Peripheral type of violation. Violation of sensitivity. Causes of numbness, or why numbness occurs

Sensory Disorders- disturbances in the body's ability to perceive various types of sensitive stimuli, which is one of the main functions nervous system. Sensory disturbances can manifest as burning, tingling, numbness, etc.

sensory symptoms are the result of receptor dysfunction nerve endings perceiving mechanical, thermal or chemical irritation. There are four types of sensations:

• tactile sensitivity - perceived by receptors located on the skin, for example, the sensation of pain, temperature, taste.
• sensory sensitivity - perceived by the senses, such as sight and hearing.
• deep sensitivity - perceived by receptors located in the muscles, tendons and labyrinth inner ear(for example, a sense of balance.)
• visceral sensitivity - perceived by receptors found in the internal organs and walls of blood vessels.

Causes of sensory disturbance

Causes of abnormal sensations very varied. They can occur as a result of developmental defects (genetic factors), pathological consequences of pregnancy, as well as:

• anomalies in the development of the spinal cord
• sciatica
• tumors, cysts
• multiple sclerosis
• Vitamin B12 deficiency
• brain diseases such as stroke
• disc protrusion

Some types of sensory impairment

analgesia- loss of pain sensitivity. It is characteristic of many diseases and traumatic lesions of the nervous system.

Thermal anesthesia- loss of temperature sensitivity

hypoesthesia- decreased sensitivity

Hyperesthesia- increased sensitivity. At the same time, the place and nature of the impact (cold, touch, etc.) is felt correctly.

hyperalgesia- excessive pain sensitivity.

Polyesthesia- a single stimulus is perceived as multiple. A possible sign of damage to the parietal lobe of the brain.

allocheiria- the patient localizes irritation not in the place of its application, but in symmetrical areas on the opposite side.

Dysesthesia- perverted perception of receptor affiliation (for example, cold can be perceived as tingling, painful irritation as heat).

Paresthesia- spontaneously arising sensations of numbness, tingling, "crawling", tightening, burning. Usually short term.

Hyperpathy- the appearance of a sharp feeling of unpleasant when applying irritation. It is characterized by an increase in the threshold for the perception of stimuli (hypesthesia), the lack of precise localization of irritation (an unpleasant sensation captures the entire area), a long latent period and a long period of aftereffect (perception lags behind the irritation in time, an unpleasant sensation persists for a long time after the cessation of the stimulus).

Sensitivity disorders: diagnosis

A patient with dysesthesia should come to a neurologist. Diagnosis is based mainly on questioning the patient and a very detailed physical examination. Sometimes you may need to analyze the cerebrospinal fluid. An important role in the diagnosis of sensory disorders is played by neurological tests (eg, electromyography).

Sensory Disorder: Treatment

There are many therapies used depending on the etiology, including pharmacology, physical-chemical methods, physical rehabilitation. Sometimes the intervention of a surgeon is necessary.

If you notice a violation of sensitivity in yourself, then the first thing you need to do is contact a neurologist, who will prescribe special procedures for you to identify the causes of this violation. The thing is that a violation of sensitivity can be a symptom of a serious disease, so it is important to accurately diagnose the disease.
You may be prescribed X-rays of the spine, MRI, lumbar puncture, electromyography, etc. And based on the data obtained, the doctor will be able to prescribe a comprehensive, effective treatment.

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 over many peripheral nerves. In the skin and related structures are the nerve endings of these fibers:

• mechanoreceptors;
• thermoreceptors;
• pain receptors.

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

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

• pressure;
• touch;
• vibrations;
• ticklish.

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 receptors are free nerve endings of sensory neurons that lack a myelin sheath. Some of them are enclosed in various kinds of capsules.

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

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, breast nipples). The speed is also perceived by the free nerve endings that are around hair follicles. Merkel discs perceive the intensity (force) of pressure.

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

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

In the tactile receptors of this group, the accuracy of sensation localization is low. The speed of impulse conduction along these nerves is even lower. They signal weak mechanical stimuli moving across the skin. It is believed that with joint irritation of them and nociceptors, a tickling sensation arises.

Excitation mechanism

With a mechanical effect on the skin, and consequently on the nerve ending, its membrane is deformed. As a result, the permeability of the membrane for Na increases in this region. The entry of this ion leads to the appearance of RP, which has all the properties of the local potential. Its summation ensures the occurrence of an action potential (AP) at the adjacent node of Ranvier. Only after this PD propagates centripetally without decrement.

Among mechanoreceptors, there are fast 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 clothes on himself. But it is worth "remembering" about it, as thanks to an increase in the sensitivity of receptors, we again begin to feel "dressed".

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

For a reflex response great importance has a reflexogenic zone - the place of application of the stimulus. Afferents entering the spinal cord along the posterior roots innervate limited areas of the skin in each segment; called dermatomes. In the spinal cord, adjacent dermatomes strongly overlap due to a 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, there is a close interaction of afferent neurons with both motor neurons and autonomic nerves (naturally, in those parts of the spinal cord where they are). As a result, motor or vegetative reflexes may occur under the action of an irritant on the skin.

Whether they appear or not, how pronounced they will be, largely depends on the specific quality of the stimulus, as well as on the descending impulses of the overlying sections of the central nervous system that control the functions of the spinal cord. The second somatosensory afferent neuron is located in the spinal cord or in the brain stem. Their fibers reach the ventrobasal 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 defined somatotopic representation from a specific area of ​​the periphery to the corresponding section 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 kind of sensitivity. Distinguish pain anesthesia (analgesia), temperature (thermanesthesia), muscular-articular (batianesthesia). The loss of the sense of localization is called topanesthesia, the loss of stereognostic sense is called astereognosis. Distinguish also total anesthesia, when all types of sensitivity disappear.

hypoesthesia

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

Hyperesthesia

An increase in the perception of sensitivity occurs due to a decrease in the threshold of excitability of sensitive points of the skin.

Dissociation

Splitting of sensitivity - an isolated loss of some types of sensitivity while maintaining its other types in the same area. Dissociation occurs in case of damage to the posterior horns and the anterior white commissure of the spinal cord.

Qualitative disturbances of superficial sensitivity are associated with a distortion of the content of perceived information and in the clinic manifest themselves:

• hyperpathy;
• dysesthesia;
• polyesthesia;
• synesthesia;
• allocheiria.

2.1. Types of sensitivity. Neurons and pathways

Sensitivity - the ability of a living organism to perceive stimuli emanating from the environment or from its own tissues and organs, and to respond to them with differentiated forms of reactions. Most people perceive the information received in the form of sensations, and for special complex types there are specialized sense organs (smell, sight, hearing, taste), which are considered as part of the nuclei of the cranial nerves.

The type of sensitivity is associated primarily with the type of receptors that convert certain types of energy (light, sound, heat, etc.) into nerve impulses. Conventionally, there are 3 main groups of receptors: exteroceptors (tactile, pain, temperature); proprioceptors located in muscles, tendons, ligaments, joints (provide information about the position of the limbs and torso in space, the degree of muscle contraction); interoceptors (chemoceptors, baroceptors located in the internal organs) [Fig. 2.1].

