Rinne Test - Indications, Clinical Significance, and Procedure

Introduction

Various types of hearing tests have been used to test hearing loss in patients. But the two most commonly used tests include the Rinne and Weber tests. These tests help differentiate hearing loss. For example, a Rinne test is commonly recommended in an individual with unilateral hearing loss. This test compares two ways the ear hears a sound from the surrounding.

Heinrich Adolph Rinne (1819 to 1868), a German otologist, introduced this test named after him. The Rinne test compares the perception of sounds sent by air conduction with the sound sent by bone conduction through the mastoid bone. Air conduction hearing happens via air near the ear and involves the inner apparatus of the ear, such as the ear canal and eardrum. Bone conduction hearing occurs via vibrations picked by the bones of the skull, bypassing the eardrum.

What Is the Anatomy of the Ear and Physiology of Hearing?

The ear consists of three parts - the outer or external ear, the middle ear, and the inner ear. The sound vibrations enter the external ear and reach the middle ear to the eardrum or tympanic membrane. These vibrations are transferred through the middle ear by the ossicles or small bones named malleus, incus, and stapes.

The vibration reaches the cochlea (a spiral-shaped bone found in the inner ear that helps in hearing) through a small oval window (fenestra ovalis). The hair cells present in the cochlea convert these vibrations into electrical signals that get transferred via nerves of the vestibulocochlear nerve (auditory nerve) to the brainstem. Any interruption in this pathway can lead to deafness.

What Are the Types of Hearing Loss?

Hearing loss can be categorized according to the damage to a certain part of the ear -

1. Conductive Hearing Loss - This type of hearing loss occurs when something prevents the sound from entering the middle ear.

2. Sensorineural Hearing Loss - This type of hearing loss occurs when the sound cannot reach the inner ear, or the auditory nerve does not function properly.

3. Mixed Hearing Loss - This is the combination of conductive and sensorineural hearing loss.‌

The hearing loss can also be classified according to the severity, which includes -

1. Mild Hearing Loss - A person may hear speech, but softer tones or light sound is difficult to understand.

2. Moderate Hearing Loss - An individual may not be able to hear any speech sound when someone speaks at normal volume.

3. Severe Hearing Loss - A person may not understand speech at normal volume and tone and can only hear louder sounds.

4. Profound Hearing Loss - Hearing loss is severe, and the patient will not understand any speech or sound, no matter the volume.

What Are the Indications for the Rinne Test?

The Rinne test is done by positioning a tuning fork on the mastoid bone adjacent to the outer ear. It is essential to know that people with normal hearing will have air conduction more than bone conduction. This means that a person can hear the tuning fork adjacent to the outer ear (air conduction) even if they can no longer hear it when held against the mastoid (bone conduction).

The indications of the Rinne test include the following -

• To check deafness in one or more ears.

• To screen babies and youngsters for hearing issues that interfere with their speaking ability.

• This test can help in identifying the type and severity of deafness.

• To evaluate any injury or trauma, or infection in the ear.

• To check for abnormal growth of bones in the inner ear preventing the ear structures from functioning correctly.

How Is This Test Performed?

• The Rinne test is performed using a 512 Hz (Hertz) tuning fork. Tuning forks of 128 Hz or 256 Hz should be avoided as these are mostly used in neurological examinations.

• Before performing this procedure, it is explained to the patient first, and the tuning fork is stuck gently against a rubber pad or any bony prominence of the examiner to create a vibration.

• The fork is about one inch away from the ear, so the prongs are parallel to the external auditory canal.

• After initiating the vibration of the tuning fork, it is placed on the mastoid process (prominence of the temporal bone behind the ear) of the tested ear.

• The patient is asked to cover the opposite ear with the hand.

• The patient is asked to report when they stop hearing the sound.

• When the patient indicates, the tuning fork is immediately placed on the mastoid process. If the patient still cannot hear sound on the mastoid cortex, it indicates that air conduction is better than bone conduction.

What Do the Results Indicate?

Normal Result - If the patient can hear the sound of the tuning fork adjacent to the ear as twice as they heard the sound over the mastoid process, this verifies that air conduction is better than bone conduction and means a positive test.

Abnormal Result - Bone conduction is better than air conduction, which indicates abnormal results. The patient cannot hear sound through the air after moving the fork away from the mastoid process. This indicates hearing loss and is referred to as a negative test.

What Is the Clinical Significance of the Rinne Test?

The clinical significance of the Rinne test includes the following problems such as -

1. Problems in the auditory canal -

• Wax in the external canal.

• Foreign objects in the ear canal.

• Outer ear canal infection.

2. Problems with the eardrum, such as perforation of the drum due to trauma or infection.

3. Problems in the middle ear -

• Acute otitis media (infection of the middle ear).

• Serous otitis media (glue ear).

4. Causes at the fenestra ovalis (oval window) -

• Otosclerosis (failure to transmit sound from the ossicles through the oval window due to abnormal bone growth).

What Is the False Negative Rinne Test?

The patient with total unilateral sensorineural hearing loss (dead ear) may show a false negative test. As with complete loss of hearing, a patient will not hear anything from the tuning fork on the mastoid or near the ear canal. The sound will travel to the other side ear (normal functioning ear) through the skull, and the patient will not be able to identify in which ear they hear the sound. This will indicate that bone conduction is better than air conduction, but the ear is non-functional, giving a false negative result.

Therefore, to differentiate between a true or false negative Rinne test, another test known as the Weber test can be performed.

Conclusion

The Rinne test is the standard test that can be done to check the hearing loss in the patient. This test has no side effects, and a treatment plan can be formulated according to the results. However, this test has some limitations that other tests can correct.