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 (the maze and semicircular canals), which are responsible for maintaining equilibrium, and in addition, for coordination of movements.
Exposure to the external part of the ear by physical factors (be it cold or heat) leads to reactions of the vestibular apparatus. This is what the so-called calorimetric test is based on. According to the theory of Austrian scientists, the effect of heat on the fluids of the inner ear can cause them to move.
The fact is that the heated endolymph goes up, but 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.
Appointment
A caloric test is carried out with the aim of a comprehensive examination of patients who have impaired vestibular functions. The reason for the appointment of such is dizziness along with vestibulopathy, cochleovestibular syndrome (we are talking about a combination of disorders of vestibular functions with hearing pathologies), Meniere's disease and sensorineural hearing loss. A caloric test with water is included in the list of studies conducted as part of a professional commission.
Contraindications
Since a 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 moderate acute otitis media, as well as for perforations of the tympanic membranes. When visiting a specialist, all pathologies and symptoms that concern the patient should be indicated. Perhaps the examination of the patient will be contraindicated.
Sample preparation
48 hours before the study itself, in no case should you take alcohol with drugs that affect the nervous central system and vestibular apparatus. Consider the progress of the procedure.
Procedure technology
Caloric test is carried out in order to establish the pathology of hearing. 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. A special mask is put on the patient, which is equipped with an eye movement recording system (a miniature video camera operating in the infrared spectrum). Its task is to register the degree of displacement of the eyeballs with the transfer of data to computer terminals. A special program calculates the amplitude of the movement of the visual organs.
Water sample
For thirty seconds, the patient is consistently irrigated with the right and left ear using warm water. Its temperature, as a rule, is forty degrees. Buried fluid in the ear. Five minutes later, cold water is irrigated. Its temperature should not be lower than 30 degrees.
Deciphering the result
The following indicators are evaluated as part of the interpretation:
- The duration of the latent period. In other words, it refers to the time from the beginning of the irrigation process until nystagmus occurs.
- The total duration of nystagmus.
- The frequency of nystagmus movement.
- The magnitude of the average and maximum amplitude of motion.
- The speed of movement of the visual organs during various phases is slow and fast.
- Additionally, a person’s ability to suppress arbitrarily nystagmal movements can be evaluated.
According to the standard, the latent period, as a rule, is from 25 to 30 seconds, the nystagmus lasts about a minute. Shortening of latent periods and nystagmus lasting more than 80 seconds indicates the presence of vestibular increased excitability. 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 schedule of eyeballs. Normally, usually a butterfly-shaped chart comes out. On it, different colors mark the areas in which the eyes would be in 90-94 percent of people.
The detection of asymmetry of caloric nystagmus is of the greatest importance. For peripheral vestibulopathy (the cause is damage to the nerves or receptor apparatus), hyperreflexia with dizziness during a caloric test is typical. Dysrhythmia 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 can affect the reliability of results. In other words, nystagmus may simply not be caused. How to be in this situation? An alternative research technique is the cold monothermal test according to Blagoveshchenskaya.
Procedure Method
As part of the caloric test, the following is done:
- The doctor should find out from the patient if he had diseases in the middle ear. If so, then an otoscopy is required. In the absence of perforation in the eardrum, you can proceed to the caloric test.
- Calorization can be carried out with cold water at a temperature of from 19 to 24 degrees or a warm liquid. At the same time, the doctor draws 100 milliliters of water into the syringe.
- The patient sits down, and his head leans back sixty degrees. In this position, the semicircular horizontal channel is located directly in the frontal plane. In this case, its ampoule is located on top.
- Within ten seconds, 100 milliliters of water is poured into the external right ear canal, a stream is directed along the upper back wall.
- The doctor determines the time from the end of the fluid injection into the ear, until the onset of nystagmus. Normally, such a period is 25-30 seconds.
- The patient is asked to fix his gaze on any fixed object (whether it is a pen along with the doctor’s finger, etc.), which is installed first on the left at the eye level, at a distance of 50-60 centimeters, and then right in front of the visual organs and to the right.
- The doctor determines nystagmus on the plane, as well as by criteria such as direction, strength, amplitude, frequency and duration. Normally, the duration of nystagmus is up to 70 seconds (with cold calorization).
- Twenty minutes later, they usually begin to calorize the left ear.
- A caloric test on the left is carried out in the same way as it is done on the right side.
- After the introduction of fluid, the patient fixes his gaze to the right.
- Twenty minutes later, doctors begin to perform a caloric test with warm water, nystagmus is directed toward the organ under investigation, and the severity of its parameters will normally be slightly less.
Normally, when the vestibular analyzer is irritated with cold water, nystagmus is directed in the opposite direction from the element being examined, and when using hot fluid 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, i.e., hyperreflexia, and a decrease in the duration indicates a decrease in excitability. This is hyporeflexia.