Hyperpathy is a violation of sensitivity, in which the threshold of perception does not correspond to the level of the stimulus. This condition is characterized by the fact that a person is not able to determine the place of exposure, as well as the source of pain, touch, can not tactilely recognize temperature changes, the feeling of vibration is greatly reduced.

For the sensation to manifest itself, the concentration of the external stimulus must be exceeded and vice versa.

If a person suffering from this disorder is asked to show the place of irritation, then this will cause difficulty. There are signs by which you can determine the location of the pathogen, among which the most obvious are: increased sweating, hyperemia of the skin, tachycardia, increased pressure.

It is worth noting that all sensations have a persistent negative connotation, which aggravates the already unstable psychological state of a sick person.

Varieties of the disorder

In medicine, it is customary to divide hyperpathy into separate types of sensitivity disorders, the most common are the following:

hyperesthesia- increased sensitivity, not justified by a real effect on the senses;
allodynia- the minimum effect of the stimulus is manifested by a pain symptom, while in a normal state, this should not happen;
hyperalgesia- excessively high perception of pain;
characterized by a violation of the conduction of nerve impulses, which is manifested by numbness of the limbs, tingling, a feeling of creeping on the skin.

Sensory disturbances occur when the central nervous system and the brain malfunction, which are associated, first of all, with the interruption of the patency of the nerves, as well as with their damage.

With damage to the thalamus (optic hillock), loss of sensitivity zones is also possible. The thalamus is an area of the brain responsible for the delivery of information from the organs of vision, hearing, skin receptors to the cerebral cortex.

What diseases is the symptom typical for?

Conservative methods, physiotherapy, as well as psychological correction and rehabilitation are widely used. Sometimes, in severe cases, surgery is required.

As a result, the conclusions:

hyperpathy is a neurological symptom, and not an independent disease, manifested by impaired sensitivity;
can develop in any person, regardless of gender and age;
is a consequence of malfunctions in the brain, nervous system and other body systems.

It should be noted that most often it is not possible to completely get rid of the manifestations of hyperpathy, but it is quite possible to significantly reduce the symptoms and improve the patient's quality of life.

Neurology and neurosurgery Evgeniy Ivanovich Gusev

Chapter 2 Sensitivity and its Disorders

Sensitivity and its disorders

Sensitivity- the body's ability to perceive irritations emanating from the environment or from its own tissues and organs. The teachings of I.P. Pavlova about analyzers laid the foundations for a natural-scientific understanding of the nature and mechanisms of sensitivity. Each analyzer consists of a peripheral (receptor) section, a conductive section and a cortical section.

Receptors are special sensitive formations that can perceive any changes inside or outside the body and convert them into nerve impulses.

Due to the specialization of receptors, the first stage of the analysis of external stimuli is carried out - the decomposition of the whole into parts, the differentiation of the nature and quality of signals. In this case, all types of external energy, being transformed into nerve impulses, enter the brain in the form of signals. Depending on their functional characteristics, receptors are subdivided into exteroreceptors (located in the skin and informing about what is happening in the environment), telereceptors (contained in the ears and eyes), proprioceptors (providing information about muscle and tendon tension, movements and body position) and interoreceptors (“ reporting "about the state inside the body). There are also osmo-, chemo-, baroreceptors, etc.

Skin receptors are divided into mechanoreceptors (touch, pressure), thermoreceptors (cold, heat), and nociceptive receptors (pain). There are many of these receptors in the skin, especially between the epidermis and connective tissue. Therefore, the skin can be viewed as a sensitive organ covering the entire surface of the body. It contains free nerve endings and encapsulated end formations. Free nerve endings are located between epidermal cells and perceive painful irritations. Merkel's tactile bodies are located mainly at the fingertips and respond to touch. Hair muffs are present where the skin is covered with hair and perceive tactile irritations. Meissner's little bodies are found on the palms, soles, lips, tip of the tongue, and the mucous membrane of the genitals and are very sensitive to touch. The lamellar bodies of Vater-Pacini, located in the deep layers of the skin, perceive pressure. Krause flasks are considered cold receptors, and Ruffini's bodies are heat receptors.

Golgi-Mazzoni bodies are thick myelin fibers "wound" around groups of collagen tendon fibers, surrounded by a connective tissue capsule. They are located between the tendon and the muscle. Like muscle spindles, they respond to tension, but their sensitivity threshold is higher.

Encapsulated, more differentiated bodies apparently provide epicritical sensitivity, a light touch sensation. vibration, pressure. Free nerve endings provide protopathic sensitivities, such as differences in pain intensity or temperature.

Receptors - peripheral endings of afferent nerve fibers, which are peripheral processes of pseudo-unipolar neurons of the spinal ganglia. In this case, the fibers emanating from the neuromuscular spindles and having a thick myelin sheath occupy the most medial part of the posterior root. The middle part of the root is occupied by fibers emanating from the encapsulated receptors. The most lateral fibers are almost not myelinated and conduct pain and temperature impulses. Only some impulses coming from muscles, joints, fascia and other tissues reach the level of the cerebral cortex and are recognized; most of the impulses are needed for automatic control of motor activity required for standing or walking.

Passing into the spinal cord through the dorsal roots, individual fibers are divided into numerous collaterals, which provide synaptic connections with other neurons in the spinal cord. All afferent fibers, when passing through the entrance zone of the dorsal roots, are deprived of the myelin coating and go in different tracts, depending on their sensitive modality.

