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.