Hearing Impairment

Hearing impairment has been sited as the third most common chronic health problem in the United States behind hypertension and arthritis.  It is estimated that hearing loss affects around 10% of the population in the United States.  Hearing impairment affects people of all walks of life and all ages.  It has been found that as many as 6 out of every 1,000 infants in the United States are born with significant hearing impairment.  So if you have difficulty hearing, you are not alone.  And the good news is that now more than ever, there are a number of options to help individuals with hearing impairment.

Types of Hearing Impairment

There are three categories of hearing loss: conductive, sensorineural, and a combination of conductive and sensorineural which is known as a mixed hearing loss.

Conductive Hearing Loss

Normally, sounds are collected by the external ear and directed into the ear canal.  These sound waves travel through the ear canal and vibrate the tympanic membane or ear drum.  The vibrations of sound are then passed along the 3 bones in the middle ear: hammer (malleus), anvil (incus), and stirrup (stapes).  A conductive hearing loss results when something blocks the passage of sounds through the ear canal, when the tympanic membrane is perforated or does not vibrate correctly, or when there is a problem with the way the three bones in the middle ear vibrate.

Common causes of conductive hearing loss include:

  • Excessive build-up of wax in the ear canal
  • Foreign objects lodged in the ear canal
  • Infection or fluid in the middle ear space
  • Head trauma resulting in a disarticulation of the bones in the middle ear
  • Otosclerosis or abnormal growth of bone in the middle ear
  • Cholesteatoma or tumor in the middle ear

Sensorineural Hearing Loss

The inner ear or cochlea is a tiny, fluid-filled structure hidden deep in the mastoid bone of the skull.  The cochlea's function is to change the vibrations of sound into a neural impulse that can then travel up the acoustic nerve to the brain.  Damage to the structures of the inner ear, such as the hair cells or nerve fibers that connect to these hair cells can result in sensorineural hearing loss.  The most common type of sensorineural hearing loss is known as presbycusis and is due to the effects of the aging process.

Other potential causes of sensorineural hearing loss include:

  • Exposure to loud sounds such as firearms, machinery, and loud music
  • Meniere's disease
  • Drugs or medications that are ototoxic (or harmful to hearing)
  • Viral inner ear infection
  • Disruption of blood flow to the cochlea
  • Viral infections
  • Head trauma
  • Acoustic neuroma or a tumor growing on the auditory and vestibular nerves
  • Congenital hearing loss

Mixed Hearing Loss

A combination of a sensorineural hearing loss and a conductive loss is called a mixed hearing loss.  For example, an individual with a long-standing senorineural hearing loss may acquire an ear infection resulting in a mixed hearing loss.  In this example, the conductive component may be improved with medication or surgery, but the sensorineural hearing loss will remain.

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