Definition of Caloric stimulation:

Caloric stimulation is a test that uses differences in temperature to diagnose damage to the ear or brainstem.

How the test is performed:

This test stimulates the inner ear and nearby nerves by delivering cold or warm water to the ear canal at different times. Rarely, the test is done using air instead of water. The person doing the test should examine the ear and especially the eardrum to make sure they are normal before doing the test.

One ear is tested at a time.

When cold water enters the ear and the inner ear changes temperature, it should cause fast, side-to-side eye movements called nystagmus. The eyes should move away from the cold water and slowly back.

Next, warm water is placed into the ear. The eyes should move toward the warm water and then slowly away.

The eyes can be looked at directly. However, often this test is done as part of electronystagmography, which uses patches called electrodes placed around the eyes to detect the movements. A computer records the results.

Ice cold water may be used if there are no responses.

How to prepare for the test:

Do not eat a heavy meal before the test. Avoid the following at least 24 hours before the test, because they can affect the results:

• Alcohol
• Allergy medications
• Caffeine
• Sedatives

However, do not stop taking medicines without first talking to your doctor.

How the test will feel:

Many people find cold water in the ear uncomfortable. Brief, but severe vertigo (sometimes with nausea) may occur during the test. Vomiting is rare.

Why the test is performed:

Caloric stimulation is done to check the ear (acoustic) nerve, which provides hearing and helps with balance. It is also used to test parts of the brain involved in balance.

This test may be recommended if you have:

• Dizziness or vertigo
• Hearing loss that may be due to certain antibiotics
• Vertigo

It may also be done to look for brain damage in persons who are in a coma.