EP2398377A1

EP2398377A1 - Head impulse testing device for assessing the functionality of the semicircular canals and for the rehabilitation of vestibular loss

Info

Publication number: EP2398377A1
Application number: EP09776350A
Authority: EP
Inventors: Stefano Ramat; Marco Mandala'
Original assignee: Universita degli Studi di Pavia
Current assignee: Universita degli Studi di Pavia
Priority date: 2009-01-30
Filing date: 2009-01-30
Publication date: 2011-12-28
Also published as: WO2010085977A1; WO2010085977A8

Abstract

The present invention concerns a system as well as a method for the evaluation of the vestibular functionality in a subject. The system comprises a display unit for showing a visual target such as an optotype to the patient, a device for measuring rotational acceleration that rotates integrally with the patient's head, and a recording unit. The method of the invention may also be suitably used for the rehabilitation of the peripheral vestibular functionality.

Description

DESCRIPTION

HE_AD IMPULSE TESTING DEVICE FOR ASSESSING THE

FUNCTIONALITY OF THE SEMICIRCULAR CANALS AND FOR THE

REHABILITATION OF VESTIBULAR LOSS The present invention pertains to the field of medicine and, in particular, it concerns a system as well as a method for the evaluation of the vestibular functionality in a subject. The method of the invention may also be suitably used for the rehabilitation of the peripheral vestibular functionality. BACKGROUND

Peripheral vestibular pathologies may frequently cause an alteration in the efficiency of the vestibular apparatus. Ethiology may be very different; for instance, infection may cause vestibular neuritis, which may be treated pharmacologically leading to a complete or sometimes partial functional recovery. Benign paroxismal positional vertigo (BPPV) represents a peripheral vertigo syndrome characterized by paroxismal vertigo attacks which are triggered by specific movements of the heads and may last few seconds. It may also occur in case of rapid and sudden movements of the head. Another common pathology is the Meniere's disease, which is caused by an increase in the quantity of endolympha, i.e. the liquid medium wherein both labyrinthine and cochlear receptors are immersed. The symptoms include rotatory vertigo which may have a duration of few hours . Pharmacological treatment may be useful for reducing the sensitivity of the vestibular hair cells, which often result in at least a partial loss, when not even complete. In some patients that do not respond to pharmaceutical treatment, the surgical resection of the vestibular nerve of the affected ear is the only intervention possible.

Labyrinthine or perilymphatic fistula defines an anomalous communication between perilymphatic space in the internal ear and the medium ear, due to a defect of the bone labyrinth or to a lesion in the "labyrinthine windows" .

Chronic patients may unconsciously learn or acquire an autonomous mechanism, which compensates the loss of the vestibular functionality; said mechanism may be so efficient that both the diagnosis and the evaluation of the residual vestibular efficiency become so difficult that even an experienced physician could not recognise it . In spite of that, studies on patients have shown that elevated rotational accelerations toward the same side of the lesion might cause visual impairment or even instability, which could prejudice some daily activities. Halmagyi et Curthoys disclosed in 1988 the "head impulse test", which allows to identify the complete loss of the peripheral vestibular function (see, as a general reference, Halmagyi GM, Curthoys IS. A clinical sign of canal paresis. Arch Neurol. 1988;45:737-739) . When performing the "head impulse test" , the clinician stands in front of the patient and asks to fixate a target, for instance, their nose, while they suddenly rotate the head of the patient in one of the planes of the semicircular canals pairs.

Said rotation may achieve angular accelerations of thousands of degrees per square second. An expert physician could detect a refixation saccade, which denotes a rapid and fast movement of the eyes in the direction opposite to head rotation, indicating that a deficit, i.e. a loss of peripheral vestibular functionality, occurred with respect to the same side of the rotation. The identification of a vestibular loss or hypofunctionality becomes difficult due to the extreme adaptability of the vestibular and of the ocular motor system, which are able to rapidly learn how to compensate, through adaptive mechanisms or substitution, for the loss of information about the orientation and/or rotation of the head, which is normally activated when semicircular canals are damaged.

The functional role of the semicircular canals has been investigated by Ewald in 1892 through experiments on the production of endolymphatic currents in the labyrinthine membranes. Ewald' s laws have then been formulated, of which the second law, in particular, concerns the horizontal semicircular canals, wherein the ampullopetal excitation, i.e. the excitation towards the utricle or the ampullae, is higher than the ampullofugal eccitation, i.e. the one in the opposite direction.

