Visual bumps. Anatomy of the brain. Thalamus. Optic thalamus

The visual thalamus are widely connected by bilateral and cross connections with the cerebral cortex, cerebellum, striopallidal system and other parts of the central nervous system. This determines their great functional significance.

The visual thalamus receives impulses of all types of sensitivity (exteroceptive, proprioceptive, interoceptive). Here the processing and transmission of impulses to the cerebral cortex occurs. The meeting of extero- and proprioceptive sensitivity with interoceptive sensitivity in the visual thalamus determines the creation of an emotional “subjective” background of sensitivity, a feeling of pleasant or unpleasant. The visual thalamus, together with the subcortical ganglia, are directly related to emotional and expressive movements. They are the afferent part of the reflex arc of the most complex unconditioned reflexes, regulated by the conditioned reflex activity of the cerebral cortex.

Symptoms of damage to the optic thalamus. When the visual thalamus is damaged, sensitivity disorders of varying degrees and quality are most pronounced. Destruction of the outer core by one pathological process or another causes a disorder of sensitivity throughout the opposite half of the body, including the face. All types of sensitivity are affected, but deep and tactile sensitivity is more affected than pain and temperature sensitivity. The distribution of the sensitivity disorder on the affected half of the body is usually uneven: the arm suffers more than the leg, the distal parts of the arms and legs suffer more than the proximal ones.

With pathological foci in the visual thalamus, against the background of a decrease in surface sensitivity, the quality of perception of irritations changes sharply, which acquires an unpleasant sensitive tone. The most insignificant and indifferent thing in normal conditions irritation can cause an extremely painful sensation, sometimes throughout the entire affected half of the body. Often, the perception of the irritation itself is distorted, when touch is felt as pain, warmth as cold, etc. (dysesthesia). Such a qualitative change in sensitivity when the visual thalamus is damaged is called hyperpathy. In this case, the patient loses the ability to localize the irritation, and the sensation caused by the latter with an unpleasant emotional sign continues for some time after the cessation of irritation (aftereffect). Damage to the optic thalamus is characterized by severe, sometimes difficult to bear, spontaneous pain in the half of the body opposite to the lesion, which does not respond even to the effects of drugs. These thalamic (central) pains are extremely painful. They are of an indefinite nature: a burning sensation, coldness, squeezing, stretching, etc. Sometimes the affected half exhibits special sensitivity to cold. Damage to the visual thalamus due to disruption of connections with the striopallidal system is often accompanied by movement disorders in the form of hyperkinesis and a peculiar change in muscle tone. One of the manifestations of these disorders is the so-called thalamic posture of the affected half of the body: the arm is bent in elbow joint, the forearm is pronated, the hand is bent, the fingers are bent in the main phalanges and extended in the nails (thalamic hand). Athetotic movements are often observed in the fingers, especially with the eyes closed. When walking, the patient places his foot on the floor - first with the heel, and then with the entire foot, which is in the pes valgus position. The entire gait takes on a slightly hemiparetic character. Often, when the visual thalamus is damaged, a peculiar disorder of the facial muscles of the face is noted, which consists in the fact that during emotional movements the affected half of the face is almost not involved in the facial movement, revealing a picture of insufficiency facial nerve, while during voluntary movements the face remains symmetrical (thalamic paresis of the facial nerve, Nothnagel's symptom).

There are several syndromes of damage to the visual thalamus:

1. Thalamic Dejerine syndrome (pure form). Most often observed with circulatory disorders in a. thalamo-geniculata (branch of the posterior cerebral artery). In these cases, pyramidal disorders are either absent or expressed only to a minor extent. The main place in clinical picture occupy the above-mentioned sensory disorders (hemianesthesia, hyperpathia, central pain, thalamic posture, mild athetosis in the affected limbs, hemiataxia).

2. Thalamic syndrome of Dejerine and Roussy (mixed form). This syndrome differs from the “pure” form in that, in addition to characteristic thalamic disorders, there are pronounced pyramidal signs in the form of hemiplegia, and often hemianopsia.

3. When vascular diseases syndromes often occur in the brain, including symptoms of simultaneous damage to the thalamus optic and the red nucleus, as well as the hypothalamic region.

4. Thalamo-rubral syndrome, or upper syndrome red nucleus - Chiari, Fua and Nicolescu syndrome. Hyperkinesis is observed in the form of slight choreaphoric movements in the limbs opposite to the lesion, as well as cerebellar disorders (intention tremor, asynergia), mild sensory disorders, and thalamic posture.

5. With simultaneous damage to the thalamus and hypothalamus, in addition to thalamic symptoms, various sympathohumoral and trophic disorders may occur in the affected half of the body.

A continuation of the brain stem anteriorly are the visual tubercles located on the sides. III ventricle (see Fig. 2 and 55, ^III).

Optic thalamus(thalamus opticus - Fig. 55, 777) is a powerful accumulation of gray matter, in which a number of nuclear formations can be distinguished.

There is a division of the visual thalamus into the thalamus itself, hupothalamus, metathalamus and epithalamus.

Thalamus - the bulk of the visual thalamus - consists of the anterior, external, internal, ventral and posterior nuclei.

Hypothalamus has a number of nuclei located in the walls of the third ventricle and its funnel (infundibulum). The latter is very closely related to the pituitary gland both anatomically and functionally. This also includes the mamillary bodies (corpora mamillaria).

Metathalamus includes the external and internal geniculate bodies (corpora geniculata laterale et mediale).

Epithalamus includes the epiphysis, or pineal gland (glandula pinealis), and the posterior commissure (comissura posterior).

The visual thalamus is an important stage in the path of sensitivity. The following sensitive conductors approach it (from the opposite side).

1. ^ Medial loop with its bulbo-thalamic fibers (touch, joint-muscular sense, vibration sense, etc.) and the spinothalamic pathway (pain and temperature sense).

