The Ear

To better understand hearing loss, first it’s important to know how the ear works. The ear is divided in three parts: outer, middle and inner ear.

The outer ear collects and sends the sound through the ear canal to the eardrum, that vibrates according to the sound waves received.

The middle ear comprises the eardrum (tympanic membrane) and three small bones: hammer, anvil, and stirrup. These ossicles vibrate together with the eardrum, amplifying the sound and relaying it to the inner ear.

Finally, the inner ear (also called cochlea) contains a fluid that receives the vibrations from the ossicles and therefore moves its hair cells. These hair cells, therefore, send electrical impulses to the auditory nerve that transmit them to the brain, which can interpret them as sounds.

Three Types of Hearing Loss

Conductive hearing loss - when hearing loss is due to problems with the ear canal, ear drum, or middle ear and its little bones (the malleus, incus, and stapes). Causes include: ◦Malformation of outer ear, ear canal, or middle ear structures ◦Fluid in the middle ear from colds ◦Ear infection (otitis media - an infection of the middle ear in which an accumulation of fluid may interfere with the movement of the eardrum and ossicles ◦Poor Eustachian tube function ◦Perforated eardrum ◦Impacted earwax ◦Infection in the ear canal ◦Otosclerosis

Sensorineural hearing loss (SNHL) - when hearing loss is due to problems of the inner ear, also known as nerve-related hearing loss.Causes include: ◦Exposure to loud noise ◦Head trauma ◦Viral and bacterial diseases, such as Meningitis ◦Autoimmune inner ear disease ◦Hearing loss that runs in the family ◦Aging (presbycusis) ◦Malformation of the inner ear ◦Meniere’s Disease

Mixed hearing loss - refers to a combination of conductive and sensorineural hearing loss. This means that there may be damage in the outer or middle ear and in the inner ear (cochlea) or auditory nerve. It is recommended to take care of the conductive component first. There have been times when the addition of the conductive component made the person a better hearing aid candidate, by flattening out the audiogram for example, while the underlying sensorineural component presented a high-frequency loss. However, still the emphasis would be on treating medically what can be treated.