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Hearing Loss

What causes hearing loss?
What Happens When A Person Has Hearing Loss?
What Can Be Done To Help?
Treatment Options
Consequences of Untreated Hearing Loss
Knowing When to Seek Help
Knowing Who to Consult
Hearing is nature’s endowment that enables us to recognise speech and other sounds, develop oral language and communicate verbally. The hearing organ itself – the ear – consists of three sections: The outer ear, the middle ear and the inner ear. The ear drum separates the outer ear from the middle ear, while the oval window marks the entrance into the inner ear.

Hearing begins with the collection of sounds in the outer ear. These sounds are then transmitted through the middle ear into the inner ear. Situated in the inner ear are highly specialised hair cells, which convert the original sounds into electrical impulses. These impulses are conveyed through the auditory nerve to the brain for processing and interpretation.

Any obstruction to the transmission of sounds along this auditory pathway constitutes an impairment, which in turn could lead to hearing loss. Whenever sounds cannot be transmitted beyond the middle ear, it results in what is known as conductive hearing loss. Common causes of such a condition in the outer or middle ear include build-up of wax in the ear canal, perforation of the ear drum, birth defects or otitis media.

It is also possible for the transmission of sounds to terminate in the inner ear or auditory pathway, giving rise to what is known as sensorineural hearing loss. This occurs when the specialised hair cells in the inner ear degenerate or are damaged as a result of prenatal and birth related problems, viral and bacterial infections, (respiratory infections, measles, meningitis etc.), heredity, trauma, excessive exposure to loud noise, use of ototoxic drugs (gentamycin, chloroquine, quinine etc.), or a tumor in the ear.

In some individuals, hearing loss may be associated with problems in both the middle and the inner ear. This condition is known as mixed hearing loss.

As people grow older, the likelihood of having hearing loss increases due to ageing, and cumulative exposure to environmental noise.
The manifestation of hearing loss varies with the degree of loss which could be mild, moderate, severe or profound. A person with mild hearing loss can miss nearly half of normal soft speech sounds. This results mainly in problems with clarity as not all the sounds are received by the brain. Someone with moderate hearing loss may miss over half of speech sounds. Such an individual will not have problems hearing at short distances or face-to-face, but will have problems if distance increase or visual contact is inadequate. A person with severe hearing loss can miss virtually all speech sounds. Such a person may not hear whispers but only loud sounds. A person with profound hearing loss tends to rely on visual cues instead of hearing, since none of the speech signals within the talking range is perceived.

The symptoms of hearing loss can also depend on whether the loss affects one ear (unilateral) or both ears (bilateral). An individual with unilateral hearing loss may have problems hearing soft speech, hearing speech in background noise and localising (finding the source of sound, or the direction). With bilateral hearing loss, the problems are greater than unilateral hearing loss. In both cases, the degree of the disability will depend on the severity of the hearing loss. Hearing loss can also be related to low or high-pitched sounds. Usually, hearing loss does not affect all speech frequencies/pitches in the same manner. For example, a person who has been around excessive loud noise will probably have what is termed as high-frequency hearing loss. This person will have difficulty with sounds that are higher in pitch (such as female or children voices). This type of hearing loss affects the high pitch (treble) sounds more than the low pitch (bass). It makes understanding difficult because the person hears low-pitched noise at a normal volume but misses out on a lot of speech sounds that bring clarity (high-pitched consonants).
In infants and young children, early detection is the key to successful treatment or intervention. The goal is always to minimise the time lag between the possible onset of a hearing problem, its detection and treatment. Previously, it was thought that it was not possible to detect hearing loss in infants until they were older. However, current technology now makes it easy to accurately detect hearing impairment in any age group, including newborns. Where hearing test is incorporated into routine medical check-up, it should be possible to detect problems quite early. In the absence of a routine infant hearing test, parental suspicion may be the first clue to detecting hearing impairment in children. Unfortunately, this often happens rather late and may result in poor outcomes even when given the right treatment.

In any age group, treatment depends on the nature of the hearing loss. Most outer and middle ear problems (such as otitis media and impacted cerumen), which could result in conductive hearing loss, can be treated medically or surgically. However, the vast majority of significant hearing losses are as a result of damage to the inner ear structures caused, for instance, by infections, neonatal jaundice, abnormal hereditary factors, intake of ototoxic drugs and excessive exposure to noise. In such cases, hearing loss is permanent and cannot, as a rule, be treated except with the use of hearing devices.

It has been found from research that children born with hearing loss who are identified and given appropriate intervention in the first year of life stand a better chance of developing good speech and language skills than those treated thereafter. Studies have also shown that detection of hearing loss during infancy followed with appropriate intervention minimises auditory problems in later years. As a result, healthcare providers in developed countries and in an increasing number of developing countries are required (by law in some countries) to offer hearing test for ALL newborns before hospital discharge or within the first month of life. Where this is not possible, targeted screening of all high-risk infants is recommended. In developing countries where majority of babies are born outside hospitals evidence from research has shown that routine immunisation clinics provide effective platforms for the early detection of infants with hearing loss regardless of the place of birth.
Where hearing loss cannot be remedied by medical or surgical treatment, as with most sensorineural hearing losses, rehabilitation with hearing devices such as hearing aids and cochlear implants; or sign language may be required. A hearing aid is an electronic device which consists of a microphone, amplifier and a receiver. Sound signal is received through the microphone and sent to the amplifier, where it is processed and amplified according to selected settings. The amplified sound is transmitted via the receiver on to the hearing aid user’s ear drum for subsequent processing. While a hearing aid may not completely restore hearing to its natural state, it helps a hearing impaired person to communicate with the residual hearing capacity they still possess, no matter how limited.

