9.1. BRAIN STEM

In the classical textbooks on neurology, the brain stem (truncus cerebri) included all its departments, except for the cerebral hemispheres. In the book "The Human Brain" (1906) L.V. Bluminau (1861-1928) calls the brainstem "all parts of the brain from the visual tubercles to the medulla oblongata, inclusive." A.V. Triumfov (1897-1963) also wrote that "the composition of the brain stem includes the medulla oblongata, the pons with the cerebellum, the cerebral peduncles with the quadrigemina and the visual tubercles." However, in recent decades, only the medulla oblongata, the pons of the brain, and the midbrain have been referred to the brainstem. In the following presentation, we will follow this definition, which has become widespread in practical neurology.

The brain stem is 8-9 cm long and 3-4 cm wide. Its mass is small, but its functional significance is extremely important and diverse, since the viability of the organism depends on the structures located in it.

If the brain stem is presented in a horizontal position, then 3 “floors” are determined on its sagittal section: base, tire, roof.

Base (basis)adjacent to the slope of the occipital bone. It is made up of descending (efferent) pathways (cortical-spinal, cortical-nuclear, cortical-bridge), and in the bridge of the brain there are also ponto-cerebellar connections occupying a transverse position.

Tire (tegmentum)It is customary to call the part of the trunk located between its base and receptacles of cerebrospinal fluid (CSF) - the fourth ventricle, the aqueduct of the brain. It consists of motor and sensory nuclei of cranial nerves, red nuclei, substantia nigra, ascending (afferent) pathways, including spinothalamic pathways, medial and lateral loops and some efferent extrapyramidal pathways, as well as the reticular formation (RF) of the trunk and their connections.

roof brainstem can be conditionally recognized as structures located above the CSF receptacles passing through the brainstem. In this case, it would be possible, although this is not accepted, to include the cerebellum (in the process of ontogenesis it is formed from the same cerebral bladder as the brain bridge, Chapter 7 is devoted to it), the posterior and anterior medullary velum. The plate of the quadrigemina is recognized as the roof of the midbrain.

The brain stem is a continuation of the upper section of the spinal cord, preserving elements of a segmental structure. At the level of the medulla oblongata, the nucleus

The (lower) spinal tract of the trigeminal nerve (the nucleus of the descending root of the fifth cranial nerve) can be considered as a continuation of the posterior horn of the spinal cord, and the nucleus of the hypoglossal (XII cranial) nerve is a continuation of its anterior horn.

As in the spinal cord, the gray matter of the trunk is located in depth. It consists of the reticular formation (RF) and other cellular structures, it also includes the nuclei of the cranial nerves. Among these nuclei are motor, sensory and vegetative. Conventionally, they can be considered as analogs of the anterior, posterior, and lateral horns of the spinal cord, respectively. Both in the motor nuclei of the trunk and in the anterior horns of the spinal cord there are motor peripheral neurons, in the sensory nuclei - the second neurons of the pathways various kinds sensitivity, and in the vegetative nuclei of the trunk, as well as in the lateral horns of the spinal cord, there are vegetative cells.

cranial nerves of the trunk (Fig. 9.1) can be considered as analogues of the spinal nerves, especially since some of the cranial nerves, like the spinal nerves, are mixed in composition (III, V, VII, IX, X). However, some of the cranial nerves are only motor (XII, XI, VI, IV) or sensory (VIII). The sensory portions of the mixed cranial nerves and the VIII cranial nerve in their composition have nodes (ganglia) located outside the trunk, which are analogues of the spinal nodes, and like them also contain the bodies of the first sensory neurons (pseudo-unipolar cells), the dendrites of which go to the periphery, and the axons - to the center, into the substance of the brain stem, where they end at the cells of the sensitive nuclei of the stem.

The motor cranial nerves of the trunk and the motor portions of the mixed cranial nerves consist of axons of motor neurons, the bodies of which are motor nuclei located at different levels of the brain stem. The cells of the motor nuclei of the cranial nerves receive impulses from the motor zone of the cerebral cortex, mainly along the axons of the central motor neurons that make up the cortical-nuclear pathways. These paths, approaching the corresponding motor nuclei, make a partial crossover, in connection with which each motor nucleus of the cranial nerve receives impulses from the cortex of both hemispheres of the brain. The only exceptions to this rule are those cortical-nuclear connections that go to the lower part of the nucleus of the facial nerve and to the nucleus of the hypoglossal nerve; they make an almost complete crossover and thus transmit nerve impulses to the indicated nuclear structures only from the cortex of the opposite hemisphere of the brain.

The reticular formation is also located in the trunk cover (formatio reticularis), related to the so-called non-specific formations of the nervous system.

9.2. RETICULAR FORMATION OF THE BRAIN STEM

The first descriptions of the reticular formation (RF) of the brain stem were made by German morphologists: in 1861 by K. Reichert (Reichert K., 1811-1883) and in 1863 by O. Deiters (Deiters O., 1834-1863); Among domestic researchers, a great contribution to its study was made by V.M. Bekhterev. The RF is a collection of nerve cells and their processes located in the tegmentum of all levels of the trunk between the nuclei of the cranial nerves, the olives, passing here by afferent and efferent pathways. To the reticular formation sometimes

Rice. 9.1.Base of the brain and cranial nerve roots. 1 - pituitary gland; 2 - olfactory nerve; 3 - optic nerve; 4 - oculomotor nerve; 5 - block nerve; 6 - abducens nerve; 7 - motor root of the trigeminal nerve; 8 - sensitive root of the trigeminal nerve; 9 - facial nerve; 10 - intermediate nerve; 11 - vestibulocochlear nerve; 12 - glossopharyngeal nerve; 13 - vagus nerve; 14 - accessory nerve; 15 - hypoglossal nerve, 16 - spinal roots of the accessory nerve; 17 - medulla oblongata; 18 - cerebellum; 19 - trigeminal nerve; 20 - leg of the brain; 21 - optic tract.

some medial structures of the diencephalon are also worn, including the medial nuclei of the thalamus.

RF cells are different in shape and size, the length of axons, they are located mainly diffusely, in some places they form clusters - nuclei that provide integration of impulses coming from nearby cranial nuclei or penetrating here along collaterals from afferent and efferent pathways passing through the trunk. Among the connections of the reticular formation of the brainstem, the most important can be considered the cortico-reticular, spinal-reticular pathways, the connections between the RF of the stem with the formations of the diencephalon and the striopallidar system, and the cerebellar-reticular pathways. The processes of RF cells form afferent and efferent connections between the nuclei of the cranial nerves contained in the trunk tegmentum and the projection pathways that are part of the trunk tegmentum. Through collaterals, RF receives “recharging” impulses from the afferent pathways passing through the brainstem and at the same time performs the functions of an accumulator and an energy generator. It should also be noted that RF is highly sensitive to humoral factors, including hormones and drugs whose molecules reach it by the hematogenous route.

Based on the results of studies by G. Magun and D. Moruzzi (Mougoun N., Morruzzi D.), published in 1949, it is generally accepted that in humans the upper parts of the RF of the brain stem have connections with the cerebral cortex and regulate the level of consciousness , attention, motor and mental activity. This part of the Russian Federation is called: ascending non-specific activating system(Fig. 9.2).

Rice. 9.2.Reticular formation of the brainstem, its activating structures and ascending pathways to the cerebral cortex (scheme).

1 - reticular formation of the brain stem and its activating structures; 2 - hypothalamus; 3 - thalamus; 4 - cerebral cortex; 5 - cerebellum; 6 - afferent pathways and their collaterals; 7 - medulla oblongata; 8 - bridge of the brain; 9 - midbrain.

The ascending activating system includes nuclei of the reticular formation, located mainly at the level of the midbrain, to which collaterals from ascending sensory systems approach. The nerve impulses arising in these nuclei along the polysynaptic pathways, passing through the intralaminar nuclei of the thalamus, subthalamic nuclei to the cerebral cortex, have an activating effect on it. The ascending influences of the nonspecific activating reticular system are of great importance in the regulation of the tone of the cerebral cortex, as well as in the regulation of the processes of sleep and wakefulness.

In cases of damage to the activating structures of the reticular formation, as well as in violation of its connections with the cerebral cortex, there is a decrease in the level of consciousness, the activity of mental activity, in particular cognitive functions, motor activity. There may be manifestations of stunning, general and speech hypokinesia, akinetic mutism, stupor, coma, vegetative state.

The Russian Federation includes separate territories that have acquired elements of specialization in the process of evolution - the vasomotor center (its depressor and pressor zones), the respiratory center (expiratory and inspiratory), and the vomiting center. The RF contains structures that affect somatopsychovegetative integration. The RF ensures the maintenance of vital reflex functions - respiration and cardiovascular activity, takes part in the formation of such complex motor acts as coughing, sneezing, chewing, vomiting, the combined work of the speech motor apparatus, and general motor activity.

The ascending and descending influences of the RF on various levels of the nervous system are diverse, which are “tuned” by it to perform one or another specific function. Ensuring the maintenance of a certain tone of the cortex of the cerebral hemispheres, the reticular formation itself experiences a controlling influence from the cortex, thus gaining the opportunity to regulate the activity of its own excitability, and also influence the nature of the effects of the reticular formation on other brain structures.

The descending influences of RF on the spinal cord primarily affect the state of muscle tone and can be activating or decreasing muscle tone, which is important for the formation of motor acts. Usually, the activation or inhibition of the ascending and descending influences of the RF is carried out in parallel. So, during sleep, which is characterized by inhibition of ascending activating influences, inhibition of descending nonspecific projections also occurs, which is manifested, in particular, by a decrease in muscle tone. The parallelism of influences spreading from the reticular formation along the ascending and descending systems is also noted in coma states caused by various endogenous and exogenous causes, in the origin of which dysfunction of nonspecific brain structures plays a leading role.

At the same time, it should be noted that in pathological conditions the relationship between the functions of ascending and descending influences can also be more complex. So, with epileptic paroxysms, with Davidenkov's hormetonic syndrome, which usually occurs as a result of gross lesions of the brain stem, inhibition of the functions of the cerebral cortex is combined with an increase in muscle tone.

All this testifies to the complexity of the relationship between the functions of various structures of the reticular formation, which can lead both to synchronous ascending and descending influences, and to their disturbances with the opposite direction. At the same time, the RF is only a part of the global integrative system, including the limbic and cortical structures of the limbicoreticular complex, in interaction with which the organization of life and purposeful behavior is carried out.

RF can participate in the formation of pathogenetic processes that are the basis of some clinical syndromes that occur when the primary pathological focus is localized not only in the brain stem, but also in the brain regions located above or below it, which is understandable from the point of view of modern ideas about vertically built functional systems operating on the principle feedback. RF communications have a complex vertical organization. It is based on neural circles between cortical, subcortical, stem and spinal structures. These mechanisms are involved in providing mental functions and motor acts, and also have a very large impact on the state of the functions of the autonomic nervous system.

It is clear that the features of pathological manifestations associated with dysfunction of the RF depend on the nature, prevalence and severity of the pathological process and on which particular departments of the RF were involved in it. Dysfunction of the limbic-reticular complex, and in particular the RF, can be caused by many harmful toxic, infectious effects, degenerative processes in brain structures, disorders of cerebral blood supply, intracranial tumor or brain injury.

9.3. MEDULLA

Medulla (medulla oblongata)- direct continuation of the spinal cord. The conditional border between them is located at the level of the large occipital foramen; it passes through the first spinal roots, or the zone of decussation of the pyramidal tracts. The medulla oblongata has a length of 2.5-3 cm, in shape it looks like an overturned truncated cone; sometimes it is called an onion (bulbus). The lower part of the medulla oblongata is at the level of the edge of the foramen magnum, and the upper, wider, borders on the bridge of the brain. The conditional border between them runs at the level of the middle of the clivus of the occipital bone.

