What pair of auditory nerves? Cranial or cranial nerves: functions and role in the brain. IV pair - trochlear nerve

The brain (encephalon) is divided into brain stem, big brain And cerebellum. The brain stem contains structures related to the segmental apparatus of the brain and subcortical integration centers. Nerves arise from the brain stem, as well as from the spinal cord. They got the name cranial nerves.

There are 12 pairs of cranial nerves. They are designated by Roman numerals in order of their arrangement from bottom to top. Unlike spinal nerves, which are always mixed (both sensory and motor), cranial nerves can be sensory, motor, or mixed. Sensory cranial nerves: I - olfactory, II - visual, VIII - auditory. There are also five pure motor: III - oculomotor, IV - trochlear, VI - abducens, XI - accessory, XII - sublingual. And four mixed: V - trigeminal, VII - facial, IX - glossopharyngeal, X - vagus. In addition, some cranial nerves contain autonomic nuclei and fibers.

Characteristics and description of individual cranial nerves:

I pair - olfactory nerves(nn.olfactorii). Sensitive. Formed by 15-20 olfactory filaments, consisting of axons of olfactory cells located in the mucous membrane of the nasal cavity. The filaments enter the skull and end in the olfactory bulb, from where the olfactory pathway begins to the cortical end of the olfactory analyzer - the hippocampus.

If the olfactory nerve is damaged, the sense of smell is impaired.

II pair - optic nerve(n. opticus). Sensitive. Consists of nerve fibers formed by processes of nerve cells in the retina. The nerve enters the cranial cavity and forms the optic chiasm in the diencephalon, from which the optic tracts begin. The function of the optic nerve is the transmission of light stimuli.

When various parts of the visual analyzer are affected, disorders occur associated with a decrease in visual acuity up to complete blindness, as well as disturbances in light perception and visual fields.

III pair - oculomotor nerve(n. oculomotorius). Mixed: motor, vegetative. It starts from the motor and autonomic nuclei located in the midbrain.

The oculomotor nerve (motor part) innervates the muscles of the eyeball and upper eyelid.

Parasympathetic fibers the oculomotor nerve is innervated by smooth muscles that constrict the pupil; They also connect to the muscle that changes the curvature of the lens, resulting in changes in the accommodation of the eye.

When the oculomotor nerves are damaged, strabismus occurs, accommodation is impaired, and the size of the pupil changes.

IV pair - trochlear nerve(n. trochlearis). Motor. It starts from the motor nucleus located in the midbrain. Innervates the superior oblique muscle of the eye.

V pair - trigeminal nerve(n. trigeminus). Mixed: motor and sensitive.

It has three sensitive cores, where the fibers coming from the trigeminal ganglion end:

Pavement in the hindbrain,

Inferior nucleus of the trigeminal nerve in the medulla oblongata,

Midbrain in the midbrain.

Sensitive neurons receive information from receptors on the skin of the face, from the skin of the lower eyelid, nose, upper lip, teeth, upper and lower gums, from the mucous membranes of the nasal and oral cavities, tongue, eyeball and from the meninges.

Motor core located in the bridge tire. Motor neurons innervate the muscles of mastication, the muscles of the velum palatine, and the muscles that contribute to the tension of the tympanic membrane.

When the nerve is damaged, paralysis of the masticatory muscles occurs, sensitivity in the corresponding areas is impaired, up to its loss, and pain occurs.

VI pair - abducens nerve(n. abducens). Motor. The core is located in the bridge tire. It innervates only one muscle of the eyeball - the external rectus muscle, which moves the eyeball outward. When it is damaged, convergent strabismus is observed.

VII pair - facial nerve(n. facialis). Mixed: motor, sensitive, vegetative.

Motor core located in the bridge tire. Innervates the facial muscles, the orbicularis oculi muscle, the mouth muscle, the auricular muscle and the subcutaneous muscle of the neck.

Sensitive - nucleus of the solitary tract medulla oblongata. This receives information from sensitive taste fibers starting from the taste buds located in the anterior 2/3 of the tongue.

Vegetative - superior salivary nucleus located in the bridge tire. From it, efferent parasympathetic salivary fibers begin to the sublingual and submandibular, as well as the parotid salivary and lacrimal glands.

When the facial nerve is damaged, the following disorders are observed: paralysis of the facial muscles occurs, the face becomes asymmetrical, speech becomes difficult, the swallowing process is disrupted, taste and tear production are impaired, etc.

VIII pair - vestibulocochlear nerve(n. vestibulocochlearis). Sensitive. Highlight cochlear And vestibular nuclei located in the lateral parts of the rhomboid fossa in the medulla oblongata and the pons tegmentum. Sensory nerves (auditory and vestibular) are formed by sensory nerve fibers coming from the organs of hearing and balance.

When the vestibular nerve is damaged, dizziness, rhythmic twitching of the eyeballs, and staggering when walking often occur. Damage to the auditory nerve leads to hearing impairment, the appearance of sensations of noise, squeaking, and grinding.

IX pair - glossopharyngeal nerve(n. glosspharyngeus). Mixed: motor, sensitive, vegetative.

Sensitive core - nucleus of the solitary tract medulla oblongata. This nucleus is common to the nucleus of the facial nerve. The perception of taste in the posterior third of the tongue depends on the glossopharyngeal nerve. The glossopharyngeal nerve also provides sensitivity to the mucous membranes of the pharynx, larynx, trachea, and soft palate.

Motor core- double core, located in the medulla oblongata, innervates the muscles of the soft palate, epiglottis, pharynx, and larynx.

Vegetative nucleus- parasympathetic inferior salivary nucleus medulla oblongata, innervating the parotid, submandibular and sublingual salivary glands.,

When this cranial nerve is damaged, taste disturbance occurs in the posterior third of the tongue, dry mouth is observed, sensitivity of the pharynx is impaired, paralysis of the soft palate is observed, and choking when swallowing.

X pair - nervus vagus(n. vagus). Mixed nerve: motor, sensory, autonomic.

Sensitive core - nucleus of the solitary tract medulla oblongata. Sensitive fibers transmit irritations from the dura mater, from the mucous membranes of the pharynx, larynx, trachea, bronchi, lungs, gastrointestinal tract and other internal organs. Most interoreceptive sensations are associated with the vagus nerve.

Motor - double core medulla oblongata, fibers from it go to the striated muscles of the pharynx, soft palate, larynx and epiglottis.

Autonomic nucleus - dorsal nucleus of the vagus nerve(medulla oblongata) forms the longest neuronal processes compared to other cranial nerves. Innervates the smooth muscles of the trachea, bronchi, esophagus, stomach, small intestine, and upper part of the large intestine. This nerve also innervates the heart and blood vessels.

