The mechanism of the formation of vestibulo-cerebello-ophthalmic reactions and vestibulo-cerebellospinal reactions in caloric tests. Theoretical foundations of the Fitzgerald-Hallpike bi-thermal caloric test and the Torok monothermal caloric test. The phenomenon of the symmetrical directional predominance - theoretical foundations. A new theory of caloric stimulations.
As it is known from the history of the research over the equilibrium system, the first researcher who discovered the involuntary eye movement during the rotation of the chair was Purkinje. The researcher was convinced that the brain was directly irritated during the rotations. Similarly, in 1853 Brown Sequard was the first who emphasized that rinsing an ear with cold water could result in nystagmus. In this case the researcher also claimed that the caused pathological eye movements result from the direct irritation of the central nervous system with a thermal stimulus. Then in 1881 the Hungarian physiologist Endre Högyes recognized that, as a result of the caloric stimulation, the labyrinth is the irritated organ. Additionally, the researcher proved that the center controlling the mechanism of the formation of nystagmus was located in the part of the brain between the entrance of the auditory nerve to the medulla oblongata and quadrigeminal bodies and removing other part of the brain does not exert any significant influence on the course of this reflex. He practically proved that the activity of one labyrinth affects the second labyrinth and they counteract. A huge development of research with the use of the caloric stimulus is credited to Robert Barany (1). His name must be associated with the origin of the clinical otoneurology. The researcher claimed that despite the pioneer discoveries which were made earlier, it was not possible to properly understand the observed phenomena because there was no true method of unilateral investigation of the activity of the vestibular apparatus. Such methods had been used for some time in reference to other sensory organs, also appearing in pairs (e.g. the sight, the hearing). The method of caloric stimulation of the vestibular apparatus which was discovered by Barany was the first, according to him, which brings some light in the darkness. The theory of thermal convection developed by Barany was his greatest scientific achievement and it is still current. According to this theory heating or cooling the interior of the external auditory meatus causes shifting the caloric stimulus as a result of thermal convection on the fluids of the inner ear, forcing the endolymph movement in semi-circular canals, and its direction depends on the character of the stimulus (warm or cold) and the position of the canal during the test. In order for the caloric stimulus to be able to cause the vestibulo-cerebello-ophthalmic reflex and the vestibulo-cerebellospinal reflex, its temperature must be higher or lower from the body temperature. Another condition which must be fulfilled is that the semi-circular horizontal canal should be situated vertically to the ampulla situated at the top, thanks to which we obtain the compatibility of the plane of the canal with the vector of the gravitational force. Such an optimum for the examination with the caloric stimulus is obtained when the examined person is in the sitting position with the head bent down by 30° to the chest or in the sitting position with the head leaned backwards by the angle of 60°. The warm stimulus causes heating of endolymph and its movement up towards the ampulla (the ampulopetal movement), and the cold stimulus causes cooling of endolymph and its movement down towards the canal (the ampulofugal movement). The reaction on the thermal stimulus does not appear in the zero-gravity conditions (2). The reaction on the caloric stimulus under earthly conditions will not appear, either, provided that the horizontal canal is put in the horizontal position, i.e. at an angle of 90° to the vector of the gravitational force. It must be mentioned that a stream of warm or cold air can be also used for investigating the excitability of labyrinths. Both the water caloric stimulus and the aerial caloric stimulus are not physiological stimuli, but they allow stimulating every labyrinth separately. In the otoneurological diagnostics the most widely used test is the Fitzgerald-Hallpike bi-thermal caloric test (3,4) with the use of hot water with the temperature of 44°C and cold water with the temperature of 30°C. So, the warm stimulus is higher on average by 7° than the body temperature and the