On the ventral surface of the medulla oblongata in the sagittal plane there is a deep longitudinal anterior median fissure (fissura mediana anterior), which is a continuation of the eponymous fissure of the spinal cord. On the sides of it are elevations - pyramids, consisting of corticospinal tracts, including axons of central motor neurons. Behind and lateral to the pyramids on each side of the medulla oblongata is located along the inferior olive (oliva inferior). From the anterolateral sulcus located between the pyramid and the olive (sulcus lateralis anterior) out the roots of the hyoid (XII) nerve. Behind the olives is the posterior lateral sulcus (sulcus lateralis posterior), through which the roots of the accessory, vagus and glossopharyngeal (XI, X and IX) nerves pass from the medulla oblongata.

In the lower part of the dorsal surface of the medulla oblongata, between the posterior median sulcus and the posterior lateral sulci, there are two longitudinal ridges, consisting of the fibers of the tender and wedge-shaped bundles that came here along the posterior cords of the spinal cord. In connection with the deployment of the central canal of the spinal cord into the fourth ventricle of the brain, the ridges formed from the tender and wedge-shaped bundles diverge to the sides and end with thickenings (tuberculi nuclei gracilis et cuneatus), corresponding to the location of the same name (tender and wedge-shaped) nuclei, consisting of the second neurons of the pathways of proprioceptive sensitivity.

Most of the dorsal surface of the medulla oblongata is the lower triangle of the bottom of the fourth cerebral ventricle - the rhomboid fossa, which is limited from below by the lower, and from above - by the upper legs of the cerebellum. If the angles of the rhomboid fossa ABCD, as suggested by L.V. Blumenau (1906), connect AC and BD with straight lines, marking the point of their intersection E, and then draw the bisector of the angle ABD and designate the points of its intersection of the lines AE and AD with the letters H and F and from the point H lower the straight line parallel to the line AD, intersecting the line AB at point G, you can pay attention to the triangles and quadrangle created within the rhomboid fossa, which allow you to imagine how the nuclei of cranial nerves located in the caudal part of the brainstem are projected onto it (Fig. 9.3).

It can be noted that the NVE triangle is occupied by an eminence located above the nucleus of the hypoglossal (XII cranial) nerve, and is designated as the triangle of the nucleus of the hypoglossal nerve (trigonum nervi hypoglossi). Triangle GHB has a recess (fovea inferior, or fovea vagi). Beneath it lies the posterior parasympathetic nucleus of the vagus nerve. Therefore, the triangle GHB is also called the triangle of the vagus nerve. (trigonum nervivagi). The outer part of the rhomboid fossa in the zone of the quadrangle AFHG inscribed in it is occupied by an elevation located above the nuclei of the auditory (VIII cranial) nerve, and therefore it is called the auditory field (area acustica), and its elevated center is designated as the auditory tubercle (tuberculum acustici).

The white matter of the medulla oblongata consists of pathways, some of which pass through it in transit, some are interrupted in the nuclei of the medulla oblongata and the RF that is part of it, or start from these structures. The cortical-spinal (pyramidal) pathways pass through the base of the medulla oblongata, participating in the formation of the pyramids in its composition, and then make an incomplete decussation. The fibers of the cortical-spinal tract that have undergone crossover immediately fall into the composition of the lateral cords of the spinal cord; the fibers of this pathway, which are not involved in the formation of the decussation, are included in the composition of the anterior spinal cord. Both the fibers of the cortical-spinal tract that have crossed to the opposite side and the fibers of the cortical-spinal tract that have remained on their side, as well as other efferent connections descending from various structures of the brain

Rice. 9.3.The geometric scheme of the rhomboid fossa (according to L.V. Blumenau). Explanations in the text.

Rice. 9.4.Location of cranial nerve nuclei in the brainstem (a, b). Motor nuclei - red; sensitive - green.

brain to the spinal cord, are sent to the peripheral motor neurons located in the anterior horns of the spinal cord.

The structure of the medulla oblongata is not identical at its different levels (Fig. 9.4). In this regard, for a more complete and systematic acquaintance with the structure of the medulla oblongata, let us consider the structure of transverse sections made through its caudal, middle and oral sections (Fig. 9.5). In the following presentation, for the same purpose, transverse sections of the pons and midbrain will be described.

The lower part of the medulla oblongata. When studying the transverse section of the caudal part of the medulla oblongata (Fig. 9.6), it is noteworthy that its structure here has a significant similarity with the spinal cord. There are still remains of the horns of the spinal cord, in particular its anterior horns, which, as it were, are cut off from the main mass of the central gray matter by pyramidal fibers that have undergone a decussation and are directed to the lateral funiculi of the spinal cord. The first anterior spinal roots emerge from the outer part of the anterior horns, and axons form the cerebral root of the XI cranial nerve from the cells of the base of the anterior horns. The central part of the gray matter at this level is occupied by the lower part of the reticular formation of the brain stem.

The lateral parts of the cut are mainly occupied by ascending and descending pathways. (tractus spinothalamicus lateralis et medialis, tracti spinocerebellaris dorsalis et ventralis etc.), occupying at this level a position close to that which is characteristic of them in the spinal cord.

Rice. 9.5.Levels of slices of the brain stem.

I - section of the medulla oblongata at its border with the spinal cord; II - section of the medulla oblongata at the level of its middle part; III - section of the medulla oblongata at the level of the upper part; IV - cut at the border of the medulla oblongata and the bridge; V - cut at the level of the middle third of the bridge; VI - cut at the level of the middle third of the bridge; VII - cut at the level of the anterior tubercles of the quadrigemina.

Rice. 9.6.Section of the medulla oblongata at its border with the spinal cord. 1 - gentle bundle; 2 - wedge-shaped bundle; 3 - the core of the tender bundle; 4 - the core of the wedge-shaped bundle; 5 - the nucleus of the descending root of the V nerve; 6 - rear horn; 7 - the nucleus of the XI nerve; 8 - front horn; 9 - posterior spinocerebellar pathway; 10 - intersection of the cortical-spinal (pyramidal) pathways.

Along the outer sections of the posterior horns on the section of the medulla oblongata under consideration, the spinal pathway of the trigeminal nerve descending from the pons of the brain (descending root of the V cranial nerve), surrounded by cells that make up its nucleus, passes. The upper part of the section is occupied by wedge-shaped and tender bundles coming here along the posterior cords of the spinal cord, as well as by the lower parts of the nuclei in which these bundles end.

Middle part of the medulla oblongata (Fig. 9.7). The base of the cut is occupied by powerful pyramids (pyramides). In the tegmentum of the medulla oblongata at this level are the nuclei of the XI, and a little higher - the nuclei of the XII cranial nerves. In the posterior part of the section, there are large nuclei of the tender and wedge-shaped bundles, in which the first neurons of the pathways of deep sensitivity end. The axons of the cells located in these nuclei go forward and medially, bending around in front of the initial segment of the central canal of the spinal cord and the gray matter surrounding it. These axons (fibre arcuatae internae), going from one side and the other, passing through the sagittal plane, completely intersect with each other, thus forming the upper, or sensitive, decussation, also known as the decussation of the loop (decussatio limniscorum). After the intersection, its constituent fibers take an upward direction and form medial loops (lemnisci medialis), which are located behind the pyramids on the sides of the midline.

Rice. 9.7.Section of the medulla oblongata at the level of its middle part.

1 and 2 - the nuclei of the tender and wedge-shaped bundles; 3 - the nucleus of the spinal root of the trigeminal (V) nerve; 4 - intersection of the bulbo-thalamic pathways; 5 - core of the accessory (IX) nerve; b - spinocerebellar pathways; 7 - nucleus of the hyoid (XII) nerve, 8 - spinothalamic path; 9 - pyramidal path; 10 - rear longitudinal beam.

The remaining pathways occupy a position approximately similar to their position in the previous section.

Upper part of the medulla oblongata (Fig. 9.8). Here, the central canal of the spinal cord is expanded into the fourth ventricle, and the cut passes through the lower triangle of the rhomboid fossa that makes up its bottom. The formations, which in the lower part of the medulla oblongata were located above the central canal, are now moved apart and occupy the posterolateral sections of the section. In the lateral part of the tire, a dissected lower olive is visible, the substance of which in the section resembles a folded sac.

The floor of the fourth ventricle is lined with ependymal cells. Under the ependyma layer is the central gray matter, in which, near the midline, on both sides, the nuclei of the XII cranial nerve are located. Outside of each of them is the posterior nucleus of the vagus nerve (nucleus dorsalis nervi vagi), and even more lateral, a transversely dissected bundle of fibers surrounded by cells, known as a single bundle, is visible. Surrounding cells form the nucleus of the solitary pathway (nucleus tractus solitary). Close to it is a small-celled vegetative salivary nucleus

Rice. 9.8.Section of the trunk at the level of the upper part of the medulla oblongata. 1 - medial longitudinal bundle; 2 - the nucleus of the XII nerve; 3 - rhomboid fossa, 4 - nuclei of the vestibular nerve; 5 - posterior nucleus of the X nerve; 6 - the core of the general sensitivity of the X nerve; 7 - the core of a single bundle (gustatory core); 8 - posterior spinocerebellar pathway; 9 - mutual core; 10 - the nucleus of the descending root of the V nerve; 11 - anterior spinal-cerebellar path; 12 - lower olive; 13 - cortical-spinal (pyramidal) path; 14 - medial loop.

(nucleus salivatorius). The lower part of the nucleus of the solitary tract and the salivary nucleus belongs to the glossopharyngeal, and the upper part to the intermediate nerves.

In the depth of the reticular formation in the center of the tegmentum there is a large cell nucleus, which is, as it were, an oral continuation of the nucleus of the XI cranial nerve. This is the motor nucleus, the lower part of which belongs to the IX, and the upper to the X cranial nerves. In this regard, the nucleus is called the mutual or double nucleus. (nucl. ambiguus), the axons of the cells of the lower part of this nucleus make up the cranial part of the accessory nerve.

The nuclei of the tender and wedge-shaped bundles on this section are dissected at the level of their upper pole, their sizes are small here. External arcuate fibers are superimposed on the nucleus of the sphenoid tract, which are a continuation of the posterior spinal cerebellar bundle of Flexig, which are involved in the formation of the inferior cerebellar peduncle. The fibers of the olivocerebellar pathway, coming from the olives, also take part in its formation, most of which previously pass to the opposite side.

Between the olives there are medial loops. Behind them are the medial longitudinal bundles and the operculo-spinal tract, which run from the nuclei of the roof of the midbrain to the spinal cord. Other long pathways pass through the lateral sections of the cut, not interrupted in the medulla oblongata. The dimensions of the reticular formation compared with the levels of the previous

cutting sections continue to grow. The reticular formation is fragmented by nerve fibers crossing it in different directions.

In the highest parts of the medulla oblongata, on the border with the bridge, the width of the IV ventricle reaches a maximum. Due to the fact that the thickness of the lower cerebellar peduncles located on the sides of the rhomboid fossa is already large here, the dimensions of the section of the medulla oblongata at this level are the largest. In addition to the formations of the medulla oblongata already mentioned, a large place is occupied by the lower sections of the cranial nuclei of the bridge, a description of which will be presented when considering this section of the brain stem.

9.4. CRANIAL NERVES OF THE medulla oblongata 9.4.1. Accessory (XI) nerve (n. accessorius)

The accessory nerve has cranial and spinal parts, and therefore it can be said that it occupies, as it were, a transitional position between the spinal and cranial nerves. It could well be called spinal-cranial. Therefore, we begin the description of the cranial nerves with it (Fig. 9.9).

