Rinne Test

Anatomy and Physiology

The external ear collects sound vibrations from the air and focuses these sounds onto the tympanic membrane. Vibrations are transmitted through the middle ear by the ossicular chain (malleus, incus, and stapes). The stapes transmits these vibrations to the cochlea through the oval window (fenestra ovalis). Sound can also be transmitted through the bones of the skull to the cochlea.

The hair cells in the cochlea convert the physical vibrations into action potentials transmitted via the nerves in the vestibulocochlear (auditory) nerve to the brainstem for further processing.

Deafness may occur due to interruption at any point along this pathway.

The Rinne test is conducted by placing a tuning fork on the mastoid bone and then adjacent to the outer ear.

• Air conduction uses the apparatus of the ear (pinna, ear canal, tympanic membrane, and ossicles) to amplify and direct the sound.
• Bone conduction allows the vibration sound to be transmitted to the inner ear. The ear bones transmit reduced volume audition via the bones of the skull to the other ear.

Indications

Before performing the Rinne test, it is important to know that individuals with normal hearing will have air conduction that is greater than bone conduction. This means that the individual will be able to hear the tuning fork placed adjacent to the outer ear, even after they are no longer able to hear it when held against the mastoid.

Equipment

The examiner should use a 512 Hz tuning fork. One should avoid using a 128 Hz or 256 Hz tuning fork, as these are used to assess vibration sensation in neurological examinations.

Preparation

The room should be reasonably quiet.

Technique or Treatment

Test Bone Conduction

1. Initiate vibration of the tuning fork and then place the vibrating tuning fork onto the patient's mastoid process of the tested ear.
2. Ask the patient to cover the opposite ear with their hand.
3. Ask the patient to report when the sound can no longer be heard.
4. After the patient can no longer hear the tuning fork placed on the mastoid process, move the vibrating tuning fork adjacent to the ear canal with the tines oriented perpendicular to the ear canal, approximately 3 to 4 cm from the ear.[4]
5. The patient should indicate when they can no longer hear the sound conducted through the air.

Interpretation

Normal finding: Air conduction is better than bone conduction. The patient should be able to hear the sound of the tuning fork adjacent to their ear, persist for approximately twice as long as the sound they heard over their mastoid process. This is considered a "positive test."

Abnormal: Bone conduction is better than air conduction. The patient cannot hear sound conducted through the air after the fork is moved from the mastoid process. This suggests conductive hearing loss and is referred to as a "negative test."

Clinical Significance

The tuning fork will be perceived as being louder when placed at the external auditory meatus.

• Rinne Positive: The patient is positive on that side (the ossicular chain is doing what it should be doing, acting as an amplifier). If the bone conduction through the mastoid process is heard louder than through the air, the patient is Rinne negative. This is always abnormal.
• If the patient has negative or abnormal Rinne negative, air vibrations are not being transmitted across the external auditory canal, the tympanic membrane, the ossicular chain, or the oval window.

Causes in the external auditory canal:

• Wax in the external canal
• Otitis externa or outer ear canal infection
• Foreign body in the ear canal

Causes due to the drum:

• Perforation of the drum due to trauma or infection

Causes in the middle ear:

• Infection (acute otitis media) in the middle ear
• Serous otitis media (glue ear) can result from repeated episodes of acute otitis media.

Causes at the oval window:

• Otosclerosis results in the failure to transmit sound from the stapes through the oval window due to abnormal bone growth. 

False Negative Rinne test

A patient with profound sensorineural deafness may have a false negative Rinne. With complete loss of innervation to that ear, the patient will not hear anything from the tuning fork on the mastoid or near the canal. The sound transmits through their skull to the ear on the other side, and they may not be able to identify in which ear they hear the sound.

It seems that bone conduction is better than air conduction, but the ear is nonfunctional.

The way to determine the difference between a true and a false Rinne negative test is to perform the Weber test.

For example, if the left ear is completely dead, the sound waves travel to the good right ear on testing the bone conduction on the left. But the sounds are not heard when the tuning fork is held next to the external auditory meatus on the side being tested (left). In this case, the patient will state that bone conduction is louder than air conduction, giving a falsely negative Rinne test.

Enhancing Healthcare Team Outcomes

Limitations of the Rinne test

Like its complementary test, the Weber test, both are screening tests that do not replace formal audiometry. Additionally, the validity of the Rinne test as a screening test is often questioned. The test is not sensitive in differentiating conductive and sensorineural loss causes of total sensorineural or severe unilateral hearing loss. False negatives are common in such situations. In any situation where there is a question about the Rinne test, the patient must be referred to an ear, nose, and throat (ENT) surgeon for formal audiometry.

Another important caveat about the Rinne test is that the technique is not uniform. The orientation of the tuning fork and its exact placement varies from individual to individual. All physicians who perform the Rinne test must pay attention to the orientation of the tines of the tuning fork relative to the long axis of the external auditory canal when testing for air conduction.