Learn more about Hearing Loss

According to a survey conducted recently, nearly 10% of Hong Kong residents have certain degree of hearing loss, which include seniors, adults, children and even new born infants.

Hearing loss in adults has many causes such as middle ear infection, head injury, tumors, viral infection in the inner ear and over-exposure to noise. The most common cause is, however, normal aging process.

Hearing loss in children is usually caused by middle ear infection. A small percentage of children have hearing loss present at birth, which can be hereditary hearing loss or hearing loss caused by other factors present during pregnancy or at the time of birth.

In the following sessions, we will explain in detail the types, causes and corresponding management options for hearing loss present in different age groups.

How we hear

How does our hearing work? Understanding the basic anatomy and function of our ear will help you identify conditions that can affect your hearing. Our ears are divided into three parts: outer ear, middle ear and inner ear.

The outer ear: The pinna collects and channels sound into the external auditory canal. Once inside the ear canal, the sound waves travel on and are further funneled towards the tympanic membrane (ear drum).

The middle ear:
In response to the movements of the sound waves, the eardrum vibrates and sends the sound on to the middle ear. The body's three tiniest bones (the malleus, the incus and the stapes) then further magnify the movements of the eardrum and the motions are transmitted to the inner ear. The eustachian tube, also located in the middle ear, serves to equalize pressure between the outer and middle ear.

Inner ear:
Cochlea, the actual sensory organ of hearing, is located in the inner ear and is fluid-filled. In response to the movements of the three little bones from the middle ear, the fluid in the cochlea also moves and the hair cells are stimulated as a result. The hair cells convert the movement into nerve impulses which are then sent to the brain.

Types of hearing loss

There are two main types of loss:

Conductive loss: Anything that prevents sound waves being transmitted to the inner ear may result in a conductive hearing loss. Conductive hearing impairment can result from:

  1. blockage of the external auditory canal e.g. wax blockage or presence of a foreign object
  2. damage to the eardrum
  3. otosclerosis
  4. middle ear infection - the most common cause of a conductive loss in young children

Early detection and treatment are vital since a conductive loss can usually be treated medically

Sensorineural loss: Damage to the cochlea or the auditory pathways to the brain can cause permanent hearing loss. It can result from:

  1. birth trauma
  2. old age
  3. disease affecting the ears e.g. measles, mumps, viruses, meningitis
  4. tumors in the inner ear
  5. trauma e.g. head injuries
  6. noise exposure
  7. ototoxic drugs
  8. family history of sensorineural loss

Sensorineural loss cannot be reversed and may affect only certain frequency ranges. Many people with sensorineural loss may also have an additional conductive loss, and we call this mixed hearing loss.