The vestibular apparatus is an organ of balance. Together with the visual and motor receptor systems (a receptor is an anatomical formation that converts perceived irritation into nerve impulses), it plays a leading role in a person’s orientation in space. The vestibular apparatus perceives information about acceleration or deceleration that occurs during any type of movement, as well as when the position of the head changes in space. The sense of gravity is also analyzed here, which is why the vestibular apparatus is also called the organ of gravity. Under resting conditions, the receptors of the vestibular apparatus are not excited. Irritation of the receptors occurs when the head is tilted or moved. In this case, reflex muscle contractions occur, helping to straighten the body and maintain balance.
Location and structure of the vestibular apparatus
Labyrinth The vestibular apparatus is located inside the temporal bone and is closely connected with the organ of hearing. In the thickness of the temporal bone there is a complex labyrinth, which is a system of interconnected canals and cavities. There is a bone labyrinth and a membranous labyrinth located inside it, which has a connective tissue wall and basically repeats the shape of the bone labyrinth. Between the bony and membranous labyrinths there is a gap filled with fluid - perilymph. The membranous labyrinth is filled with dense endolymph, the viscosity of which is 2–3 times greater than that of water.
The labyrinth contains the vestibule and semicircular canals, in which the vestibular receptors are located, as well as the cochlea, where the auditory receptors are located. There are three semicircular canals, and they lie in mutually perpendicular planes, which makes it possible to analyze the position in three-dimensional space. Each semicircular canal has two legs, one of which expands in front of the vestibule, forming an ampulla. The vestibule is an oval cavity into which the semicircular canals open on one side and the cochlea on the other.
In the corresponding bony semicircular canals lie the membranous semicircular ducts; in the vestibule there are membranous spherical and elliptical sacs. In the semicircular ducts and vestibular sacs there are clusters of receptor cells. Vestibular receptors are located on elevations, which are present only in the ampoules of the ducts in the form of scallops and in the sacs in the form of spots. The fluid contained in the labyrinth moves when the head and body move (first perilymph, and then endolymph) and irritates the receptor cells. The latter in the ampoules of the semicircular ducts are excited during the movement of the endolymph, mainly during angular accelerations, and in the spots of the sacs - during linear accelerations.
Receptor cells In spots, the part of the receptor cell protruding into the cavity of the sac ends in one longer mobile hair and 60–80 glued immobile hairs. These hairs are immersed in a jelly-like membrane containing calcareous crystals - otoliths. The receptor cells of the spots are irritated due to the sliding of the otolithic membrane along the hairs during the movements of the endolymph. The sensitivity of receptor hair cells is high: the threshold for distinguishing head tilt to the side is only about 1°, and forward and backward is 1.5–2°. When the rotation accelerates, a person notices a change of 2–3° per 1 s2.
It is believed that receptor cells in the spots of the sacs perceive the force of gravity and primarily regulate the balance of the head and body at rest (static balance), and the receptors in the ampullae of the semicircular ducts react to acceleration or deceleration of movement, that is, they regulate the balance of the body moving in space ( dynamic equilibrium).
Features of the hearing organ
Human hearing organs are paired. What does this mean? A person can listen with both the right and left ear at the same time. Binaural hearing gives more information about the sound and amplifies it under certain conditions.
If the source of mechanical vibrations is at the same distance from the right and left ears, the signal volume increases by 50%. This means that in case of unilateral impairment, compensation with the help of a hearing aid of even low power significantly improves the quality of life.
Perceiving with two ears is better for determining the localization of sound. Binaural hearing gives:
- surround sound sensation;
- idea of the location of the source.
This helps you avoid danger (such as an approaching car) and isolate useful sounds from all the background noise when talking to one person in a noisy room.
Read more about hearing characteristics in this article.
If you experience any hearing problems, you must urgently undergo a hearing test using professional equipment. If you seek help in time, you have a chance to fully restore your hearing.
Transmission of nerve impulses
Nerve impulses arising in the receptor cells of the vestibular apparatus are transmitted along the sensitive nerve fibers of the VIII pair of cranial nerves to the brain and first enter the vestibular centers of the medulla oblongata. From here, signals are sent to many parts of the central nervous system: the spinal cord, cerebellum, cerebral cortex, oculomotor nerve nuclei, reticular formation and autonomic nuclei.