Pain, temperature, cold, heat and partially tactile sensitivity is surface sensitivity. The sense of the position of the trunk and limbs in space is a muscular-articular feeling; a sense of pressure and body mass - a two-dimensional-spatial sense; kinesthetic, vibrational sensitivity refers to deep sensitivity. In the process of evolution of animals, sensitivity became more and more differentiated and complicated, reaching the greatest perfection in humans thanks to combined activity. different types receptors and higher cortical centers.

Rice. 2.1.The distribution of receptors located in the skin devoid of hair: 1 - Pacini bodies; 2 - Ruffini bodies; 3 - Merkel disks; 4 - Meissner bodies; 5 - epidermis; 6 - peripheral nerve; 7 - dermis

The propagation of impulses of superficial and deep sensitivity from receptors to the cortical sections of the analyzers is carried out through a three-neuron system, but along different pathways. Through the peripheral nerve, the spinal ganglion and the posterior roots of the spinal cord, all types of sensitivity are conducted. Bell-Magendie law says that all types of sensitivity pass through the posterior roots, fibers of the motor nerves come out of the anterior roots. The spinal ganglions (intervertebral ganglia) contain first neurons for all sensitive pathways (Fig. 2.2). In the spinal cord, the course of conductors of various types of sensitivity is not the same.

Surface Sensitivity Pathways through the posterior roots enter the posterior horns of the spinal cord of the side of the same name, where it is located second neuron. Fibers from the cells of the posterior horn pass through the anterior commissure to the opposite side, rising obliquely 2-3 segments higher in the thoracic region (in cervical region roots run strictly horizontally), and as part of the anterior sections of the lateral

Rice. 2.2.Nerve fibers of the posterior root of the spinal cord: 1, 2 - bipolar neurons, the axons of which go to the posterior cords, and the afferent fibers start from Paccini's bodies and muscle spindles; 3, 4 - bipolar neurons, the axons of which end in the posterior horns of the spinal cord, from where the spinothalamic and spinocerebellar pathways begin; 5 - bipolar neurons, the axons of which end in the posterior horns of the spinal cord, from where the anterior spinothalamic pathway begins; 6 - thin fibers of pain sensitivity, ending in the gelatinous substance: I - medial part; II - lateral part

Rice. 2.3.Pathways of sensitivity (scheme):

A- ways of superficial sensitivity: 1 - receptor; 2 - spinal (sensitive) node (first neuron); 3 - Lissauer zone; 4 - rear horn;

5 - lateral cord; 6 - lateral spinothalamic pathway (second neuron); 7 - medial loop; 8 - thalamus; 9 - the third neuron; 10 - cerebral cortex;

6 - ways of deep sensitivity: 1 - receptor; 2 - spinal (sensitive) node (first neuron); 3 - rear cord; 4 - anterior spinothalamic pathway (second neuron of tactile sensitivity); 5 - internal arcuate fibers; 6 - thin and wedge-shaped nuclei (the second neuron of deep sensitivity); 7 - medial loop; 8 - thalamus; 9 - the third neuron; 10 - cerebral cortex

cords of the spinal cord are directed upward, ending in the lower part of the outer nucleus of the thalamus (third neuron). This path is called the lateral spinothalamic (Fig. 2.3).

The topic of conductors of skin sensitivity in the lateral cords of the spinal cord obeys the law eccentric arrangement of long paths, according to which the conductors coming from the lower segments of the spinal cord are more lateral than the conductors coming from the upper segments.

Third neuron begins with the cells of the ventrolateral nucleus of the optic tubercle, forming the thalamocortical pathway. Through the posterior third of the posterior leg of the internal capsule and then as part of the radiant crown, it is directed to the projection sensitive zone - posterior central gyrus(1, 2, 3, 43 fields according to Brodman). In addition to the posterior central gyrus, sensory fibers may terminate in the cortex upper parietal region(7, 39, 40 fields according to Brodman).

In the posterior central gyrus, the projection zones of individual parts of the body (opposite side) are located so that in

Rice. 2.4.Representation of sensitive functions in the posterior central gyrus (scheme):

I - pharynx; 2 - language; 3 - teeth, gums, jaw; 4 - lower lip; 5 - upper lip; 6 - face; 7 - nose; 8 - eyes; 9 - I finger of the hand; 10 - II finger of the hand;

II - III and IV fingers of the hand; 12 - V finger of the hand; 13 - brush; 14 - wrist; 15 - forearm; 16 - elbow; 17 - shoulder; 18 - head; 19 - neck; 20 - torso; 21 - thigh; 22 - lower leg; 23 - foot; 24 - toes; 25 - genitals

the uppermost sections of the gyrus, including the paracentral lobule, are the cortical centers of sensitivity for the lower limb, in the middle sections - for the upper limb, in the lower sections - for the face and head (Fig. 2.4). The sensory nuclei of the thalamus also have a somatotopic projection. And for a person in the highest degree the principle of functional significance in the somatotopic projection is characteristic - the largest number neurons and, accordingly, conductors and areas of the cortex occupy those parts of the body that perform the most complex function.

Ways of Deep Sensibility have a number of important differences from the course of the pathways of surface sensitivity: getting through the posterior roots into the spinal cord, the central fibers of the cells of the intervertebral

ganglion (first neuron) do not enter the posterior horns, but go to the posterior cords, in which they are located on the side of the same name. The fibers coming from the underlying sections (lower limbs) are located more medially, forming thin bundle, or Gaulle's bundle. Fibers that carry stimuli from proprioceptors upper limbs, occupy the outer part of the posterior cords, forming wedge-shaped bundle, or Burdach's bundle. Since fibers from the upper limbs pass in the wedge-shaped bundle, this path is mainly formed at the level of the cervical and upper thoracic segments of the spinal cord.

As part of thin and wedge-shaped bundles, the fibers reach medulla oblongata, ending in the nuclei of the posterior columns, where they begin second neurons paths of deep sensitivity, forming the bulbothalamic path.

Ways of deep sensitivity cross at the level of the medulla oblongata, forming medial loop, to which, at the level of the anterior parts of the bridge, fibers of the spinothalamic pathway and fibers coming from the sensory nuclei of the cranial nerves join. As a result, conductors of all types of sensitivity coming from the opposite half of the body are concentrated in the medial loop.

Conductors of deep sensitivity enter the ventrolateral nucleus of the thalamus, where third neuron, from the visual mound as part of the thalamocortical path of deep sensitivity through the posterior part of the posterior leg of the internal capsule they come to the posterior central gyrus of the cerebral cortex, the superior parietal lobule, and partly to some other parts of the parietal lobe.

In addition to the paths of the thin and wedge-shaped bundles (Gaulle and Burdakh), proprioceptive impulses (cerebellar proprioception) pass along the spinal cerebellar paths - ventral (Flexig) and dorsal (Govers) to the cerebellar vermis, where they are included in a complex system of motor coordination.