The conductive part of the analyzer is represented by the spinal nodes, the nuclei of the spinal cord, the brain stem, various nuclei of the thalamus, as well as such formations as the reticular formation, structures of the limbic system and the cerebellum. The afferent impulses that enter the central nervous system propagate, first of all, along the specific projection pathways of this sensory modality and are switched in the corresponding nuclei of the diencephalon. The axons of the neurons of these nuclei reach the sensory zones of the cortex, where the highest analysis of afferent information within the given analyzer takes place. In the cortical regions of the analyzer, there are neurons that respond to only one sensory stimulus. These are specific projection neurons. Next to them are nonspecific nerve cells that respond to various sensory stimuli. At the level of the midbrain, collaterals depart from the fibers of specific sensory pathways, along which excitation radiates to the reticular formation and nonspecific nuclei of the thalamus and hypothalamus. Found that the reticular formation. as well as other subcortical formations, it has an ascending activating generalized effect on the cerebral cortex. After processing at the level of the cortical end of the analyzer, impulses can radiate both horizontally along the inter- and intracortical pathways, and vertically along the corticofugal pathways to the nonspecific structures of the mine trunk. The analyzer's activity also includes the reverse effect of higher calving on the receptor and conductive parts of the analyzer. The sensitivity of the receptors (the perceiving part), as well as the functional state of the transfer relays (the conductive part) are determined by the descending influences of the cerebral cortex, which allows the body to actively select the most adequate sensory information from many stimuli.

The most common classification of sensitivity during neurological examination of a patient is:

Superficial (exteroceptive) - pain, temperature and tactile sensitivity;

Deep (proprioceptive) - muscular-articular, vibration sensitivity, feeling of pressure, body weight, determining the direction of movement of the skin fold (kinesthesia);

Complex forms of sensitivity: a sense of the localization of an injection, touch, recognition of signs and letters written on the skin (two-dimensional spatial feeling), discrimination of injections applied simultaneously at a close distance by Weber's compass (discriminatory sensitivity), stereognosis;

A sensation caused by irritation of the receptors of the internal organs (interoceptive sensitivity).

Distinguish between protopathic and epicritical sensitivity. Protopathic sensitivity is its phylogenetically ancient type, characterized by limited possibilities for differentiating stimuli according to their modality, intensity and localization. Epicritical sensitivity is a phylogenetically new type of sensitivity that provides the possibility of quantitative and qualitative differentiation of stimuli (by modality, intensity, localization).

Exteroceptive sensations are those that are formed in sensitive formations of the skin or mucous membranes in response to external influences or changes in the environment. Otherwise, they are called superficial, or skin and emanating from the mucous membranes, types of sensitivity. There are three main types of them: painful, temperature (cold and heat) and tactile (with a light touch).

Proprioceptive sensitivity comes from the deep tissues of the body: muscles, ligaments, tendons, joints and bones.

The term "complex sensitivity" is used to describe those options, the implementation of which requires the attachment of a cortical component to achieve a sense of final perception. In this case, the leading function is perception and discrimination in comparison with a simple sensation in response to stimulation of the primary sensory endings. The ability to perceive and understand the shape and nature of objects by touching and feeling them is called stereognosis.

Different pathways correspond to different types of sensitivity. The spinal nodes contain cells of peripheral neurons of all types of sensitivity. The first neuron conductive impulses of pain and temperature sensitivity are pseudo-unipolar neurons of the spinal nodes, the peripheral branches of which (dendrites) are thin myelin and myelin-free fibers, heading to the corresponding area of the skin (dermatome). The central branches of these cells (axons) enter the spinal cord through the lateral part of the posterior roots. In the spinal cord, they are divided into short ascending and descending collaterals, which, after 1-2 segments, form a synaptic contract with the nerve cells of the gelatinous substance. This second neuron, which forms the lateral spino-thalamic pathway. The fibers of this path pass through the anterior commissure into the opposite half of the spinal cord and continue in the outer part of the lateral cord and further upward to the thalamus. The fibers of both dorsal-thalamic tracts have a somatotopic distribution: those that come from the legs are located laterally, and those that come from the higher sections have a medial - eccentric arrangement of long conductors. The lateral spinal thalamic tract ends in the ventrolateral thalamic nucleus. Fibers originate from the cells of this nucleus third neuron, which are directed through the posterior third of the posterior leg of the internal capsule and the radiant crown to the cortex of the postcentral gyrus (fields 1, 2, and 3). In the postcentral gyrus, there is a somatotopic distribution, analogous to the somatotopic projection of certain body parts in the precentral gyrus.

The course of the fibers conducting pain sensitivity from the internal organs is the same as for the fibers of somatic pain sensitivity.

Conduction of tactile sensitivity carries out the anterior dorsal thalamic pathway. The first neuron also are the cells of the spinal cord. Their moderately thick myelinated peripheral fibers terminate in certain dermatomes, and their central branches pass through the dorsal root into the dorsal cord of the spinal cord. Here they can rise by 2-15 segments and at several levels form synapses with the neurons of the dorsal horn. These nerve cells make up second neuron which forms the anterior dorsal thalamic tract. This path crosses the white commissure in front of the central canal, goes to the opposite side, continues in the anterior cord of the spinal cord, rises through the brainstem and ends in the ventrolateral nucleus of the thalamus. Nerve cells of the thalamus - third neuron conducting impulses into the postcentral gyrus through the thalamocortical bundles.