cold stimulus is lower by about 7° than the body temperature. Both the authors of this test and most researchers (5,6) showed that the cold water stimulus caused stronger vestibular reactions. The duration of the nystagmus reaction after the warm stimulus is 100 seconds, after the cold stimulus it is about 120 seconds. So far no one has introduced the theoretical foundations explaining these observations. By means of the Fitzgerald-Hallpike test we can evaluate such reaction types as the symmetrical response, the canal paresis, the canal paralysis, the symmetrical directional predominance and the real directional predominance associated with the canal paresis. As I mentioned earlier, both crests of the ampullae possess a spontaneous resting bioelectric activity. This constant impulsation, which Ewald called the labyrinthine tension, is transmitted to eye muscles and other somatic muscles, yet not directly but through the cerebellar hemispheres. In physiological conditions this resting stimulation coming from the labyrinths to the cerebellar hemispheres causes the eyeballs to be in the intermediate position and the upper limbs outstretched forward with closed eyes to remain still, without going separate ways. To date, the mechanism of stimulation with a thermal stimulus has been universally interpreted in scientific articles and manuals. Let me quote here the chapter distribution "Thermal tests" by Grzegorz Janczewski and Stanisław Bień (7) in the clinical textbook "Otoneurology" edited by Grzegorz Janczewski, whom I have often been referred to in the reviews of my papers. I was instructed I should not take so much effort because it all had been explained in the above mentioned textbook. So, the authors explain in the textbook - quotation: "In a typical position for the Fitzgerald-Hallpike test, where the examined person lies on his/her back with his/her the head bent down by 30° to the chest, the horizontal semi-circular canal is put vertically and the ampulla of the canal is at the top. The endolymph movement upwards (the ampulopetal movement) pulls the cupula towards the utricle, which results in a significant increase in the bioelectric activity of the receptor cells situated in the cupula organ. It results in an advantage of the stimulated canal over the opposite canal, paired with it. The horizontal nystagmus, caused as a result of this asymmetry, is directed with the quick phase towards the stimulated labyrinth. In the case of "the cold test" the endolymph movement downwards (the ampulofugal movement) pulls the cupula away from the utricle, which reduces the bioelectric potential of this canal to lower values than the values in the opposite canal, which was not irritated. In this situation nystagmus induced with a "cold" stimulus is directed with the quick phase opposite to the irritated labyrinth. It can be said that in fact the "warm" test directly irritates the labyrinth on the same side enlarging its bioelectric potential whereas the "cold" test, by reducing the values of the bioelectric potential cooled indirectly, results in an advantage of the opposite vestibular system".
The explanation of the mechanism of stimulation of the labyrinth by means of the cold water test, is based in this case on LeDoux's theory. I proved earlier, presenting the mechanism of stimulations of vestibules in kinetic tests, that this theory was false. What is then the mechanism of the stimulation of labyrinths by means of caloric stimuli according to the new Nakiela theory, which was for the first time introduced in the habilitation lecture on 20 November 1990? This theory is based on the principles of operation of the vestibulocerebellar system which was deciphered by the author of the new theory. If in a typical patient's position for the caloric test, i.e. in the position on the with the head bent down by 30° to the chest, we apply a warm stimulus of 44 °C to the right ear (according to the Fitzgerald-Hallpike test), we will cause the effect of heating the endolymph and its movement up towards the ampulla. It causes bending of kinocillium towards the utricle and an increase in the potential of the irritated labyrinth which is transmitted by the vestibular nuclei complex on the right to the left cerebellar hemisphere, causing its stimulation, which is symbolically marked with a bigger plus sign (fig. 1)
).
Fig. 1
Fig. 1 The diagram of formation of vestibulo-cerebello-ophthalmic reflexes and vestibulo-cerebellospinal reflexes after stimulation of the right labyrinth with water with the temperature of 44° in the Fitzgerald-Hallpike test.