Thanks to connections with the spinal cord, vestibular reflexes are carried out to maintain body balance, which involve the muscles of the neck, torso and limbs. As a result of these reflexes, muscle tone is redistributed and balance is maintained. Connections with the cerebellum give movements smoothness, precision and proportionality.
Signals that are sent from the vestibular centers to the nuclei of the oculomotor nerves make it possible to maintain the direction of gaze when changing the position of the head. This also explains nystagmus in cases of imbalance - involuntary rhythmic movements of the eyeballs in the direction opposite to rotation, followed by their spasmodic movement back. The characteristics of nystagmus serve as an important indicator of the state of the vestibular apparatus, therefore they are analyzed in aviation, marine and space medicine, and studied experimentally and clinically.
Sizes and types. What are they made of?
Most plates are made either from food-safe plastic, which provides a rigid frame, or from soft silicone. The choice of material depends on the doctor's decision. Children's plates are made in two sizes:
- first (I) for children with primary malocclusion. Its radius is 22.5 mm. The product can be distinguished by the characteristic red color of the ring;
- the second (II) for children with mixed dentition. Its radius is 30 mm. She has a dark blue ring.
There are several varieties of vestibular plates . All of them appeared later than the standard one and, in addition to the development of nasal breathing, help to cope with the problems of a “flaccid” tongue, eliminate speech defects, correct swallowing, etc. The three most popular models are: classic, with a bead, with a flap and with a visor.
Model with visor
The visor appeared on vestibular orthodontic plates when doctors realized that it was difficult for children with underdeveloped jaws and protrusion of the upper frontal teeth to hold the classic model in their mouth. For them, it constantly deviated above the sagittal protrusion, and at night it completely fell out. The presence of a visor solves this problem.
The vestibular plate with a soft or hard visor is ideal for the treatment of all class II abnormalities. It also stops the development of class III anomalies if worn with the visor up. Due to the fact that the product pushes the upper jaw forward, wearing it normalizes the position of the jaws relative to each other.
Model with damper
The tongue deflector plate is designed for those children who are accustomed to placing their tongue between their teeth when swallowing and speaking. This habit interferes with the normal growth of teeth and leads to the formation of an “open” bite. The flap pushes the tongue back and forces it into the correct position.
In addition, a vestibular plate with a tongue flap helps:
- eliminate the habit of breathing through your mouth;
- teach the child to correctly position the tongue in the mouth during speech;
- strengthen the circular muscle of the tongue, normalize lip closure.
Because the model is often used with speech therapists to demonstrate proper tongue placement, it is made transparent.
Model with bead
The vestibular bead plate is used primarily to correct speech problems. It helps stimulate “flaccid tongue” in children with speech impediments. The standard plate itself aligns the position of the tongue, teeth, lips, helping to improve diction, and an additional design element enhances the effect.
There are two models of bead plate :
- classical. It has an extended bead that stimulates the root of the tongue. This model helps with dysarthria, increased muscle tone, impaired pronunciation of hard and soft consonants, rhinolalia, tachylalia, as well as in the treatment of stuttering. It helps to train weakened tongue muscles;
- new model. Her bead is moved closer to the plastic base and teeth. This model of plate is recommended for children with reduced tone of the tip of the tongue, various forms of sigmatism, lambdacism, and problems with the pronunciation of the “r” sound.
If for some reason a parent wants to buy a record without a doctor’s recommendation, it is advisable to purchase a standard model. It is universal, easy to use, and there is no negative effect when using it. All specialized models - with a bead, a visor, a flap - must be purchased exclusively on the recommendation of a doctor.
Autonomic reactions
Through a set of nerve structures located in the central parts of the brain stem (medulla oblongata and midbrain, visual thalamus), the cardiovascular system, gastrointestinal tract and other organs are involved in vestibular reactions. With strong and prolonged stress on the vestibular apparatus, autonomic reactions occur in the form of a slowing pulse, decreased blood pressure, dizziness, nausea, vomiting, cold hands and feet, pale face, cold sweat, etc. Similar symptoms are possible with seasickness or going up in a high-speed elevator. This is due to the fact that a person is accustomed to movements in the horizontal plane, but movements up and down or to the sides are unusual for him. Special training (swings, rotation) and the use of medications reduce the excitability of the balance organ and prevent undesirable effects.
