FUNCTION -- Audition and Balance

TEST I -- Finger Rustling
The clinician should, in plain view of the patient, repeatedly rub the fingertips against the thumb, producing a noise. The patient should then be asked to identify the ear through which a similar noise is heard with the eyes closed. After the patient closes the eyes, the clinician should place his/her fingers near the ears of the patient alternately making the noise with either, both, or neither of the hands.

INTERPRETATION
Unilateral or bilateral failure to detect the noise are causes for concern.

PITFALLS AND SAFEGUARDS
As with all tests of hearing, assessment should be conducted in a quiet environment free from distractions. Also note that the test is crude and does not aid in the localization of pathology. In addition, the test should always be preceded by an otoscopic examination. In the event that the external acoustic meatus is occluded with foreign matter or exudates, cleansing should precede assessment of function.

TEST II -- Weber Test
The Weber Test involves placement of the stem of a vibrating tuning fork in the center of the forehead of the patient. The patient should be asked to indicate whether the tone is heard and whether it is heard equally well in through both ears. As the intensity of the vibration fades, the patient may be asked to indicate when the tone is no longer audible. The clinician may also wish to note the rate at which the vibrating fork loses its ability to sustain the experience of sound bilaterally during the test.

INTERPRETATION
Although marked lateralization (the tendency for the sound to be perceived as louder in one ear as compared to the other) suggests a lateralized defect in the auditory system, it does not aid in the localization of the lesion. The ear to which the sound lateralizes may, for example, may be affected by a lesion peripheral to the cochlea. In other words, the patient in this case, may suffer from unilateral conduction deafness. On the other hand, the nervous component of the auditory system opposite to the lateralization of sound may be implicated in the pathology, suggesting nerve deafness. Damage to the cochlea, cranial nerve VIII, or the dorsolateral rhombencephalon is frequently implicated (unilateral damage to higher centers may also produce asymmetrical experiences of loudness, but the effects may tend to be more subtle in such cases).

PITFALLS AND SAFEGUARDS
The test is best executed using a 128Hz fork, although a 256Hz fork is also acceptable. It is also acceptable in many instances to place the tuning fork on the top of the head. However, hair in this location may prevent good transmission of the vibrations from the fork to the skull.

TEST III -- Rinne Test
The Rinne Test involves placement of the stem of the vibrating tuning fork firmly in contact with the mastoid process. The clinician should time the period during which the noise remains audible to the patient. Once the patient indicates that the noise is no longer audible, then the tuning fork should be repositioned, with the tips of the fork placed adjacent to the external acoustic meatus (but not in contact with the pinna). The patient should once again experience the sound, and the clinician should once again time the period during which the noise remains audible to the patient. The test should be repeated for the opposite ear.

INTERPRETATION
Under normal circumstances, the noise produced by the tuning fork vibrating against the mastoid process should be audible for several seconds (e.g., 6). Also under normal circumstances, due to the amplifying properties of the bones of the middle ear, the noise should be audible for at least as long, once the tuning fork is placed in air next to the external acoustic meatus. Under such circumstances, air conduction is deemed to be greater than bone conduction (AC > BC). When bone conduction exceeds air conduction, then the conductive problem suggested by the Weber test is confirmed. When bone and air conducted sound are evident for less time than would normally be expected (given the characteristics of the tuning fork used), then the nerve problem suggested by the Weber test is confirmed.