A person is aware of the position of the limbs, movements in the joints, feels the pressure of the body on the soles of the feet. Proprioceptive impulses come from receptors in muscles, tendons, fascia, joint capsules, deep connective tissue and skin. They go to the spinal cord first along the dendrites. and then along the axons of the pseudo-unipolar neurons of the spinal nodes. Having given collaterals to the neurons of the posterior and anterior horns of the gray matter, the main part of the central branches first neuron enters the posterior cord. Some of them go down, others - up as a part of the medial thin bundle (Gaulle) and the lateral wedge-shaped bundle (Burdach) and end in their own nuclei: thin and wedge-shaped, located on the dorsal side of the lining of the lower part of the medulla oblongata. The fibers ascending as part of the posterior cords are arranged in somatotopic order. Those of them that conduct impulses from the perineum, legs, lower half of the body, go in a thin bundle adjacent to the posterior median sulcus. Others, conducting impulses from the chest, arms and neck. pass as part of a wedge-shaped bundle, and the fibers from the neck are located most laterally. Nerve cells in the thin and wedge-shaped nuclei are second neuron conducting impulses of proprioceptive sensitivity. Their axons form the bulbothalamic pathway. It goes first anteriorly immediately above the intersection of the descending pyramidal pathways, then, as a medial loop, crosses the midline and rises posterior to the pyramids and medially from the inferior olives through the cover of the upper part of the medulla oblongata, pons and midbrain to the ventrolateral nucleus of the thalamus. The nerve cells of this nucleus are third neuron... Their axons form a thalamocortical pathway that passes through the posterior third of the posterior leg of the inner capsule and the radiant crown of the white matter of the brain and ends in the postcentral gyrus (fields 1, 2, 3) and the superior parietal lobe (fields 5 and 7). The somatotopic organization is maintained throughout the entire course of the fibers to the thalamus and cortex. In the cortex of the postcentral gyrus, the projection of the body is a person standing on the head.

Not all afferent impulses are transmitted by the thalamus to the sensitive area of the cortex. Some of them end in the motor area of the cortex in the precentral gyrus. To a certain extent, the motor and sensory cortical fields overlap, so we can speak of the central gyri as a sensorimotor area. Sensitive signals here can be immediately converted into motor responses. This is due to the existence of sensorimotor feedback loops. The pyramidal fibers of these short circles usually end right on the cells of the anterior horns of the spinal cord without interneurons.

Impulses emanating from muscle spindles and tendon receptors are transmitted more rapidly by conductive myelinated fibers. Other proprioceptive impulses emanating from receptors in fascia, joints and deep layers of connective tissue are carried along less myelinated fibers. Only a small part of the proprioceptive impulses reaches the cerebral cortex and can be analyzed. Most of the impulses travel along the feedback loops and do not reach this level. These are the elements of reflexes that serve as the basis for voluntary and involuntary movements, as well as static reflexes that oppose the force of gravity.

Some of the impulses from muscles, tendons, joints and deep tissues go to the cerebellum along the spinal cord. In addition, cells are located in the posterior horn of the spinal cord, the axons of which occupy the lateral cord, along which they rise to the neurons of the brain stem. These pathways - dorsal-tegmental, dorsal-reticular, dorsal-olive, dorsal-vestibular - are connected to the feedback rings of the extrapyramidal system.

The reticular formation plays a role in conducting sensitive impulses. Along its entire length, the spinal-reticular axons and collaterals of the dorsal-thalamic tracts approach the reticular formation. The spinal reticular pathways, conducting impulses of pain and temperature sensitivity and some types of touch, discharging in the reticular formation, enter the thalamus and further into the cerebral cortex. The difference between proto- and epicritical sensitivity may be due in part to the quantitative difference and distribution of fibers in the reticular formation between sensory pathways.

In the thalamus, pain, temperature and other types of sensitivity are perceived as vague, indefinite sensations. When they reach the cerebral cortex, they are differentiated by consciousness into different types. Complex types of sensitivity (discrimination - distinguishing between two points, precise determination of the place of application of a separate irritation, etc.) are the product of cortical activity. The main role in carrying out these modalities of sensitivity belongs to the posterior cords of the spinal cord.

Research methodology. To determine whether the patient knows about subjective changes in sensitivity or spontaneously experiences unusual sensations, one should find out whether he is worried about pain, whether there is a loss of sensitivity, whether there is a feeling of numbness in any part of the body. whether he experiences a burning sensation, pressure, stretching, tingling, creeping, etc. As a rule, it is recommended to study the sensitive sphere at the beginning of the examination: this, at first glance, simple examination should be carried out carefully and carefully. Evaluation of the results is based on the patient's subjective responses, but often objective symptoms (shuddering of the patient, withdrawal of the hand) help to clarify the zone of changes in sensitivity. If data are inconsistent and inconclusive, they should be interpreted with caution. If the patient is tired, the study should be postponed and subsequently repeated. To confirm the results, the sensitivity must be tested twice.

If the patient himself does not note sensory disorders, the doctor can check the sensitivity, keeping in mind the neural and segmental innervation of the face, body, and extremities. If specific sensory disorders (or movement disorders in the form of atrophy, weakness, ataxia) are detected, a thorough examination should be carried out to determine their nature and clarify the boundaries. The identified changes are marked with a pencil on the patient's skin and indicated on the diagram. It is useful to depict different types of sensitivity (pain, tactile, muscular-articular), respectively, with horizontal, vertical and diagonal stripes.

Surface Sensitivity Study... A regular needle is used to test pain sensitivity. It is better that the patient's eyes be closed during the examination. Tingling should be done either with the tip or with the head of the needle.

The patient answers: "acutely" or "stupidly". You should "go" from areas with less sensitivity to areas with more. If the injections are applied too close and often, their summation is possible; if the conduct is slow, the patient's response corresponds to the previous irritation.

Temperature sensitivity is checked using test tubes with cold (5-10 ° C) and hot (40-45 ° C) water. The patient is asked to answer: "hot" or "cold". Both types of temperature sensations occur at the same time, although sometimes one can be partially preserved. Typically, the area of violations of thermal sensitivity is wider than cold.

To test tactile sensitivity, various means are proposed: a brush, a piece of cotton wool, a pen, paper. The examination can also be carried out with a very light touch of the fingers. Tactile sensitivity is assessed together with pain (touching alternately with the tip and the needle head). A possible test is to touch the hair. The irritation should be applied lightly without applying pressure to the subcutaneous tissue.