Thus, three-neuron circuit The structure of the pathways of superficial and deep sensitivity has a number of common features:

The first neuron is located in the intervertebral ganglion;

The fibers of the second neuron cross over;

The third neuron is located in the nuclei of the thalamus;

The thalamocortical pathway passes through the posterior part of the posterior leg of the internal capsule and ends mainly in the posterior central gyrus of the cerebral cortex.

2.2. Sensitivity Syndromes

The main differences in the course of conductors of superficial and deep sensitivity are noted at the level of the spinal and medulla oblongata, as well as the lower parts of the bridge. Pathological processes localized in these departments can in isolation affect the paths of only superficial or only deep sensitivity, which leads to the occurrence of dissociated disorders - the loss of some types of sensitivity while maintaining others (Fig. 2.5).

Dissociated Segmental Disorders observed with damage to the posterior horns, anterior gray adhesions; dissociated conductive- lateral or posterior cords of the spinal cord, decussation and lower divisions medial loop, lateral divisions of the medulla oblongata. To identify them, a separate study of different types of sensitivity is necessary.

Rice. 2.5.Sensitive disturbances in various levels damage to the nervous system (scheme):

I - polyneuritic type; 2 - damage to the cervical root (C VI);

3 - initial manifestations of intramedullary lesions of the thoracic spinal cord (Th IV -Th IX);

4 - pronounced manifestations of intramedullary lesions of the thoracic spinal cord (Th IV -Th IX);

5 - complete lesion of the Th VII segment; 6 - damage to the left half of the spinal cord in the cervical region (C IV); 7 - damage to the left half of the spinal cord in thoracic region(ThIV); 8 - defeat of the cauda equina; 9 - left-sided lesion in the lower part of the brain stem; 10 - right-sided lesion in the upper part of the brain stem;

II - defeat of the right parietal lobe. Red indicates a violation of all types of sensitivity, blue - superficial sensitivity, green - deep sensitivity

Qualitative types of sensory disturbances

Analgesia - loss of pain sensitivity.

Thermal anesthesia- loss of temperature sensitivity.

Anesthesia- loss of tactile sensitivity (in the proper sense of the word). A peculiar symptom complex is painful anesthesia (anaesthesia dolorosa), in which a decrease in sensitivity, determined during the study, is combined with spontaneously occurring pain sensations.

Hyperesthesia - increased sensitivity, often manifested as excessive pain sensitivity (hyperalgesia). The slightest touch causes sensations of pain. Hyperesthesia, like anesthesia, can spread to half of the body or to separate parts of it. At polyesthesia single irritation is perceived as multiple.

allocheiria- a violation in which the patient localizes irritation not in the place where it is applied, but on the opposite half of the body, usually in a symmetrical area.

Dysesthesia- perverted perception of the “receptor affiliation” of the stimulus: heat is perceived as cold, an injection as a touch of hot, etc.

Paresthesia- sensations of burning, tingling, tightening, crawling, etc., occurring spontaneously, without visible external influences.

Hyperpathy characterized by the appearance of a sharp feeling of "unpleasant" when applying irritation. The threshold of perception in hyperpathy is usually lowered, there is no sense of precise localization of the impact, perception lags behind in time from the moment of application of irritation (long latent period), quickly generalizes and is felt for a long time after the cessation of exposure (long aftereffect).

Pain symptoms occupy an important place among disorders of sensitivity.

Pain - this is an unpleasant sensory and emotional experience associated with real or perceived tissue damage, and at the same time the reaction of the body, mobilizing various functional systems to protect it from pathogens. Distinguish between acute and chronic pain. Acute pain indicates trouble due to injury, inflammation; it is stopped by analgesics and its prognosis depends on the etiological

factor a. Chronic pain lasts more than 3-6 months, it loses its positive protective properties, becoming an independent disease. The pathogenesis of chronic pain is associated only with a somatogenic pathological process, but also with functional changes in the nervous system, as well as a person's psychological reactions to the disease. By origin, nociceptive, neurogenic (neuropathic) and psychogenic pain are distinguished.

nociceptive pain caused by damage to the musculoskeletal system or internal organs and is directly related to receptor stimulation.

local pain occur in the area of ​​application of pain irritation.

Reflected (reflex) pain occur in diseases of the internal organs. They are localized in certain areas of the skin, called the Zakharyin-Ged zones. For certain internal organs, there are skin areas of the most frequent reflection of pain. So, the heart is mainly associated with segments and C 3 -C 4 and Th 1 - Th 6, the stomach - with Th 6 -Th 9, the liver and gallbladder- with Th 1 -Th 10, etc.; in places of localization of reflected pain, hyperesthesia is also often observed.

neuropathic pain occurs when the peripheral or central nervous system is damaged, namely those parts of it that are involved in the conduction, perception or modulation of pain (peripheral nerves, plexuses, posterior roots, thalamus, posterior central gyrus, autonomic nervous system).

Projection pain observed when the nerve trunk is irritated and, as it were, are projected into the skin zone innervated by this nerve.

Radiating pain arise in the zone of innervation of one of the branches of the nerve (for example, trigeminal) when irritation is applied in the zone of innervation of another branch of the same nerve.

Causalgia- paroxysmal pains of a burning nature, aggravated by touch, a breath of wind, excitement and localized in the area of ​​the affected nerve. Cooling and wetting reduce suffering. The characteristic symptom wet rag» Pirogov: patients apply a damp cloth to the painful area. Causalgia often occurs with a traumatic lesion of the median or tibial nerves in the zone of their innervation.

phantom pains observed in patients after amputation of limbs. The patient, as it were, constantly feels a non-existent

limb, its position, severity, discomfort it contains pain, burning, itching, etc. Phantom sensations are usually caused by a cicatricial process involving the nerve stump and supporting irritation of the nerve fibers and, accordingly, a pathological focus of excitation in the projection zone of the cortex. Psychogenic pain (psychalgia) pain in the absence of a disease or cause that could cause pain. Psychogenic pain is characterized by persistent, chronic course and mood changes (anxiety, depression, hypochondria, etc.). Diagnosis of psychogenic pain is difficult, but the abundance of bizarre or non-specific complaints in the absence of objective focal changes is alarming in her regard.

Types of sensory disorders and lesion syndromes The complete loss of all types of sensitivity is called complete, or total, anesthesia, decline - hypoesthesia increase - hyperesthesia. Half-body anesthesia is referred to as hemianesthesia, one limb - like monoanesthesia. Loss of certain types of sensitivity is possible.

The following types of sensitivity disorders are distinguished:

peripheral (violation of sensitivity in the zone of innervation of the peripheral nerve), occurs when:

Peripheral nerve;

Plexus;

segmental, radicular-segmental (violation of sensitivity in the zone of segmental innervation), occurs when:

spinal ganglion;

back spine;

back horn;

Anterior commissure;

conductive (violation of sensitivity throughout below the level of the lesion of the pathway), occurs when:

Posterior and lateral cords of the spinal cord;

brain stem;

thalamus (thalamic type);

Posterior third of the leg of the internal capsule;

White subcortical substance;

cortical type (disturbance of sensitivity is determined by the defeat of a certain area of ​​the projection sensitive zone of the cortex of the cerebral hemispheres) [Fig. 2.5].