Bioelectric impulses from the left cerebellar hemisphere return to the vestibular nuclei complex on the right, and then via the ascending tract through the medial longitudinal bundle are directed to motor nuclei of cranial nerves III, IV and VI, supporting the external eye muscles, causing nystagmus right with a suitable vector of power directed right. Simultaneously, from the right vestibular nuclei complex the bioelectric potential is transmitted to the spinal cord by means of the lateral and medial vestibulospinal track. The vestibulo-cerebellospinal reflex causes on that side adduction of the right upper limb. In the physiological conditions of kinetic stimulations, if the left cerebellar hemisphere is stimulated, the right hemisphere is inhibited and the vectors of vestibulo-cerebello-ophthalmic reflexes act in the same direction. The direction of vestibulo-cerebellospinal reflexes is realized in the direction opposite to the vestibulo-cerebello-ophthalmic reflexes. In this instance presented on figure 1 we face a different situation. Vestibulo-cerebello-ophthalmic reflexes and vestibulo-cerebellospinal reflexes resulting from stimulation of the right labyrinth with a warm stimulus and reflexes resulting from the resting activity of the left labyrinth act in the opposed directions. So, this caloric stimulus used for the right ear is not a physiological stimulus. The direction of the vector of the power arising after stimulation with a warm stimulus of the right labyrinth was marked with the full line above the left cerebellar hemisphere. Simultaneously, we see that the left labyrinth is in a state of the resting activity, constant stimuli from the left labyrinth flow through the vestibular nuclei complex to the right cerebellar hemisphere causing its stimulation. The activity of the left labyrinth was marked with a dashed line in the right cerebellar hemisphere with a smaller plus sign and a weaker vector of the power acting to the left (marked also with the dashed line over the right cerebellar hemisphere). The evoked stimulus from the right cerebellar hemisphere returns to the vestibular nuclei complex on the left and then via the ascending tract through the medial longitudinal bundle to the motor nuclei of cranial nerves III, IV and VI and it is transmitted via the descending tract to the spinal cord by means of the lateral vestibulospinal track and the vestibulospinal medial track. Then the muscles of adductors of the left upper limb are stimulated. Because the stimulus developed after stimulation of the right labyrinth with a warm stimulus caused a greater reaction than the reaction resulting from the resting activity of the left labyrinth, finally we receive nystagmus directed with the quick phase to the right and the right upper limb is adducted. The left limb remains in its original position. The abduction of the left limb to the left is prevented by the stimulated right cerebellar hemisphere. Thus, in the course of the stimulation of the labyrinth with a warm (44°C) stimulus we obtain nystagmus directed with the quick phase towards the stimulated labyrinth and the upper limb is adducted on the side of the stimulated labyrinth. An inverse, but a similar image will be obtained by irritating the left labyrinth with hot water (44°C).
Now I will present a diagram of formation of vestibulo-cerebello-ophthalmic reflexes and vestibulo-cerebellospinal reflexes after stimulation of the right labyrinth with a cold (30°C) stimulus in the Fitzgerald-Hallpike bi-thermal caloric test - figure2
.
Fig. 2
Fig.2 The diagram of formation of vestibulo-cerebello-ophthalmic reflexes and vestibulo-cerebellospinal reflexes after stimulation of the right labyrinth with water with the temperature of 30°C in the Fitzgerald-Hallpike test.
In the case of cold water (30°C) used in the right ear, endolymph will be cooled; it will cause its movement downwards, which will result in a deviation of the cupula away from the utricle (the ampulofugal movement). In the right labyrinth there will appear an increase in the negative potential, which is transmitted by the vestibular nuclei complex on the right to the left cerebellar hemisphere causing its inhibition, which was marked with a minus sign in the left cerebellar hemisphere. This potential arisen as a result of the inhibition of the left cerebellar hemisphere is transmitted to the vestibular nuclei complex on the right. From the vestibular nuclei complex, stimuli are then transmitted via the ascending tract by the medial longitudinal bundle to the motor nuclei of cranial nerves III, IV and VI, supporting the external eye muscles causing nystagmus to the left with a suitable vector of power directed to the left, which was marked with an arrow above the left cerebellar hemisphere. Simultaneously, stimuli from the right vestibular nuclei complex are transmitted to the spinal cord by means of the side and medial vestibulospinal track. The arisen vestibulo-cerebellospinal reflex causes the abduction of the right upper limb, which was marked with the dashed line with an arrow. At the same time, resting impulses from the left labyrinth are transmitted by the vestibular nuclei complex on the left to the right cerebellar hemisphere causing its stimulation, which was marked with a plus sign (the dashed line). The stimulation of the right cerebellar hemisphere causes the stimulation of the vestibular nuclei on the left. Stimuli from this complex