The "head impulse test" is based on said second law of Ewald and allows to identify a pathological state even when adapting processes have occurred. However, further examinations are required in order to evaluate the functional damages and the resulting functional limits caused. While it has been conceived in order to investigate the functionality of the horizontal semicircular canals, it has then been applied to the other semicircular canal pairs as well.

SUMMARY OF THE INVENTION

It has now been developed an apparatus and a method which allow to identify and evaluate the functionality of a single semicircular canal in a subject, as defined in the appended claims, whose definitions are integral part of the present description. The present method has an improved sensitivity with respect to the methods known in the art, in that it allows a more precise diagnosis or evaluation of the vestibular functionality.

OBJECT OF THE INVENTION As a first embodiment, the present invention relates to an apparatus for the evaluation and/or rehabilitation of the peripheral vestibular functionality.

In a second embodiment, the invention relates to a test method for the diagnosis of the loss in the peripheral vestibular functionality of each single semicircular canal .

As a third embodiment, the method of the present invention may be used for the rehabilitation of the peripheral vestibular functionality. BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 shows the structure of the vestibular apparatus; in particular, the three semicircular canals (SCC) , the ampullae and the utricle are indicated.

Fig. 2 shows a flow-chart summing up the method of the present invention.

FIG. 3 shows the embodiment of the invention relating to the diagnosis of the peripheral vestibular functionality loss.

FIG. 4 shows the embodiment of the invention relating to the rehabilitation of the peripheral vestibular functionality.

FIG. 5 and 6 show two examples of graphic output, which can be obtained from the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the present invention and unless otherwise provided, semicircular canal relates to each one of the three single semicircular canals of each vestibular labyrinth (also abbreviated as SCC) : horizontal, superior and posterior. Semicircular canals are provided symmetrically at both sides of the head and, in particular, each of them lies on the same plane of the corresponding opposite canal . "Angular acceleration" is defined as the rate of change in angular velocity over time and it may be expressed as degrees or radians per squared second (°/s² or rad/s²) . "Passive movements" relate to the movements imposed to the patient's head by the clinician, for instance, bringing the patient's head between hands posed on the temporal-parietal skull bones and turning the head to some extents to the left or to the right around its vertical axis. Accordingly, the patient cannot predict direction, speed nor the angle of the rotation determined by said motion.

"Active rotation" refers to the movement made actively by the patients themselves by rotating the head.

"Loss" is to be intended as the complete loss of the sensitivity of one SCC, which leads to the patient being completely deprived of the vestibular rotational information and thus to the inability to properly stabilize gaze in space and to the impairment of balance.

"Hypofunctionality or deficit", instead, relates to any little or severe damage to the gaze stabilization and balance systems caused by deficit in the vestibular apparatus. Damages may occur because of infections, inflammatory events, pathologies, pharmacologic treatment side-effect, accidents or even traumas .

The "optotypic line" refers to an array of letters on an optotypic chart used for assessing the visual acuity of a patient, such as the Snellen chart, the E

Chart, the Landolt C chart or the Golovin-Sivtsev chart (for a general reference, see, for instance,

Ricci F. Cerulli L. : "Standardizzazione dei criteri di valutazione dell'acutezza visiva" . Atti I;

Congresso Societa Italiana Medicina Legale

Oculisticas, pag 35-51 Mattioli Ed. 1994) .

"Visual target" refers to any images, such as drawings, symbols, numbers or letters of different sizes, which the patient is required to recognise and read.

A "Sloan's letter" refers to a visual target selected among the capital letters S, O, C, D, K, V, R, H, N or Z. "Rotational angle" is defined as the angle lying on the traverse plane and comprised between the position of a fixed point of the patient's head at the starting position and the position of the same point achieved after the rotation has been imposed. Said angle may be expressed in degrees or in radians. When rotational movements are manually produced, a certain degree of error may occur, such as, for instance ±5° with respect to the rotational angle declared.

As per the first embodiment of the invention, there is provided an apparatus for the evaluation of the peripheral vestibular functionality of a patient. In particular, said apparatus comprises: - a displaying unit (1) ;

- a rotational acceleration measuring unit (2) ; and

- a recording unit (3) .