Peripheral type of disorder of deep and superficial sensitivity occurs with damage to the peripheral nerve and plexus.

When defeated peripheral nerve trunk all kinds of sensitivity are violated. Zone of sensory disorders in case of damage peripheral nerves corresponds to the territory of innervation of this nerve (Fig. 2.6).

With polyneuritic syndrome (multiple, often symmetrical lesions of the nerve trunks of the extremities) or mononeuropathies

Rice. 2.6 a.Innervation of skin sensitivity by peripheral nerves (right) and segments of the spinal cord (left) (diagram). Front surface:

I- ophthalmic nerve(I branch of the trigeminal nerve); 2 - maxillary nerve (II branch of the trigeminal nerve); 3 - mandibular nerve (III branch of the trigeminal nerve); 4 - transverse nerve of the neck;

5 - supraclavicular nerves (lateral, intermediate, medial);

6 - axillary nerve; 7 - medial cutaneous nerve of the shoulder; 8 - posterior cutaneous nerve of the shoulder; 8a - intercostal-brachial nerve; 9 - medial cutaneous nerve of the forearm; 10 - lateral cutaneous nerve of the forearm;

II - radial nerve; 12 - median nerve; 13 - ulnar nerve; 14 - lateral cutaneous nerve of the thigh; 15 - anterior branch of the obturator nerve; 16 - anterior cutaneous branches of the femoral nerve; 17 - common peroneal nerve; 18 - saphenous nerve (branch of the femoral nerve); 19 - superficial peroneal nerve; 20 - deep peroneal nerve; 21 - femoral-genital nerve; 22 - ilio-inguinal nerve; 23 - anterior cutaneous branch of the iliac-hypogastric nerve; 24 - anterior cutaneous branches of the intercostal nerves; 25 - lateral cutaneous branches of the intercostal nerves

may be noted: 1) sensory disorders and anesthesia in the zone of innervation according to the type of "stocking and gloves", paresthesia, pain along the nerve trunks, tension symptoms; 2) movement disorders (atony, atrophy of muscles predominantly of the distal extremities, reduction or disappearance of tendon reflexes, skin reflexes); 3) vegetative disorders (disturbances in the trophism of the skin and nails, excessive sweating, cold snap and swelling of the hands and feet).

For neuralgic syndrome characterized by spontaneous pain, aggravated by movement, soreness at the exit points of the roots, symptoms of nerve tension, pain along the nerve trunks, hypoesthesia in the zone of nerve innervation.

Rice. 2.6 b.Innervation of skin sensitivity by peripheral nerves (right) and segments of the spinal cord (left) [scheme]. Back surface: 1 - large occipital nerve; 2 - small occipital nerve; 3 - large ear nerve; 4 - transverse nerve of the neck; 5 - suboccipital nerve; 6 - lateral supraclavicular nerves; 7 - medial skin branches (from the posterior branches of the thoracic nerves); 8 - lateral cutaneous branches (from the posterior branches of the thoracic nerves); 9 - axillary nerve; 9a - intercostal-brachial nerve; 10 - medial cutaneous nerve of the shoulder; 11 - posterior cutaneous nerve of the shoulder; 12 - medial cutaneous nerve of the forearm; 13 - posterior cutaneous nerve of the forearm; 14 - lateral cutaneous nerve of the forearm; 15 - radial nerve; 16 - median nerve; 17 - ulnar nerve; 18 - lateral cutaneous branch of the iliac-hypogastric nerve;

19 - lateral cutaneous nerve of the thigh;

20 - anterior cutaneous branches of the femoral nerve; 21 - obturator nerve;

22 - posterior cutaneous nerve of the thigh;

23 - common peroneal nerve;

24 - superficial peroneal nerve;

25 - saphenous nerve; 26 - sural nerve; 27 - lateral plantar nerve; 28 - medial plantar nerve; 29 - tibial nerve

When defeated plexus there is a sharp local pain at the points of the plexus and a violation of all types of sensitivity in the zone of innervation of the nerves emanating from this plexus.

Segmental type loss of deep sensitivity noted with damage to the posterior root and spinal ganglion, and segmental type of loss of surface sensitivity- with damage to the posterior root, intervertebral ganglion, posterior horn and anterior gray commissure of the spinal cord (Fig. 2.6).

Ganglionitedevelops with involvement in the pathological process spinal node:

Herpetic eruptions in the area of ​​the segment (herpes zoster);

Spontaneous pain;

Pain aggravated by movement;

Antalgic posture;

Meningo-radicular symptoms (Neri, Dezherina);

Tension of the long muscles of the back;

Hyperesthesia in the zone of segmental innervation, which is then replaced by anesthesia, a disorder of deep sensitivity of the segmental type.

An isolated lesion of the intervertebral ganglion is rare, often combined with a lesion of the posterior root.

When defeated posterior roots of the spinal cord develop sciatica, in contrast to the defeat of the ganglion with it:

All of the above symptoms are observed, except for herpetic eruptions;

The symptoms of damage to the posterior roots are accompanied by symptoms of damage to the anterior roots (peripheral muscle paresis in the zone of segmental innervation).

The level of segmental innervation can be determined using the following guidelines: the level of the armpit - the second thoracic segment - Th 2 , the level of the nipples - Th 5 , the level of the navel - Th 10 , the level of the inguinal fold - Th 12 . The lower limbs are innervated by the lumbar and upper sacral segments. It is important to remember that the segments of the spinal cord and the vertebrae do not correspond to each other. So, for example, the lumbar segments are located at the level of the three lower thoracic vertebrae, so the level of segmental damage to the spinal cord should not be confused with the level of damage to the spine.

Rice. 2.7.Segmental innervation of the skin of the trunk and extremities

The zones of segmental innervation on the trunk are located transversely, while on the limbs - longitudinally. On the face and in the perineum, segmental innervation zones have the shape of concentric circles (Fig. 2.7).

With damage to the posterior roots (radicular syndrome, sciatica) observed:

Severe spontaneous pain surrounding nature, aggravated by movement;

Soreness at the exit points of the roots;

Radicular tension symptoms;

Segmental disorders of sensitivity in the zone of innervation of the roots;

Paresthesia.

Damage to the posterior horn of the spinal cord - segmental-dissociated sensitivity disorder: loss of superficial sensitivity in the corresponding segmental zone on the side of the same name, while maintaining deep sensitivity, since the paths of deep sensitivity do not go into the posterior horn: C 1 -C 4 - half helmet, C 5 -Th 12 - half jacket, Th 2 -Th 12 - half belt, L 1 -S 5 - half leggings.

With bilateral lesions of the posterior horns, and also when damage to the anterior gray commissure, where the superficial sensitivity paths cross, a segmental type of superficial sensitivity disorder is detected on both sides: C 1 -C 4 - helmet, C 5 -Th 12 - jacket, Th 2 -Th 12 - belt, L 1 -S 5 - leggings.

