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SENSITIVITY SYNDROMES AND SENSITIVITY FUNCTIONS
Three main types of sensitivity disorders are distinguished depending on the distribution borders: peripheral - in the area of nerve innervation, segmental - in the area of innervation of the segment of the spinal cord, posterior (sensitive) root or intervertebral ganglion, conductor - below the level of damage to the conductors of sensitivity in the spinal cord or brain.
Depending on the level of lesions of the nervous system, various disturbances in sensitivity are observed (Fig. 75). In case of damage to the trunk of the peripheral nerve or nerve plexus, all types of sensitivity are disturbed in the innervation zone of this nerve (see Fig. 75, a) or nerves of this plexus (peripheral type of sensitivity disorder).
Multiple nerve damage (polyneuritis) causes a violation of sensitivity in the arms and legs, such as gloves and stockings (see Fig. 75, d).
Types of Sensitivity Disorders
a - neuritic type; b - segmental type; c - violation of sensitivity in case of damage to the optic tubercle; g - polyneuritic type
Damage to the root or intervertebral node causes a violation of all species of sensitivity in the corresponding segmental zones (see Fig. 75, B). In addition, severe girdle pain and shingles occur (with lesions of the intervertebral node).
Damage to the horn of the spinal cord causes a split (dissociated) sensitivity disorder: loss of surface sensitivity while maintaining deep sensitivity. Such violations are detected in the corresponding affected segments of the segmental zone on the affected side.
Damage to the lateral column of the spinal cord (where the fibers of the surface sensitivity pass) leads to disruption of the surface sensitivity on the opposite side of the lesion below the lesion site (conductive type of sensitivity violation). The defeat of the posterior columns of the spinal cord (where the fibers of deep sensitivity pass) leads to the loss of deep sensitivity in the conductor type on the side of the focus from the level of its localization to the bottom down. Due to the loss of joint-muscular feeling, an attack develops (sensitive, or spinal).
Sensitive attack differs from cerebellar in that it can be compensated by control over the position of the body (Fig. 76), the patient can normally stand with his eyes open, but with his eyes closed he staggers.
Damage to half of the spinal cord causes loss of articular-muscular feeling (damage to the posterior pillars) on the affected side, central paralysis down from the lesion site, and on the opposite side - loss of superficial sensitivity - pain, temperature and partially tactile (Brown-Secar syndrome) (Fig. 77).
The defeat of the entire diameter of the spinal cord causes loss of all types of sensitivity below the level of damage, bilateral central paralysis and impaired urination.
Damage to the sensory pathways in the area of the brain stem causes the loss of all types of hemi-type sensitivities on the opposite side and hemataxia.
The defeat of the visual tubercle (the subcortical center of all types of sensitivity) causes the loss of all types of sensitivity on the opposite side (see Fig. 77, c), hemataxia, as well as the same half loss of visual fields (homonymous hemianopsis).
In addition, with damage to the optic tubercle, special pain occurs in the opposite half of the body: they are characterized by a painful and extremely unpleasant burning sensation or cold and are difficult to localize to the patient. These pains are called thalamic.
The defeat of the posterior central gyrus of the cerebral cortex, which is the cortical center of the sensitive analyzer, causes hemianesthesia and hemataxia on the side opposite to the focus. In the case of limited lesions of the posterior central gyrus, monoanesthesia (arms, legs, face areas) are observed on the opposite side.
Sensory Disorders in Spinal Cord Damage
a - cerebrospinal node (shingles); b - a back root (loss of all types of sensitivity); in - a back horn (loss of pain and temperature sensitivity); d - posterior pillars (1 - loss of deep sensitivity - loss of joint-muscle feeling, 2 - sensitive ataxia); d - half the diameter of the spinal cord (/ - loss of pain and temperature sensitivity, 2 - spastic paralysis, 3 - flaccid paralysis, 4 - violation of all types of sensitivity, 5 - loss of joint-muscle feeling)
With irritation of the trigeminal nerve (one or another of its branches), very strong pains arise that radiate to all branches of the nerve. They are expressed in the forehead, scalp, eye, ear, cheek, lower jaw, and gives to the teeth. To determine the localization of the main lesion, a pain point is identified in the places where the nerve branches exit.