The accessory nerve is motor. His the main long motor nucleus is formed by the cells of the base of the anterior horns of the C II-C V segments of the spinal cord. The axons of the cells of the spinal nucleus of the XI cranial nerve exit the indicated segments of the spinal cord between the anterior and posterior spinal roots and at its lateral surface, gradually uniting, forming spinal root of accessory nerve which accepts the

Rice. 9.9.Accessory (XI) nerve and its connections.

1 - spinal roots of the accessory nerve; 2 - cranial roots of the accessory nerve; 3 - accessory nerve trunk; 4 - jugular opening; 5 - the inner part of the accessory nerve; b - the lower node of the vagus nerve; 7 - external branch of the accessory nerve; 8 - sternocleidomastoid muscle; 9 - trapezius muscle. Motor nerve structures are marked in red; blue - sensitive vegetative, green - parasympathetic, purple - afferent vegetative.

walking direction and enters the cavity of the posterior cranial fossa through the foramen magnum of axons. In the posterior cranial fossa, the cerebral (cranial) root, consisting of neurons located in the lower part of the double (mutual) nucleus, joins the spinal root next to the neurons of the vagus nerve (X cranial nerve). The cerebral root of the XI cranial nerve can be considered as part of the motor portion of the X cranial nerve, since it actually has a common motor nucleus and common functions with it.

The XI cranial nerve, formed after the fusion of the cerebral and spinal roots, emerges from the posterolateral sulcus of the medulla oblongata below the X cranial nerve root. The trunk of the XI cranial nerve, formed after this, exits the cranial cavity through the jugular foramen (foramen jugularis). After that fibers of the cranial part of the trunk of the XI cranial nerve join the X cranial nerve, and the rest spinal part, called external branch of accessory nerve down the neck and innervates the sternocleidomastoid muscle (m. sternocleidomastoideus) and the upper part of the trapezius muscle (m. trapezium).

Damage to the spinal nucleus or trunk of the XI cranial nerve and its branches at any level leads to the development of peripheral paralysis or paresis of these muscles. Over time, their atrophy occurs, leading to asymmetry, detected during external examination, while the shoulder on the side of the lesion is lowered, the lower angle of the scapula moves away from the spine. The scapula is displaced outwards and upwards ("pterygoid" scapula). Difficulty "shoulder shrug" and the ability to raise the arm above the horizontal level. Due to the excessive "sagging" of the shoulder on the side of the lesion, the arm appears to be longer. If the patient is asked to stretch his arms in front of him so that the palms touch each other, and the fingers are extended, then the ends of the fingers on the side of the lesion come forward.

Paresis or paralysis of the sternocleidomastoid muscle leads to the fact that when the head is turned on the affected side, this muscle is poorly contoured. A decrease in her strength can be detected by resisting turning the head in the direction opposite to the lesion, and slightly upward. A decrease in the strength of the trapezius muscle is clearly revealed if the examiner puts his hands on the patient's shoulders and resists their active lifting. With bilateral damage to the XI cranial nerve or its spinal nucleus, there is a tendency for the head to hang down on the chest. Damage to the XI cranial nerve is usually accompanied by deep, aching, difficult to localize pain in the arm on the side of the lesion, which is associated with overstretching of the articular bag and ligamentous apparatus of the shoulder joint due to paralysis or paresis of the trapezius muscle.

Disorder of function of the XI cranial nerve may be the result of damage to peripheral motor neurons in patients with tick-borne encephalitis, poliomyelitis, or amyotrophic lateral sclerosis. The defeat of this nerve on both sides leads to the development of a symptom of a hanging head, which may also be due to a disorder in the function of the neuromuscular synapses in myasthenia gravis. Damage to the accessory nerve is possible with craniovertebral anomalies, in particular with Arnold-Chiari syndrome, as well as with injuries and tumors of the same localization. When the cells of the spinal nucleus of the accessory nerve are irritated in the muscles innervated by it, fascicular twitches and nodding movements are possible.

The peripheral neurons that make up the spinal nucleus of the XI cranial nerve receive impulses along the cortical-spinal and cortical-nuclear tracts, as well as along the extrapyramidal tegmental-spinal, vestibulo-spinal pathways and along the medial longitudinal bundle, on both sides, but mainly on the opposite side. sides. In this regard, a change in the impulse coming from the side of the central neurons to the peripheral motor neurons of the spinal nuclei of the XI cranial nerve can cause spastic paresis of the striated muscles innervated by this nerve, more pronounced on the side opposite to the pathological process. It is assumed that a change in the nerve impulses arriving at the peripheral neurons of the spinal nucleus XI of the cranial nerve can cause hyperkinesis by the type of spastic torticollis. It is believed that the cause of this form of hyperkinesis may be irritation of the spinal root of the accessory nerve.

9.4.2. Hypoglossal (XII) nerve (n. hypoglossus)

The hypoglossal nerve is motor (Fig. 9.10). Its nucleus is located in the medulla oblongata, while the upper part of the nucleus is located under the bottom of the rhomboid fossa, and the lower part descends along the central canal to the level of the beginning of the pyramidal junction. The nucleus of the XII cranial nerve consists of large multipolar cells and a large number of fibers located between them, by which it is divided into 3 more or less separate cell groups. The axons of the cells of the nucleus of the XII cranial nerve gather into bundles that penetrate the medulla oblongata and emerge from its anterior lateral groove between the inferior olive and the pyramid. In the future, they leave the cranial cavity through a special hole in the bone - the hypoglossal nerve canal (canalis nervi hypoglossi), located above the lateral edge of the large occipital foramen, forming a single trunk.

Coming out of the cranial cavity, the XII cranial nerve passes between the jugular vein and the internal carotid artery, forms a hyoid arch, or loop (ansa cervicalis), passing here in close proximity to the branches of the spinal nerves coming from the three upper cervical segments of the spinal cord and innervating the muscles, attached to the hyoid bone. Later, the hypoglossal nerve turns forward and divides into lingual branches (rr. linguales), innervating tongue muscles: sublingual-lingual (m. hypoglossus) awl-lingual (m. styloglossus) and chin-lingual (m. genioglossus), as well as the longitudinal and transverse muscles of the tongue (m. longitudinalis and m. transversus linguae).

With the defeat of the XII cranial nerve, peripheral paralysis or paresis of the same half of the tongue occurs (Fig. 9.11), at the same time, the tongue in the oral cavity shifts to the healthy side, and when protruding from the mouth, it deviates towards the pathological process (the tongue “points to the focus”). This happens due to the fact that m. genioglossus the healthy side pushes the homolateral half of the tongue forward, while its paralyzed half lags behind and the tongue turns in its direction. The muscles of the paralyzed side of the tongue atrophy over time, become thinner, while the relief of the tongue on the side of the lesion changes - it becomes folded, "geographical".

Rice. 9.10.Hypoglossal (XII) nerve and its connections.

1 - the nucleus of the hypoglossal nerve; 2 - sublingual canal; 3 - meningeal branch; 4 - connecting branch to the upper cervical sympathetic node; 5 - connecting branch to the lower node of the vagus (X) nerve; b - upper cervical sympathetic node; 7 - the lower node of the vagus nerve; 8 - connecting branches to the first two spinal nodes; 9 - internal carotid artery; 10 - internal jugular vein; 11 - awl-lingual muscle; 12 - vertical muscle of the tongue; 13 - upper longitudinal muscle of the tongue; 14 - transverse muscle of the tongue; 15 - lower longitudinal muscle of the tongue; 16 - genio-lingual muscle; 17 - chin-hyoid muscle; 18 - hyoid-lingual muscle; 19 - thyroid muscle; 20 - sternohyoid muscle; 21 - sternothyroid muscle; 22 - upper abdomen of the scapular-hyoid muscle; 23 - lower belly of the scapular-hyoid muscle; 24 - neck loop; 25 - lower spine of the neck loop; 26 - upper spine of the neck loop. Branches extending from the medulla oblongata are marked in red, branches from the cervical spinal cord are marked in purple.

Rice. 9.11.The defeat of the left hypoglossal nerve of the peripheral type.

Unilateral paralysis of the tongue has almost no effect on the acts of chewing, swallowing, speech. At the same time, signs of paresis of the muscles that fix the larynx are possible. When swallowing in such cases, a noticeable displacement of the larynx to the side.

In the case of bilateral damage to the nuclei or trunks of the XII cranial nerve, complete paralysis of the muscles of the tongue (glossoplegia) may occur, then it turns out to be sharply thinned and motionless lying on the diaphragm of the mouth. There comes a speech disorder in the form of anartria. With bilateral paresis of the muscles of the tongue, articulation is disturbed by the type of dysarthria. During the conversation, it seems that the patient's mouth is full. The pronunciation of consonant sounds is especially significantly impaired. Glossoplegia also leads to difficulty in eating, as it is difficult for the patient to move the food bolus into the throat.

If peripheral paresis or paralysis of the tongue is the result of a gradually progressive damage to the nucleus of the XII cranial nerve, it is characteristic appearance in language on the side of the pathological process fibrillar and fascicular twitches. Damage to the nuclei of the XII cranial nerve is usually accompanied by peripheral (flaccid) paresis of the circular muscle of the mouth (m. orbicularis oris), in which the lips become thinner, wrinkles appear on them, converging to the oral fissure ("purse-string mouth"), it is difficult for the patient to whistle, blow out the candle. This phenomenon is explained by the fact that the bodies of peripheral motor neurons, the axons of which pass as part of the VII (facial) cranial nerve to the circular muscle of the mouth, are located in the nucleus of the XII cranial nerve.

If the lower part of the motor zone of the cerebral cortex or the cortical-nuclear pathways are affected,

carrying impulses from the cortex, in particular to the nucleus of the XII cranial nerve, then (since the cortical-nuclear fibers approaching this nucleus make an almost complete decussation) on the side opposite to the pathological process, there is a central paresis of the muscles of the tongue (Fig. 9.12). When protruding from the mouth, the tongue is turned in the direction opposite to the pathological focus

Rice. 9.12.Lesion of the left hypoglossal nerve in the central type.

in the brain, there is no atrophy of the tongue and there are no fibrillar twitches in it. Central paresis of the tongue is usually combined with central paresis of the facial nerve and manifestations of central hemiparesis on the same side.

The decrease in the strength of the muscles of the tongue that occurs during their paresis can be checked if the examiner asks the patient to press the tip of the tongue on the inner surface of his cheek, while he himself resists this movement by pressing on the outer surface of the patient's cheek.

Signs of bilateral damage to the nuclei and trunks of the XII cranial nerve are usually combined with manifestations of dysfunction of other cranial nerves of the bulbar group, and then a clinical picture of a more complete bulbar syndrome occurs; violation of the functions of the cortical-nuclear pathways leading to the motor nuclei of these nerves is manifested by a pseudobulbar syndrome, which is a manifestation of central paresis or paralysis of the muscles innervated by them.

9.4.3. Vagus (X) nerve (n. vagus)

Nervus vagus is mixed (Fig. 9.13). It contains motor, sensory and autonomic (parasympathetic) fibers. In accordance with this, in the cranial nerve X system there are 3 main cores, located in the tegmentum of the medulla oblongata. Motor core - double(nucl. ambiguus), its upper part belongs to the IX cranial nerve, and the lower part to the X cranial nerve and to the cerebral part of the XI cranial nerve. sensitive core(nucl. sensorium) also common to IX and X cranial nerves. In addition, the X nerve system has its own nucleus - posterior nucleus of the vagus nerve(nucl. dorsalis nervi vagi), located under the bottom of the IV ventricle, outside of the upper nucleus of the hypoglossal nerve. It consists of small vegetative cells and is directly related to the innervation of the majority internal organs and that's why sometimes it is called visceral.

