Unit 5: Early identification and prevention

Early identification of hearing loss is very important to begin timely rehabilitation. During infancy, language learning is easy and natural, whereas learning a new language in adulthood requires more effort. Therefore, identifying hearing loss as early as possible, especially in infants and children, helps in better development of speech and language skills.

The effects of hearing loss are more severe in children, as it can interfere with their overall development. Early detection and intervention lead to better rehabilitation outcomes, reduce the gap between individuals with hearing loss and those with normal hearing, and also lower the cost of treatment. Hence, it is recommended that every newborn should be screened for hearing loss.

Prevention of hearing loss can be done at different levels. Tertiary prevention focuses on preventing hearing loss from becoming a handicap through early rehabilitation and support, helping individuals cope effectively. Primary prevention involves avoiding preventable causes of hearing loss, such as infections or environmental risks, as suggested by organizations like the World Health Organization (WHO).

Thus, early identification, timely intervention, and preventive measures are essential to reduce the impact of hearing loss.

Prevention of prenatal causes

1. Genetic counselling: Genetic causes of hearing loss can be transmitted from one generation to generation. Therefore, if there is a family history of hearing loss, counselling the parents-to-be regarding the chances of having a child with hearing loss can help in preventing transmission of genetic causes from one generation to another.
2. Immunization: Occurrence of Rubella in a pregnant woman may lead to hearing loss in the child to be born. Vaccinating adolescent girls will help in prevention of hearing loss in their children to be born.
3. Proper health care: Pregnant women should be screened for diseases such as syphilis and toxoplasmosis and appropriate treatment should be given, if necessary. Women should also be educated regarding occurrence and effects of such diseases.
4. Avoiding ototoxic medicines: Pregnant women should be educated regarding side effects of medicine and should be advised to take medication only on recommendation by a medical doctor.

Prevention of natal causes

1. Nutrition: Nutrition taken by a pregnant woman has an effect on the birth weight of the baby. So care should be taken to ensure that the appropriate nutrition is provided to pregnant women.
2. Improved birth practice: Chances of birth trauma and delayed birth cry is more if delivery is not carried out under appropriate medical care and supervision.

Prevention of postnatal causes

1. Immunization: Children should also be immunized against diseases such as measles, mumps, rubella, meningitis as hearing loss may occur as a result of these diseases.
2. Avoiding ototoxic medicines: Public should be educated regarding side effects of medicines and should be advised to take medication only on recommendation by a medical doctor.
3. Proper health care: Appropriate health care and personal cleanliness can prevent occurrence of ear infection. Public should also be educated regarding proper management of cold and cough, especially in children, as it can lead to ear infection.
4. Avoid exposure to loud noise: Public should be educated regarding harmful effects of noise and should be advised to wear ear protective devices when exposed to loud noise. Laws which limit the exposure to loud sounds should be enforced.
5. Use of helmets and seat belts: Public should be educated and encouraged to use helmets and sear belts to avoid head injury during road accidents.

Early Identification and prevention

Importance of early identification

Early identification of hearing loss is essential to begin timely rehabilitation, especially during infancy when the brain shows rapid development and is highly sensitive to learning. This period is known as a critical period, during which the brain is more responsive to sensory stimulation required for developing abilities like speech and language. If proper stimulation is not received during this time, full development may not occur.

Research shows that language is best learned before the age of 3 years, and children who receive early exposure perform much better than late learners. Hearing loss during infancy or early childhood can limit the sensory input needed for speech, language, social, and emotional development, leading to long-term difficulties.

The main aim of early identification and intervention is to reduce or prevent these negative effects. Early rehabilitation may include the use of hearing aids and speech and language therapy, which help the child develop communication skills effectively.

If hearing loss is identified late, it increases the developmental gap between children with normal hearing and those with hearing impairment, and may also lead to psychological difficulties. Early intervention improves chances of academic success, social adjustment, and better career opportunities. Therefore, early detection of hearing loss is crucial for overall development and quality of life.

Hearing screening

Hearing screening tests are used to quickly identify whether an individual may have a hearing problem. These tests are time-efficient, allowing a large number of people to be screened in a short period.

The results are usually given as “Pass” or “Refer.” A “Pass” result indicates that the individual likely has normal hearing, while a “Refer” result suggests a possible hearing loss and the need for a detailed evaluation.

Hearing screening can be conducted by audiologists or trained allied professionals, making it an important step in the early detection of hearing loss.

Hearing screening methods

Hearing screening can be carried out using either formal or informal methods. Formal methods involve the use of standardized tests that have been scientifically developed and proven to be effective. These methods are more reliable and usually require special instruments or equipment for screening.

