Caloric stimulation

Definition

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

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 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.

Normal Results

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 bleeding (hemorrhage)
• Blood clots
• Brain or brainstem damage
• Cholesteatoma
• Congenital (present at birth) disorders
• Damage to the ear nerves due to certain antibiotics, antimalarial drugs, diuretics, and salicylates
• Ear tumors
• Poisoning
• 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

Risks

Too much water pressure can injure an already damaged eardrum, but this rarely occurs since the amount of water to be used is measured.

Caloric stimulation should not be done if the eardrum is torn (perforated), because it can cause an ear infection. It also should not be performed during an episode of vertigo because it can make symptoms worse.

Considerations

Caloric stimulation is about 80% accurate at diagnosing nerve damage as a cause of vertigo. Other tests may be needed to confirm the diagnosis.

References

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

Kerber KA, Baloh RW. Dizziness, vertigo, and hearing loss. In: Bradley WG, Daroff RB, Fenichel GM, Jankovic J, eds. Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 2008:chap 18.

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