Peripheral vestibular syndrome includes spontaneous pathological reactions (sensory, motor and autonomic), qualitatively specific to the organ of balance, occurring in the absence of external stimuli and caused by dysfunction of the labyrinth, ampullary apparatus, vestibule, ganglion, root of the VIII pair of cranial nerves. Most often, patients with peripheral vestibular syndrome complain of dizziness, imbalance, narrowing of visual fields, nausea, vomiting and other symptoms.
Current state of the issue
Victoria Lisotskaya, head of the hearing aid department of the Republican Scientific and Practical Center of Otorhinolaryngology. Dizziness is an illusory sensation of body movement or the surrounding space. It may be combined with other symptoms such as nausea, vomiting, and ataxia. There are central and peripheral dizziness. Peripheral is associated with damage to the labyrinth of the inner ear or the vestibular part of the vestibular-cochlear nerve. Central vertigo can be caused by damage to the vestibular nuclei of the brain stem, cerebellum, pathways, and cerebral cortex ( see Table 1 ).
According to recent scientific publications, an attack of dizziness is mainly caused by a change in the functional relationships between the sympathetic and parasympathetic nervous systems towards the predominance of the function of the parasympathetic system. These changes are accompanied by vasomotor disorders in the inner ear with an increase in the permeability of the vascular walls and a subsequent increase in the amount of endolymph in the vestibular apparatus.
During the acute onset of an attack of peripheral vertigo, patients feel the movement of objects in the direction of the diseased ear, nystagmus is also directed in the same direction, and in the depression stage - in the opposite direction. The duration of attacks can range from minutes to several hours, weeks and even months.
Peripheral vertigo is always accompanied by spontaneous nystagmus - clonic, horizontal or horizontal-rotatory, of varying intensity and degree, associated with a harmonious deviation of the torso and arms towards the slow component. Often, peripheral vestibular vertigo is a unilateral process and may be accompanied by hearing loss on the affected side.
According to literary sources, dizziness can be caused by a large number of etiological factors, such as metabolic disorders, diseases of the cardiovascular system, neoplasms of various origins, etc. About a third of patients visiting otolaryngologists report various types of dizziness.
Among the reasons for visiting doctors of various specialties, dizziness accounts for 3–4%. According to Yardley L. (1998), in a survey of more than 20 thousand people aged 18 to 64 years, it was found that over the past month more than 20% had experienced dizziness, of which more than 30% had suffered from dizziness for more than 5 years. In a survey of thousands of people over 65 years of age, 30% of respondents reported dizziness.
Table 1. Main differences between central and peripheral vestibular vertigo.
Classification
Dizziness
1. Non-vestibular (central origin).
2. Vestibular (central origin, peripheral origin):
2.1 with hearing impairments;
2.2 without hearing impairment;
3. Systemic.
4. Non-systemic ( see Table 2 ).
Table 2. Classification of dizziness based on the patient's subjective perception of the environment.
Coding according to ICD-10
Vestibular function disorders (H 81):
- H81.0 - Meniere's disease;
- H81.1 - benign paroxysmal positional vertigo (BPPV);
- H81.2 - vestibular neuronitis;
- H81.3 - other peripheral dizziness (Lermoyer's syndrome; dizziness: auricular, otogenic, peripheral NOS, bilateral peripheral vestibulopathy, vestibular paroxysm, anterior semicircular canal dehiscence syndrome);
- H 83.0 - labyrinthitis;
- H 83.1 - labyrinthine fistula.
Diagnostics
The vestibular apparatus has numerous anatomical and functional connections, therefore, when it is irritated, various reflexes arise: combined deviation of the eyes, nystagmus, compensatory ocular stop, dizziness, nausea, vomiting, imbalance. The study of vestibular function begins with a visual assessment of the direction and severity of spontaneous nystagmus.
