Caloric stimulation is used to find damage to nerves in the ear. First cold and then warm water is placed into your ears to test your reaction. A calorie is a unit of heat.
Other names for caloric stimulation are caloric test, cold-water calorics, and warm water calorics.
This test checks the function of your acoustic nerve. This nerve is involved in hearing and balance. It also evaluates the function of brain areas involved in balance.
Caloric stimulation is used to evaluate:
- hearing loss caused by antibiotic use
- vertigo (dizziness)
- certain forms of anemia
- psychological causes of vertigo
- brain damage in comatose individuals
Caloric stimulation is performed by inserting first cold and then warm water into the ear canals. This is done one ear at a time. The water stimulates the nerves of the inner ear.
Caloric stimulation usually follows these steps:
- Electrodes hooked up to a computer are placed around the eyes. These are used to measure eye movement during the test.
- A small amount of cold water is inserted into the ear canal. This changes the temperature of the inner ear and causes rapid, side-to-side eye movements called nystagmus. The cold water causes the eyes to move away from the direction of the cold water and then slowly move back.
- Warm water is then inserted into the ear. This time, the eyes should move toward the warm water and then slowly move back.
- Eye movements are detected by the electrodes and recorded by the computer. Sometimes the person conducting the test visually observes the eye movements.
The test may cause some minor discomfort, especially when cold water is inserted. The test may cause brief feelings of vertigo, which can lead to nausea in some people.
Although rare, it is possible for excessive water pressure to injure an eardrum. This is more likely if the eardrum had been damaged in the past. Your doctor should check your eardrum before the procedure. This test should not be used if it is damaged.
Some foods and medications can affect your test results. For 24 hours before your test, you should avoid the following:
- large, heavy meals
- allergy medications
Talk to your doctor about what medications to avoid before the test. Never stop taking your medication without your doctor’s approval.
Normal results mean that you do not have damage to your acoustic nerve.
If your eye movements are abnormal, it may be a sign of acoustic nerve damage.
Causes of abnormal results include:
- blood clots
- atherosclerosis of the blood supply to the ear
- some poisons
- blood vessel disorders
- ear tumors
- congenital disorders
Ear nerve damage can also be caused by certain medications, including:
- antimalarial medications
Results from this test can also be used to rule out or confirm diagnoses, including:
- Meniere’s disease
- acoustic neuroma
- benign positional vertigo