When the vagus nerve is damaged, the following symptoms occur: taste is impaired in the back third of the tongue, sensitivity of the pharynx and larynx is lost, paralysis of the soft palate occurs, sagging of the vocal cords, etc. Some similarity in the symptoms of damage to the IX and X pairs of cranial nerves is due to the presence of common nuclei in the brain stem.

XI pair - accessory nerve(n. accessorius). Motor nerve. It has two nuclei: in the medulla oblongata and in the spinal cord. Innervates the sternocleidomastoid muscle and the trapezius muscle. The function of these muscles is to turn the head in the opposite direction, raise the shoulder blades, and raise the shoulders above the horizontal.

If the injury occurs, there is difficulty turning the head to the healthy side, a drooping shoulder, and limited raising of the arm above the horizontal line.

XII pair - hypoglossal nerve(n. hypoglossus). This is a motor nerve. The nucleus is located in the medulla oblongata. The fibers of the hypoglossal nerve innervate the muscles of the tongue and partially the muscles of the neck.

When damaged, either weakness of the tongue muscles (paresis) or their complete paralysis occurs. This leads to speech impairment, it becomes unclear and slurred.

Topic 9. Medulla oblongata. The brain is divided into 5 sections from bottom to top: medulla oblongata, hindbrain, midbrain, diencephalon and telencephalon.

Medulla(medulla oblongata) is a direct continuation of the spinal cord and has a cone-shaped shape. There are ventral, dorsal and lateral surfaces.

The lower border on the ventral surface is the exit site of the roots of the first pair of cervical nerves of the spinal cord, the upper border is the lower edge of the bridge.

On the ventral surface there is a deep median fissure, which is a continuation of the fissure of the same name in the spinal cord. On the sides of it there are two longitudinal rollers - pyramids(pyramides), formed by the nerve fibers of the pyramidal tracts, which form a decussation (decussatio pytamidum) deep in the fissure at the border with the spinal cord. The anterior lateral groove runs along the side of the pyramids, from which the roots of the hypoglossal nerve emerge. In the upper part of the furrow there are convex oval formations - olives(olivae). Lateral to the olive lies the posterior lateral groove of the medulla oblongata, from which the roots of the accessory, vagus and glossopharyngeal nerves emerge.

The dorsal surface of the medulla oblongata has a different structure in the lower and upper parts. In its lower third, it is divided by the posterior median sulcus into two symmetrical parts and contains a continuation of the gentle and wedge-shaped fasciculi running in the posterior funiculi of the spinal cord, which end in two protruding tubercles of the nuclei of the same name. Approximately in the middle of the medulla oblongata, the right and left posterior cords diverge upward and to the side and pass into thick ridges - the lower cerebellar peduncles, which plunge into the cerebellum. The upper part of the dorsal surface of the medulla oblongata is expanded, forming the lower half rhomboid fossa. A median groove runs along the bottom of the diamond-shaped fossa, on the sides of which there are elevations - triangles of the vagus and hypoglossal nerves. In the lateral sections of the fossa, on the border with the bridge there is vestibular field, in the depths of which the auditory and vestibular nuclei are contained.

The lateral surface of the medulla oblongata contains a continuation of the lateral cords of the spinal cord and in the upper part ends with the trigeminal tubercle.

Internal structure of the medulla oblongata. Gray and white matter take part in the formation of the medulla oblongata, and as it moves upward, the nature of the arrangement of gray and white matter gradually changes. Gray matter gradually loses its butterfly shape and is divided by conductive pathways into separate nuclei.

Four groups of nuclei of the medulla oblongata can be distinguished. The first group is the nuclei of the posterior funiculi, thin and wedge-shaped, located in the thickness of the tubercles of the same name. The neurons of these nuclei end with fibers of the thin and wedge-shaped fasciculi, which transmit information from the proprioceptors of the body and limbs. The axons of the cells of the thin and wedge-shaped nuclei form two ascending tracts: the larger one - bulbothalamic, which in the form of a medial loop is directed to the nuclei of the thalamus and bulbocerebellar, which is sent to the cerebellum as part of the inferior cerebellar peduncles.

The second group of nuclei - olive kernels. The neurons of this nucleus terminate the descending fibers coming from the red nucleus of the midbrain. Functionally, the core is associated with maintaining posture and balance and is part of the extrapyramidal system. From it begins the large olivo-cerebellar tract, which goes to the cerebellum as part of the inferior cerebellar peduncles, and the smaller olivo-spinal tract, which descends into the spinal cord.

The third group of nuclei is represented by the nuclei of the cranial nerves. In the depths of the medulla oblongata lie the nuclei of the YIII-XII pair of cranial nerves. They are mainly located on the dorsal surface of the medulla oblongata in the region of the rhomboid fossa. Cores vestibulocochlear nerve (YIII pair) lie in the lateral parts of the rhomboid fossa in the region of the vestibular field. They are divided into 4 vestibular nuclei and 2 cochlear (auditory) nuclei. The auditory nuclei (ventral and dorsal) lie in the lateral part of the auditory field. The axons of the neurons of the spiral ganglion end on their cells, through which information from the organ of hearing (cochlea) is transmitted. The axons of the neurons of the auditory nuclei are directed to the nuclei of the trapezoidal body of the bridge. Three vestibular nuclei (lateral, medial and inferior) are also located at the level of the medulla oblongata, the fourth, the superior vestibular nucleus, is considered part of the pontine nuclei. They receive information from the receptors of the semicircular canals, the organ of balance, along the axons of the vestibular ganglion. The vestibular nuclei are distinguished by an abundance of outputs. They start from them vestibulo-spinal And vestibulocerebellar pathways functionally associated with the coordination of skeletal muscle activity depending on vestibular afferentation. Some of the bundles responsible for visual-motor coordination (image stabilization on the retina) go to the nuclei of the III, IY and YI pairs of cranial nerves. There are also pathways to the reticular formation and thalamus. Glossopharyngeal nerve (IX pair)- mixed: has sensitive, motor and autonomic nuclei located in the medulla oblongata. The sensory nucleus of the glossopharyngeal nerve is nucleus of the solitary tract(n. solitarius), which stretches along the wall of the IY ventricle in the dorsal part of the medulla oblongata. This nucleus is the common sensory nucleus for the YII, IX and X pairs of cranial nerves. This nucleus collects information from the taste buds of the tongue, as well as from the receptors of the internal organs and the eardrum. Afferents from the nucleus are sent to the thalamus and hypothalamus, as well as to the motor nuclei of the cranial nerves and to the reticular formation. Motor core - double core(n. ambiguous), located in the ventrolateral parts of the medulla oblongata. It is the common motor nucleus for the IX and X pairs of cranial nerves. It has inputs from the sensory nuclei of the Y, IX and X pairs of cranial nerves, as well as from the cerebral cortex. The axons of the neurons of this nucleus end on motor neurons that innervate the muscles of the larynx and pharynx. Participates in sneezing, swallowing and coughing. Cortical input provides voluntary muscle activity and coordination during speech. The vegetative nucleus is called inferior salivary nucleus(n. salivatorius inferior). It receives axons from neurons in the nucleus of the solitary tract and vestibular nuclei, as well as from neurons in the cerebral cortex. The nucleus regulates the functioning of the parotid glands. X pair - nervus vagus(n. vagus) - also mixed: motor, sensitive, vegetative. The motor nucleus - double, and the sensitive - nucleus of the solitary tract were discussed above. Vegetative nucleus - posterior nucleus of the vagus nerve, is located on the dorsal surface of the medulla oblongata in the region of the triangle of the vagus nerve. On the neurons of this nucleus, the axons of the neurons of the nucleus of the solitary tract and the sensory nuclei of the trigeminal nerve end. The axons of the vagal neurons end on the neurons of the parasympathetic ganglia of the internal organs of the abdominal and thoracic cavity. The nucleus participates in the regulation of the functioning of internal organs and carries out the gag reflex. XI pair - accessory nerve(n. accessorius) – motor. The nucleus is located medially in the lower corner of the rhomboid fossa, connected with the anterior horns of the spinal cord and close to them in structure. Regulates the work of the muscles of the shoulder girdle. XII pair - hypoglossal nerve(n. hypoglossus) - motor. The nucleus is located in the area of ​​the sublingual triangle of the rhomboid fossa. Some of the fibers of the cortical-nuclear tract, as well as the axons of the neurons of the sensory nuclei of the trigeminal and vagus nerves, end on its neurons. Functionally, the core is associated with the coordination of tongue movements during chewing. The presence of cortical inputs ensures voluntary movement of the tongue during speech.