Nystagmus is an involuntary, fast, rhythmic oscillatory movement of the eyes with at least one slow phase. Pathological forms of nystagmus have many causes, but are usually the result of diseases affecting the peripheral vestibular system, brainstem, cerebellum and, less commonly, the anterior visual pathways or central hemispheres.
Nystagmus can be continuous or episodic. Episodes of nystagmus may occur spontaneously only at certain gaze positions or viewing conditions, or may be triggered by specific maneuvers.
Nystagmus is characterized by numerous phenomenological features, most of which are associated with specific underlying pathological mechanisms. Specific forms of nystagmus have special names based on a combination of these attributes.
Algorithm for assessing nystagmus
1. The starting point of the gaze position, the starting point of the head position, the starting point of reference relative to the semicircular canals.
2. Binocularity: monoocular, binocular.
3. Conjugation (conjugation): conjugate eye movement, unconjugated eye movement, disjunctive eye movement (when two eyes spontaneously move simultaneously in different directions).
4. Speed: frequency, amplitude, phase of the slow component is estimated.
5. Waveform.
6. Frequency.
7. Amplitude.
8. Intensity.
9. Temporal profile (temporal characteristics).
10. Age of first manifestation (see figure).
Drawing. Registration of electronystagmography and videooculography.
Source: T. Sahin, R. Yilmaz, M.K. Akbostanci. Saccadic and smooth pursuit disorders in essential tremor: A video-oculographic study [abstract]. Mov Disord. 2020; 35 ( Addition 1 ). Retrieved November 12, 2021.
In accordance with the International Classification of Vestibular Disorders, there are:
- physiological nystagmus;
- pathological nystagmus;
- nystagmus-like movements.
The following tests are recommended to diagnose peripheral vestibular syndrome:
1. Assessment of the vestibulo-ocular reflex.
2. Hit test. Diagnosis is carried out with closed eyes and intense shaking of the head after 20 seconds of intense rotation. If more than 4 saccades occur in 10 seconds, damage to the peripheral part of the vestibular analyzer occurs.
3. Halmagi sample. The patient fixes his gaze on the bridge of the nose of the doctor located in front of him and turns his head in one direction or the other (15° from the midline). Normally, fixed eyes do not turn with the head. For peripheral vestibulopathy - corrective saccades. In case of central vestibular dysfunction with isolated systemic dizziness, the test is negative.
4. De Klein test. The patient turns his head with his eyes closed 90° to the left. Nystagmus is assessed. Repeat in the opposite direction. For the diagnosis of uncovertebral arthrosis, vertebral artery syndrome.
5. Dix-Hallpike test. The patient, in a sitting position, turns his head towards the affected labyrinth. The doctor abruptly places him in a horizontal position. With canalolithiasis of the posterior semicircular canal - nystagmus with a latent period of up to 15 seconds, directed to the underlying ear with a rotatory component (duration up to 40–50 seconds).
6. Caloric tests. Normally, horizontal rotatory nystagmus occurs within 25–30 seconds. When infusing cold liquid, the nystagmus is directed in the direction opposite to the ear being examined (ampulofugal endolymph flow), while warm liquid is directed toward the ear being examined (ampulopetal endolymph flow).
7. Pressor test.
8. Flanking gait.
9. Assessment of stability in the Romberg pose.
10. Electronystagmography.
11. Videonystagmography.
When preparing medical documentation, the following entry in the medical record of an outpatient or inpatient patient is acceptable: “When performing functional vestibular tests, spontaneous and provocative nystagmus was not detected. Caloric nystagmus is within normal limits (25–30 seconds). Stable in the Romberg position. The finger-nose test is performed without intention. Flanking gait along the midline.
Conclusion: at the time of examination, vestibular function was not changed.”
Therapy
Treatment of an attack of dizziness is carried out depending on the etiological factor.
Relief of an acute attack is carried out by an otorhinolaryngologist or neurologist when the patient contacts at the outpatient and inpatient stages.
- Metoclopramide 20–40 mg orally 2–4 times daily for 3 days.
- Dimenhydrinate 50–100 mg 2–3 times a day orally.
- Diphenhydramine 25–50 mg orally 3–4 times a day or 10–50 mg intramuscularly.