The X cranial nerve leaves the posterolateral sulcus of the medulla oblongata and goes to the jugular foramen, through which, together with the IX and XI cranial nerves, it leaves the cranial cavity. In the zone of the jugular foramen on the trunk of the X cranial nerve are located top knot (ganglion superius) and 1 cm lower, already outside the cranial cavity - bottom knot (ganglion inferius). Both of these nodes are analogues of the spinal nodes and part of the sensitive portion of the X cranial nerve. They contain the bodies of the first neurons of the sensory pathways, their axons are sent to the medulla oblongata to the mentioned sensory nucleus, and the dendrites to the periphery.

Below the jugular foramen, in section X of the cranial nerve, located between these nodes, fibers of the accessory nerve join its motor portion, which make up its cerebral root and are axons of peripheral motor neurons that make up the double nucleus.

The motor and sensory portions of the X cranial nerve provide innervation to the striated muscles of the upper parts of the digestive and respiratory systems: soft palate, pharynx, larynx, epiglottis. Of the branches of the X cranial nerve, extending from it at the base of the skull and on the neck, the largest are the following.

Rice. 9.13.The vagus nerve (X) and its connections.

1 - the core of a single path; 2 - the nucleus of the spinal tract of the trigeminal nerve; 3 - double core; 4 - posterior nucleus of the vagus nerve; 5 - spinal roots of the accessory nerve; 6 - meningeal branch (into the subtentorial space); 7 - ear branch (to the posterior surface of the auricle and external auditory canal); 8 - upper cervical sympathetic node; 9 - pharyngeal plexus; 10 - muscle that raises the palatine curtain; 11 - tongue muscle; 12 - palatopharyngeal muscle;

13 - palatine-lingual muscle; 14 - tubal-pharyngeal muscle; 15 - upper constrictor of the pharynx; 16 - sensitive branches to the mucous membrane of the lower part of the pharynx; 17 - upper laryngeal nerve; 18 - sternocleidomastoid muscle; 19 - trapezius muscle; 20 - lower laryngeal nerve; 21 - lower constrictor of the pharynx; 22 - cricoid muscle; 23 - arytenoid muscles; 24 - thyroid arytenoid muscle; 25 - lateral cricoarytenoid muscle; 26 - posterior cricoarytenoid muscle; 27 - esophagus; 28 - right subclavian artery; 29 - recurrent laryngeal nerve; 30 - thoracic cardiac nerves; 31 - cardiac plexus; 32 - left vagus nerve; 33 - aortic arch; 34 - diaphragm; 35 - esophageal plexus; 36 - celiac plexus; 37 - liver; 38 - gallbladder; 39 - right kidney; 40 - small intestine; 41 - left kidney; 42 - pancreas; 43 - spleen; 44 - stomach. Motor nerve structures are marked in red; blue - sensitive; green - parasympathetic.

Meningeal branch (r. meningeus)- sensitive, participates in the innervation of the predominantly dura mater of the posterior cranial fossa.

ear branch (r. auricularis, Arnold's nerve) - sensitive, innervates the posterior wall of the external auditory canal and the posterior surface of the auricle.

superior laryngeal nerve (n. laringeus superior) innervates the muscles of the soft palate, constrictors of the pharynx and the cricothyroid muscle, participates in the sensitive innervation of the larynx and epiglottis. With neuralgia of the superior laryngeal nerve, attacks of excruciating pain from several seconds to a minute are characteristic, localized in the larynx, sometimes accompanied by a cough. On palpation, on the lateral surface of the larynx under the thyroid cartilage, a pain point (trigger zone) is noted, pressure on which can cause an attack.

recurrent laryngeal nerve (n. laringeus recurrents)- right recurrent nerve wraps around the subclavian artery from front to back, left - aortic arch. Then both nerves rise between the trachea and esophagus, participate in their innervation and reach the larynx.

The terminal branches of the recurrent nerves are called lower laryngeal nerves they anastomose with the superior laryngeal nerves. Neuropathy of the recurrent laryngeal and lower laryngeal nerves is manifested by paralysis of the vocal cords, other muscles of the larynx, except for the cricothyroid muscle. As a result, if the branch of the X cranial nerve and its branch - the recurrent laryngeal nerve, as well as its continuation - the lower laryngeal nerve - are damaged, the sonority of the voice may be disturbed - dysphonia in the form of hoarseness without dysphagia (Ortner symptom) due to paresis or paralysis of the vocal cord on the side of the pathological process, detected during laryngoscopy.

Damage to both recurrent laryngeal nerves causes aphonia and respiratory stridor. Such dysphonia (or aphonia) may be the result of an aortic aneurysm, mediastinal tumor, surgery on the neck or mediastinum, but often the cause of recurrent laryngeal nerve neuropathy cannot be established.

After the discharge of these branches, the remaining, consisting mainly of parasympathetic fibers, part of the vagus nerve, located between the internal, then the common carotid arteries on the one hand and the jugular vein on the other, penetrates the chest. Passing through the chest

The X cranial nerve gives off bronchial and thoracic cardiac branches and then enters the abdominal cavity through the esophageal opening of the diaphragm. Here the X cranial nerve divides into the anterior and posterior vagus trunks (truncus vagalis anteror et truncus vagalis posterior); their numerous branches (gastric, celiac, renal and other branches) provide sensory and parasympathetic innervation (innervation of smooth muscles, digestive glands, urinary system, etc.).

With damage to the vagus nerve in the proximal section, the soft palate droops on the side of the pathological process; it turns out to be motionless or tenses less than on the healthy side. The palatine curtain during phonation shifts to the healthy side. Usually on the affected side of cranial nerve X uvula (uvula) deviated to the healthy side, reduced or absent pharyngeal and palatine reflexes. They are checked on both sides with a spatula, a spoon or a sheet of paper rolled into a tube, with which the examiner touches the back of the pharynx or the soft palate.

Bilateral decrease in the functions of the vagus nerves can cause manifestations of bulbar syndrome, in particular, a speech disorder in the form of aphonia and dysphagia - a violation of swallowing, choking on liquid food - a consequence of paresis of the soft palate, palatine curtain, epiglottis, pharynx. The weakening of the swallowing reflex leads to the accumulation of saliva and food debris in the oral cavity. Paresis of the pharynx and a decrease in the cough reflex contribute to obturation of the upper respiratory tract, followed by bronchial occlusion, which leads to respiratory failure and the development of obstructive pneumonia.

Irritation of the parasympathetic portion of the vagus nerves can lead to bradycardia, broncho- and esophagospasm, pylorospasm, increased peristalsis, vomiting, increased secretion of the glands of the digestive tract, and over time to the possible development of peptic ulcer of the stomach and duodenum. Damage to these nerves leads to respiratory disorders, tachycardia, inhibition of secretion of the glandular apparatus of the digestive tract etc. A pronounced bilateral disorder of the parasympathetic innervation of the internal organs can lead to the death of the patient due to impaired breathing and cardiac activity.

The cause of damage to the X cranial nerve can be syringobulbia, amyotrophic lateral sclerosis, intoxication (alcohol, diphtheria, lead poisoning, arsenic), nerve compression is possible in oncological pathology, aortic aneurysm, etc.

9.4.4. Glossopharyngeal (IX) nerve (n. glossopharyngeus)

The glossopharyngeal nerve is mixed. It contains motor, sensory, including taste, and autonomic parasympathetic fibers.

In accordance with this, the IX cranial nerve system includes those located in the medulla oblongata nucleus: motor (nucl. ambiguus) and core general types sensitivity (nucl. sensorius)- common to IX and X cranial nerves, as well as core of taste sensation - single path core (nucl. solitarius) and parasympathetic secretory nucleus - inferior salivary nucleus (nucl. salvatorius), common to IX cranial and intermediate nerves.

The IX cranial nerve emerges from the posterolateral sulcus of the medulla oblongata, located behind the inferior olive, and goes to the jugular foramen, after passing through which it leaves the cranial cavity (Fig. 9.14).

The motor portion of the IX cranial nerve innervates only one muscle - the stylopharyngeal (m. Stylopharyngeus), which raises the pharynx.

The bodies of the first sensory neurons, providing conduction of impulses of general types and taste sensitivity, are located in analogues of the spinal ganglia - in top(ganglion superius) and lower(ganglion inferius) nodes near the jugular foramen. The dendrites of these neurons

begin in the posterior third of the tongue, soft palate, pharynx, pharynx, anterior surface of the epiglottis, as well as in the auditory (Eustachian) tube and tympanic cavity, participating in providing general types of sensitivity in them, and in the posterior third of the tongue also taste sensitivity. The axons of the same pseudo-unipolar cells as part of the cranial nerve root IX penetrate the medulla oblongata, then those that conduct impulses of general types of sensitivity approach the corresponding nucleus; and those through which impulses of taste sensitivity are transmitted, to the lower part of the nucleus of the solitary pathway.

In these nuclei, sensitive impulses are switched to second neurons, whose axons pass to the opposite side, participating in the formation of the medial loop, and end in the thalamic nuclei, where are third neurons. Axons of the third neurons of the sensory pathways of the IX cranial nerve system pass through the medial sensory loop, posterior femur of the internal capsule, corona radiata, and end in the lower part of the cortex of the postcentral gyrus (fibers transmitting impulses of general types of sensitivity) and in the crust around the islet (fibers that conduct impulses of taste sensitivity, their unilateral damage does not lead to a disorder of taste sensitivity).

It should be noted that the impulses that arise in the receptor apparatus in the zone of sensitive innervation of the vagus, trigeminal and intermediate nerves also pass from the sensory nuclei of the brainstem to the projection zones of the cortex, similar to the one considered above.

Parasympathetic salivary fibers which are axons of cells laid down in the lower part of the salivary nucleus, located in the lateral part of the tegmentum of the medulla oblongata, through the branch of the glossopharyngeal nerve - tympanic nerve and small stony nerve - reach the ear parasympathetic node (gangl. oticum). Postganglionic parasympathetic fibers exit from here, which pass through the anastomosis into the branch of the trigeminal nerve (n. auriculotemporalis) and innervate the parotid gland, providing its secretory function.

With damage to the glossopharyngeal nerve there are difficulties in swallowing, a violation of the sensitivity of general types (pain, temperature, tactile) of the soft palate, pharynx, upper pharynx, anterior surface of the epiglottis, posterior third of the tongue. Due to the disorder of proprioceptive sensitivity in the tongue, the sensation of its position in the oral cavity can be disturbed, which makes it difficult to chew and swallow solid food. In the back third of the tongue, the perception of taste sensations is disturbed, mainly the sensation of bitter and salty. In addition to the glossopharyngeal nerve, the perception of taste is provided by the system of the intermediate nerve and its branch - the tympanic string. (chorda tympani).

Rice. 9.14.Glossopharyngeal (IX) nerve.

1 - the core of a single path; 2 - double core; 3 - lower salivary nucleus; 4 - jugular opening; 5 - upper node of the glossopharyngeal nerve; 6 - lower node of the glossopharyngeal nerve; 7 - connecting branch with the ear branch of the vagus nerve; 8 - the lower node of the vagus nerve; 9 - upper cervical sympathetic node; 10 - bodies of the carotid sinus; 11 - carotid sinus and its plexus; 12 - common carotid artery; 13 - sinus branch; 14 - tympanic nerve; 15 - facial nerve; 16 - knee-tympanic nerve; 17 - large stony nerve; 18 - pterygopalatine node; 19 - ear knot; 20 - parotid gland; 21 - small stony nerve; 22 - auditory tube; 23 - deep stony nerve; 24 - internal carotid artery;

25 - carotid-tympanic nerves; 26 - styloid muscle; 27 - connecting branch with the facial nerve; 28 - stylo-pharyngeal muscle; 29 - sympathetic plexus; 30 - motor branches of the vagus nerve; 31 - pharyngeal plexus; 32 - branches to the muscles and mucous membrane of the pharynx and soft palate; 33 - sensitive branches to the soft palate and tonsils; 34 - gustatory and sensitive branches to the posterior third of the tongue. Motor nerve structures are marked in red; blue - sensitive; green - parasympathetic; purple - sympathetic.