Deep Sensitivity Research... The musculo-articular sense is tested as follows. The examiner should cover a completely relaxed finger from the lateral surfaces with minimal pressure and passively move it. The finger to be examined should be separated from the other fingers. The patient is not allowed to make any active movements with his fingers. If the feeling of movement or position in the fingers is lost, other parts of the body should be examined: the leg, forearm. Normally, the examinee should determine the movement in the interphalangeal joints with a swing of 1-2 °, and even less in the more proximal joints. At first, recognition of the position of the fingers is impaired, then the sensation of movement is lost. In the future, these sensations can be lost throughout the limb. In the legs, the muscular-articular feeling is disturbed first in the little finger, and then in the thumb, in the hands - also first in the little finger, and then in the remaining fingers. The musculo-articular feeling can be checked by another method: the examiner's hand or fingers are given a certain position, and the patient's eyes must be closed; then he is asked to describe the position of the hand or to simulate this position with the other hand. The next technique: arms extended forward: in case of violation of the musculoskeletal feeling, the affected arm makes wave-like movements or falls, or does not bring it to the level of the other arm. To identify sensory ataxia, finger-nose and calcaneal-knee tests, Romberg's test, gait are examined.

Vibration sensitivity is checked using a tuning fork (128 or 256 Hz) mounted on the bony prominence. Pay attention to the vibration intensity and its duration. The tuning fork is brought to a state of maximum vibration and placed on the 1st finger or the medial or lateral ankle and held until the patient feels vibration. Then the tuning fork should be installed on the wrist, sternum or collarbone and it is clarified whether the patient feels vibration. It is also necessary to compare the feeling of vibration between the patient and the examiner. The feeling of pressure is investigated by pressing on subcutaneous tissues: muscles, tendons, nerve trunks. In this case, you can use a blunt object, as well as squeeze the tissue between your fingers. The perception of pressure and its localization are clarified. For a quantitative assessment, an esthesiometer or piezimeter is used, in which the differentiation of local pressure is determined in grams. To identify the feeling of mass, the patient is asked to determine the difference in the mass of two objects of the same shape and size, placed in the palm of the hand. Kinesthetic sensitivity (determining the direction of the skin fold): the patient must, with his eyes closed, determine in which direction the examiner moves the fold on the trunk, arm, leg - up or down.

Complex sensitivity study... The feeling of localization of injections and touching the skin is determined in a patient with closed eyes. Discriminatory sensitivity (the ability to distinguish between two simultaneous skin irritations) is examined with a Weber caliper or a calibrated two-dimensional anesthesiometer. A patient with closed eyes should determine the minimum distance between two points.

This distance varies on different parts of the body: 1 mm at the tip of the tongue, 2-4 mm on the palmar surface of the fingertips, 4-6 mm on the dorsum of the fingers, 8-12 mm on the palm, 20-30 mm on the back of the hand. There is greater distance in the forearm, shoulder, body, lower leg and thigh. The two sides are compared. Two-dimensional spatial sense - recognition of signs written on the skin: the subject with closed eyes identifies letters and numbers that the examiner writes on the skin. Stereognosis - recognition of an object by touch: a patient with closed eyes determines by touching objects placed in the hand, their shape, size, consistency.

Sensory Disorders... Pain is the most common symptom of the disease and the reason for seeking medical attention. Pain in diseases of internal organs occurs due to impaired blood flow, spasm of smooth muscles, stretching of the walls of hollow organs, inflammatory changes in organs and tissues. The defeat of the brain substance is not accompanied by pain, it occurs when the membranes, intracranial vessels are irritated.

Pain occurs during various pathological processes in organs and tissues in connection with irritation of sensitive fibers (somatic and autonomic) of the nerve trunks and roots, have a projection character, i.e. are felt not only at the site of irritation, but also distally, in the area innervated by these nerves and roots. Projection also includes phantom pain in the absent segments of the limbs after amputation and central pain, especially painful with damage to the thalamus. Pain can be radiating, i.e. spreading from one of the branches of the nerve to others, not directly affected. Pain can manifest itself in the area of segmental innervation or in a distant area, in the area directly connected with the pathological focus - reflected. Pain repercussion is carried out with the participation of cells of the spinal nodes, gray matter of the spinal cord and brain stem, autonomic nervous system and receptors in the irritation zone. Repercussion is manifested in the reflection zone by various phenomena: vegetative, sensitive, motor, trophic, etc. Reflected pain zones of Zakharyin - Ged arise when irritation is irradiated to the corresponding zone on the skin in case of diseases of internal organs. There is the following ratio between the spinal cord segment and the zones of reflected pain: the heart corresponds to the CIII-CIV and ThI-ThVI segments, the stomach - CIII-CIV and ThVI-ThIX, the intestines - ThIX-ThXII, the liver and gallbladder - ThVII-ThX, the kidney and ureter - ThXI-SI, bladder - ThXI-SII and SIII-SIV, uterus - ThX-SII and SI-SIV.

It is important to examine the muscles and nerve trunks by palpation and stretching. With neuralgia and neuritis, their soreness can be found. Palpation is performed in those places where the nerves are located close to the bones or to the surface (pain points). These are the pain points of the occipital nerve downward from the occipital tubercles, the supraclavicular, corresponding to the brachial plexus, as well as along the sciatic nerve, etc. Pain can occur when a nerve or root is stretched. Lasegue's symptom is characteristic of damage to the sciatic nerve: the leg extended at the knee joint is bent at the hip joint (the first phase of nerve tension is painful), then the lower leg is bent (the second phase is the disappearance of pain due to the termination of the nerve tension). Matskevich's symptom is characteristic of lesions of the femoral nerve: maximum flexion of the lower leg in a patient lying on his stomach causes pain on the front of the thigh. If the same nerve is damaged, Wasserman's symptom is determined: if a patient lying on his stomach is extended his leg in the hip joint, then pain occurs on the front surface of the thigh.

