FACTS ABOUT HEARING LOSS
The ear is made up of three parts: Outer Ear, Middle Ear, Inner Ear. Each part has a specific role in moving and processing sound as it moves to the brain:
The Outer Ear: This part of the ear includes the auricle or pinna (part of the ear on the outside of the head) and the ear canal. It is also called the external ear. Sound travels through the ear canal and moves or vibrates the eardrum (tympanic membrane).
The Middle Ear: This part of the ear is between the eardrum and the inner ear. The middle ear contains three tiny bones called the ossicles: malleus, incus, and stapes (you’ve probably heard them referred to as the hammer, anvil, and stirrup). The eardrum vibrates causing the middle ear bones to move and send the sound through the middle ear to the inner ear. There is also a tube that runs from the middle ear space to the back of the throat called the Eustachian tube.
The Inner Ear: The inner ear includes the cochlea (the spiraled organ of hearing), the semi-circular canals (the organ of balance), and the auditory nerve (8th cranial nerve leading from the ear to the brain). When sound vibrations enter the cochlea from the middle ear, the hair cells send nerve impulses to the brain via the auditory nerve. Once the brain receives the nerve impulses, there is a sensation of hearing.
HOW HEARING WORKS
The auditory system is very complex. It’s important to understand how the hearing process works and to compare that with what happens when this process is disrupted. This knowledge will help you to feel more comfortable and confident in understanding your child’s hearing levels and making decisions.
Sounds enter the ear canal and travel to the eardrum.
These sound waves cause the eardrum to vibrate, sending the bones in the middle ear into motion.
Tiny hair cells (cilia) inside the inner ear (cochlea) convert this motion into electric impulses/signals. The ear has over 25,000 tiny hair cells to help you hear the varying degrees of sound.
These impulses/signals go up to the hearing (auditory) nerve to the brain. The brain interprets the impulses/signals as sound and gives meaning to the information.
If any part of the outer, middle, or inner ear isn’t working properly, the ability to hear may be affected.
TYPES OF HEARING LOSS
Hearing loss can happen in any part of the ear. This includes the outer ear, middle ear and the inner ear. Hearing loss can happen in one of these places or in more than one place. Each type of hearing loss has a different name and has different possible treatments.
This type of hearing loss involves the outer and/or middle ear.
A conductive loss prevents sound from moving effectively through the outer and/or middle ear so that it can move along to the inner ear. The simplest way to perceive conductive hearing loss is to plug your ears. Sounds that normally enter the canals are reduced.
Causes of a conductive hearing status in children can include:
- Atresia – closure of the ear canal
- Malformations of the ossicles
- Middle ear infections, otitis media, or fluid in the middle ear
- Obstruction of the ear canal by ear wax or foreign objects
- Microtia – smallness of the auricle
Most types of conductive hearing losses can be treated and corrected with medication, surgery or by amplifying sound through a hearing aid. Hearing aids can be very effective in compensating for a conductive hearing loss when surgical or medical treatment is not an option.
This type of hearing loss is the most common permanent hearing loss in children and involves the inner ear.
The primary cause of sensorineural hearing loss is damage or deformity of the hair cells (cilia) in the cochlea. Sensorineural hearing loss may also occur when the auditory nerve does not function properly, though this is less common.
A sensorineural hearing loss is generally permanent and cannot be treated by medication or corrective surgery. The most common treatments to compensate for this type of hearing loss are hearing aids or cochlear implants.
(ANSD) is a type of hearing loss that causes poor transmission of nerve impulses along the auditory nerve although some of the hair cells are intact. The sound typically travels through the ear normally.
While there is no known cure for ANSD, assistive listening devices (ALDs) can help kids with ANSD make sense of sounds and develop language skills. You’ll work with a medical team to determine which devices are right for your child.
HEARING LOSS TYPES DEFINED
A mixed hearing loss occurs in both the outer/middle ear and in the inner ear. It is a combination of a conductive loss and sensorineural hearing loss.
A progressive hearing loss occurs when a child loses their hearing over time. A baby may be able to hear at birth and gradually lose their hearing. It is important to note that even if a baby passes their newborn hearing screening, this does not ensure that they will always have normal hearing. In fact, gradual losses may occur any time after birth and it is important for parents to tell their pediatrician if they have concerns about their child’s hearing and or language development.
Sometimes an infant or young child who is deaf or hard of hearing may have other signs or symptoms as well. When multiple congenital malformations appear together, they may be described as a syndrome.
A unilateral hearing loss occurs in only one ear. It can be conductive, sensorineural or mixed. Although a child with this loss has good hearing in one ear, they will have difficulty knowing where sound is coming from, hearing in noisy environments, and hearing on the affected side.
This type of hearing loss refers to hearing that changes, or fluctuates. A child may have better hearing on some days and poorer hearing on other days. Fluctuating hearing loss can be conductive or sensorineural. A common cause of fluctuating hearing loss is otitis media, or fluid in the middle ear.
SYNDROMES & COMMON CAUSES OF HEARING LOSS
This is important because if hearing loss is detected early, then hearing specialists, such as genetic professionals, may be able to test for certain syndromes that may not be physically identifiable by appearance alone.
- Usher Syndrome which is associated with loss of vision
- Jervell and Lange-Nielsen Syndrome which is associated with heart defects
- Pendreds Syndrome is associated with an enlarged thyroid and balance issues
- Waardenberg Syndrome features distinctive facial characteristics
- Kabuki Syndrome which is a genetic syndrome with varied health issues, including hearing loss
Other common causes:
- Faulty development of the inner ear
- Genetic or family history of hearing loss (Connexin 26, CHARGE Syndrome)
- Damage to the inner ear or hearing nerve from illness before birth
- Cytomegalovirus (CMV)
- Lack of oxygen at birth
- Treatment with certain drugs such as streptomycin, kanamycin, garamycin, quinine that reaches toxic levels
- Premature birth with NICU admission
- Damage to ear from loud noises
- Head injuries
- Rh Factors
- Severe jaundice