Types of Hearing Loss
There are three main types of hearing loss:
Conductive hearing loss results from a problem in the ear canal, eardrum, or the middle ear that prevents sound from being carried effectively to the inner ear. The problem can be caused by an ear infection, trauma, tumor, or fluid or an object (such as wax buildup) in the ear.
Sensorineural hearing loss most commonly results from damage to the hair cells in the inner ear. Other possible causes include damage to the 8th nerve (the nerve for hearing) or the brain. This type of hearing loss is often caused by age-related changes to the nerves and sensory cells of the inner ear. It may also be caused by noise exposure, chemotherapy medications, radiation, trauma, and genetics.
Mixed hearing loss is a combination of conductive and sensorineural hearing loss, meaning that there may be a problem in the outer or middle ear, as well as in the inner ear or auditory nerve. Mixed hearing loss can be caused by a head injury, chronic infection, or an inherited disorder.
Hearing loss can affect one or both ears. It can happen suddenly (acute) or gradually get worse over time. If you notice sudden hearing loss, you should see an ear, nose, and throat specialist as soon as possible.
Severe Hearing Loss Causes
In normal hearing, sound waves enter your outer ear and cause your ear drum and middle ear bones to vibrate. The sound waves then travel through your inner ear, which is a shell-shaped, fluid-filled tube called the cochlea. As the fluid moves, it sets in motion thousands of tiny hairs that convert the sound vibrations into nerve impulses. Those impulses are then sent to your brain where they are processed into sounds you can recognize.
Hearing loss happens when there's a problem with the structures of the ear that process sound. Any of these conditions can lead to severe hearing loss:
- Age. As people get older, the structures in the ear become less elastic. The tiny hairs get damaged and are less able to respond to sound waves. Hearing loss can progress over the course of several years.
- Loud noise. The blare of power tools, airplanes, or loud music on headphones, for examples, can damage the hair cells in the cochlea. Hearing loss depends on the loudness of the sound and the length of the exposure.
- Ear infections. During an ear infection, fluid can build up in the middle ear. Usually the hearing loss from an ear infection is mild and temporary. But if ear infections aren't treated, they can lead to serious long-term problems.
- Perforated eardrum. An ear infection, loud sounds, head trauma, or intense pressure in the ear from flying in an airplane or scuba diving can rupture the ear drum, the membrane separating the ear canal and the middle ear, leaving a hole that may or may not heal. Depending on the size of the hole, there may be mild or moderate hearing loss.
- Cholesteatoma. This is a collection of skin that develops in the middle ear from either collapse of the ear drum or in skin growth through an ear drum perforation. Cholesteatomas grow over time and can lead to hearing loss by destroying the middle ear bones or, rarely, the inner ear.
- Illnesses or infections. Measles, mumps, tertiary syphilis, and meningitis are just a few of the conditions that can cause hearing loss.
- Meniere’s disease. Symptoms of this inner ear disorder include dizziness, fluctuating hearing loss, ringing in the ear, or fullness in the ear. Hearing loss in Meniere’s disease usually gets worse, but only involves one ear.
- Tumors. Both cancerous and noncancerous tumors can cause severe hearing loss. This includes acoustic neuroma (vestibular schwannoma), paraganglioma, and meningioma. People who have a tumor might also have facial numbness or weakness and ringing in the ear.
- A foreign object in the ear. When objects get stuck in the ear, they can block hearing. Earwax -- the thick, sticky substance that normally prevents bacteria and other foreign substances from entering the ear -- can sometimes build up and harden in the ear, hurting your ability to hear.
- Malformed ear. Some people are born with poorly formed ear structures, which prevent them from hearing well.
- Trauma. Injuries such as a skull fracture or a punctured eardrum can cause severe hearing loss.
- Medications. Some types of drugs -- including the aminoglycoside class of antibiotics (streptomycin, neomycin, kanamycin), large quantities of aspirin, chemotherapy drugs (cisplatin, carboplatin), Vicodin (in large quantities), and macrolide antibiotics (erythromycin) -- can cause hearing loss. Sometimes these effects are temporary and hearing will return once you stop taking the drug. In most cases the hearing loss is permanent.
- Genes. Scientists have identified certain genes that make people more prone to severe hearing loss, particularly age-related hearing loss. Genetic hearing loss often begins with hearing loss diagnosed at birth, but can show up later.
- Autoimmune disorders. Lupus and rheumatoid arthritis, for examples, may affect hearing. Hearing loss is a one of the primary features of several autoimmune disorders, including Cogan’s syndrome, Wegener’s granulomatosis, and Behcet’s disease.