2. Lemniscus trigemini - from the sensitive nucleus of the trigeminal nerve (sensitivity of the face) and fibers from the nuclei of the glossopharyngeal and vagus nerves (sensitivity of the pharynx, larynx, etc., as well as internal organs).

3. ^ visual tracts, ending in the pulvinar of the visual thalamus and in the corpus geniculatum laterale (visual pathways).

4. Lateral loop ending in the corpus geniculatum mediale (auditory tract).

The olfactory pathways and fibers from the cerebellum (from the red nuclei) also end in the visual thalamus.

Thus, impulses of exteroceptive sensitivity flow to the visual thalamus, perceiving irritations from the outside (pain, temperature, touch, light, etc.), proprioceptive (articular-muscular feeling, sense of position and movement) and interoceptive (from internal organs).

Such a concentration of all types of sensitivity in the visual thalamus will become understandable if we take into account that at certain stages of the evolution of the nervous system, the visual thalamus was the main and final sensitive center, determining the general motor reactions of the body of a reflex order by transmitting irritation to the centrifugal motor apparatus.

With the advent and development of the cerebral cortex, the sensitive function becomes more complex and improved; the ability to finely analyze, differentiate and localize irritation appears. The main role in sensitive function passes to the cerebral cortex. However, the course of the sensory pathways remains the same; there is only a continuation of them from the visual thalamus to the cortex. The visual thalamus becomes basically just a transmission station on the path of impulses from the periphery to the cortex. Indeed, there are numerous thalamo-cortical pathways (tractus thalamo-corticales), those (mainly third) sensory neurons that have already been discussed in the chapter on sensitivity and which need only be briefly mentioned:

1) third neurons of cutaneous and deep sensitivity(pain, temperature, tactile, joint-muscular sense, etc.), starting from the ventrolateral part of the visual thalamus, passing through the internal capsule to the region of the posterior central gyrus and the parietal lobe (Fig. 55, VII);

2) visual pathways from primary visual centers (corpus geniculatum laterale - radiatio optica) or the Graciole bundle, in the area of ​​fissurae calcarinae of the occipital lobe (Fig. 55, VIII),

3) auditory pathways from the primary auditory centers (corpus geniculatum mediale) to the superior temporal gyrus and Heschl’s gyrus (Fig. 55, IX).

Rice. 55. Subcortical ganglia and internal capsule.

^I - nucleus caudatus; II- nucleus lenticularis; III- thalamus opticus; IV - tractus cortico-bulbaris; V- tractus cortico-spinalis; VI- tractus oc-cipito-temporo-pontinus; VII - tractus ttialamo-corticalis: VIII - radiatio optica; IX- auditory pathways to the cortex; X- tractus fronto-pontinus.

In addition to the connections already mentioned, the visual thalamus has pathways connecting it with the strio-pallidal system. In the same way that the thalamus opticus is the highest sensitive center at certain stages of the development of the nervous system, the strio-pallidal system was the final motor apparatus, carrying out rather complex reflex activity.

Therefore, the connections between the visual thalamus and the named system are very intimate, and the entire apparatus as a whole can be called thalamo-strio-pallidal system with a perceptive link in the form of the thalamus opticus and a motor link in the form of the strio-pallidal apparatus (Fig. 56).

The connections between the thalamus and the cerebral cortex - in the direction of the thalamus - cortex have already been said. In addition, there is a powerful system of conductors in the opposite direction, from the cerebral cortex to the visual thalamus. These paths come from various departments bark (tractus cortico-thalamici); the most massive of them is the one that begins from the frontal lobe.

Finally, it is worth mentioning the connections of the visual thalamus with the subthalamic region (hypothalamus), where the subcortical centers of autonomic-visceral innervation are concentrated.

The connections between the nuclear formations of the thalamic region are very numerous, complex, and have not yet been sufficiently studied in detail. Recently, mainly on the basis of electrophysiological studies, it has been proposed to divide the thalamo-cortical systems into specific(associated with certain projection areas of the cortex) and nonspecific, or diffuse. The latter begin from the medial group of nuclei of the visual thalamus (median center, intralaminar, reticular and other nuclei).

Some researchers (Penfield, Jasper) attribute to these “nonspecific nuclei” of the thalamus opticus, as well as the reticular formation of the brainstem, the function of the “substrate of consciousness” and the “highest level of integration” of nervous activity. In the concept of the “centroencephalic system,” the cortex is considered only as an intermediate stage on the path of sensory impulses flowing from the periphery to the “ highest level integration" in the interstitial and midbrain. Supporters of this hypothesis thus come into conflict with the history of the development of the nervous system, with numerous and obvious facts establishing that the most subtle analysis and complex synthesis (“integration”) of nervous activity are carried out by the cerebral cortex, which, of course, does not function in isolation , and in inextricable connection with the underlying subcortical, stem and segmental formations.

Rice. 56. Diagram of connections of the extrapyramidal system. Its centrifugal conductors.

N. s. nucleus caudatus; N. L. - nucleus lenticularis; gp. - globe pallidus; Pat. - putamen; Th. - thalamus; N. rub. - red core, Tr. r. sp. - rubrospinal fascicle; Tr. cort. th. - tractus cortico-thalamicus; Subst. nigra- substantia nigra; Tr. tecto-sp. - tractus tecto-spinalis; 3. cont. puch. - posterior longitudinal fasciculus; I. Darksh. - Darkshevich nucleus.

Based on the given anatomical data, as well as existing clinical observations, the functional significance of the visual thalamus can be determined mainly by the following provisions. The optic thalamus is:

1) a transfer station for conducting all types of “general” sensitivity, visual, auditory and other irritations into the cortex;

2) an afferent link of the complex subcortical thalamo-strio-pallidal system, which carries out rather complex automated reflex acts;

3) through the visual thalamus, which is also a subcortical center for visceroreception, automatic regulation of internal ones is carried out due to connections with the hypothalamic region and the cerebral cortex. processes of the body and the activity of internal organs.