The last group of nuclei are nuclei of the reticular formation. Large nuclei located within the medulla oblongata act as centers for such complex reflex acts as breathing, heartbeat, vascular tone, etc. Distinctive features of the reticular centers are poor differentiation, lack of clear boundaries, a large number of inputs and projections to various brain structures. They are located in the central parts of the medulla oblongata.

White matter The medulla oblongata is represented mainly by longitudinally running nerve fibers. Many of them are transit, i.e. pass without switching. Ascending fibers follow from the spinal cord. This - thin and wedge-shaped beams, which, having switched in the nuclei of the same name, form bulbo-thalamic and bulbo-cerebellar tracts. Along the lateral surface of the medulla oblongata there are anterior and posterior spinocerebellar tracts. The first continues into the pons, the second, as part of the inferior cerebellar peduncle, enters the cerebellum. Passes in transit more medially spinothalamic tract, formed by fibers of the anterior and lateral tracts of the spinal cord of the same name. Descending fibers are represented by bundles coming from various motor nuclei of the brain. The largest is pyramidal tract, running along the ventral surface of the medulla oblongata, its fibers will form lateral and anterior corticospinal tracts. Passes dorsal to the pyramids reticulospinal tract, and more laterally – vestibulospinal. Near the dorsal surface of the medulla oblongata there are posterior and medial longitudinal fasciculi. Ahead of them is located tegnospinal tract. Mediolaterally passes red nucleus spinal tract. In addition, pathways are formed in the medulla oblongata that connect its sensory nuclei with the overlying centers of the brain - nuclear-thalamic and nuclear-cerebellar pathways. The first transmits general information from the receptors of the head and the receptors of the internal organs. According to the second, unconscious proprioceptive impulses from the head area. On the neurons of the motor nuclei of the cranial nerves of the medulla oblongata they end fibers of the corticonuclear tract.

Topic 10. Hindbrain.

hindbrain includes the ventrally located pons and the cerebellum located behind it.

Bridge(pons) has the appearance of a transversely located ridge, tapering in the lateral direction and passing on the sides into the middle cerebellar peduncles. It has ventral and dorsal surfaces. On the ventral surface it is separated from the medulla oblongata and midbrain by horizontal grooves. The lateral border of the bridge is considered to be a longitudinal line passing through the exit site of the trigeminal nerve roots. In addition to them, the roots of the abducens, facial and vestibulocochlear nerves also exit in the area of ​​the bridge. The dorsal surface is the upper half of the rhomboid fossa and faces the cavity of the fourth ventricle.

Internal structure of the bridge. A cross-section of the bridge shows that the substance that forms it is heterogeneous. Highlight bridge base, located ventrally, dorsally located bridge tire And trapezoid body, lying between them.

Bridge base formed by gray and white matter. Gray matter represented by numerous own bridge cores(nuclei pontis). Nerve fibers end on the neurons of these nuclei corticopontine tract, coming from the cerebral cortex. Axons of neurons of the pons own nuclei are directed as part of the middle cerebellar peduncles to the cortex of the cerebellar hemispheres, forming cerebellopontine tract. The function of these nuclei is to provide connections between the cerebral cortex and the cerebellar cortex.

White matter the base of the bridge is formed by a large number of fibers having a longitudinal and transverse direction. Fibers transit longitudinally pyramidal tract, which from compact, as it was in the spinal cord and medulla oblongata, turns into many groups of fibers scattered between the nuclei of the bridge. Fibers also run longitudinally corticonuclear pathway, partially ending on the motor nuclei of the pons, partially descending into the medulla oblongata and fibers corticopontine tract. The fibers have a transverse direction pontocerebellar tract.

Bridge tire also formed by white and gray matter. Gray matter represented by the nuclei of the cranial nerves (Y, YI, YII, YIII pair), superior olive and reticular formation. Y pair - trigeminal nerve(n. trigeminus) - mixed: motor and sensitive. The tegmentum of the pons contains its motor nucleus and superior sensory nucleus. In addition, the trigeminal nerve has two more sensory nuclei: the inferior nucleus of the trigeminal nerve, located in the four upper cervical segments of the spinal cord and the mesencephalic nucleus of the trigeminal nerve. The superior sensory nucleus of the trigeminal nerve, located in the pons, is the center of tactile sensitivity of the face area, the lower spinal nucleus is the center of pain and temperature sensitivity of the face area, and the midbrain is the center of proprioceptive sensitivity of the muscles of the face, palate and upper neck. The work of these muscles is controlled by the motor nucleus of the trigeminal nerve. YI pair - abducens nerve(n. abducens) - motor. The nucleus is located in the dorsomedial sections of the pontine tegmentum. It ends with fibers coming from the vestibular nuclei and the superior olive. The nucleus carries out the oculomotor function (provides a combined rotation of the eyes towards the sound source and rotation of the eyes taking into account head movements). YII pair - facial nerve(n. facialis) - mixed: sensitive, motor, vegetative. The tegmentum of the bridge contains the motor and autonomic (superior salivary) nuclei. The motor nucleus of the facial nerve innervates the facial muscles and the stapes muscle of the middle ear. The autonomic nucleus innervates the nasal mucosa, lacrimal glands and salivary glands. The bridge tire also contains superior vestibular nucleus, related to the vestibulocochlear (YIII pair) cranial nerve.

