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Hearing Loss
Blindness separates us from things but deafness separates us from people. Helen Keller.
  • Hearing loss the most common form of human sensory deficit is the partial or total inability to hear sound in one or both ears. It may be a sudden or a progressive impairment that gradually gets worse over time. Depending on the cause, it can be mild or severe, temporary or permanent.
  • After our eyes, the most important sensory organ is our ears. This means hearing loss can have significant consequences. In most cases, hearing loss is age related .However it can also be triggered by loud noises or infections, or may be hereditary. Fortunately, in most cases hearing loss can be improved using hearing aids.

According to WHO (2018) data, the prevalence of hearing impairment (HI) in India is around 6.3%of the total population. The estimated prevalence of adult-onset deafness in India will be 7.6% and childhood onset deafness is 2%.In India hearing loss is the second most common cause of disability.

Causes of hearing loss and deafness

Childhood and adolescence

  • Chronic ear infections (chronic suppurative otitis media)
  • Collection of fluid in the ear (chronic nonsuppurative otitis media)
  • Meningitis and other infections

Adulthood and older age

  • Chronic diseases
  • Smoking
  • Otosclerosis
  • Age-related sensorineural degeneration
  • Sudden sensorineural hearing loss

Factors across the life span

  • Cerumen impaction (impacted ear wax)
  • Trauma to the ear or head
  • Loud noise/loud sounds
  • Ototoxic medicines
  • Work related ototoxic chemicals
  • Nutritional deficiencies
  • Viral infections and other ear conditions
  • Delayed onset or progressive genetic hearing loss

Signs and symptoms of hearing loss may include

  • Muffling of speech and other sounds
  • Difficulty understanding words, especially against background noise or in a crowd
  • Trouble hearing consonants
  • Frequently asking others to speak more slowly, clearly and loudly
  • Needing to turn up the volume of the television or radio
  • Withdrawal from conversation

Avoidance of some social settings

Impacts of untreated hearing loss

The hearing loss process is so gradual that one wouldn’t notice it over a period of time. Those who have been diagnosed with hearing loss, wait, on average, seven years before seeking treatment. Unfortunately, allowing hearing loss to remain untreated can lead to some serious consequences. The most recent studies highlight the social, psychological, cognitive and health effects of untreated hearing loss. Some of them are enumerated below.

  • Irritability
  • Fatigue, mental tension, stress, and depression.
  • Avoidance or withdrawal from social functions.
  • Loneliness.
  • Reduced alertness
  • Increased risk to personal safety.

Hearing loss is frustrating for those who have it and for their loved ones. But recent research from John’s Hopkins reveals that it also is linked with walking problems, falls and even dementia (memory disorders and impaired reasoning). Brain scans show us that hearing loss may contribute to a faster rate of atrophy in the brain. Frank Lin, M.D., Ph.D., (2014) found that mild hearing loss doubled dementia risk, moderate loss tripled risk, and people with a severe hearing impairment were five times more likely to develop dementia.

Hearing loss also lead to fewer educational and job opportunities due to impaired communication. Besides, it causes social withdrawal due to reduced access to services and difficulties communicating with others.

Normal hearing is a prerequisite for normal speech and language development .New born babies with normal hearing, from 0 to 3 months aroused from sleep for a sound as loud as that of flour mill. From 3 to 4 months infant begins to make a rudimentary head turn towards sounds as loud as normal conversation. From 4 to 7 months baby turns head towards direction of sounds slightly softer than conversation level and by 16 months the toddler localizes directly to the side, below and indirectly above to a sound as loud as a whisper. Any altered and discrepancies in the above behaviors warrants to consult an audiologist, else this will lead to delayed speech and language development.

How do we hear?

To understand how we hear, it is useful to know the structure of the ear. The ear is divided into three parts; the outer ear, the middle ear and the inner ear.

  • The middle ear is made up of the eustachian tube, a narrow tube which connects to the back of the nose and allows the air to reach the middle ear space, as well as the eardrum and three bones or ossicles (The hammer, the anvil and the stirrup).
  • The inner ear is made up of the snail shaped cochlea which includes the hearing nerves and the balance system.
  • Sound occurs when an object vibrates or moves and causes the air around it to move as well.