The display unit (1) , showing the letter to be recognised by the patient, is placed at a suitable distance, for instance 50 centimeters, in front of the patient, according to standard clinical procedures .

The display unit (1) may be any means suitable for showing a visual target for a period of time in the order of few milliseconds. For instance, it can be a screen on which the visual targets are displayed or projected or it may be a computer monitor.

In a preferred non limiting example, a computer software may govern the selection of the visual target to be displayed, which will be among those above disclosed.

The rotational acceleration measuring unit (2) is any device capable of measuring the angular acceleration, in particular, determined by the rotation imparted to the patient's head by the clinician. Accordingly, a gyroscope or two accelerometers may be used, which provide the advantage of being easy to handle. The rotational acceleration measuring unit (2) shall be placed in such a way that it rotates integrally with the patient's head, so that they move together. For instance, a helmet may be provided wherein the gyroscope (see, for instance, FIG. 3) or the two accelerometers are fixed thereto. In the case of the accelerometers, they need to be placed on opposite sides of the axis of the rotation (e.g. one on the forehead and the other one on the nape to measure angular accelerations in the horizontal plane) . The measured value of angular acceleration may be acquired by the device itself or, in an alternative embodiment, said unit (2) may be connected to a recording unit (3) directly, which is capable of recording and storing the rotational acceleration data introduced or directly acquired form the unit (2) . In a preferred embodiment, the recording unit (3) may be a computer software.

The recording unit (3) is also able to record the response of the patient. In fact, once the patient has read and recognised the letter shown, they will communicate it to the clinician, who will introduce said result into the recording unit (3) . Alternatively, the patient themselves may introduce the response into the unit (2) , for instance, with the use of a keyboard in the preferred embodiment, wherein the recording unit (3) is a computer software .

Optionally, the apparatus of the invention may further include an analysing unit (4) . Said analysing unit is connected to the recording unit (3) , so that it can acquire the data on patient's responses to be analysed, and may be connected to the measuring unit

(2) or to the recording unit (3) in order to acquire data on the rotational acceleration value achieved.

In a preferred embodiment, the recording unit (3) and the analysing (4) unit may be represented by a computer software.

The analysing unit (4) is also connected to the displaying unit (1) , so that it receives information on the letter shown and compares it to the response given by the patient. In particular, when they do correspond, the patient's response will be correct or positive, otherwise it will be wrong or null. The analysis unit (4) is able to analyse the results collected about rotational acceleration and patient's response in each set of experiments and to provide an output, which may be in any suitable forms, such as, signals, tables or graphs, like column graph, wherein the x and y axes report, for instance, the value of rotational acceleration and the frequency of positive results, respectively.

Accordingly, the trend in frequency of positive results when rotational acceleration increases would thus become evident . In a still further embodiment, the analysing unit (4) may provide an output in the form of signals, visual signal, for instance through the displaying unit (1) or a sound signal, through any suitable means connected thereto, informing, for example, the clinician about the correctness of each response, by comparing the letter shown on the displaying unit (1) and the response of the patient.

In a second embodiment, the present invention concerns a test method, which allows evaluation of the peripheral vestibular functionality. In a particular embodiment, said evaluation is independent from any previous functionality assessment.

In particular, the method of the invention includes the phases of : a) assessing the static visual acuity of the patient; b) evaluating the dynamic vestibular functionality and collecting the data; c) processing the data and providing an output. During phase of the static visual acuity assessment, the patient is required, while sitting or standing, to read the letters, such as 5 letters, of an optotypic line on suitably rescaled optotype chart projected onto the displaying unit (1) placed in front of them, usually at a suitable distance comprised for instance between 30 and 120, preferably 50 centimetres, as shown in Fig. 3.

The assessed static visual acuity of the patient corresponds to the line whose letters are read and recognised. In particular, for said purpose, any optotypic chart may be used, such as those listed above or other chart commonly used in clinical practise. The phase of examination and collection of data includes at least one set of experiments with the aim of evaluating the dynamic visual acuity of the patient.

During said phase, the patient is required to read and recognise a letter shown to them, while the clinician rotates their head imparting a certain rotational acceleration (see, for a general reference, "Principle of the head impulse (thrust) test or Halmagyi head thrust test (HHTT)" F. Wuyts, B-ENT, 2008, 4, Suppl . 8, 23-25). In particular, with reference to Fig. 3, the patient sits or stands in front of a displaying unit (1) at a distance of between about 30 centimetres and about 120 centimetres, preferably being about 50 centimetres, wearing an helmet to which the rotational acceleration measuring unit (2) is attached, so that said unit (2) moves integrally with the patient's head.