Cores upper olivary complex(medial and dorsal) are located immediately above the trapezoid body and belong to the auditory system. They have inputs from the cerebral cortex and from the cochlear nuclei. It starts from them olivocochlear pathway, which goes to the hair cells of the hearing organ and regulates their activity, which ensures accurate perception of sounds, perception of whispered speech and protects against excessively strong sounds.

White matter The bridge tire is formed by fibers in the longitudinal direction. The fibers of the anterior are located laterally spinocerebellar tract, passes to the center from it spinothalamic tract, even more medial - nuclear-thalamic and bulbar-thalamic pathways, united under the general name - medial loop. Descending pathways are represented as going laterally red nuclear spinal tract. Pass near the midline medial and dorsal longitudinal fasciculi and tectospinal tract. Trapezoid body formed by a massive bundle of transversely running fibers, which originate from the cochlear nuclei and nuclei of the trapezoid body (anterior and posterior), lying between its fibers, and end on the neurons of the posterior colliculi of the midbrain. The trapezoid body represents the conduction pathway of the auditory analyzer.

Cerebellum located posterior to the pons and the upper part of the medulla oblongata. Its maximum width is 11.5 cm, length - 3-4 cm. The middle part is distinguished - worm and two side parts - cerebellar hemispheres, and scrap- a small paired formation that joins the unpaired cerebellar vermis knot and is adjacent to the hemispheres on the ventral side. There are two surfaces - upper and lower. The upper surface, facing upward and backward, is convex. In the middle there is an elevation - the upper worm. The lower surface is directed downward and forward, has a wide depression - the cerebellar valley, in which the inferior vermis is located. The surface of the cerebellum is indented by a large number of transverse grooves. According to the time of formation in phylo- and ontogenesis in the cerebellum, it is customary to distinguish the ancient part – shred and knot, old part – worm And new cerebellum, including cerebellar hemispheres.

Internal structure of the cerebellum. On the sections you can see the gray matter located on the surface, forming cerebellar cortex, under the cerebellar cortex is white matter. On the median section of the cerebellum, the white matter has a leaf-like shape, which is associated with the figurative name “cerebellar tree of life.” In the thickness of the white matter of the cerebellum there are accumulations of gray matter that make up cerebellar nuclei.

Cerebellar cortex three-layered, consists of an outer molecular layer, a ganglion layer (or a layer of Purkinje cells) and a granular layer. The cortex contains five types of neurons: granular, stellate, basket, Golgi and Purkinje cells, which have a rather complex system of connections.

In the molecular layer There are 3 types of interneurons: basket, short- and long-processed stellate cells.

IN ganglion layer Purkinje cells are located.

IN granular layer– granular cells and Golgi cells. The number of granular cells in 1 mm³ is 2.8 million. The axons of granular cells ascend to the surface, branch in a T-shape, forming parallel fibers. Parallel fibers also form excitatory synapses on the dendrites of basket, stellate and Goldky cells.

There are only two types of fibers that transmit information to the cerebellar cortex.

To each Purkinje cell fits climbing(liana-shaped) fiber. Through the neurons of the inferior olive nuclei from the cerebral cortex, they receive projections from the motor (motor) and premotor areas of the cortex, as well as afferent impulses from the subcortical motor centers. In turn, Purkinje cells provide the output of signals from the cerebellar cortex through the cerebellar nuclei. These are the only output elements of the cerebellar cortex.

TO granular layer cells fit mossy fibers, forming synaptic contacts with neurons. Mossy fibers are processes of neurons in the pontine nuclei and other nuclei of the central nervous system.

Cerebellar nuclei. Deep in the cerebellum on both sides of the midline there is tire core. Lateral to this nucleus there are small spherical kernels. lies even more laterally corky core. The largest nucleus of the cerebellum is located in the white matter of the hemispheres - gear.

Tire core belongs to the ancient cerebellum, spherical And corky the nuclei are phylogenetically later formations (belong to the old cerebellum) and, finally, dentate nucleus belongs to the new cerebellum.

Functions of the cerebellum. The most ancient connections cerebellum established with organs of balance. Nerve fibers extend from the vestibular nuclei, representing part of the vestibulocerebellar tract. They penetrate the cerebellum as part of its lower peduncles and end on the neurons of the flocculus and nodule cortex. The descending (efferent) pathway begins from the neurons of these areas of the cerebellar cortex. Nerve fibers from the flocculus and nodule cortex reach the neurons of the tent nucleus, which is the oldest of the cerebellar nuclei. The axons of the neurons of the tent nucleus reach the nuclei of the reticular formation of the medulla oblongata through the inferior cerebellar peduncles. From them, along the reticular-spinal cord, efferent impulses travel to the muscles of the trunk. The described nerve connections of the cerebellum played an important role in the inhabitants of the aquatic environment, whose locomotion was carried out through the muscles of the trunk.

With the emergence of animals onto land and the development of limbs, afferent pathways from the receptors of muscles, tendons and joints of the limbs appeared in the form of the posterior and anterior spinocerebellar tracts. The fibers of these pathways end on the bark of the worm. The efferent pathway from the neurons of the vermis cortex goes to the neurons of the globular and cortical nuclei of the cerebellum. The axons of the neurons of these nuclei exit the cerebellum as part of its superior peduncles and reach the neurons of the reticular formation. Subsequently, efferent impulses along the reticular-spinal tract are sent to the muscles of the limbs.

Due to the complication of the functions of the muscles of the trunk and limbs, the bulbar-cerebellar and nuclear-cerebellar pathways were also formed, which end in the cortex of the middle part of the cerebellar vermis.

In mammals and humans, a system of precerebellar nuclei has developed: the inferior olive nuclei and the pontine nuclei. The nuclei of the inferior olive receive impulses through collaterals extending from the fibers of the extrapyramidal tract. The fibers of the olivocerebellar tract pass through the inferior cerebellar peduncles and end on the neurons of the cerebellar cortex.

The intrinsic nuclei of the pons receive impulses from the cerebral cortex along the corticopontine tracts and along collaterals from the pyramidal tracts. The axons of the neurons of the pons' own nuclei move to the opposite side and, as part of the middle legs of the pons, are directed to the cortex of the cerebellar hemispheres. The cerebellar-dentate-rednuclear-spinal cord tract begins from it. The task of this path is to carry out “corrective activity” when performing complex voluntary movements, especially of the upper limb.