    • Sound travels in waves through the air, the ear picks up the waves.
    • Sound waves travel down the ear canal and hit the eardrum in the middle ear.
    • This causes the eardrum to vibrate.
    • The three tiny bones in your middle ear link the vibrating eardrum to the cochlea in the inner ear.
    • The cochlea turns the sound vibrations into electrical information for the brain which you understand as a sound or word.
    • The cochlea is filled with liquid that carries the vibrations to thousands of tiny hair cells sitting on a membrane that stretches the length of the cochlea.
    • The hair cells on the membrane fire off tiny electrical signals.
    • These electrical signals travel up the cochlea nerves of the auditory pathway to the brain.
    • All this happens in a fraction of second.

What types of hearing loss are there?

  • Hearing loss is generally classed as sensorineural, conductive or mixed.
  • All hearing loss types can be either acquired (occur due to age, a disease process, or injury) or congenital (something occurring or identified at birth).
  • Sensorineural hearing loss occurs when there is a problem in the inner ear; of either the cochlea (sensori) or the auditory nerve (neural), which disturbs and affects the sound signals being sent to the brain for understanding. This type of hearing loss is most often seen with ageing but can be seen with noise damage. Sensorineural hearing loss is usually permanent.
  • Conductive hearing loss occurs when there is a problem in the outer or middle ear which stops the sounds reaching the hearing nerve. It can be caused by a blockage in the outer or middle ear, or problems with the function of the middle ear bones. The nerve usually works normally. This is generally temporary in nature. The treatment could be medical or surgical.
  • Mixed hearing loss occurs when there are problems with sounds travelling both the middle ear and inner ear.

How is your hearing tested?

  • Your hearing can be tested in a number of ways and this mainly depends on your age.
  • Hearing screening in newborns is very quick and is done while the baby is asleep.
  • Infants can have a test which measures how the brain responds to sounds. Infants should be asleep for this test.
  • Children aged six years and older can often be tested the same way as adults.
  • Generally, an adult is tested using headphones or insert earphones to measure the softest sound he can hear. You will be asked to listen to different sounds through the headphones and then respond when you hear them, even if they are very soft. The softest sounds you hear are called thresholds. The thresholds are used to determine the type and level of hearing loss you may have.
  • You will also have a test using a headband that sits on the bone behind your ear, which is called a bone conductor. It measures how the hearing nerve hears the sounds which are gently vibrated through the bones of the skull. The results of your hearing test are plotted on a graph called an audiogram.

What is an audiogram?

  • An audiogram is a graph which plots your hearing loss .Your hearing thresholds are graphed to show how close your hearing is to normal range. Using an audiogram helps to determine the level of your hearing loss as well as to show where in the pathway the hearing problem may be.
  • Intensity:
    • This is shown down the side of the graph. Intensity is how loud the sound is and is measured in decibels. When measuring loudness as part of a hearing assessment, we are actually looking for the softest sounds you can hear. These levels are called thresholds and are measured for each ear at each frequency. Bone conduction testing is performed in the same way and these thresholds are also plotted on the audiogram.
    • The audiogram is used to sort your hearing into the mild, moderate, severe or profound range. It also helps to show what type of hearing loss you may have (sensori-neural conductive, or mixed).
    • You may also have a speech perception test. This helps to show how the brain is receiving and understanding speech information. These results will be compared to your audiogram.
    • It’s possible you may need other specialised hearing tests. This will depend on the results of your audiogram and any other symptoms you may be having. Please speak to your hearing practitioner or your medical practitioner if you need more information about these assessments.
    Frequency:
    • This is shown across the top of the graph. Frequency is the type or pitch of noise and is measured in Hertz (Hz). Low frequencies have smaller numbers and higher frequencies have higher numbers. For example, 500Hz is a low frequency noise (such as the humming of a refrigerator) and 4000Hz is a high frequency noise (such as crickets or birds chirping).