In contrast, informal methods are simpler and may not require sophisticated tools, but formal methods are generally preferred for accurate and systematic identification of hearing problems. Some of the formal methods used for hearing screening by audiologists are:

1. High risks register
2. Behavioral Observation Audiometry
3. Auditory Brainstem Response
4. Otoacoustic Emissions
5. Immittance Screening
6. Pure-tone Screening

High risk register/Checklists

One of the simplest and least expensive methods of hearing screening is the use of checklists. These checklists vary according to the age of the individual. For newborns, infants, and young children, high-risk checklists are used. These include factors that may cause hearing loss during prenatal, natal, and postnatal periods, helping to identify both congenital and early-acquired hearing loss.

The high-risk register is divided into two categories: one for neonates (0–28 days) and another for older babies (29 days to 3 years). Information is usually collected by interviewing parents or caregivers. If any response is “yes”, the child is considered at risk for hearing loss and should be referred for detailed evaluation.

For adults, hearing screening can be done using a self-assessment scale, which is a questionnaire that evaluates communication difficulties, ability to hear sounds, speech understanding, and psychological impact. If the score exceeds a certain level (e.g., more than three), the individual should be referred for further hearing assessment.

Development of auditory behavior

Normal children show age-appropriate responses to sound, which is known as the development of auditory behaviour. During hearing screening, the mother or caregiver can be asked whether the child is showing these expected responses at different ages.

If the child is not showing normal auditory responses, it may indicate a risk for hearing loss, and the child should be referred for further evaluation. However, it is important to ensure that the lack of response is not due to other conditions such as intellectual disability or cerebral palsy, which can also affect the child’s responses to sound.

Behavioral observation

During behavioral test, sound of different frequencies and intensities are presented in free field in an audiometric room and the responses of the child to these sounds are observed.

Material required

Noise makers- choose one which makes high frequency sound (e.g. pooja bell, jingles), one which makes low frequency sound (a rattle). For checking mid frequencies, speech sounds such as/a/or word “Aha!” can be used.

Procedure for testing

Hearing screening in children is preferably conducted in a quiet room using two testers—one to present the sound stimulus and the other to observe the child’s response. The child is held by the mother facing forward, while the tester presents sound from behind the child, usually from about one foot away.

The observer, standing in front, watches for responses such as searching for the sound or turning towards it. Since responses vary with age, age-appropriate reactions should be considered. The observer also distracts the child between trials to maintain attention. Sounds are presented from different directions and should not be repeated frequently to avoid boredom or adaptation.

If the child does not show expected responses for their age, hearing loss is suspected, and the child should be referred to an audiologist for detailed evaluation.

Ling’s six sound test

Ling’s Six Sound Test is a simple method used to check a child’s ability to hear different speech frequencies. Human speech contains a wide range of frequencies, and the six sounds /a/, /i/, /u/, /s/, /ʃ/ (sh), and /m/ represent this range.

A child with normal hearing can hear and identify all these sounds even when they are presented from behind. In this test, these sounds are spoken one by one, and the child’s response is observed.

If the child is able to detect and respond to all six sounds, it indicates good access to the full range of speech sounds. If not, it may suggest a possible hearing problem, and further evaluation is required.

1. Whether the child is aware of the sounds
2. Whether the child can identify these sounds

If the child does not hear or is not able to identify these sounds, then the child needs to be referred for detailed audiological evaluation.

Otoacoustic emissions

Otoacoustic emissions (OAE) are sounds produced by the inner ear in response to stimulation. These sounds can be recorded using a small microphone placed in the ear canal. The presence of OAEs indicates normal functioning of the inner ear, making it an important sign of normal hearing.

OAE testing is a quick and efficient screening tool for detecting hearing loss. It requires minimal training and is widely used for newborn hearing screening in hospitals. Modern OAE devices are portable, hand-held, and battery-operated, making them convenient to use.

The results are displayed as “Pass” (normal hearing) or “Refer” (possible hearing loss). If the result is “Refer,” the test is usually repeated after two weeks, and if the same result persists, the child should be referred for a detailed audiological evaluation.

Hearing screening in different set-ups

Different hearing screening tools are used based on the population and setting. No single method is sufficient in all situations, so a combination of tools is often used.

1. In a hospital setting (especially for newborns), screening may include high-risk registers, behavioural observation, and otoacoustic emissions (OAE).
2. In a school setting, methods such as signs and symptoms checklists, Ling’s six sound test, and pure-tone audiometry are commonly used.
3. In camps or rural areas, pure-tone audiometry is used for children above 3 years, while behavioural observation tests are preferred for younger children.

