American Medical Association Family Medical Guide - American Medical Association [714]
Sensorineural hearing loss refers to deafness that occurs when a damaged acoustic nerve fails to transmit sounds from the inner ear to the brain. Sensorineural hearing loss is usually caused by damage to the cochlea or to the auditory nerve (the cochlea and the auditory nerve convey sound information to the brain). Some sensorineural hearing loss is common as you get older. However, loud music, machinery noise, viral infections, heredity, or side effects from some medications can cause sensorineural hearing loss at any age. If you are under age 50 and have difficulty hearing, see your doctor.
Some people may have both conductive and sensorineural hearing loss. This combination hearing loss is the result of problems in the outer or middle ear and in the inner ear.
Diagnosis
To diagnose hearing loss, your doctor will take a detailed health history and examine your ears. He or she may refer you to an otolaryngologist (a doctor who specializes in disorders of the ear, nose, and throat) or an otologist (a doctor who specializes in disorders of the ear). You will have an examination of your ears, and you may have simple hearing tests. You may also be referred to an audiologist (a health care professional who specializes in hearing evaluation and treatment), who may perform more sophisticated tests such as those described below. These tests help diagnose the cause of hearing loss and evaluate the degree of hearing loss.
Audiometry tests
Audiometry tests evaluate a person’s overall ability to hear, and determine whether hearing loss is conductive or sensorineural. These tests usually take place in a soundproof room. Pure tone tests measure a person’s ability to hear tones and frequencies at different volumes. Speech tests measure a person’s ability to distinguish and understand words spoken at different volumes. Impedance or compliance tests, also called tympanometry, measure the ability of the eardrum to reflect sound waves.
Pure tone test
The pure tone test consists of two parts. The first part of the test, called the air conduction test, measures how well you hear sounds conducted through the air. In this test, you listen through earphones, one ear at a time, to sound frequencies that range from low tones to high tones. For each frequency, the sound starts at an audible level and decreases in loudness until you can barely hear it. The softest level at which a tone can be recognized at least 50 percent of the time is your threshold for that frequency.
The second part of the test, called the bone-conduction test, measures how well sounds are conducted through the bones of your head. In this test, a special headphone is placed on the mastoid (the bone directly behind each ear) of one ear. To test one ear, the audiologist puts a competing, or masking, sound into the headphone of the ear that isn’t being tested. As in the first part of the test, sound frequencies that range from low tones to high tones are sent through the headphone on the mastoid to find your threshold. The results of both tests are recorded on the same graph.
Speech reception test
The speech reception test measures how well a person can hear and understand words at different volumes. In this test, you listen through headphones to words spoken live or on a recording at different volumes, and you are asked to repeat them. The words start at an audible level and decrease in volume. Your speech reception threshold is the softest level at which you can recognize a two-syllable word at least 50 percent of the time.
Speech discrimination test
The speech discrimination test measures how well a person can distinguish words. In this test, you listen through headphones to a list of one-syllable words at a volume that is comfortable for you. You are asked to repeat