Caloric stimulation is a test which uses differences in temperature to diagnose ear nerve damage as a cause of dizziness or vertigo. Damage to the vestibular portion of the nerve of the inner ear (acoustic nerve) is a common cause of vertigo.
How the test is performed
Each ear is tested separately using a computerized caloric stimulation machine. Nystagmus (quick movement of both eyes in response to certain stimuli, which is necessary for normal vision and balance) is measured using electrodes around the eye and recorded for analysis by the computer.
Cold water is placed in the ear canal with a bulb syringe. This should cause nystagmus. This test is then repeated using warm water. The nystagmus should occur in the opposite direction (towards the warm water then slowly away, rather than away from the water and slowly back).
The computer analyzes:
- The cold and warm water response for each ear
- Differences between ears
- Differences between cold and warm water responses
Occasionally, warm and cold air (if there is a hole in the ear drum) or ice cold water (in absence of any response) is used for this test.
How to prepare for the test
Avoid eating 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. Ask for written instructions from your doctor prior to the test.
For infants and children:
The preparation you can provide for this test depends on your child’s age, previous experiences, and level of trust. For specific information regarding how you can prepare your child, see the following topics:
- infant test or procedure preparation (birth to 1 year)
- toddler test or procedure preparation (1 to 3 years)
- preschooler test or procedure preparation (3 to 6 years)
- schoolage test or procedure preparation (6 to 12 years)
- adolescent test or procedure preparation (12 to 18 years)
How the test will feel
There is minimal discomfort. Some people find cold water in the ear uncomfortable. Brief, but severe vertigo may occur during the test.
Why the 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 someone is experiencing dizziness or vertigo
- when there is hearing loss with suspected toxicity from certain antibiotics
- with some anemias
- when psychological causes of vertigo are suspected
- to determine the presence or extent of brain damage in a comatose person
Nystagmus should occur after instillation of cold or warm water into the ear. The nystagmus should be similar on both sides.
What abnormal results mean
If nystagmus does not occur after cold or warm water is instilled or there is a difference between the responses of each ear or between cold and warm water response, there may be some damage to the nerve of the inner ear, which controls balance. If nystagmus does not occur even after ice cold water is instilled, permanent damage to the nerve has probably occurred.
Any disease or injury that damages the acoustic nerve can cause vertigo. This may include:
- congenital disorders (present at birth)
- blood vessel disorders with hemorrhage (bleeding)
- atherosclerosis of the blood supply of the ear
- cholesteatoma and other ear tumors
- some poisons
- ototoxic (toxic to the ear nerves) medications, including aminoglycoside antibiotics, some antimalarial drugs, loop diuretics, and salicylates
Additional conditions for which the test may be performed:
- acoustic neuroma
- benign positional vertigo
- 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.
Caloric stimulation is approximately 80% accurate in differentiating nerve damage as a cause of vertigo. Other tests may be required to confirm the diagnosis.
by Sharon M. Smith, M.D.
All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.