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

This test stimulates the inner ear and nearby nerves by delivering cold and warm water to the ear canal at different times. Sometimes, the test is done using air instead of water.

One ear is tested at a time.

When cold water enters the ear, 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.

Patches called electrodes, placed around the eyes, detect the movements. A computer records all the results.

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

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.)

Some people find cold water in the ear uncomfortable. Brief, but severe vertigo may occur during the test.

Caloric stimulation is done to check the acoustic nerve, which provides hearing and helps with 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.

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.

Abnormal results mean there may be damage to the nerve of the inner ear, which controls balance. If the rapid, side-to-side eye movements do not occur even after ice cold water is given, permanent damage to the nerve has probably occurred.

Abnormal results may suggest:

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

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

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

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.

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

Cummings CW, Flint PW, Haughey BH, et al. Otolaryngology: Head & Neck Surgery. 4th ed. St Louis, Mo; Mosby; 2005:3179-3189.

Casselbrant ML. Balance disorders in children. Neurol Clin. Aug 2005; 23(3): 807-29, vii.