are transmitted via the ascending tract by the medial longitudinal bundle to the motor nuclei of cranial nerves III, IV and VI, supporting the external eye muscles, causing nystagmus to the left with a suitable vector of power directed to the left, which was marked with an arrow (the dashed line) above the right cerebellar hemisphere. Simultaneously, stimuli from the left vestibular nuclei complex are transmitted to the spinal cord by means of the side and the medial vestibulospinal tract. The vestibulo-cerebellospinal reflex causes the adduction of the left upper limb, which was also marked with the dashed line with an arrow. Therefore, using a cold (30°C) stimulus to the right ear causes nystagmus to the left and deviating of both upper limbs to the right. The vector of power of vestibulo-cerebello-ophthalmic reflexes and vestibule-cerebello-spinal reflexes after stimulation of the right labyrinth with a cold stimulus and the vector of power of reflexes resulting from the resting activity of the left labyrinth act in unison in the same direction. Nystagmus to the left and a deviation of the upper limbs to the right result from stimulations of the right labyrinth with a cold stimulus and the resting activity of the left labyrinth. While using the test with hot water (44°C) in the Fitzgerald-Hallpike bi-thermal caloric test, the obtained nystagmus reactions last on average 100 seconds, however, after using a cold stimulus (30°C) the obtained nystagmus reactions last on average 120 seconds. The explanation of this phenomenon is simple. While using a warm stimulus, the nystagmus reaction arising from the stimulated labyrinth and the nystagmus reaction arising from the resting activity of the labyrinth not stimulated to act in opposite directions. The arisen reaction is a resultant of these powers. However, when using a cold stimulus the vectors of powers of reactions obtained from the stimulated labyrinth and the reaction from the labyrinth not irritated act in the same direction. Therefore the time of the obtained nystagmus reaction is longer than after the warm stimulus. As a proof of these observations I present figure 6 which was introduced in the habilitation lecture
.
18 cm 18 cm
Fig. 6
Fig. 6 Patient (female), M.J., aged 49. The equilibrium system efficient. The pattern of a vestibulo-cerebello-ophthalmic reaction and a vestibulo-cerebellospinal reaction, recorded at the 120 second after finishing the administration of the caloric stimulus in the left ear. UL-100ml -20°C -20" (100ml of water with the temperature of 20°C poured into the ear within 20s).
One can observe nystagmus to the right and a symmetrical deviation of the upper limbs to the left. The reaction results from the stimulation of the left labyrinth with a cold stimulus and a spontaneous resting activity of the right labyrinth.
Therefore, Ewald’s 2nd law, which claims that the ampulopetal flow of endolymph in semi-circular horizontal canals causes a considerably stronger nystagmus reaction than the ampulofugal (intraspinal) flow, in the light of the presented new theory explaining the mechanisms of caloric stimulations, based on the principles of operation of the vestibulocerebellar system, seems to be false. Also, the theory of caloric stimulations according to LeDoux seems to be false.
Symmetrical nystagmus reactions or the canal paralysis in the Fitzgerald-Hallpike bi-thermal caloric test introduce essential information into the assessment of the equilibrium system in the entire otoneurological research. A wider discussion is reuired for the phenomenon of the symmetrical directional predominance of nystagmus reaction which can be found only with the use of the bicaloric test. This phenomenon has not been explained since the bicaloric test was presented (3) nor have its theoretical foundations been introduced. The manner in which this phenomenon has been explained so far in scientific articles or textbooks in otoneurology will be presented based on the explanations by Janczewski et al. (7) - quotation: "Generally, the directional predominance consists in significantly stronger vestibular reactions in one direction - left or right. In spite of the 40 years which have passed since this phenomenon was described for the first time (14), it still remains controversial, both from the theoretical and the practical point of view. On the basis of our own clinical experience we are nearest the interpretation by Jung and Kornhuber (26), which clearly distinguish the so-called symmetrical directional predominance, most frequently associated with the destruction of the central part of the equilibrium organ, from the so-called real directional predominance, coexisting with the weakness or even with the paralysis of the vestibule". In order to explain the phenomenon of the symmetrical directional predominance it is essential to be aware of the foundations of the most important phenomenon in the equilibrium system, i.e. the phenomenon of habituation. The phenomenon of habituation will be discussed in detail in the next chapter. Without knowledge of this issue it is not possible to explain the symmetrical directional predominance. The theoretical foundations of the symmetrical directional predominance were presented for the first time by Nakiela (8) in 1990 in his habilitation lecture during the discussion of principles of operation of the vestibulocerebellar system. I will explain this phenomenon based on fig. 3.