Damage to the cerebellum is accompanied by disruption of many functions. Main symptoms: ataxia - drunken gait, intentional trembling, impaired coordination of movements, imbalance of the body (develops even with unilateral damage).

Cerebellar pathways. The cerebellum is connected to other parts by three pairs of peduncles. Inferior cerebellar peduncles connect it with the medulla oblongata and spinal cord, middle connect the cerebellum with a bridge and upper consist of nerve fibers running in both directions.

Included inferior cerebellar peduncle The following paths pass through:

Posterior spinocerebellar tract;

Bulbar-cerebellar tract;

Olive-cerebellar tract;

vestibulocerebellar tract;

Nuclear-cerebellar pathway;

Cerebellolive tract;

Cerebellar vestibular tract;

Cerebellar-reticular tract.

Included middle cerebellar peduncle Only the pontocerebellar tract, formed by the axons of the pons' own nuclei, passes through.

Included superior cerebellar peduncle pass:

Anterior spinocerebellar tract;

Serrated-red nuclear tract;

Dentate thalamic tract.

IV ventricle represents the remains of the cavity of the rhomboid medullary bladder. At the bottom, the ventricle communicates with the central canal of the spinal cord, at the top it passes into the aqueduct of the midbrain, and in the roof area it is connected by three openings to the subarachnoid space of the brain. The anterior, ventral wall of the ventricle (bottom of the fourth ventricle) is called the rhomboid fossa. The lower part is formed by the medulla oblongata, and the upper part by the pons and isthmus. The posterior (roof of the IV ventricle) is formed by the superior and inferior medullary sails and is supplemented posteriorly by a plate of the pia mater lined with ependyma. This area contains a large number of blood vessels that form the choroid plexus of the fourth ventricle. The rhomboid fossa contains the nuclei of the cranial nerves (V – XII).

Topic 11. Midbrain.

The midbrain, mesencephalon, comes from the mesencephalon. Compared to other sections, the midbrain is the smallest in size (length approx. 20 mm) and is the most simply structured section of the brain. Completely covered with a cloak. The cavity of the midbrain is the aqueduct of the midbrain, aqueductus niesencephali. It is a remnant of the midbrain cavity. The aqueduct is oriented along the axis of the brain, connecting the IV and III ventricles. Its length is about 15 mm, average diameter is 1-2 mm.

There are ventral and dosal parts. Its ventral part is formed by paired cerebral peduncles, pedunculi cerebri, and the posterior perforated substance located between them, substantia perforata posterior. The dorsal part is formed by the roof midbrain, tectum mesencephali.

Brain stems on the ventral side they look like two thick flattened ridges that start from the upper horizontal groove, emerging from under the upper edge of the bridge. They are directed upward and to the sides at an angle of 70-80° and are immersed in the substance of the diencephalon. The anterior border of the cerebral peduncles is the optic tract, tractus opticus, and the mamillary bodies, which belong to the diencephalon. The cerebral peduncles are white in color and have a fibrous structure due to the longitudinal arrangement of nerve fibers. At the cerebral peduncles there are base And tire. Along the medial edge of the base of the cerebral peduncles there is a groove of the oculomotor nerve, from which the root of the oculomotor nerve, III pair, emerges. Between the legs there is a depression, the interpeduncular fossa. The surface of the interpeduncular fossa is called the posterior perforated substance, substantia perforata posterior, due to the large number of holes through which numerous blood vessels pass.

The dorsal surface of the midbrain is represented plate of the quadrigeminal roof, lamina tecti. There are four rounded elevations on it - two superior colliculus, collculi superiores, and two inferior colliculus, colliculi inferiores. The mounds are separated by grooves intersecting at right angles. The lower hillocks are smaller than the upper ones. From each hillock on the lateral side there are handles of mounds, Braehia colliculi. They move forward and upward to the diencephalon. Handles of the superior colliculi, narrower and longer, end in the lateral geniculate bodies. Handles of the lower mounds, thicker and shorter, end in the medial geniculate bodies. Posterior to the inferior colliculi along the midline on each side there emerges one root of the fourth pair of cranial nerves, the trochlear nerve, the only nerve that emerges from the substance of the brain on its dorsal surface.

On the lateral surface of the midbrain, in the interval between the lateral edge of the cerebral peduncle and the handles of the inferior colliculi, a triangular-shaped area is distinguished triangle loop, trigonum lemnisci. The third side of the triangle is the lateral edge of the superior cerebellar peduncle. In the projection of the triangle, the nerve fibers that make up the lateral, medial, trigeminal and spinal loops pass through the thickness of the cerebral peduncles. Thus, in this place, in a small area near the surface of the brain, almost all the pathways of general sensitivity (conducting impulses to the diencephalon) and the auditory pathway are concentrated. In neurosurgical practice, loops are made within the triangle cordotomy- surgery for intolerable pain due to lesions of the visual tuberosities.

Internal structure of the midbrain . On a cross-section of the midbrain, its main parts are clearly defined: above the aqueduct there is roof plate, below - cerebral peduncles. A section of the cerebral peduncle shows a pigmented layer of gray

Cranial nerves(nervi craniales; synonym cranial nerves) - nerves extending from or entering the brain. There are 12 pairs of cranial nerves that innervate the skin, muscles, glands (lacrimal and salivary) and other organs of the head and neck, as well as a number of organs of the chest and abdominal cavity. The cranial nerves are designated by Roman numerals in pairs from I to XII according to their location on the base of the brain in order from front to back from the frontal lobe to the posterior part of the medulla oblongata.

Unlike spinal nerves, cranial nerves do not have a correct segmental location and are not identical in anatomical and functional terms. Based on their origin and composition of nerve fibers, they are divided into several groups. The first group consists of the nerves of special sensory organs, which consist only of afferent (sensitive) fibers. This group includes the I pair - the olfactory nerves, the II pair - the optic nerve and the VIII pair - the vestibulocochlear nerve.
The second group includes motor nerves that develop from the head myotomes and innervate the muscles of the eyeball: the oculomotor nerve (III pair), the trochlear nerve (IV pair) and the abducens nerve (VI pair). The third group combines nerves of mixed composition, associated in their development with the branchial arches of the embryo.

It includes the trigeminal nerve (V pair), facial nerve (VII pair), glossopharyngeal nerve (IX pair), vagus nerve (X pair) and accessory nerve (XI pair). The fourth group is represented by the hypoglossal nerve (XII pair), which consists of motor fibers; by origin it is a spinal nerve that has lost its sensory root and moved into the cranial cavity. Mixed cranial nerves (third group) have ganglia similar to the spinal ganglia, but they lack anterior and posterior roots. When leaving the brain, their motor and sensory fibers either unite into a common nerve trunk or are located nearby. Some cranial nerves (III, VII, IX and X pairs) when leaving the brain contain parasympathetic fibers going to the corresponding autonomic ganglia (see.
Autonomic nervous system). Many cranial nerves are interconnected by connecting branches, in which sensory, motor and autonomic fibers can pass.