Sensitive impulses received by the visual thalamus can acquire one or another emotional coloring here. According to M.I. Astvatsaturov, the visual thalamus is an organ of primitive affects and emotions, closely related to the feeling of pain; At the same time, reactions from visceral devices occur (redness, pallor, changes in pulse and respiration, etc.) and affective, expressive motor reactions of laughter and crying 26 .

^

Symptoms of damage to the optic thalamus

When the optic thalamus is damaged, there may be symptoms of hair loss its functions or symptoms of irritation.

In the first case, it is observed (on the opposite side) hemianesthesia, relating to all types of sensitivity, both superficial and deep. Sensitivity disorders are more pronounced in the distal parts of the extremities; loss of joint-muscular sensation is usually expressed especially sharply. Therefore, in anesthetized limbs there is also sensitive hemiataxia. Due to damage to the subcortical visual centers (corpus geniculatum laterale), hemianopsia - loss of vision in the visual fields opposite to the lesion.

Finally, when the optic thalamus is affected, there may be paresis of facial muscles, also on the opposite side, affecting only during emotive facial movements, for example, when smiling or laughing. During movements “on instructions,” innervation disturbances may not be noted.

When the optic thalamus is irritated, severe, sometimes unbearable pain on the opposite side of the body. The nature of these “central” pains is difficult for patients to describe; More often it is an excruciating sensation of burning, cold, unbearable pain. They are localized unclearly and are usually diffuse. Their intensity increases depending on external irritation and, especially, emotions. It is often observed increased affectivity, violent laughter and crying. It is possible to join a row autonomic disorders. All these symptoms are easily explained by the role and significance of the visual thalamus, as mentioned above.

When the optic thalamus is irritated (possibly with partial damage to some of its nuclei), not only the described peculiar thalamic pain occurs, but also sensitivity disorders on the opposite side of the body, which are of the nature hyperpathies(a sharp feeling of unpleasantness, with inaccurate localization during injection and temperature irritations, sometimes perverted perception of irritation, inaccurate localization, irradiation, prolonged sensation of irritation, or the so-called aftereffect, etc.).

Impulses emanating from the irritated optic thalamus in the direction of the strio-pallidal system, closely associated with it, can sometimes cause involuntary violent movements, or hyperkinesis, such as chorea or athetosis, described below.

Finally, in some cases they may also join cerebellar disorders, since fibers from the cerebellum and red nuclei end in the optic thalamus.

^

STRIO-PALLIDARY SYSTEM

Toward the strio-pallidal system The following anatomical formations include: nucleus caudatus and nucleus lenticularis with its outer nucleus (putamen) and two inner ones (globus pallidus). They are located in front and outside of the visual tuberosities (Fig. 55, I and II). According to morphological features, phylogenetic age and functional significance, the strio-pallidal system is more correctly divided into the striatum, or neostriatum system, which includes the nucleus caudatus and the outer nucleus of the nuclei lenticularis - putamen, and the pallidum, or palaeo-striatum, which includes the globus pallidus (inner nuclei lenticularus). The pallidal system includes the substantia nigra - substantia nigra - and the red nuclei located in the cerebral peduncles.

The strio-pallidum represents an important component extra-pyramidal (extrapyramidal) motor systems, starting from the cerebral cortex (mainly from area 6 in the premotor zone) and associated with a number of subcortical and brainstem formations.

The main paths along which impulses are carried to the striatum and pallidum are conductors from the visual thalamus. Through them, connections are established between the extrapyramidal system not only with the thalamus opticus, but through the same optic thalamus and with the cerebral cortex. In this way (bark - thalamus opticus - strio-pallidum) the extrapyramidal apparatuses are included in the system of “voluntary” cortical movements. There are also independent connections strio-pallidal system with the cerebral cortex; known, for example, are cortico-pallidal, corticonigral and other extrapyramidal motor conductors.

Striatum is closely related to pallidum. Centrifugal tracts begin from the pallidum and go to the substantia nigra, red nucleus, Darkshevich's nucleus, quadrigeminal, and olives. From these formations, impulses from the extrapyramidal system follow to the segmental motor apparatus and muscles along descending conductors (see Fig. 56):

1) from the red nuclei along the Monaco fasciculus (tractus rubro-spinalis);

2) from the Darkshevich nucleus along the posterior longitudinal fasciculus (fasciculus longitudinalis posterior) to the nuclei of the III, IV, VI nerves and through it to the nucleus of the vestibular nerve;

3) from the nucleus of the vestibular nerve along the tractus vestibulo-spinalis;

4) from the quadrigeminal tract along the tractus tecto-spinalis, etc.

Impulses from the extrapyramidal system, as well as from the cerebellum and from the pyramidal system, therefore flow to the cells of the anterior horn, where all the conductors just listed end. The final route to the muscle is through the peripheral motor neuron.

Due to the presence of this system (receptors on the periphery - thalamus - strio-pallidum - centrifugal extrapyramidal tracts - anterior horn cell - muscle), reflex activity is carried out regarding automated, sometimes quite complex movements. Thanks to inclusion in motor system The cortex ensures the auxiliary participation of extrapyramidal apparatuses in “voluntary” movements.

In addition to the connections discussed, we can once again mention the paths to the hypothalamic region (subcortical centers of visceral innervation).

During the period when the cerebral cortex was not yet developed, the strio-pallidal system was the main motor center that determined the graying of the animal. Sensitive impulses flowing from the visual thalamus were processed here into motor ones, heading to the segmental apparatus and muscles. Due to the strio-pallidal apparatuses, diffuse, mass movements of the body were carried out quite complex nature: movement, swimming, etc.

At the same time, support for general muscle tone, “readiness” of the segmental apparatus for action, and redistribution of muscle tone during movements were ensured.

With the further evolution of the nervous system, the leading role in movements passes to the cerebral cortex with its motor analyzer and pyramidal system. Finally, a person experiences complex actions that are purposeful, productive in nature, with fine differentiation of individual movements.