Fig.3
Fig.3 Patient S.M., aged 47. The destruction of the right labyrinth in the course of the Meniere's disease in the period of performed habituation. In the Fitzgerald-Hallpike test the symmetrical directional predominance to the right was found. The Torok caloric test indication: UP-4 , UL-1.0. Position tests revealed nystagmus to the right in the position of the patient on her right side. A spontaneous vestibulo-cerebello-ophthalmic reflex (the position test on the right side) and a spontaneous vestibulo-cerebellospinal reflex (the result of the Nakiela dynamic test) are also marked in this picture.
The patient was admitted to the ward because of strong vertigo of the systemic character, nausea, vomiting, noise in the right ear and weakness of hearing in the right ear. The otoneurological examination found intensive optokinetic nystagmus to the left. The deviation test found a deviation of the left upper limb right, the Unterberger test revealed a rotation to the right, the Nakiela dynamic test - a rotation to the right during the performance of the test with the left lower limb moved forward and the lack of rotation with the right lower limb moved forward during the performance of the test. Electronystagmography (ENG) recorded intensive spontaneous nystagmus to the left with eyes closed. Based on the entire otoneurologic examination the Meniere's disease was diagnosed. The follow-up examination was carried out after three weeks after vertigo appeared. The Unterberger test found laevoversion. The Nakiela test revealed rotations to the left during the performance of the test with the right lower limb moved forward and the lack of rotation with the left lower limb moved forward. Spontaneous nystagmus with eyes open and closed was not found. The position tests in the position on the right side recorded spontaneous nystagmus to the right. The Fitzgerald-Hallpike bi-thermal caloric test found the symmetrical directional predominance to the right. The process of habituation began with the destruction of the right labyrinth. As a result of this process the right cerebellar hemisphere was inhibited, which was symbolically marked with a bigger number of minus signs; however, the left hemisphere was stimulated, which was symbolically marked with a bigger number of plus signs. While using hot water (44°C) to the right ear, there occurs a growth of the bioelectric potential with a plus sign, which is transmitted to the left cerebellar hemisphere. Because the left cerebellar hemisphere is in a state of stimulation, the stimulus coming from the right labyrinth is largely strengthened. Impulses from the left cerebellar hemisphere return to right the vestibular nuclei complex causing nystagmus to the right and adduction of the right upper limb. By using a warm stimulus (44°C) to the left ear we also cause the ampulopetal endolymph flow and a growth the bioelectric potential with a plus sign which is transmitted to the right cerebellar hemisphere. Because the right cerebellar hemisphere is in a state of inhibition, the stimulus coming from the left labyrinth is distinctly inhibited. The impulses are then transmitted to the left vestibular nuclei complex, where they are further directed to the motor nuclei of cranial nerves III, IV and VI, causing nystagmus to the left, and to the spinal cord causing (or not) a deviation of the left upper limb to the right. When using a cold stimulus (30°C) in the Fitzgerald-Hallpike bi-thermal caloric test to the right ear the endolymph is cooled and its ampulofugal flow appears. There appears a growth of the bioelectric potential with a minus sign. The stimulus from the right labyrinth is directed to the left cerebellar hemisphere, which is in a state of stimulation. There appears a process of inhibition of the stimulus. Impulses from the left cerebellar hemisphere are then transmitted to the right vestibular complex. From the vestibular nuclei, impulses are transmitted via the ascending tract to the nuclei of motor cranial nerves III, IV and VI, causing nystagmus to the left and to the spinal cord causing a deviation of the right upper limb right (the abduction of the limb). The left limb also deviates to the right because of the resting activity of the left labyrinth. While using the stimulus with cold water (30°C) to the left ear we cause cooling of the endolymph and its ampulofugal movement. This causes a growth of the biooelectric potential with a minus sign. Impulses from the left labyrinth are transmitted to the right cerebellar hemisphere, which is in a state of inhibition. Stimuli are clearly strengthened in it. Afterwards impulses get to the left vestibular nuclei