With a decrease in the functions of the IX cranial nerve, the patient sometimes complains of some dryness in the mouth, but this symptom is unstable and unreliable, since the decrease and even cessation of the function of one parotid gland can be compensated by other salivary glands.

Irritation by the pathological process of the IX cranial nerve can cause pain in the pharynx, posterior pharyngeal wall, tongue, as well as in the auditory tube and tympanic cavity. These sensations may be permanent or paroxysmal in nature. In the latter case, the patient may develop neuralgia of the IX cranial nerve.

It should be noted that a certain anatomical and functional commonality of the IX and X cranial nerves usually leads to a combination of their lesions and to the practical simultaneity of checking their functions during a neurological examination. So, when checking the palatine and pharyngeal reflexes, it must be borne in mind that their decrease may be due to damage to both the X and IX cranial nerves (the afferent part of the reflex arc passes along the sensitive portion of the IX and X cranial nerves, the efferent part - along the motor portion of the X cranial nerve, and the closure of the reflex arc occurs in the medulla oblongata).

9.5. TASTE AND ITS DISORDERS

Specialized gustatory receptors are located in the taste annular and fungiform papillae of the tongue and are chemoreceptors, as they react to chemicals dissolved in water, which is the main part of saliva. Separate chemoreceptors are located in the mucous membrane of the soft and hard palate, at the top of the epiglottis.

It should be borne in mind that taste stimuli of different nature are perceived by specific receptors located in the mucous membrane of the tongue mostly like this: bitter - in the posterior third of the tongue salty - in the posterior third of the tongue and in its lateral zones, sour - in the lateral sections of the upper surface of the tongue and on its sides, sweet - in the anterior parts of the tongue. The middle part of the back of the tongue and its lower surface are practically devoid of taste buds.

The state of taste sensitivity is checked separately for each of the four main flavors (sour, sweet, bitter, salty). When checking taste sensitivity, drops of a solution containing

presenting a taste stimulus 1, while making sure that the drop does not spread over the tongue. After applying each drop, the patient should point to one of the pre-written words that reflect his taste sensations: “bitter”, “salty”, “sour” and “sweet”, and then rinse his mouth thoroughly. The examination may reveal: taste disorders - dysgeusia, lack of taste sensation ageusia, decreased taste sensitivity hypogeusia, perversions of taste parageusia, the presence of a metallic taste, often occurring when taking certain medications, - phantageusia.

Violation of taste sensitivity may indicate damage to the glossopharyngeal nerve or the intermediate nerve of Vrisberg, which is part of the facial nerve. For the detection of a topical neurological diagnosis, the detection of taste disorders can be essential. For the defeat of the IX cranial nerve, a disorder of perception of bitter and salty, detected in the posterior third of the tongue, is more characteristic.

Of undoubted importance for neurological topical diagnosis are disorders of certain types of taste sensitivity in a certain area of ​​​​the tongue on the one hand, since sensory disorders on both sides can be caused by inhibition of the receptor apparatus due to diffuse pathology of the mucous membrane of the tongue and the walls of the oral cavity. A decrease in the brightness, clarity of taste sensations can occur in older people due to progressive atrophy of part of the taste buds and a decrease in saliva secretion, which occur with aging and are provoked by wearing dentures, especially the upper jaw, prolonged smoking, prolonged being in a state of depression. A taste disorder is a possible consequence of dry mouth due to a violation of salivation, for example, in Sjogren's disease.

Hypogeusia is often noted with tongue lining, tonsillitis, glossitis (in cases of hypovitaminosis A, pellagra, with prolonged antibiotic treatment, with radiation therapy). Ageusia can be in patients with endocrinopathy (hypothyroidism, diabetes mellitus, etc.), with familial dysautonomia (Riley-Day syndrome). With Addison's disease, a significant exacerbation of taste (hypergeusia) is possible. Manifestations of dysgeusia can be the result of taking many drugs: tetracycline, d-penicillamine, ethambutol, antifungal drugs, levodopa, lithium carbonate, cytotoxic agents.

9.6. SYNDROMES INCLUDING SIGNS OF IMPAIRMENT OF THE MEMBRANE AND ITS CRANIAL NERVES

Dandy Walker Syndrome - congenital malformation of the caudal brain stem and cerebellar vermis, leading to incomplete opening of the median (Magendie) and lateral (Lushka) apertures of the IV ventricle of the brain. It is manifested by signs of hydrocephalus, and often hydromyelia. The last circumstance

1 To test taste sensitivity, you can use solutions of sugar, salt, citric acid, quinine.

The property, in accordance with the hydrodynamic theory of Gardner, can cause the development of syringomyelia, syringobulbia. Severe Dandy-Walker syndrome is characterized by manifestations of functional insufficiency of the medulla oblongata and cerebellum, symptoms of intracranial hypertension. The diagnosis is clarified by imaging methods of brain tissue - CT and MRI, while signs of hydrocephalus are revealed and, in particular, a pronounced expansion of the IV cerebral ventricle, MRI can reveal deformation of these brain structures. Described in 1921 by the American neurosurgeons W. Dandy (1886-1946) and A. Walker (born in 1907).

Laruelle syndrome characterized by signs of intracranial hypertension, in particular paroxysmal intense diffuse headache, contracture of the neck muscles, tonic convulsions, respiratory and cardiovascular disorders. Possible destruction of the edges of the foramen magnum (symptom of Babchin). Described in tumors of subtentorial localization by the Belgian neuropathologist M. Laruelle.

Arnold-Chiari-Solovtsev anomaly (see chapter 24).

Oscillopsia- the illusion of vibrations of motionless objects. Oscillopsia in combination with vertical nystagmus, instability and vestibular vertigo is observed with craniovertebral anomalies, in particular with Arnold-Chiari syndrome.

Symptom Ortner- hoarseness of voice, sometimes aphonia as a result of paresis or paralysis of the vocal cords, caused by damage to the recurrent laryngeal nerves. The cause may be their compression by a tumor of the mediastinum, as well as a hypertrophied heart or left pulmonary artery with mitral valve stenosis. Described in 1897 by the Austrian doctor N. Ortner (1865-1935).

Lermitte-Monnier syndrome (Tsokanakis symptom) - a swallowing disorder caused by spasms of the muscles of the pharynx and esophagus that occur when the vagus nerves are irritated by a pathological process at the base of the skull or in the tissues of the neck and mediastinum. It occurs, in particular, with a tumor of the mediastinum. Described by the French neuropathologists J. Lhermitte (1887-1959), Monier and the Greek physician Tsocanakis.

Glossopharyngeal neuralgia (Sicard-Robineau syndrome) - acute paroxysmal pain that begins in the root of the tongue or in the tonsil and spreads to the palatine curtain, pharynx, radiating to the ear, lower jaw, and neck. Attacks of pain can be provoked by tongue movements, swallowing, especially when taking hot or cold food. The pain attack lasts up to 2 minutes. There are essential and symptomatic forms of neuralgia. The cause of the disease can be a kink (angulation) and compression of the hypoglossal nerve at the site of its contact with the posterior inferior edge of the stylopharyngeal muscle or compression of the nerve root by the compacted vertebral or inferior cerebellar arteries, as well as inflammatory and blastomatous processes or aneurysms in the posterior cranial fossa. Described by the French neurologist R. Sicard (1872-1949), the French morphologist M. Robineau

(1870-1960).

Tympanic plexus syndrome (Reichert's syndrome) - attacks of acute pain in the depths of the external auditory canal, often radiating to the behind-the-ear region, to the temple, sometimes to the homolateral half of the face. Unlike neuralgia of the glossopharyngeal nerve, there are no pains in the tongue, tonsils, palate, changes in salivation. In addition, the occurrence of pain is not associated with movement

tongue movements and swallowing. Usually accompanied by edema and hyperemia in the area of ​​the external auditory canal. There are essential and symptomatic forms of the disease. The syndrome was described by irritation of the tympanic plexus in 1933 by the American surgeon F. Reichert (born in 1894).

Syndrome of the blockade of the cerebellar cistern - stiff neck muscles (extensors of the head), sharp pain in the occipital region, diffuse arching headache and other signs of occlusive hydrocephalus (see Chapter 20), bulbar symptoms are possible, in particular respiratory distress, congestion in the fundus and other signs of intracranial hypertension . Described in 1925 by Lange and Kindler.

Jugular foramen syndrome (Vernet syndrome, Sicard-Collet syndrome) - a combination of signs of damage to the IX, X and XI cranial nerves emerging from the cranial cavity through the jugular foramen. It occurs due to a fracture of the base of the skull, passing through the jugular foramen of the occipital bone, or the presence of a tumor in the area of ​​the jugular foramen, often metastatic.

Described in 1918 by French doctors: neuropathologists M. Vernet (1887-1974), J. Sicard (1872-1929) and otorhinolaryngologist F. Collet (1870-1966).

Retroparotitis syndrome (Villaret syndrome) - a combination of signs of unilateral lesions of the IX, X, XI and XII cranial nerves and the cervical sympathetic trunk, which leads to a combination of manifestations of the Sicard-Colle syndrome and Horner's syndrome. Usually indicates an extracranial location of the pathological process, more often in the retroparotid space (tumor, lymphadenitis of the parotid region). Described in 1922 by the French neurologist M. Villaret (1887-1944).

Serjean's syndrome- a combination of signs of damage to the vagus nerve or its branch - the upper laryngeal nerve with Horner's syndrome in the pathological process (tumor, tuberculous focus, etc.) in the upper lobe of the lung. Described by the French therapist F. Sergent (1867-1943).

Arnold's nerve syndrome - reflex cough caused by irritation of the external auditory canal and the lower back of the tympanic membrane - the zone innervated by the ear branch of the vagus nerve, also known as Arnold's nerve.

The nerve is named after the German anatomist F. Arnold (1803-1890).

Angle-Sterling Syndrome - congenital or acquired elongation or curvature of the horns of the hyoid bone, fibrosis of the stylohyoid fold, causing irritation of the X-XII cranial nerves on the same side. There may be attacks of contraction of the muscles of the larynx, suffocation, a feeling of “turning over” the tongue, difficulty in phonation and swallowing, head rotation. With the styloid-pharyngeal type of this syndrome, pain occurs in the throat (in the tonsillar fossa and tonsil), radiating to the ear and to the hyoid bone. With the styloid-carotid type of the syndrome, pain usually occurs in the forehead, orbit, in the eyeball and from here radiates to the temple and crown. Described by the American dentist E. Angle (1855-1930) and the Polish neuropathologist W. Sterling (born in 1877).

Retroolivar syndrome (McKenzie syndrome) - a combination of hoarseness (dysphonia), swallowing disorders (dysphagia), hypotrophy and paresis of the tongue, in which fibrillar twitches are possible. Occurs when the double (related to the systems of IX and X cranial nerves) and hyoid (XII) motor nuclei or the axons of their constituent motor neurons, which form the corresponding cranial nerves in the months, are damaged in the tegmentum oblongata.

those of their exit from the medulla oblongata in the anterior lateral groove between the lower olive and the pyramid. Described by the English doctor S. McKenzie (1844-1909).

Jackson Syndrome - alternating syndrome, in which the pathological focus is located on one side of the medulla oblongata, while the root of the hyoid (XII cranial) nerve and fibers of the cortical-spinal pathway passing to the other side at the border of the medulla oblongata and spinal cord are affected. It is characterized by the development of peripheral paresis or paralysis of half of the tongue on the side of the pathological focus, while central hemiparesis or hemiplegia occurs on the opposite side. Described in 1864 by the English neurologist J. Jackson (1835-1911).

