ear, nose, and throat disorders
Hearing Loss
Evaluation of Hearing Loss
The following information can help people decide when to see a doctor and know what to expect during the evaluation. In people with hearing loss, certain symptoms and characteristics are cause for concern. They include Hearing loss in only one ear Any neurologic abnormalities (such as difficulty chewing or speaking, numbness of the face, dizziness, or loss of balance) People with warning signs should see a doctor right away. People with hearing loss and no warning signs should see their doctor very soon. Because people may not notice gradual hearing loss, doctors recommend routine screening hearing tests for children and older people. Childhood screening should begin at birth so that hearing deficits can be found and treated before they interfere with language development. Doctors often routinely Screening older people by asking them specific questions about their ability to hear in certain situations. Such screening, while important, should be followed up with formal audiologic testing because many older people who might benefit from treatment do not realize or may even deny that they have a hearing problem. Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination may suggest a Causes and the tests that may need to be done, including Doctors ask how long people have noticed hearing loss, whether the loss is in one or both ears, and whether the loss followed any sudden event (for example, a head injury, sudden change in pressure, or starting of a drug). It is also important for them to note the following: Ear symptoms, such as pain or fullness, ringing or buzzing in the ears ( Ear Ringing or Buzzing ), or discharge Balance symptoms, such as disorientation in the dark or a false sensation of spinning or moving ( Benign Paroxysmal Positional Vertigo ) Neurologic symptoms, such as headache, weakness of the face, or an abnormal sense of taste In children, important associated symptoms include delays in speech or language development and delayed motor development. Doctors explore people's medical history for disorders that might cause hearing loss, including repeated ear infections, chronic exposure to loud noise, head injury, and autoimmune disorders such as Rheumatoid Arthritis (RA) and The physical examination focuses on the ears and hearing and the neurologic examination. Doctors inspect the external ear for obstruction, infection, malformations that are present at birth (congenital), and other visible abnormalities. The eardrum is examined for tears (perforations), drainage, and signs of acute or chronic infection. Doctors often do several tests using a tuning fork to differentiate conductive from sensorineural hearing loss. Loudness is measured on a logarithmic scale. This means that an increase of 10 decibels (dB) represents a 10-fold increase in sound intensity and a doubling of the perceived loudness. Thus, 20 dB is 100 times the intensity of 0 dB and seems 4 times as loud; 30 dB is 1,000 times the intensity of 0 dB and seems 8 times as loud. Decibels Example 0 Faintest sound heard by human ear 30 Whisper, quiet library 60 Normal conversation, sewing machine, or typewriter 90 Lawnmower, shop tools, or truck traffic (90 dB for 8 hours per day is the maximum exposure without protection*) 100 Chainsaw, pneumatic drill, or snowmobile (2 hours per day is the maximum exposure without protection) 115 Sandblasting, loud rock concert, or automobile horn (15 minutes per day is the maximum exposure without protection) 140 Gun muzzle blast or jet engine (noise causes pain, and even brief exposure injures unprotected ears, and injury may occur even with hearing protectors) 180 Rocket launching pad * This level is the mandatory federal standard, but protection is recommended for anything more than very brief exposure to sound levels above 85 dB. Testing includes Audiologic tests Sometimes MRI or CT Doctors perform audiologic tests on all people who have hearing loss. Audiologic tests help doctors understand the type of hearing loss and determine what other testing may be needed. Audiometryis the first step in hearing testing. In this test, a person wears headphones that play tones of different frequency (pitch) and loudness into one ear or the other. The person signals when a tone is heard, usually by raising the corresponding hand. For each pitch, the test identifies the quietest tone the person can hear in each ear. The results are presented in comparison to what is considered normal hearing. Because loud tones presented to one ear may also be heard by the other ear, a sound other than the test tone (usually white noise) is presented to the ear not being tested. Tuning fork testsare sometimes done during a person's first evaluation by a doctor, but rarely by specialists or audiologists, who have more precise ways to assess hearing. Tuning fork tests can help distinguish between conductive and sensorineural hearing loss. The Rinne test and the Weber test are two types of tuning fork tests: