Overview of Caloric Testing
Caloric testing is a method doctors use to check the health and working condition of the balance organs in your ears. One of these organs is known as the vestibular system. This test can identify if there’s a difference in the performance of these organs in each ear.
The procedure relies on the “vestibulo-ocular reflex” – a function in your body that allows your eyes to stay focused on a static object, even while your head is moving. This process keeps the object you’re looking at in the middle of your field of vision, maintaining a steady line of sight.
The caloric test works by stimulating this reflex to check the health of a part of your inner ear called the lateral semicircular canals, as well as the nerves that carry signals from these canals to your brain. Any inconsistencies might indicate a problem with these areas.
Notably, this test can also provide valuable insights on people suffering from hearing loss in one ear. So it can be a supplementary tool for diagnosing issues linked to hearing loss.
Anatomy and Physiology of Caloric Testing
The semilunar canals are small, curved tubes located within your inner ear. They’re important because they help you stay balanced and know where your body is in space. There are three of these canals, each named for their direction — horizontal, superior (upper), and posterior (back). Inside each canal is a liquid called endolymph that senses when your head turns or rotates.
Each canal widens at one end into a bag-like shape known as the ampulla. This contains the sensory tissues of the vestibular system, a part of your inner ear responsible for balance. When your head moves, the liquid within the canals stimulates these sensory tissues, informing your brain of your body’s orientation.
Why do People Need Caloric Testing
If you’re experiencing a sensation of dizziness or spinning distress, known as vertigo, there are various ways doctors might try to find out why. One method is ‘caloric testing’. This is a simple procedure that helps differentiate between issues related to the inner ear or more complex issues concerning the brain.
‘Bithermal caloric testing’ is usually employed when a doctor suspects the dizziness is due to an issue with the inner ear. However, if there’s a low possibility of an inner ear issue, ‘monothermic caloric testing’ might be performed. If the results show that responses are symmetrical (or equal on both sides) – a good sign – the test may be stopped, as it suggests that the dizziness is due to a brain-related issue rather than an ear-related one.
Caloric testing has several benefits. It’s especially helpful with patients whose symptoms worsen when moving their heads or for those who can’t move their necks easily.
There’s more to caloric testing though. Doctors also use it to check how well the brainstem – a part of the brain that controls many vital functions – is working, especially in patients who are in a coma. As this test checks reflexes that require a functioning brainstem, the absence of these reflexes can suggest a potential issue in the brainstem itself.
And then, if there are problems like chronic hearing loss or a condition named Meniere’s disease (characterized by dizziness, hearing loss, and ringing in the ear), caloric testing can actually help evaluate how well the cochlea – the hearing part of the inner ear – is functioning.
When a Person Should Avoid Caloric Testing
Medicines that can change the way the balance system in your body works should not be taken two days before undergoing a type of ear test called caloric testing. This balance system is known as the vestibular system.
Several medicines can affect your balance system and may change the results of caloric testing. Here’s how they may alter the results:
* Antihistamines, often used for allergies, can make you feel tired and dizzy.
* Tricyclic antidepressants, a kind of medication for depression, can lead to problems with your balance.
* Antipsychotics, which are used to manage mental health issues, can cause a condition called tardive dyskinesia that affects the balance system.
* Narcotics (strong painkillers) can cause feelings of dizziness and sleepiness.
* Diuretics, medicines that help the body get rid of excess water, can result in dehydration, causing dizziness again.
Equipment used for Caloric Testing
A water caloric irrigation system is a type of testing equipment that uses water at different temperatures to help diagnose problems with balance and dizziness. This system includes two baths, each containing 250 milliliters of distilled water. One bath is heated to 44 degrees Celsius (about 111 degrees Fahrenheit), and the other bath is heated to 30 degrees Celsius (about 86 degrees Fahrenheit).
Some other equipment used in the test includes:
- A catch basin, which is a container used to hold and collect the water. It can hold up to 250 milliliters of water.
- An emesis basin, which is a shallow dish that you can use if you feel the need to vomit, as this test can sometimes cause nausea.
- A stopwatch, which is used to time different parts of the test.
- A dry towel, for you to dry off after the test.
- Optional equipment: Electro-oculography or video-oculography. These are fancy words for types of eye tracking systems. They are used to monitor eye movements during the test, as changes in eye movement can indicate whether the test is working properly.
Who is needed to perform Caloric Testing?