Conductive dropout type deep sensitivity observed starting from the central process of the first neuron, which forms the posterior funiculi, and surface sensitivity - in case of damage, starting from the axon of the second neuron, which forms the lateral spinothalamic pathway in the lateral cords of the spinal cord.

At defeat white matter of the spinal cord posterior cords there are disorders of deep sensitivity (musculo-articular feeling, vibrational, partially tactile

sensitivity) according to the conductive type on the side of the focus, all the way below the level of its localization. At the same time, the so-called posterior columnar, or sensitive, ataxia develops - a violation of coordination of movements associated with the loss of proprioceptive control over movements. The gait in such patients is unstable, coordination of movements is disturbed. These phenomena are especially enhanced when the eyes are closed, since the control of the organ of vision makes it possible to compensate for the lack of information about the movements being made - "the patient does not walk with his feet, but with his eyes." A kind of "stamping gait" is also observed: the patient steps on the ground with force, as if "printing" a step, since the sense of the position of the limbs in space is lost. With milder disorders of the muscular-articular feeling, the patient cannot recognize only the nature of passive movements in the fingers.

With damage to the spinal cord in the region of the lateral funiculus there is a disorder of surface sensitivity (pain and temperature) according to the conduction type on the opposite side of the focus, below the site of the lesion. The upper limit of sensory impairment is determined 2-3 segments below the site of the lesion in the thoracic region, since the lateral spinothalamic pathway crosses 2-3 segments above the corresponding sensory cells in the posterior horn. With partial damage to the lateral spinothalamic pathway, it should be remembered that the fibers from the lower parts of the body are located more laterally in it.

If the entire trunk of the lateral spinothalamic tract is damaged at the level of any segment of the spinal cord, for example, at the level of Th 8, all conductors that come here from the posterior horn of the opposite side, including the Th 10 segment, will be involved (the fibers from the Th 8 segment of the posterior horn join the lateral spinothalamic path of the opposite side only at the level of segments Th 5 and Th 6). Therefore, there is a loss of surface sensitivity on the opposite half of the body entirely below the level of Th 10-11, i.e. contralateral and 2-3 segments below the level of the lesion.

At half spinal cord injury develops brownsequard syndrome, characterized by a loss of deep sensitivity, central paresis on the side of the focus and a violation of superficial sensitivity on the opposite side, segmental disorders at the level of the affected segment.

With transverse spinal cord injury there is a bilateral lesion of all types of sensitivity according to the conduction type.

Syndrome of extramedullary lesion. Initially, the adjacent half of the spinal cord is compressed from the outside, then the entire diameter is affected; the zone of disorder of superficial sensitivity begins with the distal parts of the lower limb, and with further growth of the tumor, it spreads upward (ascending type of sensory impairment). Three stages are distinguished in it: 1 - radicular, 2 - stage of Brown-Sequard syndrome, 3 - complete transverse lesion of the spinal cord.

Syndrome of intramedullary lesion. First, the medially located conductors, coming from the overlying segments, are affected, then laterally located, coming from the underlying segments. Therefore, segmental disorders - dissociated anesthesia, peripheral paralysis mainly in the proximal sections and conduction disorders of temperature and pain sensitivity spread from the level of the lesion from top to bottom. (descending type of sensory disorder, symptom of "oil stain"). The defeat of the pyramidal pathway is less pronounced than in the extramedullary process. There is no stage of radicular phenomena and Brown-Sequard syndrome.

With a complete lesion of the lateral spinothalamic pathway, in both cases, there is a contralateral loss of sensitivity 2-3 segments below the level of the lesion. For example, with an extramedullary lesion at the Th 8 level on the left, a disorder of superficial sensitivity on the opposite half of the body will spread from below to the Th 10-11 level, and with an intramedullary process at the Th 8 level, it will spread on the opposite half of the body from the Th 10-11 level down (symptom of "oil stain").

In case of damage to the conductors of sensitivity at the level brain stem, in particular medial loop, there is a loss of superficial and deep sensitivity on the opposite half of the body (hemianesthesia and sensitive hemiataxia). With a partial lesion of the medial loop, dissociated conduction disorders of deep sensitivity occur on opposite side. With simultaneous involvement in the pathological process cranial nerves alternating syndromes may be observed.

When defeated thalamus a violation of all types of sensitivity is detected on the side opposite to the focus, and hemianesthesia and sensitive hemiataxia are combined with symptoms of hyperpathy, trophic disorders, visual impairment (homonymous hemianopsia).

thalamic syndrome characterized by hemianesthesia, sensitive hemiataxy, homonymous hemianopia, thalamic pain (hemialgia) on the opposite side. A thalamic arm is observed (the hand is extended, the main phalanges of the fingers are bent, choreoathetoid movements in the hand), vegetative-trophic disorders on the side opposite to the focus (Harlequin syndrome), violent laughter and crying.

In case of defeat posterior 1/3 posterior leg of inner capsule hemianesthesia, sensitive hemiataxia occur, on the opposite side of the focus - and homonymous hemianopsia; in defeat entire hind thigh- hemiplegia, hemianesthesia, hemianopsia (sensitive hemiataxia is not detected on the paralyzed side); in defeat anterior leg- hemiataxia on the opposite side (break of the cortical-bridge pathway connecting the cortex of the cerebral hemispheres with the cerebellum).

When defeated cerebral cortex in the region of the posterior central gyrus and superior parietal lobule there is a loss of all types of sensitivity on the opposite side. Since partial lesions of the posterior central gyrus are more common, cortical sensory disorders have the form of monoanesthesia - loss of sensitivity only on the arm or leg. Cortical disturbances of sensitivity are more expressed in distal departments. Irritation of the region of the posterior central gyrus may give rise to the so-called sensory jacksonian seizures- a paroxysmal burning sensation, tingling, numbness in the corresponding parts of the opposite half of the body.

When defeated right upper parietal region arise complex disorders sensitivity: astereognosis, violation of the body scheme, when the patient has a misconception about the proportions of his body, the position of the limbs. The patient may feel that he has "extra" limbs (pseudopolymelia) or, conversely, one of the limbs is missing (pseudo-amelia). Other symptoms of damage to the upper parietal region are autopagnosia- inability to recognize parts own body, "disorientation" in one's own body, anosognosia -"Unrecognition" of one's own defect, illness (for example, the patient denies that he has paralysis).