TheRinne testcompares how well a person hears sounds conducted by air with how well the person hears sounds conducted by the skull bones. To test hearing by air conduction, the tuning fork is placed near the ear. To test hearing by bone conduction, the base of a vibrating tuning fork is placed against the head so the sound bypasses the middle ear and goes directly to the nerve cells of the inner ear. If hearing by air conduction is reduced but hearing by bone conduction is normal, the hearing loss is conductive. If both air and bone conduction hearing are reduced, the hearing loss is sensorineural or mixed. People with sensorineural hearing loss may need further evaluation to look for other conditions, such as Meniere disease or brain tumors. In theWeber test,the stem of a vibrating tuning fork is placed on the top of the head in the middle. The person indicates in which ear the tone is louder. In one-sided conductive hearing loss, the tone is louder in the ear with hearing loss. In one-sided sensorineural hearing loss, the tone is louder in the normal ear because the tuning fork stimulates both inner ears equally and the person hears the stimulus with the unaffected ear. Speech threshold audiometrymeasures how loudly words have to be spoken to be understood. A person listens to a series of two-syllable, equally accented words (spondees), such as "railroad," "stairway," and "baseball," presented at different volumes. The volume at which the person can correctly repeat half of the words (spondee threshold) is recorded. Discrimination,the ability to hear differences between words that sound similar, is tested by presenting pairs of similar one-syllable words. The percentage of words correctly repeated is the discrimination score. People with a conductive hearing loss usually have a normal discrimination score, although at a higher volume. People with sensorineural hearing loss may have abnormal discrimination at all volumes. Doctors sometimes test people's ability to recognize words within full sentences. This test helps decide which people who do not have acceptable results with a hearing aid might benefit from an implanted device. Tympanometrytests how well sound can pass through the eardrum and middle ear. This test does not require the active participation of the person being tested and is commonly used in children. A device containing a microphone and a sound source is placed snugly in the ear canal, and sound waves are bounced off the eardrum as the device varies the pressure in the ear canal. Abnormal tympanometry results suggest a conductive type of hearing loss. Auditory brain stem responseis a test that measures nerve impulses in the brain stem resulting from sound signals in the ears. The information helps determine what kind of signals the brain is receiving from the ears. Test results are abnormal in people with some sensorineural types of hearing loss and in people with many types of brain disorders. Auditory brain stem response is used to test infants and also can be used to monitor certain brain functions in people who are comatose or undergoing brain surgery. Electrocochleographymeasures the activity of the cochlea and the auditory nerve by means of an electrode placed on, or through, the eardrum. This test and the auditory brain stem response can be used to measure hearing in people who cannot or will not respond voluntarily to sound. For example, these tests are used to find out whether infants and very young children have profound hearing loss (deafness) and whether a person is faking or exaggerating hearing loss (psychogenic hypacusis). testing uses sound to stimulate the inner ear (cochlea). The ear itself then generates a very low-intensity sound that matches the stimulus. These cochlear emissions are recorded using sophisticated electronics and are used routinely in many nurseries to screen newborns for congenital hearing loss and to monitor the hearing of people who are using Ear Disorders Caused by Drugs . This test is also used in adults to help determine the reason for a hearing loss. Other testscan measure the ability to interpret and understand distorted speech, understand a message presented to one ear when a competing message is presented to the other ear, fuse incomplete messages to each ear into a meaningful message, and determine where a sound is coming from when it is presented to both ears at the same time. People who have an abnormal neurologic examination or who have certain findings on audiologic tests also need a gadolinium-enhanced MRI of the head. This type of MRI can help doctors detect certain disorders of the inner ear, brain tumors near the ear, or tumors in the nerves coming from the ear. Many genetic causes of deafness also cause problems in other organ systems. Therefore, children with unexplained hearing loss should also have additional testing, such as an eye exam, an electrocardiogram (ECG) to look for Torsades de Pointes Ventricular Tachycardia , or other organ-specific tests, and genetic testing. 