The treatment usually involves the main doctor carrying out a test known as the caloric test. This test is used to check how your inner ear and brain respond to changes in temperature. Additionally, one or two other members of the healthcare team are usually required to help with important jobs. These tasks include holding a container (catch basin) where any fluids or materials can be collected, operating a stopwatch to keep track of time, and managing a dry towel. These assistants are there to ensure everything runs smoothly and safely during your test.
Preparing for Caloric Testing
When doctors look inside your ears with a special tool called an otoscope, they are checking to make sure there is nothing blocking the ear or causing any problems, such as an infection or a buildup of earwax (also known as cerumen). During the check-up, your head will be slightly raised at about a 30-degree angle. This helps to properly position a part of your inner ear, known as the horizontal semicircular canal. A catch basin is put under your ear to capture any fluid during the treatment.
In some situations, the doctor might use an electrode or a special pair of goggles to observe your eye movements — these movements can tell them a lot about how well your ears are working! During this part of the test, you’ll be asked to do a simple task that keeps you alert, like counting backwards from seven, naming different animals, or saying words that all start with the same letter.
How is Caloric Testing performed
The procedure we’re discussing is a type of ear test which uses temperature-controlled water. This test will help detect any problems in the balance system of your inner ear, which might be causing symptoms like dizziness or spinning sensations. For this test, we use a careful method to ensure your comfort and accurate results. Let’s break it down.
Firstly, we’ll gently pour a warm water solution into your ear, which might be causing issues. This is done over a period of 25 to 30 seconds using a free-flow system that allows any excess water to safely drain out from your ear into a small basin. After around 30 seconds from the start of this process, your eyes might start to make small rhythmic movements called nystagmus. You might also be asked to do certain small tasks to ensure these movements aren’t reduced or suppressed.
We’ll then wait for about 5 minutes before repeating the process with your other ear. In some cases, we might have to use cool water instead of warm water. If there’s no response to either warm or cool water, we might choose to use ice water. If we do, you’ll be asked to lay in a semi-upright position with the affected ear facing up. You’ll then experience a brief, 2 milliliter injection of ice water into your ear. After half a minute, you’ll turn your head back to a normal position, while we monitor your eyes as you do some simple tasks.
To conduct this test accurately and methodically, remember the acronym WARMCOLD:
- W – Warm and A – Alternate: The warm and then cold stimuli are introduced to your ear to stimulate your balance system and induce these rhythmic eye movements, nystagmus.
- R – Return: We’ll introduce the warm/cold stimuli again to get the same effect as before.
- M – Measure and C – Compare: We’ll keep a check on these eye movements and compare them to what’s normally expected, allowing us to see how your inner ear is functioning.
- O – Observe: We’ll watch for any spontaneous or position-induced nystagmus, as they can be an indicator of central nervous system issues.
- L – Look: We’ll also look out for any other symptoms that you might be experiencing, such as spinning sensation, dizziness, feeling sick or ringing in the ears.
- D – Document: All our observations and measurements during the test will be recorded, and compared with normal parameters to assess the health and function of your inner ear and balance system.
To remember the pattern of eye movements in response to temperature changes, remember COWS: Cold water will cause eye movements in the Opposite direction, while Warm water causes eye movements in the Same direction.
Possible Complications of Caloric Testing
Caloric testing, a procedure used to check your inner ear and brain activity, generally has side effects that are mild and don’t last long. Just after the test, some patients might feel some fullness or pressure in the ear, and may feel a bit dizzy or off balance. But don’t worry: these feelings usually disappear within minutes after the test is done. In very rare cases, some people might feel more serious effects like intense dizziness, nausea, or even vomiting. However, it’s uncommon for people to have any long-term problems after caloric testing.
What Else Should I Know About Caloric Testing?
Caloric testing is a special technique used to figure out the cause of dizziness. It helps doctors identify whether the problem causing the dizziness is in the brain (central) or in the ears (peripheral), which contain our balance system called the vestibular system. To do this test, doctors typically use a warm substance. This approach works best in patients who are unlikely to have a problem in their ear.
However, this method doesn’t always accurately reveal ear-related problems. So, for patients who are highly suspected to have an ear-related issue, doctors use a method called bithermic testing, which involves the use of both a warm and a cold substance.
Even though a warm substance is commonly used, testing with warm air can also be highly accurate in finding weakness in the ear’s balance system. That being said, a cold substance can cause a stronger reaction and make it easier for doctors to spot an issue in the ear.
For patients who cannot undergo air or water testing due to certain ear conditions like chronic ear infection or eardrum perforations, a method using a near-infrared radiation can serve as an effective alternative for the caloric test.