The defeat of the trigeminal nerve node and the sensitive root of the trigeminal nerve causes a violation of sensitivity in the innervation zone of all nerve branches, as well as rashes of bubbles on the face along separate nerve trunks.
The defeat of one of the branches of the trigeminal nerve leads to a violation of all types of sensitivity innervated by this branch, to the appearance of pain and to the extinction of the corresponding reflexes (in case of damage to the ocular branch, the superciliary, corneal and conjunctival reflexes disappear; in case of damage to the mandibular branch, the mandibular reflex).
Visual Impairment Syndromes
Decreased visual acuity is called amblyopia; lack of vision - amaurosis.
In adults and older children, visual acuity is 1.0. Such visual acuity is established only after 5 years. In the first half of life, it is 0.02 - 0.04, by 1 year it reaches 0.1.
With a sharp decrease in vision, when the patient does not distinguish letters or pictures on the table, he is asked to count the fingers of the researcher at a distance of 1 m from the eyes (in this case, visual acuity is 0.02). If the patient considers fingers from a distance of 0.5 m, then this corresponds to visual acuity of 0.01. If the patient distinguishes only light and shadow, then visual acuity is designated 1 /? (infinitely small).
A decrease in visual acuity (amblyopia) may be a result of damage to the eyeball, optic nerve and other parts of the visual analyzer. Amblyopia is often the result of optic neuritis.
Optic neuritis may be part of the symptom complex of various diseases (meningitis, arachnoiditis, hereditary degenerative diseases), but it can also be an independent disease.
Optic neuritis is manifested by a decrease in visual acuity in one or both eyes; in some cases, it can lead to complete blindness - amaurosis. There is no direct reaction of the pupil to light on the affected eye; a friendly reaction is preserved only in those cases when the other optic nerve is not affected.
With bilateral neuritis, there is no direct or friendly reaction of the pupils to light. Sometimes nystagmus and strabismus are detected.
The course of optic neuritis can be different and depends on the cause of the disease, the nature of the underlying pathological process and the time of its development.
Pathology of the optic nerve in the neonatal period develops due to the influence of various harmful factors in the prenatal period and during childbirth. These disorders are manifested by the underdevelopment of the optic nerve and can be combined with abnormalities in the development of the nervous system and eye. Children are born with reduced vision or blind. They have reduced or no protective blinking reflex to bright light, fixing the gaze on an object, tracking is not formed for a moving object. Motor and mental development of the child depend on the characteristics of the formation of the nervous system; with congenital atrophy of the optic nerve, this development is most often impaired.
The diagnosis of optic neuritis is confirmed by a study of visual acuity and fundus. Blanching of the optic nerve disc, narrowing of blood vessels (especially arteries) are detected. Retrobulbar optic neuritis can proceed unchanged in the fundus. If optic atrophy develops due to increased intracranial pressure (secondary atrophy), the optic nerve head is pale and has fuzzy borders. Narrowing of arteries and expansion of veins can take place.
Disorders of color perception can be in the form of complete color blindness (achromatopsia), partial impairment of color perception (dyschromatopsia). Color blindness - the inability to distinguish between green and red - is a type of dyschromatopsia and is quite common. A peculiar type of color perception disorder is the vision of the environment in one color. This is sometimes found in cases of poisoning with certain drugs (acrychin, santonin). In children's practice, violations of color perception do not matter much. They acquire practical importance in the choice of profession and employment. An absolute contraindication is the device of people with color impairment to work for transport and for work associated with the need to strictly distinguish between primary colors.
Violations of the visual fields are expressed in concentric narrowing, loss of its individual sections (scotomas) and loss of half of the visual fields (hemianopsia).
Concentric narrowing of the visual fields is more often the result of retrobulbar optic neuritis - damage to the optic nerve after it leaves the orbit in the cranial cavity. Scotomas can also appear with optic neuritis. But they can not be observed with small foci of damage in the region of the occipital lobe of the brain.