Chapter 2

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

Thanks to the specialization of receptors, the first stage of the analysis of external stimuli is carried out - the decomposition of the whole into parts, differentiation of the nature and quality of signals. At the same time, all types of external energy, being transformed into nerve impulses, enter the brain in the form of signals. Depending on the functional characteristics, receptors are divided into exteroreceptors (located in the skin and inform about what is happening in the environment), telereceptors (found in the ears and eyes), proprioceptors (provide 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 considered as a sensitive organ that covers the entire surface of the body. It has free nerve endings and encapsulated terminal formations. Free nerve endings are located between the epidermal cells and perceive pain stimuli. Merkel's tactile corpuscles are localized mainly at the fingertips and respond to touch. Hair muffs are present where the skin is covered with hair and perceive tactile stimuli. Meissner's bodies are found on the palms, soles, lips, tip of the tongue, genital mucosa and are very sensitive to touch. Lamellar bodies of Vater-Pacini, located in the deep layers of the skin, perceive pressure. Krause flasks are considered cold receptors, and Ruffini bodies are heat receptors.

The 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.

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

Receptors - peripheral endings of afferent nerve fibers, which are peripheral processes of pseudo-unipolar spinal ganglia. At the same time, fibers emanating from the neuromuscular spindles and having a thick myelin sheath occupy the most medial part of the posterior root. middle part roots are occupied by fibers emanating from encapsulated receptors. The most lateral fibers are almost unmyelinated and conduct pain and temperature impulses. Only some impulses coming from the muscles, joints, fascia and other tissues reach the level of the cerebral cortex and are realized; most of the impulses are needed for automatic control motor activity necessary for standing or walking.

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

The conductive part of the analyzer is represented by spinal nodes, nuclei of the spinal cord, brain stem, various nuclei of the thalamus, as well as formations such as the reticular formation, structures of the limbic system and the cerebellum. The afferent impulses that have arrived in the CNS propagate, first of all, along the specific projection pathways of a given sensory modality and switch in the corresponding nuclei of the diencephalon. The axons of the neurons of these nuclei reach the sensory areas of the cortex, where the highest analysis of afferent information takes place within a given analyzer. In the cortical parts of the analyzer there are neurons that respond to only one sensory stimulus. These are specific projection neurons. Next to them are non-specific 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. It was found that the reticular formation. as well as other subcortical formations, it has an upward activating generalized effect on the cerebral cortex. After processing at the level of the cortical end of the analyzer, the impulses can radiate both horizontally along the inter- and intracortical pathways, and vertically along the cortico-fugal pathways to non-specific structures of the mine trunk. The activity of the analyzer also includes the reverse influence of higher calves on the receptor and conductor parts of the analyzer. The sensitivity of the receptors (the receptive part), as well as the functional state of the transmission 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 when conducting a neurological examination of a patient is the following classification of sensitivity:

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

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

complex shapes sensitivity: a sense of localization of an injection, touch, recognition of signs and letters written on the skin (two-dimensional-spatial sense), distinction between injections applied simultaneously at close range with a Weber compass (discriminatory sensitivity), stereognosis;

Sensation due to irritation of the receptors of internal organs (interoceptive sensitivity).

There are protopathic and epicritical sensitivity. Protopathic sensitivity is its phylogenetically ancient type, characterized by handicapped differentiation of 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 (according to 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 environmental changes. Otherwise, they are called superficial, or skin and outgoing from the mucous membranes, types of sensitivity. There are three leading varieties: pain, 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 sensing" is used to describe those options that require the attachment of a cortical component to achieve a sense of final perception. In this case, the leading function is perception and discrimination compared to 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.

Certain types sensitivity correspond to different conductive paths. The cells of peripheral neurons of all types of sensitivity are located in the spinal nodes. First neuron, conducting impulses of pain and temperature sensitivity, are pseudo-unipolar neurons of the spinal nodes, the peripheral branches of which (dendrites) are thin myelinated and non-myelinated fibers heading to the corresponding area of ​​\u200b\u200bthe skin (dermatome). The central branches of these cells (axons) enter the spinal cord through the lateral part of the dorsal roots. In the spinal cord, they are divided into short ascending and descending collaterals, which through 1-2 segments form a synaptic contract with the nerve cells of the gelatinous substance. This second neuron, which forms the lateral spinothalamic pathway. The fibers of this pathway pass through the anterior commissure into the opposite half of the spinal cord and continue in the outer part of the lateral funiculus and further up to the thalamus. The fibers of both spinal-thalamic pathways have a somatotopic distribution: those that come from the legs are located laterally, and those that come from higher sections have a medial-eccentric arrangement of long conductors. The lateral dorsal thalamic pathway terminates in the ventrolateral nucleus of the thalamus. 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 similar to the somatotopic projection of certain parts of the body in the precentral gyrus.

The course of the fibers that conduct pain sensitivity from the internal organs is the same as the fibers of somatic pain sensitivity.

Conduction of tactile sensitivity is carried out by the anterior spinal thalamic pathway. First neuron are also cells of the spinal ganglion. Their moderately thick myelinated peripheral fibers terminate in specific dermatomes, and their central branches pass through the posterior root into the posterior funiculus of the spinal cord. Here they can rise by 2-15 segments and form with neurons of the posterior horn at several levels. These nerve cells are second neuron, which forms the anterior spinal thalamic pathway. This path crosses the white commissure in front of the central canal, goes to the opposite side, continues in the anterior funiculus of the spinal cord, ascends through the brainstem and ends in the ventrolateral nucleus of the thalamus. Nerve cells of the thalamus third neuron, which conducts impulses to 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 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 go up as part of the medial thin bundle (Goll) and the lateral wedge-shaped bundle (Burdakh) and end in their own nuclei: thin and wedge-shaped, located on the dorsal side of the tegmentum of the lower part of the medulla oblongata. The fibers ascending in the composition of the posterior cords are located in the 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 the wedge-shaped bundle, and the fibers from the neck are located most laterally. Nerve cells in the thin and sphenoid 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 tracts, then, as a medial loop, crosses the midline and rises posteriorly from the pyramids and medially from the lower olives through the tegmentum of the upper part of the medulla oblongata, bridge 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 pedicle of the internal capsule and the corona radiata of the white matter of the brain and ends in the postcentral gyrus (fields 1, 2, 3) and superior parietal lobule (fields 5 and 7). The somatotopic organization is maintained throughout the 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 his head.

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

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

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

The reticular formation plays a role in conducting sensitive impulses. Throughout its length, spinal reticular axons and collaterals of the spinal thalamic pathways approach the reticular formation. The spinal-reticular pathways, which conduct impulses of pain and temperature sensitivity and some types of touch, discharge in the reticular formation, enter the thalamus and then to the cerebral cortex. The difference between proto- and epicritical sensitivity may be partly related to the quantitative difference and distribution of the fibers of 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 kinds. Complex types of sensitivity (discrimination - the distinction between two points, the exact 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 is aware of subjective changes in sensitivity or spontaneously experiences unusual sensations, one should find out if he is bothered by pain, if there is a loss of sensitivity, if there is a feeling of numbness in any part of the body. whether he experiences a sensation of burning, pressure, stretching, tingling, crawling, etc. As a rule, it is recommended to conduct an examination of the sensitive area at the beginning of the examination: this simple, at first glance, examination should be carried out carefully and carefully. The evaluation of the results is based on the subjective responses of the patient, but often objective symptoms (shuddering of the patient, withdrawal of the hand) help to clarify the zone of changes in sensitivity. If the 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 of sensitivity, it is necessary to examine twice.