Nevertheless, the strio-pallidal (extrapyramidal) system has not lost its importance in humans. It only moves into a subordinate, subordinated position, providing “tuning” of the motor apparatus, their “readiness for action” (M.I. Astvatsaturov) and the muscle tone necessary for the rapid implementation of movement.

The extrapyramidal system in humans automatically creates that background of “preparedness” against which fast, precise, differentiated movements are carried out, determined by the activity of the cortex.

As noted above, the extrapyramidal system is divided into its more ancient section (palaeo-striatum, or pallidum) and a new, later one (neostriatum, or striatum). The relationships between them are the same as those that generally exist between phylogenetically more ancient and newer, more advanced apparatuses: the activity of the pallidal system is inhibited and regulated (subordinated) by the striatal system. Therefore, the symptoms of damage to the pallidal region are sharply different and in many ways opposite to the symptoms of damage to the striatal region.

^

Symptoms of damage to the extrapyramidal system

1. Symptom complex of pallidal lesions may be called hypertensive-hypokinetic, since the main features that characterize it are an increase in muscle tone and a decrease in mobility, impoverishment of movements.

^ Extrapyramidal hypertension, or rigidity muscles differs significantly from that with pyramidal lesions. With pallidal rigidity, the resistance experienced by the examiner during passive movements remains the same all the time from the beginning to the end of the movement, while with central paralysis or paresis, spasticity is especially great at the beginning of the movement and noticeably weakens at the end (the “jackknife” symptom). Pallidal rigidity is called “waxy”. With passive extension of the forearm, lower leg, circular movements in wrist joint You can sometimes feel a kind of intermittency, a stepwise pattern of muscle stretching, called the “gear wheel” symptoms.

Hypokinesia, or oligokinesia, is not at all determined by the presence of paralysis; the study reveals that voluntary movements are performed in sufficient volume and with satisfactory muscle strength. The main ones are the patient’s inactivity, a sharp decrease in motor initiative, and difficulty in transitioning from rest to movement. The patient, having taken a certain position, for a long time preserves it, even if it is uncomfortable, “freezes” in the accepted position, resembling a statue or mannequin.

^ Normal pose The patient's position is quite characteristic: the back is bent, the head is tilted to the chest, the arms are bent at the elbows, the hands at the wrists, the legs at the knee joints (flexor posture).

Gait slow, reminiscent of an old woman, small steps. It is not possible to move forward immediately, but in the future the patient can “disperse” and move faster. But he cannot stop quickly: if necessary or when ordered to stop, he still continues to be “pulled” forward (propulsio).

Facial expressions extremely poor, the face takes on a frozen, mask-like expression (hypomimia). A smile, a grimace of crying with emotions occurs with a delay, and also with a slowdown the face returns to normal facial expressions.

Speech patients are quiet, monotonous, deaf, without sufficient modulation and sonority.

Characteristic is the absence or reduction of physiological friendly or accompanying movements, synkinesias that exist normally and contribute to one or another basic movement. Thus, patients do not experience the usual waving of their arms in time with walking, no wrinkling of the forehead when looking up, no extension in the wrist joint when clenching the hand into a fist, etc. Not only is the transition from rest to movement difficult, but usually all voluntary movements are sharply slowed down (bradykinesia). The patient performs all actions slowly, as if with difficulty, reminiscent of an automatic machine with his movements.

In addition to the described symptoms, with pallidal lesions there is often a peculiar trembling, which is observed at rest, is expressed in the distal parts of the limbs, sometimes in the lower jaw and is usually characterized by low amplitudes, frequency and rhythm. In contrast to cerebellar intention tremor, which appears during movement and is absent at rest, it is typically present at rest and decreases or disappears during movements.

The described pallidal lesion syndrome is also called parkinsonism, or amyostatic symptom complex.

In the absence of changes from tendon reflexes limbs for another reason, with parkisonism, the so-called axial reflexes and, first of all, the group of reflexes of oral automatism can come to life (see Chapter II). Reflexes of position or posture (postural reflexes) 27 are significantly impaired.

II. ^ Symptom complex of striatal lesions. IN unlike pallidar, it can be called hypotonic-hyperkinetic. Against the background of muscle hypotonia existing at rest, various involuntary violent movements arise, or extrapyramidal hyperkinesis.

If turning off the pallidum entails impoverishment of movements and difficulty in transition from rest to action, then the defeat of the striatum, disinhibiting the pallidum, causes the appearance of motor automatisms that are diffuse and massive in nature. Phylogenetic data and the role of the strio-pallidal system at previous stages of evolution explain the fact that these pathological movements sometimes resemble individual elements of crawling, climbing, throwing, etc.

In contrast to pallidal stiffness of movements, hypomimia and the absence of physiological accompanying movements, with striatal lesions, motor restlessness, speed, sweeping movements, an abundance of synkinesis, and grimacing are often observed. The main forms of extrapyramidal hyperkinesis are the following.

Athetosis, which is observed more in the distal parts of the extremities, for example in the hands and fingers. Slow, writhing, worm-like movements are observed at certain intervals, during which the limb assumes unnatural positions. Athetosis can be limited, or it can be widespread, sometimes involving the entire body musculature. There is reason to believe that athetosis occurs when the nuclei caudati is damaged.

^ Torsion spasm represents athetosis of the trunk. It is characterized by bending, sometimes corkscrew-like movements of the body that occur when walking, which is often significantly difficult.

Chorea differs from athetosis in the speed of twitching: the latter are observed in various muscle groups, often in the proximal parts of the limbs, in the face. Characterized by a rapid change in the localization of the cramp: either the facial muscles twitch, or the muscles of the leg, at the same time eye muscles and hand, etc. In severe cases, the patient becomes like a clown. Grimacing and smacking are often observed; speech gets upset. Movements become sweeping, excessive, and the gait becomes “dancing.” It is possible that chorea occurs when the outer nucleus of the nuclei lenticularis (putamen) is damaged with simultaneous involvement of the dento-rubral system (nucleus dentatus of the cerebellum and nucleus ruber) in the process.