Sensory impairment can be characterized as hypesthesia- decrease in sensitivity, anesthesia- lack of sensitivity, dysesthesia- perversion of the perception of irritation (tactile or thermal irritation is felt as painful, etc.), analgesia- loss of pain sensitivity, topanesthesia- lack of a sense of localization, thermoanesthesia- lack of temperature sensitivity, astereognosis- violation of stereognosis, hyperesthesia or hyperalgesia- increased sensitivity, hyperpathy- an increase in the threshold of excitability (light irritations are not perceived, with more significant ones, excessive intensity and persistence of sensations occurs, paresthesias- a feeling of crawling, itching, cold, burning, numbness, etc., arising spontaneously or as a result of nerve pressing, irritation of nerve trunks, peripheral nerve endings (with local circulatory disorders), causalgia- excruciating burning sensation against the background of intense pain with incomplete break of some large nerve trunks, polyesthesia- the perception of a single irritation as multiple, alloesthesia- perception of sensation elsewhere; allocheiria- a feeling of irritation in a symmetrical area on the opposite side, phantom pain- the feeling of a missing part of the limb.

Topical diagnosis of sensitivity disorders. Sensory impairment syndromes differ depending on the localization of the pathological process. Peripheral nerve damage causes a neural type of sensitivity disorder: pain, hypesthesia or anesthesia, the presence of pain points in the innervation zone, symptoms of tension. All kinds of sensitivity are impaired. The zone of hypesthesia detected when a given nerve is damaged is usually smaller than the zone of its anatomical innervation, due to overlapping by neighboring nerves. The nerves of the face and trunk usually have a midline overlap (larger on the trunk than on the face), so organic anesthesia almost always ends before the midline. Neuralgia is noted - pain in the area of the affected nerve, sometimes hyperpathy, hyperalgesia or causalgia. The pain increases with pressure on the nerve, excitement (trigeminal neuralgia). Plexalgic type (with damage to the plexus) - pain, symptoms of tension in the nerves coming from the plexus, impaired sensitivity in the innervation zone. Usually, there are also movement disorders. Radicular type (with damage to the posterior roots) - paresthesias, pain, disturbances of all types of sensitivity in the corresponding dermatomes, symptoms of root tension, pain in the paravertebral points and in the area of spinous processes. If the damaged roots innervate the arm or leg, hypotension, areflexia, and ataxia will also occur. For loss of radicular-type sensitivity, damage to several adjacent roots is necessary. Polyneuritic type (multiple lesions of peripheral nerves) - pain, sensory disorders (in the form of "gloves" and "socks") in the distal segments of the extremities. Ganglionic type (with lesions of the spinal node) - pain along the root, shingles (with ganglioniculalgia), sensitive disorders in the corresponding dermatomes. Sympathetic type (with the defeat of the sympathetic ganglia) - causalgia, sharp radiating pains, vasomotor-trophic disorders.

At damage to the central nervous system(spinal cord, brain stem, thalamus, postcentral cortex and parietal lobe), the following sensory disturbance syndromes are observed. Segmental sensitivity disorders (with damage to the posterior horns and anterior white commissure of the spinal cord), a dissociated type of sensitivity disorder - a violation of pain and temperature sensitivity in the corresponding dermatomes while maintaining deep and tactile sensitivity. Usually seen with syringomyelia. Dermatomes correspond to certain segments of the spinal cord, which is of great diagnostic value in determining the level of its lesion. The tabetic type of sensitivity disorder (with damage to the posterior cords) is a violation of deep sensitivity with the preservation of superficial sensitivity, sensitive ataxia. Sensory disorders in Brown-Séquard syndrome (with damage to half of the spinal cord) is a violation of deep sensitivity and movement disorders on the side of the lesion, and superficial sensitivity on the opposite side.

The conductive type of disorder of all types of sensitivity below the level of the lesion (with complete transverse lesion of the spinal cord) is paraanesthesia. An alternating type of sensitivity disorder (with damage to the brain stem) is hemianesthesia of superficial sensitivity in the extremities opposite the focus with damage to the spinal thalamic tract, but the segmental type on the face on the side of the focus with damage to the trigeminal nerve nucleus. Thalamic type of sensitivity disorder (with damage to the thalamus) - hemihypesthesia in the extremities opposite to the focus against the background of hyperpathy, the predominance of deep sensitivity disorders, "thalamic" pain (burning, periodically intensifying and difficult to treat). If the sensitive pathways in the posterior leg of the inner capsule are affected, all types of sensitivity in the opposite half of the body (hemihypesthesia or hemianesthesia) drop out. Cortical type of sensitivity disorder (with damage to the cerebral cortex) - paresthesia (tingling, creeping, numbness) in half of the upper lip, tongue, face, in the arm or leg on the opposite side, depending on the localization of the lesion in the postcentral gyrus. Paresthesias can also occur as focal sensitive paroxysms. Sensory disorders are limited to half of the face, arm or leg, or torso. With damage to the parietal lobe, disorders of complex types of sensitivity occur.

Functions similar to object recognition by touch (stereognosis) require the inclusion of additional associative fields of the cortex. These fields are localized in the parietal lobe, where individual sensations of size, shape, physical properties (sharpness, softness, hardness, temperature, etc.) are integrated and can be compared with those tactile sensations that were present in the past. Damage to the inferior parietal lobe manifested by astereognosis, i.e. loss of the ability to recognize objects when touching them (by touch) on the side opposite to the hearth.

Syndrome of impaired muscle-joint sensitivity can manifest itself in the form of afferent paresis, i.e. disorders of motor functions, which are caused by a violation of muscular-articular feelings. It is characterized by a disorder of coordination of movements, slowness, awkwardness when performing a voluntary motor act, and hypermetria. Afferent paresis syndrome can be one of the signs of damage to the parietal lobe. Afferent paresis with damage to the posterior cords of the spinal cord is characterized by spinal ataxia: movements become disproportionate, inaccurate, and when a motor act is performed, muscles that are not directly related to the performed movement are activated. At the heart of these disorders is a violation of the innervation of agonists, synergists and antagonists. Ataxia is detected with a fingertip test, in the study of diadochokinesis. when asked, draw a circle with your finger, write a number in the air, etc. Ataxia in the lower extremities manifests itself with a calcaneal-knee test, standing with eyes closed. When walking, the patient excessively extends his legs and throws them forward, stomps heavily (“stamping gait.” Asynergy is observed, the trunk lags behind the legs when walking. When vision is turned off, ataxia increases. It is found when walking, if the patient is given the task to walk in a narrow voice. In mild cases, ataxia is detected by the Romberg test with closed eyes.In spinal lesions, in addition to afferent paresis, areflexia, ataxia, muscle hypotonia, and sometimes imitation synkinesias are observed.