Medial medullary syndrome (Dejerine's syndrome) - alternating syndrome, in which peripheral paralysis of half of the tongue develops on the side of the pathological focus, and central hemiparesis or hemiplegia in combination with a violation of deep, vibrational and decreased tactile sensitivity on the opposite side. It usually occurs in connection with the occlusion of the short branches of the basilar artery and the upper part of the anterior spinal artery, which feed the paramedian region of the medulla oblongata. Described by the French neurologist J.J. Dejerine (1849-1917).

Dorsolateral medulla oblongata syndrome (Wallenberg-Zakharchenko syndrome, inferior posterior cerebellar artery syndrome) - alternating syndrome resulting from ischemia in the basin of the inferior posterior cerebellar artery. Manifested by dizziness, nausea, vomiting, hiccups, dysarthria, hoarseness, swallowing disorder, decreased pharyngeal reflex, while on the side of the lesion there are hypesthesia on the face, a decrease in the corneal reflex, paresis of the soft palate and pharyngeal muscles, hemiataxia, Horner's syndrome, nystagmus when looking towards the lesion. On the opposite side, a decrease in pain and temperature sensitivity according to the hemitype is revealed. Described in 1885 by the German doctor A. Wallenberg (1862-1949), and in 1911 by the domestic doctor M.A. Zakharchenko (1879-1953).

Avellis syndrome - an alternating syndrome that occurs in connection with the lesion of the medulla oblongata at the level of the location of the double nucleus, related to the IX and X cranial nerves. With Avellis syndrome, paralysis or paresis of the palatine curtain, vocal cord, and esophageal muscles develops on the side of the pathological focus. Dysphonia and dysphagia appear, and on the opposite side - central hemiparesis, sometimes hemihypesthesia. Described in 1891 by the German otorhinolaryngologist G. Avellis (1864-1916).

Schmidt syndrome- an alternating syndrome, in which damage to the medulla oblongata leads to the development of peripheral paralysis of the soft palate, pharynx, vocal cord, sternocleidomastoid muscle and the upper part of the trapezius muscle on the side of the pathological focus (a consequence of damage to the IX, X, XI cranial nerves ), and on the opposite side - central hemiparesis, sometimes - hemihypesthesia. Described in 1892 by the German doctor A. Schmidt (1865-1918).

Sestan-Chene Syndrome - alternating syndrome that occurs when the medulla oblongata is damaged at the level of the double nucleus. It is manifested by paralysis or paresis of the muscles innervated by the IX and X cranial nerves, cerebellar insufficiency and signs of Horner's syndrome on the side of the pathological focus, and on the opposite side - conduction disorders (central hemiparesis, hemihypesthesia). Described in 1903 by French neuropathologists E. Cestan (1872-1933) and L. Chenais (1872-1950).

Babinski-Najotte syndrome - alternating syndrome, in which on the side of the pathological focus there is a lesion of the inferior cerebellar peduncle, the olivocerebellar tract and sympathetic fibers, as well as the pyramidal, spinothalamic tracts, and the medial loop. On the side of the lesion, cerebellar disorders (hemiataxia, hemiasynergia, leteropulse), Horner's syndrome are noted, on the opposite side - central hemiplegia (hemiparesis) in combination with hemianesthesia (hemihypesthesia). Described in 1902 by the French neurologists J. Babinski (1857-1932) and J. Nageotte (1866-1948).

Wollstein syndrome - alternating syndrome, in which the upper part of the double nucleus and the spinothalamic pathway are affected in the tegmentum of the medulla oblongata. On the side of the pathological focus, paresis of the vocal cord is detected, and on the opposite side, a violation of pain and temperature sensitivity. Described by the German doctor K. Wollestein.

Tapia syndrome- an alternating syndrome caused by a lesion of the medulla oblongata, in which on the side of the pathological focus there is a lesion of the nuclei or roots of the XI and XII cranial nerves (peripheral paralysis of the sternocleidomastoid and trapezius muscles, as well as half of the tongue), and on the opposite side - central hemiparesis . Described in 1905 in thrombosis of the inferior posterior cerebellar artery by the Spanish otorhinolaryngologist A. Tapia (1875-1950).

Grenove's syndrome - alternating syndrome, in which on one side of the medulla oblongata, the lower nucleus of the trigeminal nerve and the spinothalamic pathway suffer. Homolaterally, it manifests itself as a disorder of pain and temperature sensitivity according to the segmental type on the face, contralaterally - a violation of pain and temperature sensitivity according to the conduction type on the trunk and extremities. Described by the German doctor A. Groenouw (1862-1945).

Pyramid Syndrome - an isolated lesion of the pyramids located on the ventral side of the medulla oblongata, through which approximately 1 million axons pass, which make up the cortical-spinal tract proper, leads to the development of a central, predominantly distal tetraparesis, with more significant paresis of the hands. Muscle tone in such cases is low, pyramidal pathological signs may be absent. The syndrome is a possible sign of a tumor (usually a meningioma), a clivus of the base of the skull (Blumenbach's clivus).

9.7. BULVAR AND PSEUDOBULBAR SYNDROMES

Bulbar syndrome, or bulbar paralysis, - combined lesion of the bulbar group of cranial nerves: glossopharyngeal, vagus, accessory and hypoglossal. Occurs when the function of their nuclei, roots, trunks is impaired. It is manifested by bulbar dysarthria or anarthria, in particular, a nasal tone of speech (nazolalia) or loss of sonority of the voice (aphonia), swallowing disorder (dysphonia). Possible atrophy, fibrillar and fascicular twitching in the tongue, "purse-string mouth", manifestations of flaccid paresis of the sternocleidomastoid and trapezius muscles. Usually palatal, pharyngeal and cough reflexes fade. The resulting respiratory and cardiovascular disorders are especially dangerous.

Bulbar dysarthria - a speech disorder caused by flaccid paresis or paralysis of the muscles that provide it (muscles of the tongue, lips, soft palate, pharynx, larynx, muscles that lift the lower jaw, respiratory muscles). The voice is weak, muffled, exhausted. Vowels and voiced consonants are stunned. The timbre of speech is changed according to the type of open nasality, the articulation of consonant sounds is blurred. Simplified articulation of fricative consonants (d, b, t, p). Selective disorders in the pronunciation of the mentioned sounds are possible due to the variability in the degree of flaccid paresis of individual muscles of the speech motor apparatus. Speech is slow, quickly tires the patient, he is aware of speech defects, but it is impossible to overcome them. Bulbar dysarthria is one of the manifestations of the bulbar syndrome.

Brissot syndromecharacterized by the fact that a patient with bulbar syndrome periodically, more often at night, has general trembling, blanching of the skin, cold sweat, respiratory and circulatory disorders, accompanied by a state of anxiety, vital fear. Probably, it is a consequence of dysfunction of the reticular formation at the level of the brain stem. Described by the French neurologist E. Brissaud (1852-1909).

Pseudobulbar syndrome or pseudobulbar palsy - combined dysfunction of the bulbar group of cranial nerves, due to bilateral damage to the cortical-nuclear pathways leading to their nuclei. The clinical picture at the same time resembles the manifestations of the bulbar syndrome, but the paresis is of a central nature (the tone of the paretic or paralyzed muscles is increased, there is no malnutrition, fibrillar and fascicular twitches), and the pharyngeal, palatine, cough, mandibular reflexes are increased. In addition, the severity of reflexes of oral automatism is characteristic, uncontrolled emotional reactions - violent crying, less often - violent laughter.

Pseudobulbar dysarthria - a speech disorder caused by central paresis or paralysis of the muscles that provide it (pseudobulbar syndrome). The voice is weak, hoarse, hoarse; the pace of speech is slow, its timbre is nasal, especially when pronouncing consonants with a complex articulation pattern (r, l, w, w, h, c) and back vowels (e, i). Stop consonants and "r" are usually replaced by fricative consonants, the pronunciation of which is simplified. The articulation of hard consonants is disturbed to a greater extent than soft ones. The ends of words often do not agree. The patient is aware of articulation defects, actively tries to overcome them, but this only increases the tone of the muscles that provide speech, and the increase in the manifestations of dysarthria. Pseudobulbar dysarthria is one of the manifestations of pseudobulbar syndrome.

Reflexes of oral automatism - a group of phylogenetically ancient proprioceptive reflexes, the V and VII cranial nerves and their nuclei, as well as the cells of the nucleus of the XII cranial nerve, the axons of which innervate the circular muscle of the mouth, take part in the formation of their reflex arcs. They are physiological in children under the age of 2-3 years. Later, the subcortical nodes and the cerebral cortex exert an inhibitory effect on them. With the defeat of these brain structures, as well as their connections with the marked nuclei of the cranial nerves, reflexes of oral automatism appear. They are caused by irritation of the oral part of the face and are manifested by pulling the lips forward - by sucking or kissing movement. These reflexes are characteristic, in particular, for the clinical picture of pseudobulbar syndrome.

Rice. 9.15.Proboscis reflex.

Proboscis reflex (oral ankylosing spondylitis) - involuntary protrusion of the lips in response to a light tapping with a hammer on the upper lip or on the finger of the subject placed on the lips (Fig. 9.15). Described by the domestic neurologist V.M. Bekhterev (1857-1927).

Sucking reflex (Oppenheim sucking reflex) - the appearance of sucking movements in response to stroke irritation of the lips. Described by the German neurologist H. Oppengeim (1859-1919).

Wurp-Toulouse reflex (Wurp labial reflex) - involuntary stretching of the lips, reminiscent of

satelnoe movement that occurs in response to the stroke irritation of the upper lip or its percussion. This is one of the reflexes of oral automatism. Described by French doctors S. Vurpas and E. Toulouse.

Oral Oppenheim reflex - chewing, and sometimes swallowing movements (except for the sucking reflex) in response to stroke irritation of the lips. Refers to the reflexes of oral automatism. Described by the German neurologist H. Oppenheim.

Escherich's reflex- a sharp stretching of the lips and their freezing in this position with the formation of a "goat's muzzle" in response to irritation of the mucous membrane of the lips or oral cavity. Refers to the reflexes of oral automatism. Described by the German doctor E. Escherich (1857-1911).

Bulldog reflex (Yanishevsky reflex) - tonic closure of the jaws in response to irritation with a spatula of the lips, hard palate, gums. Refers to the reflexes of oral automatism. It usually manifests itself with damage to the frontal lobes of the brain. Described by the domestic neuropathologist A.E. Yanishevsky (born in 1873).

Nasolabial reflex (nasolabial reflex of Astvatsaturov) - contraction of the circular muscle of the mouth and protrusion of the lips in response to tapping with a hammer on the back or tip of the nose. Refers to the reflexes of oral automatism. Described by the domestic neuropathologist M.I. Astvatsaturov (1877-1936).

Oral Henneberg reflex - contraction of the circular muscle of the mouth in response to irritation with a spatula of the hard palate. Described by the German psychoneurologist R. Genneberg (1868-1962).

Distant oral reflex of Karchikyan-Rastvorov - protrusion of the lips when approaching the lips of the hammer or some other object. Refers to the symptoms of oral automatism. Russian neuropathologists I.S. Karchikyan (1890-1965) and I.I. solutions.

Bogolepov's distant-oral reflex. After evoking the proboscis reflex, the approach of the hammer to the mouth leads to the fact that it opens and freezes in the “ready to eat” position. Refers to the reflexes of oral automatism. Described by the domestic neuropathologist N.K. Bogolepov (1900-1980).

Babkin's distal chin reflex - contraction of the muscles of the chin when approaching the face of the hammer. Refers to the reflexes of oral automatism. Described by the domestic neuropathologist P.S. Babkin.

labiochin reflex - contraction of the muscles of the chin with irritation of the lips. It is a sign of oral automatism.