If the patient himself does not notice sensory disorders, the doctor can check the sensitivity, remembering the neural and segmental innervation of the face, body, limbs. 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 revealed changes are marked with a pencil on the patient's skin and are indicated on the diagram. Healthy different types sensitivity (pain, tactile, musculo-articular) should be depicted as horizontal, vertical and diagonal stripes, respectively.

Surface Sensitivity Test. To test pain sensitivity, use a regular needle. It is better that the patient's eyes be closed during the examination. Pricking should be done either with the tip or with the head of the needle.

The patient answers: "acutely" or "stupidly". You should “go” from zones with less sensitivity to zones with more. If the injections are applied too close and often, their summation is possible; if the conduction 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 varieties of temperature sensations fall out at the same time, although sometimes one may be partially preserved. Usually, the area of ​​violations of thermal sensitivity is wider than that of cold.

To test tactile sensitivity, various means have been proposed: a brush, a piece of cotton wool, a pen, paper. The study can also be done with a very light touch of the fingers. Tactile sensitivity is assessed together with pain (touching alternately with the tip and the head of the needle). possible way check is touching the hair. Irritation should be applied lightly, without exerting pressure on the subcutaneous tissues.

Deep Sensitivity Study. Muscular-articular feeling is checked as follows. The completely relaxed finger of the examiner should cover from the side surfaces with minimal pressure and passively move it. The finger to be examined must be separated from other fingers. The patient is not allowed to make any active movements fingers. If the sense of movement or position in the fingers is lost, other parts of the body should be examined: leg, forearm. Normally, the subject must determine the movement in interphalangeal joints with a span of 1-2°, and even less in the more proximal joints. Initially, the recognition of the position of the fingers is disturbed, then the sensation of movement is lost. In the future, these sensations may be lost in the entire 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 muscular-articular feeling can also be checked by another method: the examiner attaches a certain position to the patient’s hand or fingers, and the patient’s eyes must be closed; then ask him to describe the position of the hand or imitate this position with the other hand. The next technique: the arms are extended forward: in case of violation of the muscular-articular feeling, the affected arm makes wave-like movements or falls, or is not brought to the level of the other arm. To identify sensory ataxia, finger-nose and heel-knee tests, Romberg's test, and gait are examined.

Vibration sensitivity is tested using a tuning fork (128 or 256 Hz) mounted on a bony prominence. Pay attention to the intensity of the vibration and its duration. The tuning fork is brought to a state of maximum vibration and placed on the first finger or the medial or lateral ankle and held until the patient feels the vibration. Then the tuning fork should be installed on the wrist, sternum or collarbone and clarify whether the patient feels the vibration. It is also necessary to compare the feeling of vibration of the patient and the examiner. The feeling of pressure is examined by pressing on the subcutaneous tissues: muscles, tendons, nerve trunks. In this case, you can use a blunt object, as well as compress the tissues between your fingers. The perception of pressure and its localization are specified. For quantification an esthesiometer or piesimeter 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 his 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 his eyes closed. Discriminatory sensitivity (the ability to distinguish between two simultaneous skin irritations) is examined with a Weber compass or a calibrated two-dimensional anesthesiometer. The patient with his eyes closed must determine the minimum distance between the two points.

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

Sensitivity disorders . pain sensation is the most common symptom of the disease and the reason for contacting. 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. Damage to the substance of the brain is not accompanied by pain, it occurs when the membranes, intracranial vessels are irritated.

Pain occurs during various pathological processes in organs and tissues due to irritation of the sensitive fibers (somatic and vegetative) of the nerve trunks and roots; they 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 missing limb segments after amputation and central pain, especially painful when the thalamus is affected. 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 remote area, in the area directly associated with the pathological focus - reflected. Pain repercussion is carried out with the participation of cells of the spinal nodes, the gray matter of the spinal cord and brain stem, the autonomic nervous system and receptors in the zone of irritation. Repercussion manifests itself in the reflection zone by various phenomena: vegetative, sensitive, motor, trophic, etc. The reflected pain zones of Zakharyin-Ged arise when irritation irradiates to the corresponding zone on the skin in diseases of the internal organs. There is the following ratio of the segment of the spinal cord and the zones of reflected pain: the heart corresponds to segments CIII-CIV and ThI-ThVI, the stomach - CIII-CIV and ThVI-ThIX, the intestines - ThIX-ThXII, the liver and gallbladder - ThVII-ThX, kidney and ureter - ThXI-SI, bladder- ThXI-SII and SIII-SIV, uterus - ThX-SII and SI-SIV.

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

Sensory disturbances can be characterized as hypoesthesia- decrease in sensitivity, anesthesia- lack of sensitivity dysesthesia- perversion of the perception of irritation (tactile or thermal irritation is felt as pain, etc.), analgesia- loss of pain sensation topanesthesia- lack of 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 (mild irritations are not perceived, with more significant ones, excessive intensity and persistence of sensations occur, paresthesia- a feeling of crawling, itching, cold, burning, numbness, etc., arising spontaneously or as a result of nerve compression, irritation of nerve trunks, peripheral nerve endings (with local circulatory disorders), causalgia- excruciating burning sensations against the background of intense pain with an incomplete break of some large nerve trunks, polyesthesia- perception of a single stimulus as multiple, alloesthesia- perception of sensation in another place; allocheiria- a feeling of irritation in a symmetrical area on the opposite side, phantom pains- sensation of a missing part of a limb.

Topical diagnosis of sensory disorders. Syndromes of sensory disturbances differ depending on the location 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, tension symptoms. All kinds of sensitivity are violated. The zone of hypesthesia detected when this nerve is damaged is usually smaller than the zone of its anatomical innervation due to overlap by neighboring nerves. The nerves of the face and trunk usually have an area of ​​overlap in the midline (larger on the trunk than on the face), so organic anesthesia almost always ends before reaching 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 of the nerves coming from the plexus, impaired sensitivity in the zone of innervation. Usually, there are also movement disorders. Radicular type (with damage to the posterior roots) - paresthesia, pain, violations of all types of sensitivity in the corresponding dermatomes, symptoms of root tension, pain in the paravertebral points and in the region of the spinous processes. If damaged roots innervate an arm or leg, hypotension, areflexia, and ataxia will also be noted. Loss of sensitivity in the radicular type requires the defeat of several neighboring roots. Polyneuritic type (multiple lesions of peripheral nerves) - pain, sensitivity disorders (in the form of "gloves" and "socks") in the distal segments of the extremities. Ganglionic type (with damage to the spinal node) - pain along the root, herpes zoster (with ganglioradiculalgia), sensory disturbances in the corresponding dermatomes. Sympathetic type (with damage to the sympathetic ganglia) - causalgia, sharp irradiating pain, vasomotor-trophic disorders.