- Diazepam 10 mg intramuscularly to relieve imbalance.
If it is impossible to relieve an attack of peripheral dizziness at the outpatient stage of medical care, hospitalization in the otorhinolaryngology department is indicated; in case of central dizziness, inpatient treatment in the neurology department is indicated.
Pathogenetic treatment:
- in the presence of hearing impairment, betahistine 24 mg, 1 tablet 2 times a day orally, is recommended for 2–3 months;
- for the treatment of vestibular neuronitis, intravenous administration of 8 mg of dexamethasone for 3 days is indicated;
- In the case of verification of hydrops of the labyrinth using the contrast method during MRI, bypass surgery of the tympanic cavity with endotympanic administration of dexamethasone is recommended.
Surgical treatment is indicated for labyrinthine fistula and dehiscence of the anterior semicircular canal, depending on the severity, frequency, and duration of the dizziness attack; as well as in the presence of neurovascular activity in patients with vestibular paroxysmia.
Spatial orientation
Under normal conditions, spatial orientation is ensured by the joint activity of the vestibular apparatus and vision. However, the vestibular apparatus helps the body navigate in space both during active movement and during passive transfer from place to place blindfolded. With the help of the vestibular apparatus and the cerebral cortex, the direction of movement, turns and distance traveled are analyzed and remembered. Clinical observations indicate that the loss of vestibular function in a person (for example, as a complication of meningitis) causes instability of posture and at the same time makes him not susceptible to seasickness. In deaf and mute people, the vestibular apparatus does not function and they feel a tilt of the head due to contraction of the neck muscles.
The vestibular apparatus is in close interaction with the visual and motor systems, which ensures a person’s orientation in space, maintaining balance and coordination of movements.
Author: Olga Gurova, Candidate of Biological Sciences, Senior Researcher, Associate Professor of the Department of Human Anatomy of the RUDN University
Bibliography
- "Biological encyclopedic dictionary." Ch. ed. M. S. Gilyarov; Editorial team: A. A. Babaev, G. G. Vinberg, G. A. Zavarzin and others - 2nd ed., corrected. - M.: Sov. Encyclopedia, 1986.
- "Otorhinolaryngology". Textbook ed. I.B. Soldatov and V.R. Hoffman. – St. Petersburg, 2000. – p.41-45, p.75-96.
- Soldatov I.B. "Lectures on otorhinolaryngology: Textbook." – M.: Medicine, 1994. – pp. 40-56., pp. 261-277.
- How the vestibular apparatus works - https://theoryandpractice.ru (Access date: 07/01/2019)
- How to train the vestibular apparatus at home - www.sovsport.ru (Date of access: 07/02/2019)
Conclusions. Expert advice
The vestibular plate is a simple and effective method for correcting malocclusion and speech problems at an early age. It helps get rid of the following problems:
- mouth breathing and poor development of nasal breathing;
- low tone of the orbicularis oris and lingual muscles;
- speech defects, infantile type of swallowing, incorrect development of the jaws.
Wearing the product helps stimulate natural self-regulation processes, so the capabilities of the plates are limited. But choosing one of the modifications will help expand them. The following types of records exist:
- standard,
- with damper,
- with a bead,
- with a visor.
Each has additional capabilities and specifics. For example, a model with a bead is recommended mainly by speech therapists, and a plate with a visor is recommended to be worn for abnormalities in the development of the jaws.
You should not buy vestibular plates for children without a doctor’s recommendation. It is better to visit an orthodontist so that he can confirm the need for the product and that it will not cause harm. Also, be sure to keep the product clean: wash it regularly and treat it with an antibacterial agent.
Advantages and disadvantages
Vestibular plates are prescribed to children quite often because they are very effective and have almost no contraindications. The advantages of records are:
- ease of use and maintenance;
- need to be worn overnight and for several hours during the day (does not require use all the time like braces);
- low cost;
- training in a playful way;
- possibility of use from an early age;
- presence of other effects (strengthening speech organs, etc.)
The disadvantages include, first of all, a narrow range of influences. Plates cannot cope with all problems. Also, due to the ability to remove the product, the treatment time is extended.