Rybalkin's mandibular reflex - intense closing of the parted mouth when hitting with a hammer on a spatula placed across the lower jaw on her teeth. May be positive in bilateral corticonuclear pathways. Described by the domestic doctor Ya.V. Rybalkin (1854-

1909).

Clonus of the lower jaw (symptom of Dana) - clonus of the lower jaw when tapping with a hammer on the chin or on a spatula placed on the teeth of the lower jaw of a patient whose mouth is ajar. It can be detected with bilateral damage to the cortical-nuclear pathways. Described American

doctor Ch.L. Dana (1852-1935).

Guillain's nasopharyngeal reflex - closing the eyes when tapping with a hammer on the back of the nose. May be caused by pseudobulbar syndrome. Described by the French neurologist G. Guillein (1876-1961).

Palmar-chin reflex (Marinescu-Radovici reflex) - later exteroceptive skin reflex (in comparison with oral reflexes). The reflex arc closes in the striatum. Inhibition of the reflex is provided by the cerebral cortex. It is caused by stroke irritation of the skin of the palm in the area of ​​​​the eminence of the thumb, while on the same side there is a contraction of the chin muscle. Normally caused in children under 4 years of age. In adults, it can be caused by cortical pathology and damage to the cortical-subcortical, cortical-nuclear connections, in particular with pseudobulbar syndrome. Described by the Romanian neurologist G. Marinesku (1863-1938) and french doctor I.G. Radovici (born in 1868).

Violent crying and laughter - spontaneously arising, not amenable to volitional suppression and not having adequate reasons, facial expressions inherent in crying or laughter, not conducive to resolving internal emotional stress. One of the signs of pseudobulbar syndrome.

Medulla is located in the lower half of the brain stem and connects to the spinal cord, being, as it were, its continuation. It is the posterior part of the brain. The shape of the medulla oblongata resembles an onion or cone. At the same time, its thick part is directed upward to the hindbrain, and the narrow part is directed downward to the spinal cord. The longitudinal length of the medulla oblongata is approximately 30-32 mm, its transverse size is about 15 mm, and the anteroposterior size is about 10 mm.

The place where the first pair of cervical nerve roots exits is considered the border of the spinal cord and medulla oblongata. The bulbar-pontine groove on the ventral side is the upper border of the medulla oblongata. The striae (auditory grooves of the medulla oblongata) represent the upper border of the medulla oblongata from the dorsal side. The medulla oblongata is limited from the spinal cord on the ventral side by the crosshairs of the pyramids. There is no clear border of the medulla oblongata on the dorsal side, and the place where the spinal roots exit is considered to be the border. At the border of the medulla oblongata and the pons, there is a transverse groove that delimits these two structures together with the medullary stripes.

On the outer ventral side of the medulla oblongata there are pyramids in which the corticospinal tract passes and olives containing the nuclei of the lower olive, which are responsible for balance. On the dorsal side of the medulla oblongata there are wedge-shaped and thin bundles, which end in tubercles of the wedge-shaped and thin nuclei. Also on the dorsal side is the lower part of the rhomboid fossa, which is the bottom of the fourth ventricle and the lower cerebellar peduncles. The posterior choroid plexus is located there.

Contains many nuclei that are involved in a variety of motor and sensory functions. In the medulla there are centers responsible for the work of the heart (heart center), respiratory center. Through this part of the brain, emetic and vasomotor reflexes are controlled, as well as autonomic functions of the body, such as breathing, coughing, blood pressure, and the frequency of contractions of the heart muscle.

The formation of Rh8-Rh4 rhombomeres occurs in the medulla oblongata.

Ascending as well as descending paths in the medulla oblongata go from the left to the right side and inherit from the right.

The medulla oblongata includes:

• glossopharyngeal nerve
• part of the fourth ventricle
• accessory nerve
• nervus vagus
• hypoglossal nerve
• part of vestibulocochlear nerve

Lesions and injuries of the medulla oblongata are usually always fatal due to its location.

Functions performed

The medulla oblongata is responsible for certain functions of the autonomic nervous system, such as:

• Breathing by controlling the level of oxygen in the blood by sending signals to the intercostal muscles, increasing the speed of their contraction to saturate the blood with oxygen.
• reflex functions. These include sneezing, coughing, swallowing, chewing, vomiting.
• Heart activity. Through sympathetic excitation, cardiac activity increases, and parasympathetic inhibition of cardiac activity also occurs. In addition, blood pressure is controlled by vasodilation and vasoconstriction.

The medulla oblongata is a continuation of the spinal cord, its place of origin is the upper border of the first cervical vertebra (C 1). In shape, it resembles an inverted cone with a truncated top and is relatively small in size: average length 25 mm, width at the base 22 mm, thickness 14 mm. The medulla oblongata weighs an average of about 6 grams.

Development

During ontogenesis, the medulla oblongata develops from the neural tube. In the fifth week of embryonic development, there is a stage of three cerebral vesicles, where it originates from the rhomboid brain, rhombencephalon. Morphological features of the relief of the medulla oblongata are due to metamorphoses in the process of organogenesis. The lateral walls of the neural tube become thicker, while the dorsal wall, on the contrary, becomes thinner and remains only in the form of a thin plate with a layer of ependymal epithelium and the choroid of the fourth ventricle adjacent to it from the outside.

Structure

Now let's talk about the morphological component. In the medulla oblongata, the ventral, dorsal and lateral sides, as well as white and gray matter, are distinguished. Let's start with the relief of the sides and the important anatomical structures that are located there.

The most variable in its structure is the dorsal surface. In the center of it is the posterior median sulcus, sulcus medianus posterior. On the sides of it there are two bundles: a thin bundle of Gaulle and a wedge-shaped bundle of Burdakh - these are continuations of the posterior cords of the spinal cord. On both sides, lateral to the sphenoid bundle, there are lateral cords, which form small thickenings in the middle of the medulla oblongata, they are called the lower legs of the cerebellum, pedunculus cerebellaris inferior. A platform in the shape of a triangle is formed between these legs - this is the lower half of the rhomboid fossa. It is important to note that this structure is distinguished only anatomically.

Now let's move on to the sides. Lateral to the pyramids is the anterior lateral sulcus, sulcus anteriolateralis, which is also a continuation of the sulcus of the same name on the spinal cord. Behind it are olives, olive. Behind the olives is the posterior lateral groove, sulcus posteriolateralis, which has no analogues on the spinal cord. The roots of the cranial nerves will come out of it: additional (n. accessorius XI pair), wandering (n. vagus X pair), glossopharyngeal (n. Glossopharyngeus IX pair).

And finally, on the ventral side are the pyramids of the medulla oblongata, pyramides medullae oblongatae. They are located on the sides of the anterior median fissure, fissura mediana anterior, which is a continuation of the sulcus of the same name on the spinal cord. At the border with the spinal cord, the fibers of the pyramids intersect, forming a decussation of the pyramids, decussatio pyramidum.

Nuclei

Now let's talk about the internal structure of the medulla oblongata. It is made up of gray and white matter. Gray matter is represented by nuclei, and white matter by nerve fibers of the longitudinal direction, which subsequently form descending pathways. But first things first.

We will begin the study of the internal structure with gray matter. It differs in form from that in the spinal cord: here it is represented exclusively by nuclei. They are traditionally divided into four groups:

The first group: thin and wedge-shaped nuclei. They are located in the hillocks of the same name and represent the terminal neurons of the fibers of the thin and wedge-shaped bundles. An important feature here is the course of the fibers. The main part of the axons of these nuclei in a single bundle is directed ventrally, and then to the opposite side and up. In the region of the midline, these fibers form a decussation of the medial loops, decussatio lemniscorum medialium. The end of the medial loop is located on the nuclei of the thalamus, which leads to the second name for the Gaulle's bundle - the bulbar-thalamic tract, tr. bulbothalamicus. The remaining axons make up another path - bulbar-cerebellar, tr. bulbocerebellaris. These fibers go in an anterior direction, exit to the ventral surface of the medulla oblongata near the anterior median fissure, go around the pyramids and enter it as part of the lower cerebellar peduncles.

The second group of kernels are olive kernels. From the cortex of the cerebral hemispheres and from the red nuclei of the midbrain, nerve fibers go to the nuclei of the olive. Here, as in the previous group of nuclei, the path goes contralaterally, that is, most of the axons pass to the opposite side and enter the cerebellum as part of its lower pedicle, forming the olive-cerebellar path, tr. olivocerebellaris. The rest of the axons will form the descending olivo-spinal tract, tr. olivospinalis.

Slightly dorsal to the olive is the third group of nuclei - the nuclei of the reticular formation, nuclei formation reticularis. It is known that the medulla oblongata is a rather important part of the central nervous system, since it contains the nerve centers of complex reflex acts of breathing, heartbeat, and the center for regulating vascular and muscle tone. Representatives of these centers are large nuclei of the reticular formation. There are also so-called non-specific nuclei, which are intercalary neurons of the segmental apparatus of the brain stem.

The fourth group of nuclei is represented by the nuclei of the cranial nerves of the IX-XII pairs. All of them are located on the posterior surface of the medulla oblongata, closer to the cavity of the IV ventricle. Let's start with the XII pair - the hypoglossal nerve, its nuclei lie in the region of the hypoglossal triangle, in the medial part of the lower angle of the rhomboid fossa. Rostral (above) lies the nucleus of the accessory nerve, n. accessorius. In the medulla oblongata on the dorsal surface, within the triangle of the vagus nerve, a small area is isolated - the gray wing, ala cinerea. It contains a projection of the autonomic parasympathetic dorsal nucleus of the vagus nerve, nucleus dorsalos nervi vagi. Even higher than the dorsal nucleus of the vagus nerve lies the autonomic parasympathetic nucleus of the IX pair, n. glossopharyngeus - lower salivary nucleus, nucleus salivatorius inferior. Lateral to the autonomic nuclei that we have just examined lies an elongated structure containing sensory nuclei for the X and IX pairs of cranial nerves - this is the nucleus of the solitary pathway, nuclei tractus solitarii. An interesting point follows, most textbooks say that the double nucleus, nucleus ambiguous, is common to two pairs of cranial nerves - X and IX pairs, but this is not entirely accurate. There is information that it is common to three pairs, so the nucleus ambiguous is also the motor nucleus for the XI pair, n. accessories. It has a projection in the region of the posterior median sulcus, in the lower part of the rhomboid fossa. This concludes our consideration of gray matter and moves on to white matter.

The white matter of the medulla oblongata consists of nerve fibers of the longitudinal direction. These fibers are divided into two types: afferent, carrying information to the nervous structures of the central nervous system (ascending) and afferent, carrying information to the periphery, to the working organs and tissues (descending).

Ascending fibers mainly come from the spinal cord. The bundles of Gaulle and Burdach already known to us, which are located on the sides of the posterior median sulcus, end on the neurons of the nuclei of the same name and make up the ascending tracts: bulbo-thalamic and bulbo-cerebellar. Closer to the lateral surface lie the anterior and posterior spinal cerebellar tracts: Gowers and Flexig's bundles. The first goes laterally and enters the cerebellum as part of its lower pedicle, and the ventral bundle of Gowers, which follows contralaterally (makes a cross), bypassing the thalamus, continues into the bridge. Medial to the Gowers bundle lies the spinothalamic pathway, tr. spinothalamicus, which has a second name - lemniscus spinalis, spinal loop. It combines the fibers of the tracts of the same name that run along the sides and in front of the spinal cord.

The bulk of the paths are fibers going down. Descending fibers are tracts that start from various motor nuclei of the brain.