complex causing nystagmus to the right and the abduction of the left upper limb to the left. The right limb also deviates to the left as a result of the resting activity of the right labyrinth. Summing up the reactions obtained after the warm stimulus from the right ear and the cold stimulus from the left ear, we obtain clearly longer nystagmus reactions than from the warm stimulus from the left ear and the cold stimulus from the right ear. In this way we obtain a symmetrical directional predominance right after the earlier destruction of the right labyrinth in the course of the Meniere's disease. Summing up the reactions obtained from the warm and cold stimulus from the right ear and the left ear we receive similar values within symmetry. In this particular case the symmetrical directional predominance consists in the occurrence of a significantly stronger nystagmus reaction to the right, in a situation when the entire reaction to the warm and cold stimulus in one and the other vestibule are equal. The value of the symmetrical directional predominance in the otoneurological diagnostics has been widely discussed. Because this phenomenon can be found in peripheral and central injuries, her its diagnostic value in injuries of the equilibrium system began to be undermined. That is why Torok (9) proposed a monothermal differential caloric test for the diagnostics of the equilibrium system. In the United States this test gained a quite large popularity (10) because, according to the author, it allows differentiating peripheral and central injuries of the equilibrium system. However, so far the theoretical foundations of the activity of this test have not been provided. The detailed technique how to perform this test was provided in the earlier publications (9, 10, 11). In this test labyrinths are stimulated with water with the same temperature (20°C), but with different quantities of water and different periods of time in which the water is administered. In the weak stimulus 10 ml water is administered with temp. 20°C within 5 seconds, in the stronger stimulus 100 ml water is administered with temp. 20°C within 20 seconds. The recorded nystagmus (after every stimulation) is analyzed in respect of the number of saccadic eye movements in subsequent 5-second periods. The greatest nystagmus activity was found when in two subsequent 5-second periods the highest number of saccadic eye movements is achieved. Kumar (10) reports that for the weaker stimulus in the culmination phase, from 3 to 29 saccadic eye movements are gained, for the stronger stimulus - from 10 to 39 movements. The heart of the matter is to obtain a coefficient calculated by dividing the number of saccadic eye movements obtained in the culmination phase of the stronger stimulus by the number of saccadic eye movements in the culmination phase of the weaker stimulus (standard from 1.2 to 3.5). When the response to the stronger stimulus is disproportionately bigger than to the weaker stimulus, there appears a phenomenon called "vestibular recruitment", and the indicator then exceeds the value of 3.5. Sometimes the response to the stronger stimulus is equal to or lower than the response to the weaker stimulus, when the indicator is equal 1.1 or smaller. Torok calls this phenomenon "vestibular decruitment". According to the author (12, 13), this "vestibular decruitment" has a large significance in the diagnostics of central injuries. Kumar et al. (14), Nakiela (15) frequently found "vestibular decruitment" in injuries of the cerebellar hemispheres. I will explain the phenomena appearing in the Torok test based on fig. No. 3, which was the basis for I explanation of the symmetrical directional predominance. After using the weak stimulus to the right ear in the nystagmus reaction in the culmination phase 5 saccadic eye movements were obtained and after using the strong stimulus 20 saccadic eye movement were obtained, therefore the ratio is -4. However, after using the weak stimulus to the left ear in the culmination phase 23 saccadic eye movements were obtained and after using the strong stimulus also 23 saccadic eye movements. In the right ear the ratio "4" was obtained, which we call the phenomenon of "vestibular recruitment" and which, according to the author of the test, is supposed to be a proof of the peripheral destruction of the labyrinth. There is conformity in this case. However, in the left ear the ratio 1.0 was obtained, which we call the phenomenon of "vestibular decruitment" and which, according to the author of the test, is supposed to be the proof of the central damage. There is no compatibility in this particular case. Why were such