Thus, the choice of screening method depends on the age, environment, and available resources to ensure effective identification of hearing loss.

Advantages and limitations of screening

1. It is not time consuming. A large number of babies can be tested in less time.
2. It is cost effective. Does not require expensive instruments to carry out these tests.
3. It is easy to train personnel to carry out these tests.
4. It can be carried out anywhere.

The results of informal hearing screening methods should be interpreted with caution. These methods often have a higher chance of errors, leading to false “referrals” and false “pass” results.

A false referral occurs when an individual with normal hearing is incorrectly identified as having a hearing problem, while a false pass occurs when a person with hearing loss is mistakenly considered to have normal hearing.

Another limitation is that informal tests are not standardized, meaning the procedures may vary from one tester to another. This lack of uniformity makes it difficult to compare results across different settings or evaluators.

Therefore, informal screening should be followed by formal testing for accurate diagnosis.

Care and maintenance of audiological equipment.

1. Do not keep the audiometer in places with extreme temperature. Store in a cool, dry place.
2. Do not drop the instrument or transducer. Make sure it is kept in a place where it is not in danger of falling.
3. Keep the instrument covered when not in use to avoid dust collecting on it.
4. Avoid dropping water or any other liquid on the instrument.
5. Wipe the instrument with a clean dry, soft cloth.
6. Make sure that there is no vibration transmitted to the instruments. This precaution should be taken especially when transporting the instruments for outreach programs.
7. Do not apply force on the switches or dials of the instrument. The controls should move freely.
8. Do not twist the cords of the instruments when storing them. Make sure that they are kept untangled when in use. Never bend or twist the cords where they enter the transducers.
9. Always keep a stock of extra cords, which are stopped properly, since they are likely to go out of order more frequently when compared to other parts.
10. Place the transducer on a hanger or hook when not in use. Do not hang the transducer using the cords, rather they should be hung from the headband.
11. Do not stretch the headband as it will loose its tension.
12. The audiological instruments should be electroacoustically calibrated to meet the standards at least once in six months. This should be done by qualified professionals.
13. While using instruments which work on AC power supply ensure that it works on 220 volts, 50 Hz stable power supply.
14. While using instruments which work on DC power supply, check the voltages of the battery before using the instrument.
15. Ensure that there is no internal hum from the audiometer.

Daily before using any audiological equipment, a visual inspection of the instrument is required. Following this, a listening test needs to be carried out. Given below is a list of things that need to be done on order to check an audiometer.

Checklist to be maintained before using audiological equipment

1. Check to see if all cords are correctly connected.
2. Check if the cords are cracked or worn out.
3. Check the audiometer to see if the dials move properly.
4. Check that the earphones are properly attached to the headset (headband).
5. Check the instrument for any crack or damage, especially the transducers.
6. Check if the power supply is present.
7. Make sure that the audiometer is switched on.
8. After putting on the headsets, present tones through each of the head phones and make sure it comes through the correct earphone.
9. Turn the attenuator dial from minimum to maximum levels and listen for increases and decreases in loudness.
10. Check if the signals are clear even at high intensity levels.
11. Check that when the frequency is changed, there is a change in the pitch of the signal. This should be done with the intensity set at a comfortable loudness.
12. Check the thresholds of someone who has normal hearing and whose thresholds are known and see if they match. This should be done for both air conduction and bone conduction.
13. Check if the signals are heard continuously even if the headphone cords are moved or twisted gently.
14. Check if no additional sounds are present through the transducer other than the signal that is being presented.

The above information should be checked and recorded daily. The form in which you record this information is called the ‘Daily Listening Check form’.

List of equipment, specification for the same

Audiologists should be consulted before buying any audiological equipment. They would give you a list of instruments which should be bought for an audiological set-up. They would also provide the specifications for each of the audiological equipment that should be procured. The specifications of any instrument are a detailed set of arameters / features that the instruments should have. The specification for each audiological instrument would vary depending on the type of instrument being procured. (e.g. audiometers or immittance auditor and the purpose for which the instruments are being got (e.g. screen diagnostic).

Once your audiological center has got the necessary equipment it is important that you maintain a record of the instruments that you have got. Open a register and maintain the following information in the format given:

Name of instrument (Model name)

Accessories got with the instrument

Serial number

Date of purchase; Company from which purchased; Invoice no; Cost

Present location of the instrument

Name and signature of staff in-charge of the instrument

The above information should be maintained separately for each category of instrument. For example, this should be done separately for each of the following: screening audiometer, diagnostic audiometer; screening immittance audiometer, diagnostic immittance audiometer.