Investigation pcl 9

Exams and Tests

In most medical offices or in the emergency department, doctors do not have access to equipment to directly test your hearing (an audiometer). In these settings the doctor will most likely evaluate your hearing with a tuning fork. The examination may include the following:

• Each ear will be tested separately to see if you can hear the sound coming from a tuning fork.

• The ear canal and tympanic membrane will be inspected with an otoscope (a special instrument with a light and a tip to look into the ear canal).

• The nose, nasopharynx (the part of your throat that your ears drain into, located just above your soft palate), and upper respiratory tract usually will be carefully examined.

• A general neurologic exam, which includes tests of the nerves that control movement, sensation, and reflexes, will be done.

• If a process inside the brain (such as an acoustic neuroma) is suspected, a CT scan of the brain may be performed.

• If an infection, vascular problem, or drug interaction is suspected, blood tests may be performed.

• Tympanometry may be indicated if a problem with the tympanic membrane (eardrum) is suspected. This test evaluates the middle ear’s ability to receive sound waves.

Audiogram

An audiogram is a chart of a persons hearing ability. There are some different styles of audiograms, but most use a standard set of symbols for representing items on the chart. It is always a good idea to review the key that accompanys each audiogram to verify that it uses symbols you are familiar with. .

The audiogram reads in frequency (pitch) across the top or horizontal axis and it reads in decibels (loudness) down the side or vertical axis. Just like a piano's keyboard, the pitches are low on the left side (125 or 250Hz), and then gradually climb to higher pitches on the right side (8000Hz). The loudness scale goes from very soft sounds at the top (-10 or 0dB) to very loud sounds at the bottom (110 dB). It is important to remember that 0 dB does not mean that there is no sound at all. It is simply the softest sound that a person with normal hearing ability would be able to detect at least 50% of the time. Normal conversational speech is about 45 dB.

The softest sounds a person hears at each pitch at least 50% of the time are considered their hearing threshold. Thresholds are obtained and marked for most of the pitches across the audiogram. Typically, when testing is done with headphones, we call them "air" thresholds as the sound must travel through the air of the ear canal to be heard. An O is used for the right ear and an X is used for the left ear to represent the air thresholds. When a bone-conduction vibrator is used to test for thresholds, a <> symbol is used for the left ear. A bone-conduction vibrator is a device that gently rests on the mastoid process of the skull (the bone behind the ear) and is held in place by a small metal band stretching over the top of the head. This device transmits sound via direct vibration of the bone. The vibrations are carried through the bones and tissues and fluids within the skull directly to the cochlea (the hearing organ of the inner ear). This process allows the examiner to bypass the entire outside and middle ear areas and test the sensitivity of the inner ear directly.

By comparing the headphone thresholds with the bone vibrator thresholds at each pitch, we can determine if a hearing loss is conductive, sensorineural or mixed. If the air conduction thresholds show a hearing loss but the bone conduction thresholds are normal, then we call it a conductive hearing loss. If both the air conduction thresholds and the bone conduction thresholds show the same amount of hearing loss, we call it a sensorineural hearing loss. And finally, a mixed hearing loss is when the bone conducted thresholds show a hearing loss and the air conducted thresholds show an even greater hearing loss.

Thus, when the hearing test is completed, the person should be able to tell how well they hear at low, medium and high pitches. If a hearing loss is present, they should also be able to tell which part of the hearing mechanism (the outside, middle or inner ear) is causing the loss.

Ranges have been established to help people identify how much difficulty they should expect from their hearing loss. The typical ranges for an adult are:

-10 dB to 25 dB = Normal range

26 dB to 40 dB = Mild hearing loss

41 dB to 55 dB = Moderate hearing loss

56 dB to 70 dB = Moderately Severe hearing loss

71 dB to 90 dB = Severe hearing loss

over 90 dB = Profound hearing loss.

Tympanometry

The tympanogram is an objective measure of middle ear effusion

or eustachian tube dysfunction. It provides information about the compliance or mobility of the tympanic membrane, the pressure within the middle ear and the volume of the external ear canal. Tympanograms are classified as type A (normal), type B (indicating fluid behind the tympanic membrane) or type C (indicating eustachian tube dysfunction).

How does it works

Tympanometry measures the relative compliance of the middle

ear as air pressure is altered in the external auditory canal.

Compliance reflects the degree of mobility of the tympanic

membrane. It represents the volume of air displaced by movement of the tympanic membrane.The examination is performed with a probe inserted into the external ear canal. A 226-Hz tone is transmitted through the probe, and the compliance of the tympanic membrane is measured while the external canal pressure is varied. The pressure at which peak compliance occurs is recorded. Most tympanometry equipment also provides an estimate of the external ear canal volume.

Results

-Pics will be shown during pcl!..