During the execution of the test the clinician stands, for instance, behind the patient and poses his hands on the temporal-parietal skull bones. In each experiment the clinician rotates the patient's head to the left or to the right around its vertical axis, thus imposing a certain rotational acceleration. Said acceleration value is measured by the measuring unit (2) and may be recorded by the recording unit (₃) . _When said acceleration reaches or overcomes a threshold value formerly set by the clinician, a Sloan's letter appears on the displaying unit (1) . Said threshold value may for instance determine a 600 degrees/s² range of acceptable head acceleration; for example, it can be set to about 1000 deg/s², thereby defining a bin ranging between about 700 and about 1300 deg/s² in the course of the first set of experiments, while during the subsequent set the head acceleration may achieve about 1.700-2.300 deg/s²

.In particular, with respect to the size of the Sloan's letter shown in said first experiments, this has the size of the letters of the optotypic line immediately superior to the ones read by the patient during the static acuity assessment phase of step a) . For instance, if the patient was able to read the letters of the ninth optotypic line, then during the dynamic test the letters belonging to the eight line, having a larger size, are shown. As for the appearance time of the letter, it may be within 10-30 milliseconds and, preferably, between 15-25 milliseconds from the time when the acceleration of the head reaches the threshold. The patient is required to read and to recognise it and the response is then recorded in the recording unit (3 ) .

The first experiment is thus concluded and is subsequently repeated for a number of times sufficient enough to collect a statistically significant number of results with respect to each direction of head rotation. For example, a number between 10 and 20, such as 15, may provide a sufficient number of data, which, once analysed, give a significant result. In particular, the analysis unit may provide the statistical power of the progressively adjusted ratio of correct answers. Step b) follows with a second set of experiments, wherein, in particular, the same conditions above disclosed apply, the only difference being that an higher rotational acceleration is required to be imposed by the clinician to the patient's head. Thresholds may be generally increased in steps of about 1000 deg/s², up to a value of about 7000 deg/s². The patient is again required to recognise and to indicate the letter shown.

The experiment is repeated until a statistically significant number of results are collected for said higher rotational acceleration value as well. For example, depending on the subject's ability a number between 10 and 20, automatically adjusted by the analysing unit (4) may provide a sufficient number of samples for establishing a directional asymmetry with p values below 0.05.

A third set of experiments may thus be performed, wherein the rotational acceleration of the head of the patient is still increased under the same conditions above disclosed. Within the presently disclosed method, the last set of experiment required for the evaluation of the dynamic vestibular functionality of the patient will be the one wherein the rotational acceleration imposed by the clinician to the head of the patient is so elevated that they are unable to read and recognise the letter shown on the displaying unit (D .

Accordingly, phase c) for the elaboration of the results by the analysing unit (4) follows. In a preferred embodiment, the analysis phase may be performed within a suitable software.

As above disclosed, tables or graphs, such as the ones of FIG. 5 and 6 may be obtained from the results collected during phase b) .

Taking into account the results of the method of the invention, the clinician will be able to evaluate the functional performance of the vestibular system. In particular, diagnosis may be performed with respect to the functionality of the opposed semicircular canal, in case a lesion involved the vestibular apparatus of one side only, or diagnosis may be made by comparing the results of the experiments with standard tables. For instance, for saccadic movements it is possible to define range of normality for the relationships between amplitude and duration or between amplitude and peak velocity on the basis of the main sequence (see, as a general reference "Saccadic palsy after cardiac surgery: characteristics and pathogenesis"; Solomon D, Ramat S, Tomsak RL, Reich SG, Shin RK, Zee DS, Leigh RJ. - Ann Neurol. 2008 Mar; 63 (3) : 355-65) or "Velocity characteristics of normal human saccades" - Boghen D, Troost BT, Daroff RB, Dell'Osso LF, Birkett JE- Invest Ophthalmol. 1974 Aug; 13 (8) :619-23.