The olfactory and optic nerves (I and II pairs) do not have their own ganglia and nuclei. The nuclei of the remaining nerves are located throughout the brain stem and enter the spinal cord. There are motor, or initial, nuclei (nuclei originis), from which motor fibers emerge; sensitive, or terminal, nuclei (nuclei terminationis), where sensory fibers end; vegetative (autonomous) nuclei, in which preganglionic parasympathetic fibers originate.

I pair - olfactory nerves (nn. olfactorii). They start from the mucous membrane of the olfactory region of the nasal cavity, pass through the cribriform plate into the cranial cavity and approach the olfactory bulb, where the 1st neuron of the olfactory pathway ends and the central olfactory pathway originates.

II pair - optic nerve (n.
opticus), which contains about 1 million thin nerve fibers, which are the axons of multipolar neurons of the retina (3rd neuron of the visual pathway). The nerve has an external and internal sheath, which serve as a continuation of the membranes of the brain. Through the optic canal, the nerve enters the cranial cavity. Anterior to the sella turcica, both nerves form the optic chiasma (chiasma opticum), where fibers from the medial (nasal) halves of the retinas pass to the opposite side. After the chiasm, the optic tract (tractus opticus) is formed, which goes around the cerebral peduncle and sends its fibers to the subcortical visual centers.

Ill pair - oculomotor nerve (n. oculomotorius) It originates from the motor nuclei located in the tegmentum of the midbrain at the level of the superior colliculus. The nerve exits in the interpeduncular fossa from the medial surface of the cerebral peduncle, enters the lateral wall of the cavernous sinus and enters the orbit through the superior orbital fissure. Here it is divided into upper and lower branches.
The superior branch enters the levator palpebrae superioris muscle and the superior rectus muscle of the eyeball, while the inferior branch innervates the inferior and medial rectus and inferior oblique muscles. The oculomotor nerve contains parasympathetic fibers that begin in its accessory nucleus and pass through the connective branch to the ciliary ganglion. The sphincter of the pupil and the ciliary muscle of the eye receive innervation from the cells of this ganglion.

IV pair - trochlear nerve (n. trochlearis), the thinnest of the cranial nerves. It starts from the nucleus lying in the tegmentum of the midbrain at the level of the inferior colliculi, exits on the posterior surface of the brain stem, goes around the cerebral peduncle, runs in the wall of the cavernous sinus and penetrates the orbit through the superior orbital fissure, innervating the superior oblique muscle of the eyeball.

V pair - trigeminal nerve (n. trigeminus), which is the main sensory nerve of the head. The area of ​​innervation of the scalp by the trigeminal nerve is limited by the parietal-ear-mental line. The trigeminal nerve also innervates the eyeball and conjunctiva, dura mater, mucous membrane of the nasal and oral cavity, most of the tongue, teeth and gums. Its motor fibers go to the muscles of mastication and the muscles of the floor of the mouth.

The trigeminal nerve exits the brain at the border between the pons and the middle cerebellar peduncle. It has thicker sensory and thinner motor roots. The fibers of the sensory root are processes of neurons of the trigeminal ganglion (ganglion trigeminale), which lies in the recess of the temporal pyramid near its apex in a special cavity formed by splitting the dura mater. These fibers end in the pontine nucleus of the trigeminal nerve, located in the upper part of the rhomboid fossa, and in the nucleus of the spinal tract, which from the bridge continues into the medulla oblongata and further into the cervical segments of the spinal cord. The fibers that bring proprioceptive stimuli from the masticatory muscles are processes of the cells of the nucleus of the midbrain tract of the trigeminal nerve, which lies in the tegmentum of the midbrain. The motor root fibers originate from the motor nucleus of the trigeminal nerve, located in the pons.

Three main branches of the nerve arise from the trigeminal ganglion - the ophthalmic, maxillary and mandibular nerves. The optic nerve (n. ophthalmicus) is purely sensitive. It is divided, in turn, into three branches - the lacrimal, frontal and nasociliary nerves, which pass through the superior orbital fissure. The lacrimal nerve (n. lacrimalis) innervates the skin of the lateral corner of the eye and the conjunctiva, gives off secretory branches to the lacrimal gland. The frontal nerve (n. frontalis) branches in the skin of the forehead, upper eyelid and supplies the mucous membrane of the frontal sinus. The nasociliary nerve (n. nasociliaris) gives long ciliary nerves to the eyeball. From it, the anterior and posterior ethmoidal nerves enter the nasal cavity, innervating the mucous membrane of the nasal cavity, the ethmoid and sphenoid sinuses, as well as the skin of the dorsum of the nose. Its final branch, the subtrochlear nerve, branches in the skin of the medial corner of the eye and innervates the lacrimal sac.

The maxillary nerve (n. maxillaris) is also sensitive, it passes through the round foramen into the pterygopalatine fossa, from where it continues into the orbit and, having passed the infraorbital canal, exits under the name of the infraorbital nerve (n. infraorbitalis) to the anterior surface of the face; innervates the skin of the cheek, lower eyelid, upper lip, wing and vestibule of the nose. The superior alveolar nerves (nn. alveolares sup.) extend from the maxillary and infraorbital nerves to the teeth of the upper jaw and gums.

The zygomatic nerve (n. zygomaticus) innervates the skin of the lateral part of the face. The pterygopalatine nerves run from the maxillary nerve to the pterygopalatine ganglion. The sensory fibers included in their composition pass from the pterygopalatine ganglion along the posterior nasal nerves to the mucous membrane of the nasal cavity, along the palatine nerves to the mucous membrane of the palate, along the pharyngeal branch to the mucous membrane of the nasopharynx. The nerves arising from the pterygopalatine ganglion contain sympathetic and parasympathetic fibers. Among the latter there are fibers that innervate the lacrimal gland; they follow the branch connecting the zygomatic and lacrimal nerves.

The mandibular nerve (n. mandibularis) is mixed. It consists of fibers of the motor root of the trigeminal nerve. The mandibular nerve passes through the foramen ovale and gives off branches to all the muscles of mastication. Its sensitive branches include: the buccal nerve (n. buccalis), which supplies the mucous membrane of the cheek and the buccal surface of the gums of the lower premolars and 1st molar; auriculotemporal nerve (n. auriculotemporalis), innervating the skin of the temporal region and part of the auricle; lingual nerve (n. lingualisi), supplying the mucous membrane of the tip and back of the tongue.

