Hearing Loss

Along with arthritis, hypertension and heart disease, hearing loss is one of the most common physical disorders in the United States. It is second only to lower back pain as the most common physical disability in this country. About 10 percent of the United States' population--including one third of Americans over age 65--has some degree of hearing loss, However, the significance of hearing loss and the impact on the health and productivity of those affected by it often go unrecognized.
 

Anatomy and physiology of hearing
The ear consists of three components: the external ear, middle ear and inner ear. Each is designed to increase the sound delivered to the cochlea, a spiral-shaped cavity of the inner ear that resembles a snail shell and contains nerve endings essential for hearing.

External and middle ear
The external ear includes the outer portion of the ear that is visible on the side of the head, and the ear canal that leads to the tympanic membrane, also known as the eardrum. The outer portion of the ear is made up of skin and cartilage. Its shape helps us distinguish from what direction sounds in the environment are coming.

The middle ear is the part of the ear between the external and the inner ear. Its outer border is the tympanic membrane. As sound reaches the tympanic membrane, it vibrates, setting into motion the three middle ear bones: the malleus, incus and stapes, commonly known as the hammer, anvil and stirrup. As the stapes (stirrup) vibrates, the end of it, known as a footplate, moves in and out like a piston, transmitting sound to the inner ear.

Inner ear
The cochlea is the hearing mechanism inside the inner ear. It converts sound waves entering the inner ear from mechanical to electrical energy. These waves cause the movement of tiny hair cells within the cochlea. As these hair cells vibrate, they send signals to the brain, which can then be interpreted as sound. The inner ear also plays an important role in maintaining balance.

Types of hearing loss
The three types of hearing loss are conductive, sensorineural and mixed.

Conductive
Conductive hearing loss occurs when the external or middle ear fails to work properly, "blocking" sounds from being transferred to the inner ear. Conductive hearing losses can be caused by a variety of factors including fluid buildup in the middle ear (frequently due to infection), a build-up of wax in the ear canal or a perforated eardrum. Conductive hearing losses are often successfully treated with either medicine or surgery.

Sensorineural
Sensory hearing losses are caused by disorders in the inner ear, specifically, the cochlea. This type of hearing loss may be congenital (present at birth), resulting from abnormal cochlea development or inherited conditions, or the hearing loss may be the result of an acquired condition, such as meningitis.

The most common cause of sensorineural hearing loss is presbycusis, better known as age-related hearing loss. Everyone who lives long enough will develop some degree of age-related hearing loss. Those who are frequently exposed to noisy environments will develop presbycusis sooner than people who frequent quieter environments.

Another cause of senorineural hearing is retrocochlear hearing loss. It is related to an actual problem with the hearing nerve or parts of the brain that process speech. Tumors, multiple sclerosis or stroke can cause retrocochlear loss. Therefore, recognition of these disorders is important.

Mixed
Combined conductive and sensorineural hearing loss in the same ear is referred to as mixed hearing loss. It can occur when a person has a permanent sensorineural hearing loss and then also develops a temporary conductive hearing loss.

Diagnosis
In diagnosing hearing loss, a thorough medical history can detect diseases that cause a patient to be more prone to developing a hearing loss. Family history is also critical, because many hearing disorders, both congenital and acquired, run in families. The doctor will also take note of any history of trauma to the ear or head.

Age at onset also helps determine whether the cause of hearing loss is congenital or acquired. For example, the cause of hearing loss in one ear present since birth is most likely congenital, whereas adult-onset hearing loss in one ear may raise suspicion of a medical condition. Sudden onset of hearing loss suggests a disorder (e.g. viral infection) that requires further tests and treatment. Gradual onset of hearing loss is more common with presbycusis or noise-induced hearing loss. A progressive hearing loss is characteristic of an ongoing disorder and requires careful diagnostic evaluation and follow-up.

Some of the symptoms a doctor will look for when making a hearing loss diagnosis include:

The doctor will also review any medications a patient is currently taking or has taken in the past. The group of antibiotics, known as aminoglycosides, is most commonly linked to drug-induced hearing loss. The chemotherapy drug cisplatin also  has been shown to damage hearing. Other drugs that have been shown to cause hearing loss in some patients include salycilates, quinine and diuretics.

Drug-related hearing loss complications often affect patients with kidney failure. This is because medications are often eliminated through the kidneys, and kidney failure or malfunction can lead to a build up in the drug's toxicity. Most of these medications affect the cochlea by damaging the auditory hair.

Hearing loss is often attributed to occupational or recreational noise exposure. Patients who work in settings such as factories or automotive garages commonly complain of hearing loss at a young age. Hearing loss caused by noise exposure is irreversible, but the use of hearing protection can minimize further damage.

Treatment and management
In some cases of conductive hearing loss, the removal of impacted cerumen (earwax) may be all that is needed to correct the problem. When the doctor determines that surgery is needed, most procedures are quite successful in restoring hearing. For some patients, hearing aids will be the best option.

Sensorineural hearing loss cannot be cured; however, progression may be slowed through medications or surgery, depending on the causes.

Prevention
Ear protection is essential in helping to prevent noise-induced hearing loss by reducing the level of exposure to loud sounds. For people who have already experienced some hearing loss--as well as for those who have not--earmuffs, custom-fitted earplugs and disposable earplugs can provide hearing protection. Protective devices should be recommended to patients who are exposed to high noise levels.

 

 

Resources

American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS)
One Prince St
Alexandria, VA 22314-3357
703-836-4444
http://www.entnet.org/patient

World's largest organization of physicians dedicated to care of the ear, nose, and throat. Web site has information sheets on a variety of topics.

Better Hearing Institute
PO Box 1840
Washington, DC 20013
800-327-9355
http://www.betterhearing.org

Comprehensive information on hearing loss, tinnitus, and hearing aids, including booklets, a self-hearing evaluation, and a newsletter as well as a directory of hearing care providers and a physicians' guide to hearing loss.

Ear, Nose, and Throat Information Center
http://www.netdoor.com/entinfo

Site with information sheets divided by topic, many originating from the AAO-HNS.

Hear Now
800-648-4327

Recycles used hearing aids and donates them to those who cannot afford them.

Self-Help for Hard-of-Hearing People
7910 Woodmont Ave, Suite 12
Bethesda, MD 20814
301-657-2248 (voice); 301-657-2249 (TTY)
http://www.shhh.org

An international, nonprofit consumer organization serving hearing-impaired people through education, advocacy, and self-help.

Copyright 1995-2006 The Cleveland Clinic Foundation. All rights reserved

 

This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. For additional health information, please contact the Center for Consumer Health Information at the Cleveland Clinic (216) 444-3771 or toll-free (800) 223-2273 extension 43771. If you prefer, you may visit www.clevelandclinic.org/health/ or www.clevelandclinicflorida.org. This document was last reviewed on: 3/27/2002

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