Caloric stimulation is a procedure used to find damage to nerves in the ear. Although people commonly associate the term calorie with food, a calorie is fundamentally a unit of heat. During caloric stimulation, cold and warm water are placed into your ear canals and your reaction is monitored.
Other names for caloric stimulation are caloric reflex test, cold water calorics, and warm water calorics.
This test checks the function of your acoustic nerve, which 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)
- 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:
1. The eardrum is checked
Before the test the eardrum is checked to make sure it is healthy and not perforated. Inserting water into an ear with a compromised eardrum could lead to an ear infection.
2. Electrodes are placed
Electrodes are placed around the eyes and connected to a computer. The electrodes are used to measure eye movement during the test.
2. Cold water is inserted into ear canal
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 move slowly back.
3. Warm water is inserted into ear canal
Warm water is then inserted into the ear. This time, the eyes should move toward the warm water, and then move slowly back. The test is then performed on the other ear.
4. Eye movements are monitored
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. For this reason, only a small amount of water is used for this test. An injury is more likely to occur if the eardrum has been previously damaged. Your doctor should check your eardrum before the procedure, and 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 consuming 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, damage to the balance sensors in your ears, or brain damage.
Causes of abnormal results include:
- blood clots
- atherosclerosis leading to poor 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
Caloric stimulation is a test used to check for damage to your acoustic nerve, which could be caused by various medical disorders and diseases, or by certain medications. Abnormal results may point to acoustic nerve damage, damage to the ear’s balance sensors, or brain damage. Be sure to discuss the results of your test with your doctor, and ask any questions you may have.