Caloric Stimulation Test - Procedure, Indications, and Risks

What Is a Caloric Stimulation Test?

Caloric stimulation test is a medical maneuver that is performed to assess the degree of damage to the auditory nerves of the ear. The caloric stimulation test is also used to diagnose the damage caused to the brain stem. These acoustic nerves in the ear are associated with hearing and maintaining balance.

As the name of the test suggests, many people might get confused by the term calorie and link it to food. But actually, calorie is a fundamental unit of heat produced. So, taking reference from this, hot and cold water is passed into the auditory canals of the affected individual during this caloric stimulation test, and the response is then recorded. The test was described by Robert Barrany to assess vestibular canal dysfunction laterally.

What Are the Alternative Names of the Caloric Stimulation Test?

The other names for this test include:

• Cold water caloric test.

• Warm water caloric test.

• Caloric reflex test.

• Bi-thermal caloric test.

• Air caloric testing.

What Is the Procedure for the Caloric Stimulation Test?

The caloric stimulation test is performed by placing cold water followed by warm water into the ear canal. This will stimulate the nerves of the ear, and the physician can then record the reflexes of an individual. So, when cold air or cold water is inserted into the auditory canal, the temperature of the inner ear changes. This, in turn, causes the eyes to move faster and exhibit side-to-side movements rapidly. This condition is known as nystagmus.

The caloric stimulation test is performed in the following steps.

• Checking of the Eardrum - The eardrum needs to be assessed thoroughly before the commencement of the test procedure to see if it is in a normal state. In case the eardrum is compromised or perforated, the insertion of water into the ear canal might lead to an ear infection.

• Placement of the Electrodes - The electrodes are placed near the eyes and connected to the computer. With the help of electrodes, the eye movements of the patient are recorded.

• Insertion of Cold Water Into the Ear Canal - A minimal quantity of cold water is passed through the ear canal. The eyes will therefore show rapid side-to-side eye movements. This involuntary eye movement is called nystagmus. The eyes turn away from the direction of the cold water and then slowly turn back. Once this step is done, the cold water is allowed to drain off the ear.

• Insertion of Warm Water Into the Ear Canal - Warm water is gently passed through the ear in a small amount. The eyes are again noticed for nystagmus. However, this time, the eyes turn toward the warm water and then gradually turn back. The test is then repeated on the other side.

• Monitoring the Eye Movements- The healthcare provider then monitors the eye movements that are recorded by the attached computer.

After the test is completed, the patient may find the presence of cold water or air in the ear a little bit uncomfortable. The person may suffer from dizziness, vertigo, and nausea. However, these are temporary side effects that do not last for long.

How to Prepare for the Caloric Stimulation Test?

The person undergoing the caloric test should not take a heavy meal before the commencement of the test. The following things should be avoided before the test procedure such as,

• Alcohol consumption.

• Intake of allergy medications.

• Caffeine intake.

• Sedatives and hypnotics.

However, the regular medications that are being taken by an individual should not be stopped without the prior consent of the doctor.

What Is the Clinical Significance of a Caloric Stimulation Test?

The caloric stimulation test is used to diagnose the proper functioning of the nerves in the ear that are responsible for hearing and maintaining balance. This test is also used to evaluate the areas of the brain that are involved in the regulation of balance.

Caloric stimulation is mainly used to check the following.

• Loss of hearing caused as a side-effect of inadvertent antibiotic or other drug abuse.

• Dizziness (sensation of vertigo).

• Panic attacks, stress disorders, depression, anxiety attacks (psychological causes of dizziness).

• Damage of the brain in comatose patients.

The test may also be carried out to exclude other diseases, such as,

• Acoustic neuroma (tumor of the auditory nerve).

• Benign positional vertigo (a type of dizziness that occurs due to changes in positions).

• Labyrinthitis (inflammation and swelling of the labyrinth of the inner ear).

• Meniere’s disease (a disorder of the inner ear that causes hearing impairment and affects balance).

What Do the Caloric Stimulation Test Results Mean?

Normal Results:

When the test results are normal, rapid side-to-side movements of the eye are recorded on both eyes when cold and hot water is delivered, but the movements should be similar.

Abnormal Results:

If the rapid side-to-side movements of the eyes did not take place even after delivering cold water, then it is comprehended that the damage has occurred either in the.

• Acoustic nerves of the inner ear.

• Sensors of the inner ear that regulate balance.

• Brain and brainstem.

Abnormal results may be observed due to the following,

• Impaired blood supply to the ears.

• Bleeding in the ear.

• Blood clots.

• Injury to the brain stem.

• Cholesteatoma (cyst formation in the middle ear and mastoid bone of the cranium).

• Deformities in the ear at the time of birth.

• Viral infections such as rubella.

• Drug poisoning.

• Brain stroke.

• Injury.

What Are the Limitations of a Caloric Stimulation Test?

• The test is time-consuming.

• The test can be biased with compromised inter-rater dependency.

• The patient may not be compliant enough.

• The patient usually suffers from discomfort after the test.

• The size of the ear canal plays a role in the test results.

• The current generated also influences the test results.

• The lateral semicircular canal is stimulated at low frequency.

Conclusion

The caloric stimulation test is a precious tool that aids in diagnosing any generalized or localized disorders of the brain, brainstem, or nerves of the ear. The test also helps in the assessment of the disease's prognosis. The caloric stimulation test is utilized mostly in cases where the patient is in a state of coma. There are certain limitations of the test that should be overcome.