For instance, Fig. 5 depicts a column graph showing the trend of the correct trials, i.e. the exact responses given by the patient, at different rotational acceleration both for the left (A) and for the right (B) . The graphs show that the lesion involved the vestibular apparatus of the left side. Fig. 6 shows in a different representation, which may be called a vestibulograms, the data resulting from a test method performed according to the present invention (CW=clockwise; CCW=counterclockwise) In a third object, the present invention relates to a method for the rehabilitation of the peripheral vestibular functionality. In fact, it has been demonstrated that the stimulation of the vestibular- ocular reflex allows the improvement of the vestibular function, in particular, when the stimulation occurs with head movement dynamics that are potentiality close to the actual residual capacity of the patient.

More in particular, the rehabilitation experiment includes the steps of : a) evaluating the peripheral vestibular functionality of the patient; b) performing a set of experiments for the increasing the peripheral vestibular functionality of the patient through gain adaptation experiments tailored to the residual functionality of the patient; c) repeating the set of experiments of step b) for a number of times.

The evaluation of the peripheral vestibular functionality of the patient as per step a) above is performed according to the method of the present invention above disclosed.

In step b) during each rehabilitation experiment the patient is required to actively rotate the head from left to right (see, for instance, FIG. 4) . When the rotational acceleration imparted by said active movements achieves a threshold value set by the clinician or by the patient itself according to the clinician's instructions, a visual target will appear on the displaying unit (1) for as long as the head velocity of the patient stays above the value reached at threshold acceleration. As disclosed above, the patient is again required to read and recognise it . The data concerning the threshold value is set into the analysing unit (4) , which is thus able to govern the displaying of the visual target onto the displaying unit (1) . In particular, said threshold value is 500 deg/s² above the highest acceleration value at which the patient was still able to read and recognise the letter as per the last set of experiments performed for evaluating the dynamic vestibular functionality.

The experiment above disclosed is then repeated for a number of times, which is decided by the clinician according to his experience. In addition, before and after each rehabilitation experiment, the vestibular functionality of the patient may be evaluated with the method according to the present invention, thus providing useful information to the clinician and motivational drive to the patient about the actual improvement achieved.

Claims

₁. _An apparatus for the evaluation of the peripheral vestibular functionality, said apparatus comprising: - a displaying unit (1) ;

- a rotational acceleration measuring unit (2) ; and

- a recording unit (3) .

2. The apparatus of claim 1, further comprising an analysing unit (4) .

3. The apparatus according to claims 1 or 2, wherein the displaying unit (1) may be a screen on which visual targets are displayed or projected. 4. The apparatus according to claims 1 to 3, wherein the displaying unit (1) may be a computer monitor.

5. The apparatus according to claims 1 to 4 , wherein the rotational acceleration measuring unit (2) is placed in such a way that it rotates integrally with the patient's head.

6. The apparatus according to claims 1 to 5 , wherein the rotational acceleration measuring unit (2) may be represented by a gyroscope or by two accelerometers .

7. The apparatus according to claims 1 to 6 , wherein the two accelerometers are placed on opposite sides of the axis of the rotation.

8. The apparatus according to claims 1 to 7 , wherein the recording unit (3) may be a computer software.

9. The apparatus according to claims 1 to 8, wherein the recording unit (3) records the data concerning the values of rotational acceleration and the responses of the patient.

10. The apparatus according to claims 1 to 9, wherein the patient's response is introduced by the patient itself into the recording unit (3) .

11. The apparatus according to claims 1 to 10, wherein the recording unit (3) is connected to the rotational acceleration measuring unit (2) and/or to the analysing unit (4) .

12. The apparatus according to claims 2 to 11, wherein the analysing unit (4) analyses the results collected about rotational acceleration and patient's responses.

13. The apparatus according to claims 2 to 12, wherein the analysing unit (4) is connected to the displaying unit (1) . 14. The apparatus according to claims 2 to 13 , wherein the analysing unit (4) provides an output .

₁5. The apparatus according to claims 14, wherein said output may be in the form of signals, tables or graphs.

16. A test method for the evaluation of the peripheral vestibular functionality with the use of the apparatus according to any preceding claims, said test method including the phases of: a) assessing the static visual acuity of the patient ; b) evaluating the dynamic vestibular functionality and collecting the data; c) processing the data.

17. The test method for the evaluation of the peripheral vestibular functionality according to claim 16, wherein in step a) the patient is required, while sitting or standing, to read the letters of an optotypic line on an optotype chart .