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The bodies of the neurons that innervate the skin lie in the anterior horns of the gray matter of the spinal cord. Their afferent fibers do not form special sensory nerves, but are distributed along many peripheral nerves. The nerve endings of these fibers are located in the skin and related structures:

mechanoreceptors;
thermoreceptors;
pain receptors.

They are not collected in separate senses, but are scattered throughout the skin. The density of skin receptors is not uniform everywhere.

Mechanoreception (touch) includes a number of qualities such as sensation:

pressure;
touching;
vibration;
tickling.

It is believed that each type of sensation has its own receptors. In the skin, they are located at different depths and in its various structural formations. Most of the receptors are free nerve endings of sensory neurons that lack the myelin sheath. Some of them are enclosed in various kinds of capsules.

Each type of skin receptor responds predominantly to “its own” modulation of the stimulus, to which it is more sensitive. However, some receptors also respond to stimuli of a different kind, but its sensitivity to them is much lower. Meissner's bodies are speed sensors.

The irritation in them is perceived only when the object moves. They are located in the skin devoid of hairy cover (fingers, palms, lips, tongue, genitals, nipples of the breast). The speed is also perceived by the free nerve endings located around the hair follicles. Merkel discs perceive the intensity (force) of pressure.

They are found in hairy and hairless skin. Pacini's bodies are receptors for pressure and vibration. They are found not only in the skin, but also in tendons, ligaments, mesentery. The sensation of vibration occurs as a result of rapidly changing stimuli. All these formations are the ends of the dendrites of the myelin fibers of group II, the speed of excitation in which is 30-70 m / s.

Along with them, unmyelinated fibers can be found in the cutaneous nerve. In some nerves, they make up 50% of all fibers. Some of them transmit impulses from thermoreceptors, while others respond to weak tactile stimuli. But most of these fibers are related to pain-sensing nociceptors.

In the tactile receptors of this group, the accuracy of sensation localization is low. The speed of conduction of impulses along these nerves is even lower. They signal weak mechanical stimuli moving along the skin. It is believed that when they and the nociceptors are stimulated together, a tickling sensation arises.

The mechanism of arousal

Under mechanical action on the skin, and therefore on the nerve ending, its membrane is deformed. As a result, the membrane permeability to Na in this region increases. The arrival of this ion leads to the appearance of a RP, which has all the properties of the local potential. Its summation ensures the emergence of an action potential (AP) in the neighboring interception of Ranvier. Only after this does the PD propagate centripetally without decrement.

Among mechanoreceptors, there are rapidly and slowly adapting receptors. For example, due to the property of adaptation of skin receptors, a person soon after dressing ceases to notice the presence of clothing. But it is worth "remembering" about it, as thanks to the increased sensitivity of receptors, we again begin to feel "dressed".

Under real conditions, when an irritant acts on the skin, PD occurs in several types of receptors. From here, excitement is transmitted to the spinal cord, and then through the lateral and posterior columns to the thalamus and cerebral cortex. In the course of transmission at each of the levels (spinal cord, trunk, thalamus, cerebral cortex), afferent information is analyzed. At the same time, the formation of the corresponding reflexes is possible at each level.

For the reflex response, the reflexogenic zone is of great importance - the place where the stimulus is applied. Afferents entering the spinal cord along the posterior roots, in each segment, innervate limited areas of the skin; called dermatomes. In the spinal cord, adjacent dermatomes overlap strongly due to the redistribution of fiber bundles in the peripheral plexuses. As a result, each peripheral nerve contains fibers from several dorsal roots, and each root contains fibers from different nerves.

At the level of the spinal cord, afferent neurons interact closely with both motor neurons and autonomic nerves (naturally, in those parts of the spinal cord where they exist). As a result, when an irritant acts on the skin, motor or autonomic reflexes can occur.

Whether they appear or not, how pronounced they will be, depends largely on the specific quality of the stimulus, as well as on the descending impulses of the overlying parts of the central nervous system that control the functions of the spinal cord. The second neuron of somatosensory afferentation is located in the spinal cord or in the brain stem. Their fibers reach the ventro-basal nuclei of the thalamus of the contralateral half, where the second neurons of the ascending pathways are located.

Here, as well as in the spinal cord, there is a fairly clearly expressed somatotopic representation from a specific area of the periphery to the corresponding part of the thalamus. From these nuclei of the thalamus, impulses are directed either to other nuclei of the thalamus, or to the somatosensory zones of the cerebral cortex.

Skin sensitivity disorders

Anesthesia

Complete loss of either type of sensitivity. Distinguish between pain anesthesia (analgesia), temperature (termanesthesia), muscular-articular (batianesthesia). The loss of the sense of localization is called topanesthesia, the stereognostic feeling is called astereognosis. There is also total anesthesia, when all types of sensitivity disappear.

Hypesthesia

Decrease in sensitivity, decrease in its intensity. It can also relate to other types of sensitivity.

Hyperesthesia

An increase in the perception of sensitivity arises from a decrease in the threshold of excitability of sensitive points of the skin.

Dissociation

Splitting of sensitivity is an isolated loss of some types of sensitivity while preserving other types of it on the same site. Dissociation occurs in the case of damage to the posterior horns and the anterior white commissure of the spinal cord.

