Hearing Loss

Causes of Hearing Loss

• In about 50% of the cases, we are unable to determine the exact cause of the hearing loss.
• It is estimated that about 1 in 35 people carry a gene for hearing loss. If two people that carry this gene have a child, the likelihood of the child having a hearing loss is 25%.
• Almost all activities performed by the mother before birth (food choices, accidental falls) would not affect her child’s hearing. Only certain types of infections contracted during pregnancy could affect the baby’s hearing (i.e. Rubella, CMV, etc).
• About 30% of children with permanent hearing loss have additional health or developmental problems. They should also be tested for other health issues such as heart, kidney and visual problems. Your Ear Nose and Throat Specialist will determine if further testing is necessary.
• Sometimes babies who are very small or sick at birth undergo life-saving procedures that can potentially cause a hearing loss.
• Parents are encouraged to discuss their particular case with their paediatrician, family doctor or audiologist for more information.

There are several risk factors that suggest your child should be monitored for late onset or progressive hearing loss. Some congenital and neonatal risk factors for permanent childhood hearing impairment include:

• Very low to extremely low birth weight (less than 1200 grams)
• The baby was in need of some or certain types of ventilatory support
• Meningitis in the baby
• Family history (any sibling, parent, aunt, uncle, or grandparent of the child with permanent childhood hearing loss)
• Craniofacial abnormality (obvious/marked anatomical abnormality of the external ear, normally an absent, very small or malformed pinna, or an absent or very small canal opening. The abnormality may be in one or both ears. An obvious cleft lip is the only other abnormality that is considered a risk factor
• Other illnesses or infections requiring an extended stay in a special care nursery

 

Ear Infections and Speech and Language Development

What is an Ear Infection (otitis media)?
Acute otitis media is an infection that happens when either bacteria or viruses invade the middle ear. It often follows a cold and is most common in children three months to three years of age. A young child with acute otitis media is likely to be fussy and irritable. They may have trouble sleeping, feeding and hearing. Older children often complain about ear pain, fullness or pressure in the ear and difficulty hearing. A child of any age may have a fever and cold symptoms. Some children may show little to no discomfort despite having an ear infection. You may need to become very aware of your child’s attention to their ears or ask them specifically how their ears are feeling, if possible.

What Causes Fluid in the Ear?
An ear infection can cause fluid to collect in the middle ear. Even once the infection has ended, fluid may be present for six weeks or longer. Blockage of the tiny passageway that connects the middle ear to the back of the throat (eustachian tube) can also cause fluid to collect in the middle ear. This may be due to problems with allergies or adenoids.

Why Is It So Important to See a Doctor?
Any child with symptoms of otitis media or fluid in the ears should be checked by a doctor. In the case of an infection your doctor may prescribe an antibiotic. Your doctor will help you decide what kind of treatment is best for your child. Fluid in the ear may make it even more difficult for your child to hear and further decrease their ability to understand speech. This may affect your child’s ability to learn speech and language.

Can Ear Infections Be Prevented?
There are some things you can do that may help reduce your child’s risk of ear infection.
Common colds can lead to ear infections. You can help reduce the risk of ear infections by reducing risk factors associated with the common cold:

• Limit exposure to large crowds
• Teach children to cover their mouth and nose with a tissue when coughing or blowing their nose
• Encourage your child to wash their hands frequently
• Exposure to second-hand smoke may also increase your child’s risk for ear infections, so keep your home smoke-free
• In infants, breastfeeding helps prevent ear infections by passing along immunity from mom to baby

 

What Is Sound? 

Sound is an invisible vibration. It travels in waves, spreading outwards from the source of a sound. Sounds are different in loudness and in frequency. Loudness is measured in decibels (dB). Audiologists sometimes describe loudness as ‘intensity’.

Frequency is measured in Hertz (Hz). Frequency is sometimes thought of as the pitch of the sound. Most sounds are made up of a range of different frequencies. An example of a high frequency, or ‘high pitched’ sound is the noise made by a whistle. An example of a low frequency, or ’low pitched’ sound is the noise made by a big drum.

Speech is usually a mix of high, middle and low frequency sounds. Consonants, like ‘p’, ‘k’ and ‘s’, tend to be higher in frequency than some vowel sounds like ‘aa’ as in ‘part’.

The Audiogram below shows the approximate level of many environmental and speech sounds.

The Hearing System

The ear has two main functions. It receives sound and converts it into signals that the brain can understand. It also helps us to balance. The two functions are closely connected.

The ear can be divided into three parts: the outer, middle and inner ear.

 

 

 

How the Hearing System Works

1. The outer ear is the first part of the hearing system. The pinna (the outside part of the ear) catches sound waves and directs them down the ear canal.
2. The waves then cause the eardrum to vibrate.
3. These vibrations are passed across the middle ear by three tiny bones, the malleus, incus and stapes (sometimes known as the hammer, anvil and stirrup), collectively known as the ossicles.
4. The bones increase the strength of the vibrations before they pass into the inner ear through the oval window into the cochlea.
5. The cochlea looks like a snail’s shell. It is filled with fluid and contains thousands of tiny sound-sensitive cells. These cells are known as hair cells. The vibrations entering the cochlea cause the fluid and hair cells to move, much like the movement of seaweed on the seabed when waves pass over it. As the hair cells move, they create a small electrical current or signal.
6. The auditory nerve carries these signals to the brain where they are understood as sound.

Hearing loss happens when one or more parts of the system are not working effectively.

Balance
The brain uses information from the eyes (what we see), our body (what we feel) and the inner ear to balance. The vestibular system (the balance system) is comprised primarily of the semicircular canals in the inner ear filled with liquid and movement-sensitive hair cells. As we move, the fluid moves. This creates signals that are sent to the brain about balance and where we are in space.

 

Levels of Hearing Loss

The level of your child’s hearing loss can be described in two ways:
• as a decibel (dB) hearing level
• as a degree from mild to profound.

Understanding these ways of describing your child’s hearing loss can help you to explain it to others.

The table below shows the terms used to describe levels and the decibel levels that they refer to:

Degree of Hearing Loss	Hearing Level in dB (loudness)
Mild	15-40
Moderate	41-55
Moderately-Severe	56-70
Severe	71-90
Profound	91+

If your child’s hearing level is close to the next level of hearing loss they may be described as having mild/moderate, moderate/severe or severe/profound hearing loss.

Any hearing that a child with hearing loss has, is described as residual hearing.

 

Reference:
Early Support Programme. (2007). In National Deaf Children's Society (Ed.), Information for parents: Deafness (2nd ed.). Nottingham: Crown Press. Phonak. Children's hearing: A guide for parents.

Erinoak Central West Infant Hearing Program. (2006). Central west infant hearing program screener's manual.

Oticon. Pediatrics counseling. Denmark: Oticon Pediatrics.

smallTALK. (2005). Ear infections and speech and language development., Retrieved 2008,
from http://www.smalltalkinfo.ca/ear_infections.html