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Caloric stimulation How the Test is Performed:
Each ear is tested separately. One teaspoon of cold water is gently instilled in the ear canal with a bulb syringe. This should cause nystagmus (quick movement of both eyes away from the direction of ice water and then slowly back). If it does not cause
nystagmus, 2 teaspoons of cold water are instilled in the ear canal. If nystagmus still fails to occur, 4 and then 8 teaspoons of cold water are used.
At times, hot water may be used in addition to cold water. The nystagmus should occur in the opposite direction (toward the hot water then slowly away). Use of both cold water and hot water makes the test more accurate.
How to Prepare:
Adults:
No special preparation is necessary.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How it Feels:
There is minimal discomfort. Some people find cold water in the ear uncomfortable. Brief, but severe vertigo may occur during the test.
Risks:
Excessive water pressure can injure a previously damaged eardrum, but this rarely occurs, since the amount of water is measured. Caloric stimulation should not be performed if the eardrum is perforated because of the risk of causing ear infection .
Why this Test is Performed:
Caloric stimulation is performed to evaluate the acoustic nerve, which provides hearing and helps with balance. This test may be recommended when the person is experiencing dizziness or vertigo , when there is impaired hearing, with suspected toxicity from certain antibiotics, with some anemias , when psychologic causes of vertigo are suspected, and to determine the presence or extent of brain damage in a comatose person.
Normal Values:
Nystagmus should occur after instillation of 1 teaspoon of cold or hot water into the ear canal.
Abnormal Results:
If nystagmus does not occur until after 2 or more teaspoons of water are instilled, there may be some damage to the nerve of the inner ear. If nystagmus does not occur even after 8 teaspoons of water are instilled, it may be assumed that there is permanent damage to the nerve.
Any disease or injury that damages the acoustic nerve can cause vertigo . This may include congenital disorders; trauma; rubella ; vascular (blood vessel) disorders with hemorrhage ( bleeding ), thrombosis (clots), or atherosclerosis of the blood supply of the ear; cholesteatoma and other ear tumors ; some poisons; and ototoxic (toxic to the ear nerves) medications including aminoglycoside antibiotics, some antimalarial drugs, loop diuretics, and salicylates.
Additional conditions under which the test may be performed:
Cost:
The estimated cost is $10 to $15.
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.
vertigo . Damage to the vestibular portion of the acoustic nerve (the nerve of the inner ear) is one of the more common causes of vertigo. Learn to make informed health care decisions with the Medical Encyclopedia at
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