Hearing Loss

Types of Hearing Loss

Hearing loss is generally categorized by location—that is, what part of the ear is damaged—as well as by severity and age of onset. There are three main types of loss: conductive, sensorineural, and a combination of both, known as mixed hearing loss.

Conductive Hearing Loss

Conductive hearing loss results from sound waves being conducted through the outer and/or middle ear inefficiently. Sound waves are blocked or muffled before they can reach the inner ear, which is still functioning properly.

Conductive hearing loss can frequently be treated with medication or surgery. Conductive hearing loss in adults is much less common and much more common in children.

Sensorineural Hearing Loss

Sensorineural hearing loss results from damage to the inner ear (cochlea) or the nerve pathways that transmit sound information to the brain. The normal aging process and exposure to loud noise can lead to sensorineural loss. Generally, sensorineural loss cannot be reversed and is not treatable with surgery or medication – but it can be significantly improved through the use of hearing aids.

Noise-Induced Hearing Loss is generally considered a form of or a sub-category of sensorineural loss. This is one of the most common types of loss, and, fortunately, it is also the most preventable. Onset is gradual, painless, and frequently undetectable until significant hearing loss has occurred.

Mixed Hearing Loss

Mixed Hearing Loss is simply a combination of sensorineural and conductive hearing loss.

What Causes Hearing Loss?

Anyone, at any age, may experience hearing loss. There are cases in which hearing loss is temporary, but more often than not, it is permanent. In most cases, there is no single cause for hearing loss. In order to better understand what causes hearing loss, let’s first explore how we hear.

The ear is made of three main parts: the outer ear, the middle ear, and the inner ear. The outer ear receives sound in the form of waves, which is amplified in the middle ear and sent to the inner ear, where it is transformed by hair cells into signals that are sent to the brain to be processed and registered as specific sounds.

When one or more of these parts, or a step in this process, malfunctions, hearing loss occurs. There are three types of hearing loss: conductive (which relates to the outer and middle ear), sensorineural (which relates to the inner ear), and mixed (a combination of the former two).

Hearing loss could occur in a singular instance with exposure to loud noises or gradually progress over a long period of time.

Presbycusis – otherwise known as age-related hearing loss – happens gradually and naturally over time. Presbycusis is considered a form of sensorineural hearing loss, in which signals of sound are no longer sent to the brain. Presbycusis affects speech recognition as well.

Occupations - Certain occupations pose higher risks for noise-related hearing loss, such as construction, dentistry, coal mining, musicians, and war veterans. An explosion which causes sudden loss of hearing is referred to as acoustic trauma

Otitis Media - More commonly known as an ear infection, this affects the middle ear. Fluid build-up in the middle ear may interfere with the ear drum and bones. Colds may also cause fluid build-up in this area.

Physical dysfunctions - Physical dysfunctions and conditions relating to the outer and middle ear. Congenital conditions, such as the malformation of the outer ear, ear canal, and middle ear, may cause hearing loss. There may be malformations of bones in the middle ear as well as poor Eustachian tube formation. Otosclerosis is a hereditary disorder in which overgrowth in ear bones lead to deafness.

Abnormal Bone Growths or Tumors - These generally affect the outer and middle ear and may be a cause for hearing loss.

Head or Neck Trauma - The muscles, bones and nerves around this area of the body are connected to the auditory system. Damage to these parts may lead to hearing loss.

Ruptured Ear Drum - Eardrums may be damaged from exposure to loud noises or changes in pressure, as well as being poked with an object such as a cotton swab.

Meniere's Disease - The cause of this disease is unknown, but it has been found to develop in adults ages 30 to 50. Meniere's Disease - Meniere’s disease generally affects the inner ear and has been linked to vertigo and tinnitus.

Ototoxicity – or poisoning of the ear – occurs as a side effect of over 100 classes of drugs. Some of these include:

• Aminoglycosides (an antibiotic)
• Loop diuretics
• Drugs used in chemotherapy.

These drugs cause inner ear hair cells to die, which leads to hearing loss.

Can Hearing Loss Be Prevented?

In some cases, hearing loss can be prevented. For more on this topic, read about the prevention of hearing loss.