Descending paths are divided into pyramidal and extrapyramidal, and the latter, in turn, into old and new. Pyramidal and old extrapyramidal tracts run through the medulla oblongata. The first group of pathways includes: cortico-spinal, tr. corticospinalis, and subsequently - tr. corticospinalis lateralis et anterior. The largest descending path is the cortico-spinal, tr. corticospinalis lies on the ventral surface of the medulla oblongata. Before entering it, he goes on his side, and after that he crosses and goes to the lateral funiculus of the spinal cord under a different name - tr. corticospinalis lateralis. A small part of the fibers that entered the decussation continue their way in the anterior funiculus, forming the anterior cortical-spinal tract, tr. corticospinalis anterior.

On the dorsal surface there are two bundles that contain the pathways of the autonomic nervous system: the posterior and medial longitudinal bundles, fasciculus longitudinalis posterior et medialis. The medial longitudinal bundle is an important associative pathway that connects the nuclei of the nerves of the eye muscles with each other, which leads to the closure of the reflex of the combined turn of the head and eyes towards the sound at the level of the medulla oblongata.

The old extrapyramidal tracts passing through the medulla oblongata include: the roof-spinal tract, tr. tectospinalis, reticular-spinal path, tr. reticulospinalis, vestibulo-spinal path, tr. vestibulospinalis, red nuclear-spinal path, tr.rubrospinalis. Roof-spinal tract, tr. tectospinalis, lies in front of the medial bundle. Dorsal of the pyramids is the reticular-spinal tract, tr. reticulospinalis. Lateral lies the pre-door-spinal path, tr. vestibulospinalis, and medially to the spinal-thalamic path is the red-nuclear-spinal path, tr.rubrospinalis. The functional anatomy of these pathways determines the performance of complex reflex acts, for example: in fast motor reactions in response to unexpected stimuli or may participate in the inhibition of the activity of motor neurons of the spinal cord.

This concludes our consideration of the main pathways through the medulla oblongata. There are also tracts connecting the sensory nuclei of the cranial nerves (IX and X pairs) with the integration centers of the large brain - these are the nuclear-thalamic pathways, tr. nucleothalamicus and nuclear-cerebellar, tr. nucleocerebellaris. Together, they will provide general sensitivity in the head area and are responsible for receiving information from the interoreceptors.

Functions

After a detailed study of all important structures of the medulla oblongata, namely its morphological components and transit pathways, we can conclude about the main functions of the medulla oblongata:

1. Sensory - perception of afferent influences from receptors and their processing

2. Conduction - conduction of nerve impulses through the medulla oblongata to other parts of the central nervous system and to effector structures

3. Reflex - important vital reflexes are closed at the level of the medulla oblongata: organization and regulation of breathing and blood circulation, maintaining posture and protective reflexes (coughing, sneezing, vomiting)

4. Integrative - algorithms of complex regulatory processes are programmed on the neurons of the medulla oblongata, which require interaction with other centers of other parts of the nervous system.

The medulla oblongata is an important link in the structure of the brain. Together with other components, it forms the brain stem and performs a number of vital functions for a living organism.

The most important function of the medulla oblongata, without which the existence of a living organism is impossible, should include the formation and support of autonomic reflexes.

Irritations coming through the nerve fibers from the medulla oblongata to various parts and organs of the body lead to the occurrence of such processes as heartbeat, respiration, digestion, cutaneous and vascular phenomena, to the beginning or end of the digestion process, to blinking of the eyelids and lacrimation, lacrimation, cough , vomiting and many others.

In addition to autonomic reflexes, the medulla oblongata is also responsible for the somatic unconditioned reactions of the human body. It determines muscle tone, balance support, coordination of movements and the work of the entire human motor apparatus. Under the influence of commands from the medulla oblongata, the newborn child unconsciously begins to suck on the mother's breast.

In addition to independently generating various nerve impulses, the medulla oblongata also provides a strong neural connection between the spinal cord and various parts of the brain and is the physical boundary between these two organs of the central nervous system.

Structure of the medulla oblongata

The medulla oblongata is located directly next to the spinal cord on one side, and on the other side it connects to the hindbrain. It has the shape of an inverted truncated cone. The base of this cone, which is large in area, is located at the top, and narrowing begins in the downward direction. Due to its characteristic expanded shape with a smooth narrowing, in medicine it is sometimes called bulbus, which means bulb.

Despite its small size, only up to 25 mm for an adult, the medulla oblongata has a heterogeneous structure. Inside it is gray matter, surrounded on the periphery by separate clots - nuclei. Outside, a series of surfaces separated from each other by furrows can be clearly distinguished.

Ventral surface

In front, on the outer part of the medulla oblongata directed towards the skull along its entire length, the ventral surface is located. This surface is divided into two parts by a vertical anterior median fissure passing in the middle, connected to the median fissure of the spinal cord.

Two convex rollers located along the gap on both sides are called pyramids. They contain bundles of fibers, which also smoothly pass into the fibers of the spinal cord.

On the opposite side of the slit of the pyramids in the upper part of the medulla oblongata there is another elevation, which, because of their characteristic shape, is called olives. Olives are a link between the spinal cord and the cerebellum, and also connects them with certain parts of the brain responsible for the coordination of movements and muscle work, the so-called reticular formation.

Dorsal surface

The posterior surface of the medulla oblongata, directed inside the cranium, is called the dorsal surface. It is also divided by the median sulcus and has roller-like thickenings of fiber bundles for communication with the spinal cord.

Side surfaces

Between the ventral and dorsal surfaces are two lateral surfaces. Each of them is clearly separated by two lateral furrows. These furrows are a continuation of the same furrows extending from the spinal cord.

The medulla oblongata is a direct continuation of the spinal cord. Its lower border is the exit point of the first pair of spinal nerves. The length of the medulla oblongata is about 25 mm. The cranial nerves from the IX to XII pairs depart from the medulla oblongata. In the medulla oblongata there is a cavity (a continuation of the spinal canal) - the fourth cerebral ventricle filled with cerebrospinal fluid.

Functions medulla oblongata: conductive and reflex, some also secrete sensory.

touch function. The medulla oblongata regulates a number of sensory functions: the reception of skin sensitivity of the face - in the sensory nucleus of the trigeminal nerve; primary analysis of taste reception - in the nucleus of the glossopharyngeal nerve; reception of auditory stimuli - in the nucleus of the cochlear nerve; reception of vestibular stimuli - in the upper vestibular nucleus. In the posterior superior sections of the medulla oblongata, there are paths of skin, deep, visceral sensitivity, some of which switch here to the second neuron (thin and sphenoid nuclei). At the level of the medulla oblongata, the enumerated sensory functions implement the primary analysis of the strength and quality of stimulation, then the processed information is transmitted to the subcortical structures to determine the biological significance of this stimulation.

Conductor function: ascending and descending nerve pathways pass through the medulla oblongata, connecting the brain and spinal cord.

In the medulla oblongata there are olives associated with the spinal cord, the extrapyramidal system and the cerebellum - this is a thin and wedge-shaped nucleus of proprioceptive sensitivity (the nucleus of Gaulle and Burdach). Here are the intersections of the descending pyramidal paths and the ascending paths formed by the thin and wedge-shaped bundles (Gaulle and Burdakh), the reticular formation.

Rice. 9 Medulla oblongata:

1 - olive cerebellar tract;

2 - olive core;

3 - the gate of the core of the olive;

5 - pyramidal tract;

6 - hypoglossal nerve;

7 - pyramid;

8 - anterior lateral furrow;

9 - accessory nerve

The nuclei of the medulla oblongata include the nuclei of the cranial nerves (from VIII to XII pairs) and switching nuclei:

Nuclei of the cranial nerves include:

Motor nuclei XII, XI, X;

Vagus nuclei (vegetative, sensitive nucleus of a single path and mutual - motor nucleus of the pharynx and larynx);

Nuclei of the glossopharyngeal nerve (IX) (motor nucleus, sensory nucleus - the taste of the posterior third of the tongue) and the autonomic nucleus (salivary glands);

The nuclei of the vestibulocochlear nerve (VIII) (cochlear nuclei and vestibular nuclei - medial Schwalbe, lateral Deiters, superior Bekhterev).

Switching cores include:

Goll and Burdakh - to the thalamus;

Reticular formation (from the cortex and subcortical nuclei - to the spinal cord);

Olivary nuclei - from the cortex and subcortical nuclei and the cerebellum - to the spinal cord, and from the spinal cord - to the cerebellum, thalamus and cortex; from the auditory nuclei to the midbrain and quadrigemina.

Reflex function: in the medulla oblongata are the centers of many of the most important reflexes for human life.

The medulla oblongata, due to its nuclear formations and the reticular formation, is involved in the implementation of autonomic, somatic, gustatory, auditory, and vestibular reflexes. A feature of the medulla oblongata is that its nuclei, being excited sequentially, ensure the implementation of complex reflexes that require the sequential inclusion of different muscle groups, which is observed, for example, when swallowing.

Centers of the medulla oblongata:

Vegetative (vital) centers

Respiratory (inspiratory and expiratory center);

Cardiovascular (supports the optimal lumen of arterial vessels, ensuring normal blood pressure and cardiac activity);

Most of the autonomic reflexes of the medulla oblongata are realized through the nuclei of the vagus nerve located in it, which receive information about the state of activity of the heart, blood vessels, digestive tract, lungs, digestive glands, etc. In response to this information, the nuclei organize motor and secretory reactions of visceral organs.

Excitation of the nuclei of the vagus nerve causes an increase in the contraction of the smooth muscles of the stomach, intestines, gallbladder and, at the same time, relaxation of the sphincters of these organs. At the same time, the work of the heart slows down and weakens, the lumen of the bronchi narrows.

The activity of the nuclei of the vagus nerve is also manifested in increased secretion of the bronchial, gastric, intestinal glands, in the excitation of the pancreas, secretory cells of the liver.

Centers of protective reflexes

Tearing;

These reflexes are realized due to the fact that information about irritation of the receptors of the mucous membrane of the eye, oral cavity, larynx, nasopharynx through the sensitive branches of the trigeminal and glossopharyngeal nerves enters the nuclei of the medulla oblongata, from here comes the command to the motor nuclei of the trigeminal, vagus, facial, glossopharyngeal, accessory or hypoglossal nerves, as a result, one or another protective reflex is realized.

Eating behavior reflex centers:

Salivation (the parasympathetic part provides increased general secretion, and the sympathetic part provides protein secretion of the salivary glands);

2. swallowing;

Posture reflex centers.

These reflexes are formed by afferentation from the receptors of the vestibule of the cochlea and the semicircular canals to the superior vestibular nucleus; from here, the processed information for assessing the need for a change in posture is sent to the lateral and medial vestibular nuclei. These nuclei are involved in determining which muscle systems, segments of the spinal cord should take part in a change in posture, therefore, from the neurons of the medial and lateral nuclei, along the vestibulospinal pathway, the signal arrives at the anterior horns of the corresponding segments of the spinal cord, innervating the muscles, whose participation in changing the posture in necessary at the moment.

Posture change is carried out due to static and statokinetic reflexes. Static reflexes regulate skeletal muscle tone in order to maintain a certain body position. The statokinetic reflexes of the medulla oblongata provide a redistribution of the tonus of the trunk muscles to organize a posture corresponding to the moment of rectilinear or rotational movement.

Damage symptoms. Damage to the left or right half of the medulla oblongata above the intersection of the ascending pathways of proprioceptive sensitivity causes disturbances in the sensitivity and work of the muscles of the face and head on the side of the injury. At the same time, on the opposite side relative to the side of the injury, there are violations of skin sensitivity and motor paralysis of the trunk and limbs. This is due to the fact that the ascending and descending pathways from the spinal cord and into the spinal cord intersect, and the nuclei of the cranial nerves innervate their half of the head, i.e., the cranial nerves do not intersect.