Myoclonus is close in nature to chorea. Here the twitching is also very fast, observed in individual muscle groups or single muscles. Unlike chorea, myoclonus is often not accompanied by significant motor effects.

^ Localized spasm and some forms teak may also be a manifestation of extrapyramidal hyperkinesis. Localized spasm, as the name itself shows, is observed in isolation in any one muscle group, most often in the muscles of the face or neck. This is especially often observed in the muscles innervated by the facial or accessory nerve (n. accessorius). These rather rare forms should not be confused with the frequently observed neurotic tics, which are habitual obsessive movements not caused by organic damage to the nervous system.

The common features characteristic of all types of extrapyramidal hyperkinesis are their usual disappearance during sleep (as opposed to cortical convulsions) and intensification with excitement and voluntary movements.

As noted above, with striatal lesions hypotension is observed, with pallidal lesions - muscle hypertension. It can be assumed that if the cerebellum with its function of maintaining tone is under the inhibitory influence of the pallidal system, then when the pallidum is damaged, hypertension is observed due to the increasing function of the cerebellum in this regard. When the striatum is damaged, the pallidum is disinhibited, increasing its inhibitory effect on the cerebellum; as a result, its stimulating effect on tone decreases and hypotension occurs (V.V. Kramer).

^

INTERNAL CAPSULE, SYMPTOMS OF LESION

Inner capsule(capsula interna) is a strip white matter, located between the subcortical ganglia of the base (see Fig. 55). It is divided into three main sections: the anterior thigh, posterior thigh and knee (genu capsulae internae). The anterior femur is located between the nucleus caudatus and the nucleus lenticularis, the posterior femur is located between the thalamus opticus and the nucleus lenticularis. The internal capsule is a very important formation, where in a relatively small area conductors are compactly located, both going to the cortex and from the cortex to the underlying parts of the central nervous system. The following conductors are located here.

1. ^ Tractus corfico-bulbaris - the path of central motor neurons from the cortex to the nuclei of the cranial nerves, located in the knee of the internal capsule (see Fig. 55, IV).

2. ^ Tractus cortico-spinatis - fibers of Central motor neurons from the cortex to the anterior horns of the spinal cord, passing in the anterior two-thirds of the posterior thigh: anteriorly - paths for the upper, posteriorly - for the lower limb (see Fig. 55, V).

3. ^ Tractus thalamo-corticalis - the third sensitivity neurons from the visual thalamus to the cerebral cortex, located in the posterior part of the hind thigh behind the tractus cortico-spinalis (see Fig. 55, VII).

4. visual pathways, following from the subcortical or primary visual centers (corpus geniculatum laterale) to the occipital lobes (radiatio optica, Graciole bundle).

5. ^ Hearing conductors from the subcortical or primary auditory centers (corpus geniculatum mediale) to the temporal lobes.

Both last conductors are located in the very posterior part of the internal capsule, behind the paths of general sensitivity (see Fig. 55, VIII And IX).

6. ^ Frontal bridge path (tractus fronto-pontinus) from the frontal lobe to the pons and cerebellum, occupying the anterior thigh of the internal capsule (see Fig. 55, X).

7. Occipitotemporal tract bridge(tractus occipito-temporo-pontinus) from the occipital and temporal lobes, following in the same direction and passing through the posterior thigh of the capsule (see Fig. 55, VI).

8. Paths from the bark brain to visual thalamus, passing in both the anterior and posterior thigh (tractus cortico-thalamici).

Lesions in the area of ​​the internal capsule, interrupting the pathways passing here, cause motor and sensory disorders on the opposite side of the body (sensitive conductors cross in the spinal and medulla oblongata, pyramidal ones - at their border). Foci in the area of ​​the internal capsule are characterized by a half type of disorder, since the arrangement of fibers here, as already mentioned above, is very close.

When the internal capsule is completely damaged, the so-called "three hemi syndrome": hemiplegia and hemianesthesia on the opposite side of the body and hemianopsia of opposite visual fields.

Hemiplegia, It is clear that it has all the features of central paralysis. Usually, both upper and lower extremities are equally affected; at the same time there is a central type of paresis of the tongue and lower facial muscles. Capsular hemiplegia is especially characterized by Wernicke-Mann type contracture (see chapter on movement disorders).

Hemianesthesia although it has a half type, it is most pronounced in the distal parts of the limbs. Since the focus is located above the visual thalamus, only some types of sensitivity are lost (articular-muscular, tactile, stereognosia, subtle pain and temperature sensation, etc.). Severe pain and temperature irritations cause a sharp sensation of unpleasantness with irradiation, imprecise localization, and aftereffects, i.e., hyperpathy is observed.

Hemianopsia occurs as a result of damage to the Graciole bundle, is homonymous and is observed, of course, in the visual fields opposite to the lesion (see the chapter on cranial nerves).

There are no distinct hearing disorders, despite damage to the auditory conductors; this will become clear if we recall the bidirectionality of the auditory pathways from the nuclei to the subcortical auditory centers and, therefore, the conduction of impulses from each ear to both hemispheres. With subtle research methods, it is still possible to detect some hearing loss in the ear opposite to the lesion.

Damage to the internal capsule is not always complete. More often observed limited lesions. With lesions in the knee and anterior posterior thigh, only hemiplegia is observed in the absence or presence of only mild sensory disturbances. In case of defeat posterior section of the posterior thigh, naturally, sensory disorders predominate, and here, too, “three hemi syndrome” of a slightly different nature can be observed: hemianesthesia, hemianopsia and hemiataxia (as a result of loss of joint-muscular sensation). However, in these cases there are usually at least mild pyramidal disorders.

The close location of the internal capsule to the visual thalamus and the ganglia of the extrapyramidal system easily explains the addition sometimes to the capsular syndrome, for example, of thalamic pain or extrapyramidal disorders. Often there is simultaneous damage to both the large ganglia of the base and the internal capsule.