Qualitative violations of superficial sensitivity are associated with perversion of the content of perceived information and in the clinic are manifested:

hyperpathy;
dysesthesia;
polyesthesia;
synesthesia;
allocheiria.

Pathology and causes

Sensory disturbances can manifest as symptoms of decrease (weakening or absence of one or more types of sensitivity) and / or symptoms of intensification (pathological sensations in the form of paresthesia, such as tingling or numbness, or hypersensitivity to sensory stimuli - pain, hyperesthesia).

Causes: pathological processes that damage peripheral receptors located in various tissues and organs, sensory fibers of peripheral nerves, afferent pathways of the spinal cord and brain stem, thalamus and cortical centers in the parietal lobe.

Causes of various types of sensitivity disorders, depending on the level of damage to the nervous system →. Short-term and transient paresthesias do not indicate damage to the nervous system. Causes of paresthesia, depending on the level of the lesion →.

Table 1.26-1. Symptoms and causes of sensory impairment, depending on the location of damage

Damage location	Type of violations	Causes
peripheral nerve	pain and paresthesia in the innervation area, later loss of all types of sensitivity	mononeuropathies (trauma)
spinal nerve roots	increased pain with increased intracranial pressure (eg, cough, defecation), segmental paresthesia, then loss of all types of sensitivity	radiculitis of the lumbosacral or cervical spine (herniated disc), tumors, acute inflammatory demyelinating polyradiculoneuropathy, significant degenerative changes in the spine
	bilateral loss of all types of sensitivity below the lesion site	trauma, tumor, inflammation or ischemia of the spinal cord, hemorrhage in the spinal cord
transverse spinal cord injury	damage to sensitivity below the level of damage: deep and tactile - on the affected side, pain and temperature - on the opposite side	extramedullary tumor, trauma, multiple sclerosis
intramedullary lesions	dissociated sensory disturbances: loss of pain and temperature sensitivity with preserved deep and partially tactile sensitivity	intramedullary tumors, syringomyelia, post-traumatic intramedullary hemorrhage, thrombosis of the anterior spinal artery
posterior columns of the spinal cord	loss of deep sensitivity, sensory ataxia, decreased muscle tone and lack of deep reflexes	funicular myelosis (vitamin B12 vitamin deficiency), tabes dorsalis (syphilis of the nervous system), sometimes diabetes mellitus
	very unpleasant, severe, paroxysmal or constant pain in half of the body, resistant to drugs, hemianesthesia, especially in the case of impaired sensory orientation	ischemic or hemorrhagic stroke, tumor, trauma
parietal cortex	the inability to assess the strength and localization of the stimulus, violation of dermatolexia (the ability to recognize symbols written on the skin), the inability to discriminate (to distinguish between two simultaneously acting stimuli), the phenomenon of extinction (i.e., the extinction of an impulse - the inability to feel one of the sensitive sensations when two points are irritated, located in the same places on both sides of the body), astereognosia (inability to recognize objects that the patient holds in his hands without the aid of vision)	ischemic or hemorrhagic stroke, tumors

Table 1.26-2. Causes of paresthesia, depending on the location

half face	vasospasm during the aura with migraine, simple partial epileptic seizure, transient ischemic attack (often also hemiparesis)
	tetany, hyperventilation
one upper limb	paresthesias in the fingers can be a symptom of median nerve damage (eg, carpal tunnel syndrome), ulnar or radial; epileptic seizure, cerebral ischemia
both upper limbs	neuropathy, multiple sclerosis, syringomyelia
torso	Lermitte's symptom, characteristic of multiple sclerosis - spontaneous or caused by a rapid tilt of the head (sensation of a current passing along the spine)
lower limbs	more often a symptom of the initial stage of polyneuropathy, also funicular myelosis of the posterior columns, multiple sclerosis, restless legs syndrome
hemianesthesia (upper and lower limb on one side)	stroke, simple partial epileptic seizure

Diagnostics

1. History and physical examination: the type, severity, circumstances of the onset and localization of sensitivity disorders should be assessed. Tactile sensitivity examine, touching the body with a piece of tissue paper or cotton on a stick, pain sensitivity- with a needle, feeling of temperature- using two test tubes with warm and cold water (from the tap). Investigating sensitivity, it is compared on symmetrical parts of the body, the limits of sensitivity disorders are determined as accurately as possible and they are compared with the areas of innervation of individual peripheral nerves and individual dermatomes →.

2. Ancillary studies: neuroimaging (CT, MRI) of the brain and / or spinal cord, electrophysiological studies (sensory conduction; evoked sensory potentials) depending on the expected level of damage.

Sensitivity (we are considering the concept within the framework of physiology) is one of the most important properties that both humans and any other living organism have. Therefore, it requires detailed consideration. In the article we will present the types of sensitivity for a number of classifications, as well as the types of its violations.

What's this?

All types of sensitivity in physiology are:

The part of the reception perceived by the psyche. Reception is an afferent impulse that enters the central nervous system.
The ability of a living organism to perceive various stimuli that emanate both from its own organs and tissues, and from the environment.
The ability of the body, preceding the differentiated response to a stimulus, is reactivity.

And now - classifications of types of sensitivity.

General sensitivity

Several groups stand out here at once - we will present their content separately.

The exteroceptive type (superficial sensitivity) within oneself is divided into:

tactile (rough);
painful;
temperature (cold and heat).

Proprioceptive type (deep sensitivity) - the feeling of oneself in space, the position of one's body, limbs relative to each other. This view has the following categories within itself:

feeling of own body weight, pressure;
vibration;
feeling of touch (tactile light);
articular-muscular;
kinesthesia (the so-called definition of the movement of skin folds).

Complex types of sensitivity:

The feeling is two-dimensional - with its help we determine the place of touching our body. It helps to find out what symbol, number or letter is "written" on the skin with another person's finger.
Interoceptive - this sensitivity causes irritation of internal organs.
Discriminatory - helps to distinguish between touches, skin pricks that are applied at a close distance to each other.
Stereognosis - this type of sensitivity helps to recognize an object by touch.

