The calorimetric test is related to vestibulometric tests, which allow a more objective study of dysfunction of the vestibulocochlear apparatus. We are talking about the structures of the inner ear (about the labyrinth and semicircular canals), which are responsible for maintaining balance, and in addition, for the coordination of movements.
Influences on the outer part of the ear by physical factors (be it cold or heat) lead to reactions of the vestibular apparatus. This is the basis of the so-called calorimetric test. According to the theory of Austrian scientists, exposure to heat on the fluids of the inner ear can cause them to move.
The fact is that the heated endolymph goes up, and directly cooled down. This leads to irritation of all vestibular receptors. In turn, the response consists in the appearance of involuntary eye twitching, that is, thermal nystagmus.
Destination
The caloric test is carried out for the purpose of a comprehensiveexamination of patients with impaired vestibular functions. The basis for the appointment of such are dizziness along with vestibulopathy, cochleovestibular syndrome (we are talking about a combination of vestibular dysfunction with hearing pathologies), Meniere's disease and sensorineural hearing loss. A caloric test with water is included in the list of studies carried out within the framework of a professional commission.
Contraindications
Since the caloric test is a study of hearing impairment, the test is not performed for inflammatory diseases of the middle ear, for example, in the presence of acute otitis media, as well as perforations of the eardrums. When visiting a specialist, you should indicate all the pathologies and symptoms that bother the patient. It is possible that the examination of the patient will be contraindicated.
Preparing for the test
For 48 hours before the study, in no case should you take alcohol with drugs that affect the nervous central system and the vestibular apparatus. Consider the course of the procedure.
Procedure technology
A caloric test is performed to establish hearing pathology. For its implementation, the patient must take a reclining position. In this case, the head should be located along the axis of the body with an inclination of thirty degrees to the horizontal. The patient is put on a special mask, which is equipped with an eye movement recording system (a miniature video camera operating in the infrared spectrum). Its task is to registerdegree of displacement of the eyeballs with data transmission to computer terminals. A special program calculates the amplitude of movement of the visual organs.
Water test
For thirty seconds, the patient's right and left ears are successively irrigated with warm water. Its temperature, as a rule, is forty degrees. The liquid is instilled into the ear. After five minutes, irrigation with cold water is performed. Its temperature should not be below 30 degrees.
Deciphering the result
As part of the interpretation, the following indicators are evaluated:
- The duration of the latent period. In other words, it refers to the time from the beginning of the irrigation process to the onset of nystagmus.
- Total duration of nystagmus.
- Frequency of nystagmus movement.
- The value of the average and maximum range of motion.
- The speed of movement of the visual organs during various phases - slow and fast.
- Additionally, a person's ability to suppress voluntary nystagmus movements can be assessed.
According to the standard, the latency period, as a rule, is from 25 to 30 seconds, nystagmus lasts about a minute. Shortening of latent periods and nystagmus lasting more than 80 seconds indicates the presence of vestibular hyperexcitability. An increase in the latent period to 50 seconds with a shortening of nystagmus indicates a decrease in vestibular excitability.
In addition to such simple indicators, a special program builds a traffic scheduleeyeballs. Normally, a butterfly-shaped diagram usually comes out. On it, different colors mark the areas in which the eyes of 90-94 percent of people would be.
The detection of asymmetry of caloric nystagmus is of the greatest importance. For peripheral vestibulopathy (the cause is damage to the nerves or the receptor apparatus), hyperreflexia with dizziness during a caloric test is typical. Dysrhythmicity with tonic (convulsive) nystagmus speaks in favor of central vestibulopathy, in which the lesions are located directly in the cerebellum or in the region of the central brain.
Additional information
Complications as a result of a caloric test, as a rule, do not arise. Exophthalmos may affect the reliability of the results. In other words, nystagmus may simply not be called. How to be in such a situation? An alternative research technique is a cold monothermal test along Blagoveshchenskaya.
Method of the procedure
As part of the caloric test, the following is done:
- The doctor should find out from the patient if he had any diseases in the middle ear. If yes, then an otoscopy is required. Provided there is no perforation in the eardrums, you can proceed to the caloric test.
- Calorification can be carried out with cold water at a temperature of 19 to 24 degrees or with warm liquid. The doctor draws 100 milliliters of water into the syringe.
- The patient sits down, and his head deviatesback sixty degrees. In this position, the semicircular horizontal canal is located directly in the frontal plane. At the same time, its ampoule is located on top.
- For ten seconds, 100 milliliters of water is poured into the external right auditory meatus, a jet is directed along the back upper wall.
- The doctor determines the time from the end of fluid injection into the ear, until the onset of nystagmus. Normally, this period is 25-30 seconds.
- The patient is asked to fix his gaze on some immovable object (be it a pen along with the doctor's finger, and so on), which is first placed on the left at the eye level, at a distance of 50-60 centimeters, and then right in front of the visual organs and right.
- The doctor determines nystagmus along the plane, as well as according to such criteria as direction, strength, amplitude, frequency and duration. Normally, the duration of nystagmus is up to 70 seconds (with cold calorization).
- After twenty minutes, they usually start calorizing the left ear.
- The caloric test on the left is carried out in the same way as it is done on the right side.
- After the fluid is injected, the patient fixes his gaze to the right.
- Twenty minutes later, doctors begin to perform a caloric test with warm water, nystagmus is directed towards the organ under study, and the severity of its parameters will normally be somewhat less.
Normal with irritation of the vestibularanalyzer using cold water, nystagmus is directed in the direction opposite to the element being examined, and when using hot liquid, in the same area. An increase in the duration of caloric nystagmus and a parallel reduction in the latent stage indicates an increase in the excitability of the labyrinth, that is, hyperreflexia, and a decrease in duration indicates a decrease in excitability. This is already hyporeflexia.