^ White matter of the hemispheres. Between the basal ganglia with their internal capsule and the cerebral cortex in the hemispheres there is a continuous mass of white matter (centrum semiovale), in which fibers of various directions are located. They can be divided into two main groups - projection and association.

^ Projection fibers connect the cerebral cortex with the underlying parts of the central nervous system and are located more or less perpendicular to the cortex. Here we meet the already familiar cortical and cortical conductors. From the cerebral cortex, from the anterior central gyrus, the tractus cortico-bulbaris and cortico-spinalis, the frontal and occipito-temporal tracts of the bridge (from the corresponding lobes), the corticothalamic tracts (from all lobes, but mainly from the frontal lobe) go downwards. In the direction of the cortex, the newly disassembled thalamo-cortical sensory conductors follow, going to the sensitive areas of the cortex: the posterior central gyrus, the parietal lobes; in the occipital lobes - visual, in the temporal - auditory conductors. A powerful bundle of projection fibers that penetrates the centrum semiovale and fan-shapedly diverges from the internal capsule to the cortex is called corona radiata, or corona radiata.

^ Association fibers connect different lobes and areas of the cortex within each hemisphere; here we encounter fibers of various directions and lengths. They can be short, connecting, for example, neighboring gyri; such fibers are called V-shaped. Long routes establish connections with more distant territories of their hemisphere; these include, for example, fasciculus longitudinalis superior, inferior, uncinatus, cingulum, etc. (Fig. 57).

^ Commissural fibers are a type of association; they connect the cortex not within one hemisphere, but both hemispheres with each other. The direction of the fibers is predominantly frontal (Fig. 57). The most powerful and important of the commissural bundles is the corpus callosum (corpus callosum).

^ Corpus callosum connects the lobes of the same name with each other: both frontal, parietal, etc. In addition, commissural fibers pass into the comissura anterior (anterior white commissure) and posterior. The last two spikes are related to the olfactory function.

Lesions in the centrum semiovale cause symptom complexes close to those with damage to the internal capsule. Since here the fibers of various significance diverge more widely and are not located as compactly as in the internal capsule, movement disorders can be observed more isolated from the sensory ones, and vice versa. The complete half type of lesion may also be impaired, i.e. lower limb, for example, may be more affected than the upper one, etc.

Rice. 57. Projection, commissural and association fibers of the cerebral cortex.

F.l. sup. - fasciculus longitudinalis superior; r. aps. - fasciculus uncinatus; ^ Cin. - cingulum; F.l. inf. - fasciculus longitudinalis inferior.

Bilateral lesions localized in the white matter of the hemispheres (centrum semiovale, internal capsule) can cause the appearance of pseudobulbar speech and swallowing disorders due to damage to both tractus cortico-bulbares and bilateral pyramidal symptoms as a result of disruption of the conductivity of both tractus cortico-spinales. Violent laughter and crying, hypomimia and other pseudobulbar symptoms are also often observed.

The thalamus is a structure of the brain, which in prenatal development is formed from the diencephalon, making up the bulk of its mass in an adult. It is through this formation that all information from the periphery is transmitted to the cortex. The second name of the thalamus is the visual hillocks. More details about it later in the article.

Location

• specific;
• associative;
• nonspecific.

Specific kernels

The specific nuclei of the thalamus have a number of distinctive features. All formations of this group receive sensory information from second neurons (nerve cells) of sensitive pathways. The second neuron, in turn, can be located in spinal cord or in one of the structures of the brain stem: medulla oblongata, pons, midbrain.

Each of the signals coming from below is processed in the thalamus and then goes to the corresponding area of ​​the cortex. Which area the nerve impulse goes to depends on what information it carries. Thus, information about sounds enters the auditory cortex, about objects seen - into the visual cortex, and so on.

In addition to impulses from the second neurons of the pathways, specific nuclei are responsible for the perception of information coming from the cortex, reticular formation, and brain stem nuclei.

The nuclei, which are located in the anterior part of the thalamus, ensure the conduction of impulses from the limbic cortex of the brain through the hippocampus and hypothalamus. After processing the information, it again enters the limbic cortex. Thus, it circulates in a certain circle.

Associative kernels

The association nuclei are located closer to the posteromedial part of the thalamus, as well as in the cushion area. The peculiarity of these structures is that they do not participate in the perception of information that comes from the underlying formations of the central nervous system. These nuclei are necessary to receive already processed signals in other nuclei of the thalamus or in overlying brain structures.

The essence of the “associativity” of these nuclei is that any signals are suitable for them, and the neurons are able to adequately perceive them. Signals from these structures enter the correspondingly named areas of the cortex - association zones. They are located in the temporal, frontal and parietal parts bark. Thanks to the receipt of these signals, a person is able to:

• recognize objects;
• connect speech with movements and objects seen;
• be aware of the position of your body in space;
• perceive space as three-dimensional and so on.

Nonspecific nuclei

This group of nuclei is called nonspecific because it receives information from almost all structures of the central nervous system:

• reticular formation;
• nuclei of the extrapyramidal system;
• other nuclei of the optic thalamus;
• brain stem structures;
• formations of the limbic system.

The impulse from nonspecific nuclei also goes to all areas of the cerebral cortex. Such selectivity, as in the case of associative and specific nuclei, is absent here.

Since it is this group of nuclei that has the largest number of connections, it is believed that thanks to it, the harmonious, coordinated work of all parts of the brain is ensured.

Metathalamus

A separate group of nuclei of the visual thalamus is distinguished called the metathalamus. This structure consists of the medial and lateral geniculate bodies.

The medial geniculate body receives hearing information. From the underlying parts of the brain, information arrives through the upper humps of the midbrain, and from above the structure receives impulses from the auditory cortex.