As for the examples given, their identification will be possible only with the further arrival and processing of the impulse from the primary cortical layer of the analyzer (it will be the central posterior gyrus) into the associative or secondary cortical fields. The latter are predominantly located in the parieto-postcentral zones, in the inferior and superior parietal lobe.

Let's move on to the next classification.

General and special sensitivity

The same concepts are used here, only for a slightly different classification.

The general sensitivity is divided into simple and complex.

Special sensitivity is represented by the following categories:

visual;
gustatory;
olfactory;
auditory.

Complex sensitivity

In this classification, we will consider various types of sensitivity - characteristic not only for humans, but for all living things in general.

This is the following:

Vision is the body's perception of light.
Echolocation, hearing - the perception of sounds by living systems.
Smell, taste, stereochemical sense (typical for insects and hammerhead sharks) - chemical sensitivity of the organism.
Magnetoreception is the ability of a living creature to feel a magnetic field, which allows one to navigate the terrain, determine the height, and plan the movement of its own body. The type of sensitivity is characteristic of some sharks.
Electroreception is the ability to sense electrical signals from the surrounding world. It is used to search for prey, orientation, and various forms of biocommunication.

According to phylogenetic criteria of formation

The classification was proposed by the scientist G. Head. There are two types of sensitivity of a person, a living being:

Protopathic. A primitive form with its center in the thalamus. He cannot give an exact definition of the localization of the source of irritation - neither external, nor inside his own body. Reflects no longer objective states, but subjective processes. Protopathic sensitivity provides the perception of the most powerful, coarse forms of irritants, pain and temperature, which are dangerous to the body.
Epicritical. It has a cortical center, is more differentiated, objectified. Phylogenetically considered younger than the first. Allows the body to perceive more subtle irritations, to assess their degree, quality, localization, character, etc.

By location of receptors

This classification was proposed in 1906 by the English physiologist C. Sherrington. He proposed to divide all sensitivity into three categories:

Varieties of skin sensitivity

Classical physiology distinguishes the following types of skin sensitivity:

Pain. It arises under the influence of irritations that are destructive in their strength and nature. She will talk about direct danger to the body.
Thermal (temperature) sensitivity. It allows us to define hot, warm, cold, icy things for us. Its greatest importance is for the reflex regulation of the body.
Touch and pressure. These sensations are related. Pressure is essentially a strong touch, so no specific receptors are allocated for it. Experience (with the participation of vision, muscular feeling) makes it possible to accurately localize the area affected by the stimulus.

In some classifications, the varieties of skin sensitivity will be divided in this way:

Pain.
Feeling cold.
Touch.
Feeling warm.

Types of thresholds of sensation

Now let's consider the classification of the types of sensitivity thresholds:

An absolute lower threshold for sensation. This is the smallest strength or magnitude of the stimulus, which retains its ability to cause nervous excitement in the analyzer, sufficient for the emergence of one or another sensation.
An absolute upper threshold for sensation. On the contrary, the maximum value, the strength of the stimulus, above which the organism ceases to perceive it.
The discrimination threshold (or the difference threshold of sensation) is the smallest difference in the intensity of two identical stimuli that a living organism is able to perceive. Note that not every difference will be felt here. It is necessary that it reaches a certain value or strength.

Varieties of disorders

And now - the types of sensitivity disorders. The following stands out here:

Anesthesia is the name for the complete loss of any type of sensitivity. There is heat (thermoanesthesia), tactile, painful (analgesia). There may be a loss of a sense of stereognosis, localization.
Hypesthesia - this is the name of a decrease in sensitivity, a decrease in the intensity of certain sensations.
Hyperesthesia is the opposite of the previous phenomenon. Here the patient has an increased sensitivity to certain stimuli.
Hyperpathy - cases of perversion of sensitivity. The quality of sensation changes - point stimuli disintegrate, some qualitative differences between stimuli in the patient are erased. The sensation is colored in painful tones, it can be especially unpleasant. The aftereffect is also diagnosed - the sensation continues to remain after the cessation of the stimulus.
Paresthesia - a person experiences any sensations without the presence of their stimuli. For example, "creeping creeps", a sharp sensation - "as if thrown into a fever", burning, tingling, and so on.
Polyesthesia - with such a violation, a single sensation will be perceived by the patient as multiple.
Dysesthesia is a perverse perception of a certain irritation. For example, a touch is felt as a blow, and the effect of cold is felt as an effect of heat.
Synesthesia - a person will perceive an irritant not only in the location of its direct impact, but also in a different zone.
Allocheiria is a violation related to the previous one. The difference is that a person feels the effect of the stimulus not in the location of its impact, but in a symmetrical area of the opposite part of the body.
Thermalgia - cold, warmth is perceived painfully by the patient.
Dissociated sensitivity disorder is a case in which a certain sensation is disturbed, but all others persist.

Types of Disorders

The types of sensory impairment can be divided into the following categories:

Cortical type. This is a sensitivity disorder that will occur on the opposite side of the body.
Conductor type. The defeat of the pathways of sensitivity. Disorders will be detected downward from the location of the lesion.
Dissociated (segmental). It will be observed in case of damage to the sensitive nuclei of the cranial nerve of the brain trunks, as well as damage to the sensitive apparatus related to the spinal cord.
Distal (polyneuric) type. Multiple lesions affecting peripheral nerves.
Peripheral type. It is characterized by damage to the peripheral nerves and their plexuses. Here there is a disorder of all kinds of sensations.

Sensitivity is a fairly broad phenomenon in understanding. Evidence of this is a large number of classifications that within themselves subdivide it into multiple groups. Also today, a variety of types of sensitivity disorders have been established, the gradation of which is associated with the localization of the lesion, the manifestation of sensations in the patient.