With continuing advances in digital technology, hearing aids are rapidly overcoming their acoustical limitations in achieving improved hearing. In fact, some brands offer such amazing capabilities that make them invaluable personal communication devices for individuals that are hard-of-hearing. The manufacturers are also paying greater attention to making the hearing aids more cosmetically acceptable without unduly sacrificing the functionality of the instruments.

Hearing aids may not be suitable for some individuals due to the severity of their hearing loss. For such people, cochlear implants may be the only option. A cochlear implant is also an electronic device similar to a hearing aid. It can only be fitted through a surgical procedure by which the device is inserted into the cochlear within the inner ear. For those who cannot be helped with either hearing aids or cochlear implants, the only rehabilitation option may be sign language. This may entail enrolment in a school for deaf children.
Hearing loss can occur before birth, at birth, or anytime from birth to adulthood. If left untreated, hearing loss in infants can result in speech and language delays and some behavioural problems. In latter years, this can lead to poor academic achievements and limited prospects for gainful employment. For infants and children with severe hearing losses, the chances are that such children will end up in a deaf school or not catered for at all, if the problem is not detected promptly and treated with appropriate hearing devices. Infants identified promptly with hearing loss can be fitted with amplification devices as young as 4 weeks of age. The language, cognitive, and educational development of these infants will be superior to those who were helped later than one year.

For an adult with hearing loss, the psychological, physical and emotional handicap is profound. Every attempt to communicate with others presents difficulties in trying to listen, interpret and understand speech. The problems and frustrations associated with impaired hearing often manifest in one or more of the following:

  • Missing out on vital information in a conversation, meeting or public gathering.

  • Inability to use the telephone effectively.

  • Inability to enjoy the pleasure of TV, Radio or Music.

  • Inability to hear warning or danger signals.

Trying to cope with hearing impairment as if nothing were wrong or to “keep up appearances” places hearing impaired persons under a great deal of stress. Their energy is taxed because they constantly monitor whether they are speaking too softly or too loudly. They also strain to hear and depend upon lip-reading to follow a conversation.

Moreover, it may be stressful for a person with normal hearing to converse with a hearing impaired individual if such a person has to shout or repeat what is being said in order to be heard. This could be embarrassing for such a person especially in a public place, and may sometimes create a tendency to avoid the hearing impaired person. It is therefore, not unusual to find that people with hearing loss eventually decide that they can no longer enjoy social activities. Such individuals may withdraw, first from friends and later from their families. Perhaps, the most disliked consequence is the stigma of being labelled as “deaf”, “dumb” or “dull” particularly when a hearing device is needed but not used. The consequences of trying to hide or cope with a hearing loss are therefore far greater that the perceived embarrassment of using hearing devices.
In newborns hearing loss cannot be detected by the baby’s appearance. In the absence of a hearing test, newborns and infants with hearing loss cannot be reliably detected by merely observing the child’s behaviour. In at least a third of infants with hearing loss, the exact cause may not be known. However, in countries like Nigeria where hearing test is not routinely offered to newborns a number of potential causes of hearing loss can serve as early warning signs which should prompt parents and care givers to seek hearing test. These conditions or risk factors include any one or combination of the following:

  • Premature birth (less than 34 weeks gestation)

  • Low birthweight (less than 1500 g)

  • Illness in the first week of life necessitating hospital admission

  • Neonatal jaundice requiring treatment with phototherapy or exchange blood transfusion

  • Absence of skilled attendant at birth or if baby was born outside hospital

  • Family history of hearing loss

  • Both parents are related (consanguinity)

Infants and young children exhibiting one or more of the following symptoms may have hearing loss:

  • Failure to startle to loud sounds.

  • Inability to locate sounds.

  • Failure to engage in age-appropriate communication (especially by age 12 months).

  • Recurrent ear infections.

  • Inability to respond when called from another room or from behind.

  • Unusual behaviours such as inattentiveness, hyperactivity and restlessness.

  • Poor academic performance.

There are many other clues to possible hearing loss. The above list simply provides examples of the more frequent indicators.

For most adults, hearing loss can be suspected if they have been:

  • Experiencing a nervous tension, irritability or fatigue from the effort to hear.

  • Inclined to believe that “everybody” mumbles or “people don’t speak as clearly as they used to.”

  • Straining to understand conversion in social settings or at work; frequently misunderstanding or needing to have things repeated; watching people’s faces intently when someone is listening to them.

  • Increasing the television or radio volume to a level that others complain as too loud.

  • Identified with a family history of hearing loss.

  • Diagnosed with diabetes, heart or circulation problems.

  • Exposed to ototoxic drugs.

  • Having reoccurring ear infections, constant ringing in the ears or dizziness.

  • Exposed to high noise levels, such as from tractors, machinery in factories, firearms, power tools or aircrafts without adequate ear protection.

Since hearing loss may result from a medical condition and co-exist with other medical problems, it is advisable that consultation should be made first with a general medical practitioner, a physician or surgeon that specialises in hearing health care. From the initial medical examination, the doctor should be able to refer to an appropriate ear care provider who has the facilities and experience to undertake age-appropriate audiological evaluation and the requisite management within the context of the overall medical condition of the patient. Otherwise, there could be misdiagnosis or avoidable delays in treatment which may lead to further deterioration of the problem.

Click here for a useful parental check list on infant hearing loss
Click here for a useful rapid self-test for persons 50 years and above.