The lateral geniculate body belongs to visual system. Sensitive information to the nuclei of this group comes from the retina through the optic nerves and optic tract. The information processed in the thalamus then goes to occipital region cortex, where the primary center of vision is located.

Functions of the thalamus

How is the processing of sensitive information coming from the periphery, which is then transmitted to the cortex? forebrain? This is the main role of the visual thalamus.

Thanks to this function, in case of damage to the cortex, it is possible to restore sensitivity through the thalamus. Thus, reparation of pain, temperature, as well as rough touch is possible.

Another one important function The thalamus is the coordination of movements and sensitivity, that is, sensory and motor information. This is due to the fact that not only sensory impulses enter the thalamus. It also receives impulses from the cerebellum, ganglia of the extrapyramidal system, and cerebral cortex. And these structures, as is known, take part in the implementation of movements.

The visual thalamus is also involved in maintaining conscious activity, regulating sleep and wakefulness. This function is carried out due to the presence of connections with the locus coeruleus of the brain stem and the hypothalamus.

Symptoms of the lesion

Since almost all signals from other structures of the nervous system pass through the thalamus, damage to the thalamus can manifest itself in a variety of symptoms. Extensive damage to the thalamus can be diagnosed by the following clinical signs:

• disturbance of sensitivity, primarily deep;
• burning, sharp pain that first appears when touched, and then spontaneously;
• motility disorders, among which there is the so-called thalamic hand, manifested by excessive flexion of the fingers in the metacarpophalangeal joints and extension in the interphalangeal joints;
• visual disturbances - hemianopsia on the side opposite to the lesion).

Thus, the thalamus is an important structure of the brain, which ensures the integration of all processes in the body.

Thalamic syndrome is a condition caused by damage to an area of ​​the brain called the thalamic thalamus. The thalamus is a paired formation represented by gray matter and consisting of the anterior tubercle, body and pillow. Refers to the intermediate section of the brain. The nuclei of the optic thalamus are responsible for vision, hearing, tactile sensations, and balance. The thalamus performs the functions of processing information, regulating attention, and coordinating the work of the musculoskeletal system. The part of the brain that coordinates speech, memory, and emotions. Damage to the visual thalamus entails disruption of the described functions.

Main symptoms of thalamic syndrome

The set of symptoms caused by damage to the visual thalamus is otherwise called Dejerine-Roussy syndrome. The painful condition resulting from damage to the thalamus was first described in the 19th century. A detailed definition of the symptoms and causes was given by the French scientists Dejerine and Roussy at the beginning of the 20th century.

The signs of the syndrome are:

• loss of pain and skin sensitivity on one side of the body;
• increased pain perception threshold with the inability to accurately determine its location;
• intensive burning pain on one side of the body;
• perversion of sensitivity (temperature stimulus is felt as painful, light touches cause discomfort);
• loss of sensitivity to vibration effects;
• exhaustion and weakening of the muscles of the affected part of the body;
• erratic chaotic movements of the fingers of the upper limb;
• formation of the so-called thalamic hand: the forearm is bent and turned back, the hand is bent, the distal phalanges are straight with the proximal and middle phalanges half-bent;
• unilateral motor coordination disorder;
• partial blindness – lack of perception of the right or left half of the visual field;
• drooping of one corner of the mouth, unilateral facial paralysis;
• impaired concentration.

The patient's psychological state is characterized by mood swings, depression, and suicidal thoughts.

Causes of pathology

Thalamic syndrome is not a disease, but a set of symptoms and clinical manifestations. The symptom complex can be caused by vascular disorders of the deep branches of the posterior cerebral artery, damage to the ventral posterolateral nucleus of the thalamus. These conditions can lead to:

• injury;
• malignant brain tumor with metastases in the thalamus;
• ischemic stroke;
• hemorrhagic stroke.

The origin of hyperpathic pain and severe psycho-emotional disorders accompanying thalamic syndrome is not fully explained. Other neurological symptoms are caused by the following reasons:

• damage to the structures of the cerebellar dentate-thalamic tract;
• dysfunction of the medial lemniscus;
• damage to the hypothalamic nuclei.

Diagnosis and treatment

Diagnosis is based on a set of measures that involve clinical and instrumental examination methods:

• collecting anamnesis, studying patient complaints and determining possible causes of pathology;
• checking superficial and deep skin sensitivity;
• establishing muscle strength of the limbs;
• visual field check;
• determination of reactions to auditory, visual and taste stimuli;
• computed and magnetic resonance imaging;
• cerebral angiography.

Treatment of the pathology - symptomatic and pathogenetic - is based on the use of antipsychotics and antidepressants. A polypharmacotherapy regimen, a combination of drugs: an anticonvulsant, an antidepressant and an opioid, is considered effective. In cases where conservative methods do not bring results, it is indicated surgical intervention, during which the doctor destroys the ventrolateral nucleus of the thalamus. The operation is performed using a minimally invasive stereotactic method.

Along with traditional medicine, treatment of thalamic pain syndrome with folk remedies may be effective. Such therapy is aimed at relieving painful symptoms, but does not affect the causes and mechanisms of pathology.

ethnoscience suggests treating the syndrome by pain relief or by trying to restore sensitivity to the skin, for which the following recipes can be used.

1. Ginger infusion for bathing (to remove pain): 50 grams of crushed dry root of the plant are placed in a thermos, poured with a liter of boiling water and infused for one hour. The contents are added to the bath. It is necessary to take water procedures for 15 minutes. Daily use of this infusion for bathing is contraindicated. Before taking your first bath with ginger, you need to determine whether allergic reactions per plant. With a cotton swab moistened with the prepared solution, wipe a small area of ​​skin on the wrist or elbow and wait 15-20 minutes.
2. In case of loss of sensitivity healing effect provides alcohol tincture of dandelions. To prepare it, take 100 grams of the dry matter of the plant and pour half a liter of vodka. Infuse the medicine for a week, leaving the jar in a dark place and periodically shaking the contents. The tincture is used to rub the parts of the body that have lost sensitivity.

