this is often, but not always, the case.
Digital hearing aids process sound in a fundamentally different way to analogue aids, by dividing up the sound into ‘packets’ and then processing them. This means that it is possible for digital aids to be more selective in filtering out irritating background noise, but no hearing aid, digital or analogue is capable of only amplifying the sounds that you want to hear.
Cochlear implant
People who have such a severe deafness that they hardly derive any benefit from conventional hearing aids (i.e. those people with a profound sensorineural hearing loss) may benefit from a cochlear implant.
In this type of implantable hearing aid a wire electrode is surgically inserted into the inner ear (the cochlea). Intense speech and hearing therapy is required often for several years following this operation. Cochlear implants can be used for children and adults. It can be very expensive and unaffordable for the common people.
If you (or people around you) notice a gradual deterioration of your hearing you should seek advice from your doctor who will advise you of the appropriate action to be taken, and will be able to organize a hearing test.
If some one gets impaired vision, they run to the opticians and fit eye glasses at whatever cost, similarly if one is hard of hearing they are not very enthusiastic to see an audiologist or ENT doctor and get a hearing aid.