The mixed composition has the lower alveolar nerve (n. alveolaris inf.), which runs in the canal of the lower jaw, giving branches to the teeth and gums; its final branch is the mental nerve (n. mentalis), which branches in the skin of the chin, skin and mucous membrane of the lower lip. Before the inferior alveolar nerve enters the mandibular canal, the mylohyoid nerve branches off from it, carrying motor fibers to the muscles of the oral diaphragm. The branches of the mandibular nerve are connected to the autonomic ganglia, the auriculotemporal nerve is connected to the auricular ganglion, from which the parotid gland receives parasympathetic innervation, and the lingual nerve is connected to the submandibular ganglion, which provides innervation to the submandibular and sublingual glands.

VI pair - abducens nerve (n. abducens). It has a motor nucleus in the upper part of the rhomboid fossa, exits the brain between the edge of the pons and the pyramid of the medulla oblongata, passes through the cavernous sinus to the superior orbital fissure, and innervates the external rectus muscle of the eye.

VII pair - facial nerve (n. facialis). It is formed mainly by motor fibers originating from the nucleus, which is located in the upper part of the rhomboid fossa. The facial nerve includes the intermediate nerve (n. intermedius), which contains sensitive taste and parasympathetic fibers. The former are processes of neurons of the geniculate ganglion and end in the nucleus of the solitary tract along with the taste fibers of the glossopharyngeal and vagus nerves. The second originate in the lacrimal and superior salivary nuclei, lying next to the motor nucleus of the facial nerve.

The facial nerve leaves the brain at the cerebellopontine angle and enters the internal auditory canal, from where it passes into the facial canal of the temporal bone. Here are located the chorda tympani (chorda tympani), the ganglion of the knee, and the greater petrosal nerve begins, through which parasympathetic fibers pass to the pterygopalatine ganglion. The chorda tympani passes through the tympanic cavity and joins the lingual nerve, containing taste fibers from the anterior two thirds of the tongue and parasympathetic fibers reaching the submandibular ganglion. The facial nerve leaves the temporal bone through the stylomastoid foramen and enters the parotid gland, forming a plexus in it. From this plexus, the branches of the facial nerve fan out across the face, innervating all the facial muscles, as well as the posterior belly of the digastric muscle and the stylohyoid muscle. The cervical branch of the facial nerve branches in the saphenous muscle of the neck. The branches of the facial nerve form connections with the branches of the trigeminal, glossopharyngeal, vagus nerves and cervical plexus.

VIII pair vestibular-cochlear nerve (n. vestibulocochlearis), which conducts stimuli from the receptors of the inner ear to its own nuclei located in the lateral part of the rhomboid fossa. The nerve consists of the vestibular and cochlear roots. The vestibular root is formed by the processes of neurons of the vestibular ganglion (ganglion vestibulare), located in the internal auditory canal. The cochlear root consists of processes of cells of the spiral ganglion (ganglion spirale), located in the cochlea. The vestibulocochlear nerve exits the internal auditory canal and enters the brain at the cerebellopontine angle.

IX pair - glossopharyngeus nerve (n. glossopharyngeus). It carries motor fibers to the pharyngeal constrictors and stylopharyngeal muscle, sensory fibers from the mucous membrane of the pharynx, tonsils, tympanic cavity and auditory tube, taste fibers from the circumvallate papillae of the tongue, and preganglionic parasympathetic fibers to the ear ganglion for the parotid gland. The nerve nuclei are located in the lower part of the rhomboid fossa, in the triangle of the vagus nerve. Here lie the motor nucleus ambiguum, common with the vagus nerve, and the nucleus of the solitary tract, common with the facial and vagus nerves. Parasympathetic fibers originate in the inferior salivary nucleus. The glossopharyngeal nerve emerges from the medulla oblongata behind the olive and leaves the cranial cavity through the jugular foramen.

It forms the superior and inferior sensory ganglia. Upon exiting the skull, the glossopharyngeal nerve passes between the stylopharyngeal and styloglossus muscles to the base of the tongue. The tympanic nerve (n. tympanicus) departs from its inferior ganglion, forming a plexus in the tympanic cavity. The tympanic nerve contains parasympathetic fibers that continue along the lesser petrosal nerve to the auricular ganglion. Next, the glossopharyngeal nerve gives off pharyngeal, tonsil and lingual branches. The latter innervate the mucous membrane of the root of the tongue. The carotid branch of the glossopharyngeal nerve carries afferent fibers from the carotid sinus and glomus. The IX pair and its branches form connections with the auriculotemporal, facial, vagus nerves, and internal carotid plexus.

X pair - vagus nerve (n. vagus), which has the most extensive area of ​​innervation. It is the main parasympathetic nerve of the internal organs, and also conducts most of the afferent fibers from the organs in which it branches. In the head and neck region, the vagus nerve gives off a branch to the dura mater, provides sensitive and motor innervation of the palate and pharynx (together with the trigeminal and glossopharyngeal nerves), completely innervates the larynx, and participates in the taste innervation of the root of the tongue. The vagus nerve belongs to the nucleus ambiguus, the nucleus of the solitary tract and the dorsal (parasympathetic) nucleus in the medulla oblongata. The nerve emerges in several roots behind the olive along with the glossopharyngeal nerve and passes through the jugular foramen, where its superior and inferior ganglia are located.

In the neck, the vagus nerve runs as part of the neurovascular bundle (see Neck). The auricular branch of this nerve innervates the skin of the external auditory canal and the adjacent area of ​​the auricle. The pharyngeal branches, the superior and inferior cervical cardiac branches, and the superior laryngeal nerve arise from the cervical part of the vagus nerve. In the chest cavity, the recurrent laryngeal nerve (n. laryngeus recurrens) originates from the vagus nerve, which rises to the neck and continues into the lower laryngeal nerve, which, together with the upper laryngeal nerve, innervates the mucous membrane and muscles of the larynx.

XI pair - accessory nerve (n. accessorius), which starts from the motor nucleus located in the lower part of the medulla oblongata and the first to fourth cervical segments of the spinal cord. Accordingly, it has cranial and spinal roots that unite into a nerve trunk. The latter passes through the jugular foramen and is divided into internal and external branches. The internal branch joins the vagus nerve and contains fibers involved in the motor innervation of the pharynx and larynx. The external branch supplies the sternocleidomastoid and trapezius muscles; it often connects to the cervical plexus.

XII pair - hypoglossal nerve (n. hypoglossus), which is the motor nerve of the tongue. Its nucleus lies in the inferomedial region of the rhomboid fossa. The roots of the hypoglossal nerve emerge from the medulla oblongata between the pyramid and the olive. From the cranial cavity, the nerve passes through the hypoglossal canal of the occipital bone, is located on the neck behind the posterior belly of the digastric and stylohyoid muscles, crosses the external carotid artery from the outside and enters the musculature of the tongue, where it divides into its terminal branches. The hypoglossal nerve gives off a connecting branch to the cervical plexus, which takes part in the formation of the cervical loop (ansa cervicalis).

