Hearing loss has a lot of different causes and manifestations. It can be sudden or gradual. It can occur in one ear or both ears. It can be temporary or permanent. It happens to people of all ages and is associated with the aging process. Before discussing causes and treatments for hearing loss, it is important to understand how hearing works.
How We Hear
There are three sections of the ear: the outer ear, middle ear and inner ear. Each section helps move sound through the process of hearing. When a sound occurs, the outer ear feeds it through the ear canal to the eardrum. The noise causes the eardrum to vibrate. This, in turn, causes three little bones inside the middle ear (malleus, incus, stapes) to move. That movement travels into the inner ear (cochlea), where it makes tiny little hairs move in a fluid. These hairs convert the movement to auditory signals, which are then transmitted to the brain to register the sound.
Causes of Hearing Loss
Hearing loss occurs when sound is blocked in any of the three areas of the ear. The most common cause of hearing loss — and one of the most preventable — is exposure to loud noises. Infections, both of the ear or elsewhere in the body, are also a major contributor to hearing loss.
- In the Outer Ear: Earwax build-up, infections that cause swelling, a growth in the ear canal, injury or birth defects can restrict hearing in the outer ear.
- In the Middle Ear: Fluid build-up is responsible for the most common infections and blockages in the middle ear. Fluid in the middle ear prevents the bones from processing sounds properly. Tumors, both benign and malignant, can also result in hearing loss in the middle ear.
- In the Inner Ear: The natural process of aging diminishes hearing from damage to the cochlea (mechanism for converting sound vibrations to brain signals), vestibular labyrinth (which regulates balance), or the acoustic nerve (nerve that sends sound signals to the brain). Additionally, inner ear infections, Meniere’s disease and other nerve-related problems contribute to hearing loss in the inner ear.
Other causes of hearing loss include:
- Presbycusis: Age-related hearing loss, such as having difficulty hearing in noisy places, having trouble understanding what people are saying or not registering softer sounds.
- Heredity and Genetic Causes: There is a wide variety of diseases and syndromes that are either genetic or hereditary that can cause hearing loss. Some, like rubella (German measles) occur when a pregnant mother has the disease, which causes hearing loss in the baby. Other, rarer types of hereditary and genetic causes include CHARGE Syndrome, Connexin 26 disorder, Goldenhar Syndrome,Treacher Collins Syndrome, Usher Syndrome, Waardenburg Syndrome and otosclerosis (growth of spongy bone tissue in the middle ear).
Most causes of outer ear hearing loss can be remedied. But problems of the middle and inner ear can lead to permanent hearing loss, which is why it is important to seek medical attention quickly if you are experiencing a problem hearing.
Types of Hearing Loss
There are four types of hearing loss:
- Conductive hearing loss: Caused by conditions that block the transmission of sound through the outer ear and eardrum to the middle ear.
- Sensorineural hearing loss: Inner ear damage that occurs as part of the natural process of aging.
- Mixed hearing loss: Mixed hearing loss refers to people who have both conductive and sensorineural hearing loss. Most people experience more than one type of hearing loss.
- Central hearing loss: This occurs when the central nervous system fails to send a readable signal to the brain, which is called a central auditory processing disorder. People with central hearing loss generally can hear all sounds, but can’t separate or process them.
Hearing loss is measured in four degrees: mild, moderate, severe or profound. The degree of hearing loss drives the selection of the best form of treatment on a case-by-case basis.