Weber and Rinne Test The clinical examination of hearing loss
should include differentiating between conductive and sensorineural hearing
loss. There are different causes of
sensorineural hearing loss, such as inner- ear disease or damage to the cochlear
nerve. In all cases, the perception of sound waves via both air and bone
conduction is impaired. Sounds reaching the affected ear will therefore be
perceived to be quieter than on the unaffected side. Conductive hearing loss on the other
hand, is caused by diseases of the middle ear, such as otosclerosis or otitis media. Obstruction of the outer auditory canal,
as seen in cerumen impaction, for example, can also lead to conductive hearing loss.
In this case, air conduction of sound waves from middle to inner ear is
impaired. Bone conduction, however, is unaffected
and causes sounds on the affected side to appear louder. There are two hypotheses that attempt to
explain this phenomenon. First, it is assumed that impaired sound conduction
causes up-regulation of the inner ear, which makes it more sensitive towards
stimuli received by a bone conduction. It also causes these sounds to be perceived
as louder. Second, if sound waves cannot easily reach the inner ear, they probably
cannot exit it easily either. These trapped sound waves could therefore make
patients perceive sounds as louder. The Rinne and Weber Test can help
differentiate between sensorineural and conductive hearing loss. The Rinne Test enables unilateral
comparison of bone to air conduction and takes advantage of the fact that
physiologically, sound conduction is more efficient via air, than via bone. Place a
vibrating tuning fork against the mastoid bone. Sound waves now travel to
the inner ear, via bone conduction. As soon as the patient can no longer hear
the sound, hold the tuning fork next to the patient's ear. The sound waves are
now conducted via the air. Patients with conductive hearing loss are no longer
able to hear this sound, since air conduction is severely impaired.
Therefore the Rinne test is negative. In healthy patients, but also in patients
with sensorineural hearing loss, air conduction will always be more efficient
than bone conduction, and, as such the sound of the vibrating tuning fork
should still be heard. This describes a positive Rinne test. Alternatively, the
test can be sped up by first placing the tuning fork against the mastoid bone, and
then, after a few seconds, holding it next to the patient's ear on the same side. If
the sound is perceived as louder, the test is positive, and air conduction is
intact. Should the sound not be perceived as louder, the Rinne test is negative and
conductive hearing loss should be suspected.
The Rinne Test should always be accompanied by the Weber Test, to detect
the origin of hearing loss and possible inner ear damage. The Weber Test compares bone conduction in both sides. Start by placing a vibrating tuning fork medially on the
patient's head. The sound is now transmitted by a bone
conduction. Physiologically, it should be heard centrally -- or, in other words,
equally loud in both ears. Unfortunately, the patient reports the same finding in
both bilateral conductive and bilateral sensorineural hearing loss. This can be
the cause of falsely diagnosing a patient as healthy. If the sound is heard
louder on one side, this is called lateralization. It can have two different
causes. In the case of unilateral sensorineural hearing loss, sound lateralizes to the unaffected side. For example, in right-sided inner ear damage,
the sound is louder on the left side. If unilateral conductive hearing loss is
present, sound lateralizes to the affected side, since, as mentioned before,
bone conduction results in a sound that is perceived as louder.
For example, damage to the right middle ear make sounds louder on that side. Differentiating between sensorineural
and conductive hearing loss is only possible by interpreting results from
both the Rinne and Weber Test. To illustrate, the following test results
show the clinically relevant constellations. Weber: lateralized to the right. Renee:
positive bilaterally. Lateralization to the right during Weber
tests could indicate conductive hearing loss on the right side, or, left sided
sensory neural hearing loss. A bilaterally positive Rinne Test
indicates that air conduction surpasses bone conduction on both sides, thereby
ruling out conductive hearing loss. This test result constellation supports
left-sided sensory neural hearing loss, as seen in inner ear damage. Weber: lateralized to the right. Rinne:
negative on the right. Lateralization of the Weber test to the
right indicates either conductive hearing loss on the right side, or, left
sided sensorineural hearing loss. The negative Rinne Test on the right
side underlines that air conduction is inferior to bone conduction on this side,
making conductive hearing loss more likely. This can be seen in, for example,
right-sided middle ear damage. Weber: no lateralization. Rinne: positive
bilaterally. A normal Weber test can be either
physiological or indicate bilateral conductive or sensorineural hearing
loss. The bilaterally positive Rinne test
signifies that air conduction surpasses bone conduction on both sides. This rules
out significant conductive hearing loss. In conclusion, the test results indicate
either normal findings or bilaterally equal sensorineural hearing loss. Weber: no lateralization. Rinne: negative
bilaterally. Contrary to the last case, the
bilaterally negative Renee test means that air conduction is inferior to bone
conduction on both sides, indicating conductive hearing loss. The unremarkable Weber test points to a
symmetrical conductive hearing loss. The Rinne and Weber tests are easy and
quick methods for differentiating simple forms of conductive and sensorineural
hearing loss. Complex illnesses, such as combined
conductive and sensory neural hearing loss, often result in test results that
are difficult to interpret.