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Close concepts: weakness, faintness, a syncope, fog before eyes, front sights before eyes, a poshatyvaniye, nausea
Dizziness — feeling of a roundabout. Faintness all other the similar and accompanying it symptoms. Of course, these definitions of terms dizziness and faintness considerably simplify numerous complaints of patients who see a doctor at balance disturbances. Quite often after collecting the anamnesis at such patients the doctor himself can feel some faintness.
The simplified definition of these terms is provided intentionally. Dizziness almost always assumes disturbances of a vestibular mechanism, i.e. pathology of a labyrinth of an inner ear. The condition of faintness usually assumes not vestibular pathology of neurologic, metabolic or ophthalmologic character. When collecting the anamnesis at the patient it is necessary to look for precisely communication of dizziness with pathology of an inner ear. The full understanding of symptomatology of dizziness and faintness requires understanding of physiological bases of system of balance. The term "vestibular system" came from the concept labyrinthine vestibule (a labyrinth threshold). The threshold connects semicircular channels and a snail. Three semicircular channels are connected in three vzaimnoperpendikulyarny planes. Each channel near a threshold comes to an end with an ampoule. Hollow bone semicircular channels, thresholds and the snail channel connecting them, also containing its educations which are reported with a subarachnoid space are filled with a perilympha of an ultrafiltrate of cerebrospinal fluid.
In these bone channels there is a number of the hymenoid cavities known as eidolimfatichesky system, they swim in a perilympha and make with it completely closed system. In these cavities, or bubbles, there is an endolymph which probably cosecretes labyrinth cells. Three main endolymphatic cavities are a webby sack and semicircular channels, a sack and a snail channel, an endolymphatic bag and a channel. Sacks and semicircular channels make the main receptor body of the movement and position of a body (fig).
Structure of a vestibular analyzer.
Normal the equilibrium state is provided with symmetric functioning right and left vestibular systems as they are urged to support the correct interrelation between the individual and environment. Vestibular receptor bodies at rest constantly send impulses to the central nervous system. In the conditions of stimulation semicircular channels react to radial acceleration. If function of one of vestibular receptor bodies is broken, then it sends asymmetric signals to the central nervous system which then are interpreted as the movement even if actually the body is in rest (fig. 2).
Fig. 2. Function of a vestibular analyzer. The symmetric afferent impulsation provides balance (And). The asymmetrical afferent impulsation creates illusory feeling of rotation (B).
In response to the movement of the head causing acceleration of an endolymph in each labyrinth system there are movements of eyeglobes which are shown in the form of a nystagmus. The nystagmus can be horizontal, vertical, diagonal or rotary depending on nature of stimulation. Thus, the nystagmus is an indicator of function of an inner ear and is used both at clinical, and at tool research in documentation of a disease
The orienting function of bodies of a labyrinth is part of the coordinating mechanisms consisting of both labyrinths, vestibular nerves, the central visual pathways, a spinal cord, a cerebellum, a median longitudinal bunch, a red kernel, a thalamus, a hypothalamus and bark of a cerebellum. At the same time the role of a median longitudinal bunch is most important as its fibers connect to the vestibular fibers conducting to muscles of eyeglobes, and also to other cranial nerves and cells of front horns of a spinal cord which innervate muscles of an extremity (fig. 3).
Fig. 3. The peripheral and central nerve pathways participating in emergence of a syndrome of dizziness.
Interaction of symmetric impulses of vestibular bodies, stable visual function, and reflexes of the central nervous system provides normal vertical position of a body and balance at the movement. Usually pathology of one of these components leads to balance disturbances. The doctor needs to make the exact diagnosis at the patient who addresses with complaints to balance disturbances.