18. The test method for the evaluation of the peripheral vestibular functionality according to claim 17, wherein in step a) said optotype chart is placed in front him at a distance of between about 30 and about 120 centimetres and preferably at about 50 centimetres.

19. The test method for the evaluation of the peripheral vestibular functionality according to claim 18, wherein in step b) comprises at least one set of experiments.

20. The test method for the evaluation of the peripheral vestibular functionality according to claim 19, wherein in each experiment the patient is required to read and recognise a letter shown to them, while the clinician rotates their head to the left or to the right around its vertical axis, imparting it a certain rotational acceleration. 21. The test method for the evaluation of the peripheral vestibular functionality according to claim 20, wherein in step b) the angular acceleration measuring unit (2) moves integrally with the patient's head. 22. The test method for the evaluation of the peripheral vestibular functionality according to claim 21, wherein in step b) when said acceleration reaches or overcome a threshold value, a Sloan's letter appears on the displaying unit (1) .

23. The test method for the evaluation of the peripheral vestibular functionality according to claim 22, wherein said threshold value is set by the clinician thereby defining an acceptable range of angular accelerations.

24. The test method for the evaluation of the peripheral vestibular functionality according to claim 23, wherein said threshold value may be between about 700 and about 1300 deg/s² in the course of the first set of experiments.

25. The test method for the evaluation of the peripheral vestibular functionality according to claims 16 to 24, wherein the Sloan's letter shown in step b) has the size of the letters of the optotypic line immediately superior to the ones read by the patient during the static acuity assessment phase of step a) .

26. The test method for the evaluation of the peripheral vestibular functionality according to claims 16 to 25, wherein in step b) the appearance time of the letter is between 10-30 milliseconds from the time when the acceleration of the head reaches the threshold.

27. The test method for the evaluation of the peripheral vestibular functionality according to claims 16 to 26, wherein each set of experiments of step b) is subsequently repeated for a number of times sufficient to collect a statistically significant number of results with respect to each rotational acceleration.

28. The test method for the evaluation of the peripheral vestibular functionality according to claims 16 to 27, wherein in each repeated set of experiment the angular rotational acceleration is increased by about 1000 deg/s² with respect to the previous set and up to about 7000 deg/s².

29. The test method for the evaluation of the peripheral vestibular functionality according to claims 16 to 28, wherein step b) is concluded and step c) begins when the rotational acceleration imposed by the clinician to the head of the patient reaches a value at which the patient is unable to read and recognise the letter shown on the displaying unit (1) .

30. The test method for the evaluation of the peripheral vestibular functionality according to claims 16 to 29, wherein step c) comprises the elaboration of the results by the analysing unit (4) .

₃₁. The test method for the evaluation of the peripheral vestibular functionality according to claim 30, wherein the analysis phase is performed by a suitable software.

32.A method for the rehabilitation of the peripheral vestibular functionality with the use of the apparatus of claims 1 to 15, comprising the steps of: a) evaluating the peripheral vestibular functionality of the patient; b) performing one or more experiments for the stimulation of the peripheral vestibular functionality of the patient.

33. The method for the rehabilitation of the peripheral vestibular functionality according to claim 32, wherein step a) is performed according to the method of claims 16-31. 34. The method for the rehabilitation of the peripheral vestibular functionality according to claims 32 and 33, wherein in step b) in each experiment of each set of experiment the patient is required to actively rotate the head from left to right.

35. The method for the rehabilitation of the peripheral vestibular functionality according to claim 33, wherein, when the rotational acceleration imparted by said active movements achieves a threshold value a visual target will appear on the displaying unit (1) .

36. The method for the rehabilitation of the peripheral vestibular functionality according to claim 34, wherein said threshold value is set by the clinician or by the patient itself according to the clinician's instructions into the analysing unit (4) .

37. The method for the rehabilitation of the peripheral vestibular functionality according to claim 35, wherein said threshold is increased by about 500 deg/s² from the value corresponding to the highest acceleration at which the patient was still able to read and recognise the letters as per the last set of experiments performed for evaluating the dynamic vestibular functionality.

38. The method for the rehabilitation of the peripheral vestibular functionality according to claim 36, wherein the patient is required to read and recognise said visual target on the displaying unit (1) .

39. The method for the rehabilitation of the peripheral vestibular functionality according to claims 30 to 37, wherein in step b) each experiment is repeated for a number of times decided by the clinician according to his experience .