Caloric stimulation is a test that uses differences in temperature to diagnose damage to the acoustic nerve. This is the nerve that is involved in hearing and balance. The test also checks for damage to the brainstem.
Caloric test; Bithermal caloric testing; Cold water calorics; Warm water calorics; Air caloric testing
How the Test is Performed
This test stimulates your acoustic nerve by delivering cold or warm water or air into your ear canal. When cold water or air enters your ear and the inner ear changes temperature, it should cause fast, side-to-side eye movements called nystagmus. The test is done in the following way:
- Before the test your ear, especially the eardrum, will be checked. This is to make sure they are normal.
- One ear is tested at a time.
- A small amount of cold water or air is gently delivered into one of your ears. Your eyes should show an involuntary movement (nystagmus). Your eyes will move slowly towards the ear containing the water and then move quickly away from that ear. If water is used, it is allowed to drain out of the ear canal.
- Next, a small amount of warm water or air is gently delivered into the same ear. Again, your eyes should show an involuntary movement (nystagmus). This time, your eyes will move slowly away from the ear containing the warm water, and then move quickly towards that ear.
- Your other ear is tested in the same way.
During the test, the health care provider may observe your eyes directly. Most often this test is done as part of another test called electronystagmography. In this case, patches called electrodes are placed around your eyes to detect nystagmus. A computer records the results.
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:
- Allergy medicines
But do not stop taking your regular medicines without first talking to your doctor.
How the Test will Feel
During the test, you may:
- Find the cold water or air in the ear uncomfortable.
- Feel your eyes scanning back and forth during nystagmus.
- Have brief vertigo, sometimes with nausea. This lasts a very short time. Vomiting is rare.
Why the Test is Performed
This test may be recommended if you have:
- Hearing loss that may be due to certain antibiotics
It may also be done to look for brain damage in persons who are 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.
What Abnormal Results Mean
Abnormal results mean:
- Damage to the acoustic nerve
- Function of the balance sensors of the inner ear have declined
- Brain damage
Abnormal results may be due to:
- Atherosclerosis of the blood supply of the ear
- Bleeding (hemorrhage)
- Blood clots
- Brain or brainstem damage
- Congenital (present at birth) defects of the ear structure or brain
- Damage to the acoustic nerve
- Rubella that damages the acoustic nerve
The test may also be done to diagnose or rule out:
Too much water pressure can injure an already damaged eardrum. This rarely occurs because the amount of water to be used is measured.
Water caloric stimulation should not be done if the eardrum is torn (perforated). This is because it can cause an ear infection. It also should not be done during an episode of vertigo because it can make symptoms worse.
Baloh RW, Jen J. Hearing and equilibrium. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 436.
Kerber KA, Baloh RW. Neuro-otology: diagnosis and management of neuro-otological disorders. In: Daroff RB, Fenichel GM, Jankovic J, Mazziotta JC, eds. Bradley's Neurology in Clinical Practice. 6th ed. Philadelphia, PA: Elsevier Saunders; 2012:chap 37
Ashutosh Kacker, MD, BS, Associate Professor of Otolaryngology, Weill Cornell Medical College, and Associate Attending Otolaryngologist, New York-Presbyterian Hospital, New York, NY. Review provided by VeriMed Healthcare Network. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, Bethanne Blackman, Stephanie Slon, and Nissi Wang.
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