coefficients obtained in this case. Using a weak stimulus to the right ear in the right labyrinth causes the ampulofugal endolymph flow. Bioelectric potential arises with the sign "minus" and is transmitted to the left cerebellar hemisphere, which is in the state of stimulation, as we know it. The stimulus which reached this hemisphere is clearly inhibited and therefore it causes such a slight nystagmus reaction to the left. However, the stronger stimulus, despite the fact that the left cerebellar hemisphere is in the position if stimulation is capable of inhibiting it more and we obtain a bigger nystagmus reaction. However, using a weak stimulus to the left ear we cause an endolymph flow in the ampulofugal direction. Bioelectric potential arises with the sign "minus" and it is transmitted to the right cerebellar hemisphere, which is in the inhibitory phase, as we know. This small stimulus which reached this hemisphere is strengthened very much and then it is transmitted to the left vestibular nuclei complex, causing a strong nystagmus reaction to the right. After using a stronger stimulus to the left ear we will cause a bigger bioelectric stimulus which, marked with the sign "minus" travels to the inhibited cerebellar hemisphere. Here, the stimulus is strengthened as well, but the right cerebellar hemisphere cannot be inhibited more. A stronger stimulus no longer causes a stronger reaction. The weak stimulus already caused the maximum inhibition of the right cerebellar hemisphere, using all its capacity and therefore the ratio "1.0" was obtained in this test, which means that the phenomenon of "vestibular decruitment" occurred. In this case we deal with the peripheral destruction and not a central one. From my experience I know that these indicators can be smaller than "1.0", e.g. 0.7; 0,8; 0.9. It all depends on the degree of inhibition of the cerebellar hemisphere in habituation. This example shows that for the diagnostics of the destruction of the equilibrium system the bicaloric test should be used and it is best to use water as a stimulus not air. The monothermal Torok test also has its value in the diagnostics of injuries of the equilibrium system. An especially weak stimulus can indicate to the side of the damaged labyrinth when a distinct asymmetry is obtained after using it, and the indicator on the side of the weaker reaction is often smaller than "3,5". Therefore, in my Laboratory of Research in the Equilibrium System I enhance the Torok test by adding a warm stimulus (44°C) in the quantity of 100 ml, which is administered for 20 seconds. The Nobel Prize winner Robert Barany, while introducing caloric tests into the research of the equilibrium system, was convinced that every labyrinth could be evaluated separately, like one of the paired organs of other senses (the sight, the hearing) had been evaluated earlier. My research clearly shows that we are not in a position to evaluate the excitability of every labyrinth separately. The activity of one labyrinth clearly affects the excitability of the other labyrinth, because both labyrinths are connected on the level of the cerebellum. The vestibulo-cerebellar system is the only so specifically built sense organ in the human body and therefore is was so in available in the recognition of its principles of operation.
Robert Barany's observations concerning vestibulo-cellebrospinal reflexes after using caloric stimuli in healthy people are not fully true, either. The researcher found that after using a warm stimulus there appeared nystagmus towards the irritated labyrinth and a deviation of the upper limbs in the opposite direction to the direction caused by nystagmus. However, when using the cold stimulus, nystagmus is directed in the opposite direction to the irritated labyrinth, and both upper limbs deviate in the opposite direction, i.e. towards the side of the stimulated labyrinth. On the basis of my discoveries it can be concluded that my observations after using the cold stimulus are compatible with Robert Barany's observations. However, my findings after using the warm stimulus are incompatible with the Nobel Prize winner's observations. So, after using the warm stimulus, the nystagmus which arose is directed towards the stimulated labyrinth, however, only the upper limb on the side of the irritated labyrinth deviates towards the free phase of nystagmus, the other upper limb remaining still. These issues were discussed in detail earlier, where the theoretical foundations of vestibulo-cerebello-ophthalmic reflexes and vestibular-cerebellospinal reflexes were introduced for the first time.
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