Hemianopsia occurs when the intersection of the optic nerves, optic tracts, optic tubercle or the occipital lobes of the cerebral cortex are damaged due to the fact that the optic tracts carry nerve fibers in themselves from the half of the retina (externally the eyes of their side and from the half of the retina (inner) of the opposite eye. Each half of the retina corresponds to an opposite field of view (see Fig. 26, a). Therefore, the outer halves of the retina of both eyes perceive light from the internal (nasal) fields of vision, and the inner halves of the retina of both eyes perceive light with external field of view.
Hemianopsies can be opposites (heteronymous) when opposite fields of vision in both eyes (right and left fields) fall out, and homonymous when fields of the same name fall out. Heteronymous hemianopsia occurs when the intersection of the optic nerves is affected, homonymous - with the defeat of the optic tract, optic tubercle, occipital lobes of the cerebral cortex (see Fig. 26, b).
When individual parts of the occipital lobes of the cerebral cortex are damaged, a quarter of the visual fields of the eye can fall out on its side and in the opposite eye (quadrant or quaternary hemianopsia) (see Fig. 26, c).
Hearing Impairment Syndrome1
Hearing impairment is indicated by the term “hypacusia”; hearing loss i.e. deafness, denoted by the term “cashew,” or “surditas.” Unilateral damage to the auditory zone of the cerebral cortex, the pathways from the nuclei of the auditory nerve and the optic tubercle does not lead to hearing impairment, since impulses from the nuclei of the auditory nerve come into the cerebral cortex of their own and opposite sides. In this case, irritations from both ears are carried out in one of the hemispheres of the cortex on the unaffected side.
Unilateral hearing damage occurs only in the case of damage to the middle and inner ear, the auditory nerve and its nuclei. In case of damage to the middle ear (eardrum, auditory ossicles), hearing impairment at low tones and the preservation of bone conduction of sound are characteristic. In the study of bone conduction (produced using a sounding tuning fork. Mounted on the crown of the subject), the sound is more intensely perceived by a sick ear. In case of damage to the spiral (Corti) organ (inner ear), the auditory nerve and its nuclei, mainly the perception of high tones falls out and the sound conduction along the bone is lost.
1 Hearing pathology is examined in detail in the course “Anatomy, physiology, theology of the organs of hearing and speech”.
A common cause of hearing loss is an inflammatory lesion of the auditory nerve - neuritis. It can develop due to exposure to various infectious agents and toxic substances. It can occur in many infectious diseases, when using large doses of certain drugs (streptomycin, kanamycin, quinine, etc.). Neuritis can be part of the symptom complex of many hereditary diseases. Neuritis is characterized by progressive hearing loss, sometimes even to complete deafness. First of all, the perception of high tones is disturbed. Bilateral congenital decline or lack of hearing leads to the formation of specific characteristics of the psyche and impaired speech formation. With a complete lack of hearing in the early stages of the development of the child, the impression of his mental inferiority may be created. In such children, visual-figurative thinking prevails. In the process of understanding the world, they make the most of safe analyzers - vision and tactile sensitivity. As the child learns, he learns dactyl and oral speech. On this basis, he develops and verbal-logical, that is, abstract, thinking. Most deaf and hard of hearing people are mentally safe. However, with organic lesions of the nervous system (consequences of meningitis, encephalitis, etc.), hearing loss or deafness can be combined with other neurological disorders and may be accompanied by various forms of intellectual disability.
If deafness or hearing loss occurs at a later age, then features such as isolation, irritability, distrust, etc. can develop.
The diagnosis of auditory nerve neuritis is confirmed by audiometry, which allows you to distinguish between damage to the sound pickup and sound conduction apparatus and to establish the degree of hearing loss.
Deaf and hard of hearing children are trained in special institutions.
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SENSITIVITY SYNDROMES AND SENSITIVITY FUNCTIONS
- Syndromes of impaired sensory and sensory functions
Three main types of sensitivity disorders are distinguished depending on the distribution borders: peripheral - in the area of nerve innervation, segmental - in the area of innervation of the segment of the spinal cord, posterior (sensitive) root or intervertebral ganglion, conductor - below the level of damage to the conductors of sensitivity in the spinal cord or brain. Depending on the level of lesions
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