At CNS damage(spinal cord, brain stem, thalamus, postcentral gyrus cortex and parietal lobe) the following syndromes of sensory impairment are observed. Segmental sensitivity disorders (with damage to the posterior horns and the 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. Tabetic type of sensitivity disorder (with damage to the posterior cords) - a violation of deep sensitivity while maintaining superficial sensitivity, sensitive ataxia. Sensitivity disorders in Brown-Sequard syndrome (with damage to half of the spinal cord) - a violation of deep sensitivity and motor disorders on the side of the lesion, and superficial sensitivity on the opposite side.

Conduction type of disorder of all types of sensitivity below the level of the lesion (with complete transverse spinal cord injury) - paraanesthesia. An alternating type of sensitivity disorder (in case of damage to the brain stem) - hemianesthesia of superficial sensitivity in the extremities opposite to the focus with damage to the spinal-thalamic tract h but segmental type on the face on the side of the focus with damage to the nucleus of the trigeminal nerve. 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" pains (burning, periodically increasing and difficult to treat). If the sensory pathways in the posterior leg of the internal capsule are affected, all types of sensitivity on the opposite half of the body fall out (hemihypesthesia or hemianesthesia). Cortical type of sensitivity disorder (with damage to the cerebral cortex) - paresthesia (tingling, crawling, numbness) in half of the upper lip, tongue, face, 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 disturbances are limited to half of the face, arm or leg, or torso. When the parietal lobe is damaged, disorders of complex types of sensitivity occur.

Functions like recognition of objects 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 available in the past. Injury to the inferior parietal lobule manifested by astereognosis, i.e. loss of the ability to recognize objects when touched (by touch) on the opposite side of the focus.

Syndrome of impaired musculoskeletal sensitivity may manifest as afferent paresis, i.e. disorders of motor functions, which are caused by a violation of the muscular-articular feeling. It is characterized by a disorder of coordination of movements, slowness, awkwardness when performing an arbitrary motor act, and hypermetry. Afferent paresis syndrome may be one of the signs of damage to the parietal lobe. Afferent paresis in case of damage to the posterior cords of the spinal cord is characterized by spinal ataxia: movements become disproportionate, inaccurate, and when performing a motor act, muscles that are not directly related to the movement being performed are activated. At the heart of dashing disorders is a violation of the innervation of agonists, synergists and antagonists. Ataxia is detected with a finger-to-nose test, in the study of diadochokinesis. when asked, draw a circle with your finger, write a number in the air, etc. Ataxia in lower limbs manifests itself with a heel-knee test, standing with eyes closed. When walking, the patient unbends his legs excessively and throws them forward, stomps strongly (“stamping gait”. Asynergy is observed, the torso lags behind the legs when walking. When the vision is turned off, ataxia increases. It is detected when walking, if the patient is given the task to walk in a narrow voice. In mild cases, ataxia is detected with a Romberg test with closed eyes.In spinal lesions, in addition to afferent paresis, areflexia, ataxia, muscle hypotension, and sometimes imitation synkinesis are observed.

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

What is this?

All types of sensitivity in physiology are:

• Part of the reception perceived by the psyche. Reception - afferent impulses entering the departments of the central nervous system.
• The ability of a living organism to perceive various stimuli that come from both its own organs and tissues, and from the environment.
• The ability of the organism, preceding a differentiated response to a stimulus - reactivity.

And now - the classification 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 itself is divided into:

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

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

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

Complex types of sensitivity:

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

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

Let's move on to the next classification.

General and special sensitivity

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

General sensitivity is divided into simple and complex.

Special sensitivity is represented by the following categories:

• visual;
• taste;
• olfactory;
• auditory.

Complicated Sensitivity

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

It's the following:

• Vision is the body's perception of light.
• Echolocation, hearing - perception by living systems of sounds.
• Smell, taste, stereochemical sense (typical for insects and hammerhead sharks) - the chemical sensitivity of the body.
• Magnetoreception - the ability of a living being to feel the magnetic field, which allows you to navigate the terrain, determine the height, plan the movement of your own body. The type of sensitivity is characteristic of some sharks.
• Electroreception - the ability to sense the electrical signals of the surrounding world. Used to find prey, orientation, various forms biocommunications.

According to phylogenetic criteria of formation

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

• Protopathic. A primitive form that has its center in the thalamus. Cannot give a precise definition of the localization of the source of irritation - neither external nor inside one's own body. It no longer reflects objective states, but subjective processes. Protopathic sensitivity ensures the perception of the strongest, coarsest forms of stimuli, pain and temperature, which are dangerous to the body.
• Epicritical. Has a cortical center, is more differentiated, objectified. Phylogenetically considered younger than the first. Allows the body to perceive more subtle stimuli, evaluate their degree, quality, localization, nature, and so on.

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 highlights the following types skin sensitivity:

• Pain. Occurs under the influence of stimuli that are destructive in their strength and nature. She will talk about a direct danger to the body.
• Thermal (temperature) sensitivity. It allows us to determine hot, warm, cold, icy. Its greatest importance is for the reflex regulation of the body.
• Touch and pressure. These feelings are connected. Pressure, in fact, is a strong touch, so there are no special receptors for it. Experience (with the participation of vision, muscle feeling) allows you 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 sensation thresholds

Now consider the classification of types of sensitivity thresholds:

• The absolute lower threshold of sensation. This is the smallest strength or magnitude of the stimulus at which its ability to cause nervous excitation in the analyzer is preserved, sufficient for the occurrence of one or another sensation.
• The absolute upper threshold of sensation. On the contrary, the maximum value, the strength of the stimulus, beyond which the body no longer perceives it.
• The threshold of discrimination (or difference threshold of sensation) is the smallest difference in the intensity of two identical stimuli that a living organism can sense. Note that not every difference will be felt here. It needs to reach a certain size or strength.

Varieties of disorders

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

• Anesthesia is the name given to the complete loss of some type of sensation. There is thermal (thermoanesthesia), tactile, pain (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 hypersensitivity to certain stimuli.
• Hyperpathia - cases of perversion of sensitivity. The quality of sensation changes - point irritations crumble, some qualitative differences between the stimuli in the patient are erased. The sensation is painted in painful tones, it can be purely 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, "crawling", 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 perverted perception of a particular stimulus. For example, touch feels like a blow, cold feels like heat.
• Synesthesia - a person will perceive the stimulus not only in the location of its direct impact, but also in a different zone.
• Allocheiria - a violation, something related to the previous one. The difference is that a person feels the impact of the stimulus not in the location of its impact, but in a symmetrical area of ​​the opposite part of the body.
• Thermalgia - cold, heat are painfully perceived by the patient.
• Dissociated sensory disorder - a case in which a certain sensation is disturbed, but all others are preserved.

Types of disorders

Types of sensory impairment can be divided into the following categories:

• Cortical type. This is a sensory disorder that will be observed on the opposite side of the body.
• Conductor type. Defeat of the conducting ways of sensitivity. Disorders will be found downward from the location of this lesion.
• Dissociated (segmental). It will be observed in case of damage to the sensitive nuclei of the cranial nerve of the brain stems, as well as in case of damage to the sensitive apparatus related to 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 the large number of classifications that internally divide 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.