Thalamic syndrome is a complex of neurological symptoms caused by damage to the thalamus opticus. Diagnosis of pathology involves the use of clinical and instrumental methods. Treatment is symptomatic and pathogenetic.

Thalamic syndrome - observed when the visual thalamus is damaged. Clinical symptoms are varied and depend on functional role damaged structures.

SYMPTOMS OF THALAMIC SYNDROME:

When turning off a. thalamo-geniculata on the side opposite to the lesion in the thalamus, the following symptoms develop:

1. hemihypesthesia or hemianesthesia with a pronounced disturbance of deep sensitivity, sometimes without disturbances of sensitivity on the face,
2. Hyperpathy - (increased sensitivity) or dysesthesia (perverted perception of irritations), paroxysmal or constant severe pain, spreading to the entire half of the body (thalamic pain syndrome),
3. loss of vibration sensitivity,
4. transient hemiparesis without pronounced muscle spasticity and pathological Babinski reflex,
5. atrophy of the muscles of the affected half of the body,
6. trochaic and athetoid movements in the fingers, pseudo-athetotic movements when stretching the arm forward and with other tensions, a peculiar position of the hand (“thalamic hand”) - the hand is slightly bent, the fingers are extended in the distal phalanges and half-bent in the main phalanges, the forearm is slightly bent and pronated ,
7. Hemiataxia - impaired coordination of limb movements on 1 side
8. sometimes homonymous hemianopsia - (bilateral blindness in half the visual field)
9. Nothnagel facial paresis,
10. attention gap.
CAUSES OF THALAMIC SYNDROME:

Most common cause the occurrence of classic thalamic syndrome are vascular disorders in the system of deep branches of the posterior cerebral artery that supplies the visual thalamus - a.thalamo-geniculata.

TREATMENT OF THALAMIC SYNDROME:

Treatment of the underlying disease. Thalamic pain is reduced when taking antipsychotics in combination with antidepressants. For particularly severe and persistent pain, surgical intervention is indicated - stereotactic destruction of the posterior ventrolateral nucleus of the thalamus.

Syndromes of impaired praxial functions (dyspraxia).

Apraxia– loss of skills and actions developed during life without signs of paralysis and impaired coordination of movements

A) ideatorial– due to the loss of an action plan; the sequence of actions is disrupted (the patient cannot show how to light a match)

Cause: damage to the marginal gyrus of the parietal lobule of the dominant hemisphere

b) constructive– violation of the correct direction of action, the inability to create a whole from individual parts (a square or a house of matches)

Cause: lesion of the angular gyrus of the parietal lobe of the dominant hemisphere, always bilateral

V) motor– inability to perform purposeful actions while retaining the idea; spontaneous actions and actions on instructions are disrupted; often unilateral

Cause: defeat corpus callosum

G) frontal– the inability to perform complex movements and draw up a program of actions in violation of their spontaneity and purposefulness; characterized by echopraxia (repetition of movement)

Cause: damage to the frontal lobe.

Visual impairment syndromes.

System optic nerve

II pair - optic nerve (n. opticus)

The peripheral visual apparatus is represented by three cellular layers of the retina.

The first layer consists of visual cells, the photoreceptors of which are divided into rods and cones. The rods are primarily responsible for the perception of weak light signals and perceive the movement of objects. They are located on the periphery of the retina. Cones are located primarily in the center and are responsible for perceiving the shape and color of objects.

Second neurons are bipolar cells third- ganglionic, the axons of which form the optic nerve.

Vision disorders

1.1. Amaurosis - blindness. Occurs when the retina or articular nerve is damaged at any level before its decussation.

1.2. Amblyopia is decreased vision due to partial nerve damage.

2. Hemianopsia- loss of half the visual field of each eye.

2.1. Homonymous hemianopsia is loss of both right or left visual fields. It is observed with damage to any parts of the optic tract from the chiasm to the cortex.

2.2. Heteronymous hemianopsia is loss of both internal (binasal) or both external (bitemporal) halves of the visual field. Bitemporal hemianopsia occurs when the internal parts of the optic chiasm are damaged. Binasal hemianopsia occurs when the outer, non-crossed optic fibers are affected.

2.3. Quadrant hemianopsia is loss of a quarter of the visual field.

3. Scotoma- a visual field defect that does not merge with its peripheral boundaries. Occurs when small areas of the visual analyzer are damaged.

3.1. Positive scotoma - the patient sees in the field of vision black spot(this and violations can also be in the form of light spots).

3.2. Negative scotoma - scotoma is detected only when examining the perimeter.

3.3. Physiological scotoma is a visual field defect in the area of ​​the blind spot, corresponding to the shape of the optic nerve head.

4. Visual agnosia- disorder of recognition of objects and phenomena while maintaining their visual perception. It is observed when the outer parts of the occipital lobes are affected.

5. Visual hallucinations- simple (photopsias - the appearance of flickering sparks, spots, zigzag lines in the field of vision) and complex (figures of people and animals, moving pictures). They occur when the external and internal parts of the occipital lobes are irritated.

6. Metamorphopsia- disturbance of visual perception, characterized by distortion of the shape and size of visible objects (micropsia, macropsia).

Just in case! Optic nerve function test

The study of visual acuity (determination of central vision) is carried out for each eye separately using special tables (most often in our country the Golovin-Sivtsev tables are used).

The study of the visual field (the space that the fixed eye sees) is carried out using the perimeter. With a normal field of vision, a person sees with each eye White color outward by 90°, downward by 70°, upward and inward by 60°. For other colors of light the fields of view are more limited.

If the patient cannot get out of bed, the visual field can be approximately determined using a towel, newspaper, or cord. The patient looks straight ahead, the doctor suggests dividing the towel in half (test with a towel). If the patient succeeds, then the visual fields are preserved. The field of view can be examined by moving a finger around a circle in different planes.

Color perception is studied using special tables. The fundus is examined using an ophthalmoscope.