Caloric stimulation

Definition

Caloric stimulation is a test which uses differences in temperature to diagnose ear nerve damage.

Alternative Names

Caloric test; Cold water calorics; Warm water calorics

How the test is performed

This test stimulates the inner ear and nearby nerves by delivering cold and 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 it is 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 rapid, 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 now move towards the warm water then slowly away.

The eyes can be observed visually, but more 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 all 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 caffeine, alcohol, allergy medications, and sedatives at least 24 hours prior to the test, as these can affect the results. (However, do not stop taking medicines without first talking to your doctor.)

How the test will feel

Some people find cold water in the ear uncomfortable. Brief, but severe vertigo may occur during the test. You may have nausea associated with that feeling. Vomiting is rare.

Why the test is performed

Caloric stimulation is done to check the acoustic (ear) 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
• Certain types of anemia
• Possible psychological causes of vertigo

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

Normal Values

Rapid, side-to-side eye movements should occur when cold or warm water is placed into the ear. The eye movements should be similar on both sides.

What abnormal results mean

Abnormal results mean there may be damage to the nerve of the inner ear. If the rapid, side-to-side eye movements do not occur even after ice cold water is given, there may be damage to the nerve, the balance sensors of the inner ear, or the brain.

Abnormal results may be due to:

• Atherosclerosis of the blood supply of the ear
• Blood vessel disorders with hemorrhage (bleeding)
• Blood clots
• Certain types of poisonings
• Cholesteatoma and other ear tumors
• Congenital (present at birth) disorders
• Damage to the ear nerves due to certain antibiotics, antimalarial drugs, diuretics, and salicylates
• Rubella that damages the acoustic nerve
• Trauma

The test may also be done to diagnose or rule out:

• Acoustic neuroma
• Benign positional vertigo
• Labyrinthitis
• Meniere's disease

What the risks are

Excessive water pressure can injure a previously damaged eardrum, but this rarely occurs since the amount of water to be used is measured in advance. Caloric stimulation should not be performed if the eardrum is perforated because of the risk of causing ear infection. Caloric testing should not be performed during an acute vertigo episode as it can make symptoms worse.

Special considerations

Caloric stimulation is approximately 80% accurate in differentiating nerve damage as a cause of vertigo. Other tests may be required to confirm the diagnosis.

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References

Baloh R. Hearing and equilibrium. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 454.