Pathology:

Dysfunction of the cranial nerve at different levels of damage to their trunks or nuclei is manifested by differentiated neurological symptoms, the analysis of which plays an important role in making a topical diagnosis of intracranial pathological processes. Simultaneous unilateral damage to the fibers or nuclei of the cranial nerves with the conductors of the pyramidal and extrapyramidal systems arriving in the brain stem, as well as sensory and autonomic pathways, is accompanied by the occurrence of alternating (or cross) syndromes, which are characterized by the appearance on the affected side of dysfunctions corresponding to the cranial nerves, and on on the opposite side - symptoms associated with damage to the pathways.

Often there are combined dysfunctions of a number of anatomically closely located cranial nerves, which can be caused by an intracranial tumor, abscess, arachnoid cyst, as well as vascular malformations and other processes, in particular the infringement of certain cranial nerves in the openings of the base of the skull in the region of the anterior, middle and posterior cranial pits. Symptom complexes of combined damage to the nuclei, roots or trunks of the glossopharyngeal vagus and hypoglossal nerves both in the cranial cavity and outside it are called bulbar palsy, the detection of which is always an alarming sign of the proximity of the pathological process to the vital centers of the brain stem.

The specificity of the functional purpose of each of the cranial nerves and knowledge of their topography in relation to other structures of the nervous system allow, during a clinical examination of the patient, not only to identify the affected cranial nerve, but also to clearly determine the localization of the pathological process. For a more detailed study of individual cranial nerves, special instrumental techniques are used. Modern ophthalmological equipment makes it possible to obtain detailed information about the condition of the fundus of the eye, the optic nerve head, its trophism, to determine the boundaries of the visual field and focal loss in it; A computerized technique for studying visual evoked potentials makes it possible to identify disorders of the visual analyzer of various localizations.

A special ophthalmological examination allows you to detect dysfunctions of the III, IV and VI pairs of nerves, determine the degree of exophthalmos, limitations in the range of movements of the eyeballs, etc. Craniography is used to study the canal of the optic and auditory nerves; the pathology of these nerves can be caused by both a narrowing of the bone canal (for example, due to a congenital malformation) and its expansion as a result of an inflammatory or tumor process. This method allows you to assess the condition of the superior orbital fissure, round, lacerated, jugular and other foramina of the skull. Vertebral and carotid angiography have a certain diagnostic value in recognizing volumetric intracranial processes and vascular malformations that cause compression or displacement of cranial nerves.

However, computed tomography is more informative, allowing one to visualize individual trunks of cranial nerves, diagnose a tumor of the auditory or optic nerve, and other pathological changes in the cranial nerves. Methods of cortical somatosensory evoked potentials are used to study the functions of the trigeminal nerve, auditory stem evoked potentials - the functions of the vestibulocochlear nerve. In the study of the auditory analyzer, audiography is used (including modern computer devices), the vestibular analyzer - nystagmography techniques. With the development and computerization of electromyography, the possibilities for studying cranial nerves have expanded; the state of spontaneous muscle activity of the facial and chewing muscles, sternocleidomastoid and trapezius muscles, tongue, soft palate is recorded, the speed of impulse conduction along the trunks of the VII, XI and XII pairs of nerves is determined, the reflex blink response provided by the fibers of the V and VII pairs of nerves is studied , and etc.

During a neurological examination of a patient, the study of cranial innervation is traditionally carried out in a certain sequence, starting with the first pair - the olfactory nerve. To do this, the patient is presented with a set of olfactory stimuli (camphor, valerian, perfume, etc.); The cotton wool soaked in them is alternately brought to one and the other nostril. It is not recommended to use strong-smelling substances for this purpose (for example, ammonia), because they irritate not only the olfactory receptors, but also the receptors related to the trigeminal nerve system.

Bilateral complete loss of smell (anosmia) or its decrease (hyposmia) can be caused by damage to the nose or be congenital (in this case, it is sometimes combined with endocrine disorders). Unilateral disturbances of the sense of smell are associated mainly with pathological processes in the area of ​​the anterior cranial fossa (tumor, cyst, abscess, vascular malformation, hematoma or damage to the base of the skull and brain contusion). Impaired recognition of presented odors (olfactory agnosia) is observed relatively rarely, since olfactory receptors have bilateral cortical representation. However, in cases of irritation of the hippocampal region, a sensation of non-existent odors may occur - olfactory hallucinations.

Unusual and often vague paroxysmal olfactory sensations, often in the form of a false perception of some unpleasant odor, are harbingers (aura) of an epileptic seizure caused by irritation of the temporal lobe of the brain. The olfactory analyzer is the main “channel” of afferent information support for the limbic system, which is of particular importance in early childhood. Insufficient sense of smell in infants can lead to a delay in the maturation of the structures of the limbic system and subsequently to its dysfunction.

The second pair (optic nerve) is examined mainly during an ophthalmological examination: visual acuity, visual fields are determined, and the condition of the fundus is studied. In this case, it is possible to identify not only direct damage to the optic nerve, visual conductors and centers, but also secondary changes in the visual analyzer associated with focal or generalized pathological processes in the cranial cavity and orbit. When the optic nerve is completely destroyed, blindness occurs on the same side with loss of pupillary response to light. When the optic chiasm, optic tracts, overlying visual pathways and centers are damaged, hemianopia occurs, the nature of which depends on the level of the lesion.

The pathology of the optic nerve can be inflammatory (neuritis), stagnant or dystrophic in nature, which is revealed by ophthalmoscopy. Optic neuritis occurs with meningitis, arachnoiditis, encephalitis, multiple sclerosis, local inflammatory processes in the anterior cranial fossa, orbit, paranasal sinuses and is manifested by decreased visual acuity, scotomas, and blanching of the optic nerve head. A congestive optic nerve papilla is a symptom of increased intracranial pressure or impaired venous outflow from the orbital cavity, which is usually caused by a tumor, abscess, brain cyst, thrombosis of the venous system of the brain and its membranes.

Optic nerve atrophy during ophthalmoscopy is characterized by blanching of the optic disc and other changes in the retina and blood vessels. Optic nerve atrophy can be primary (with neuritis or injury to the optic nerve, as well as with tabes dorsalis, multiple sclerosis, etc.) or secondary, occurring with brain tumors and other processes that cause increased intracranial pressure, for example with decompensated hydrocephalus (in this case pallor of the optic disc is preceded by its stagnation). If the central cortical parts of the visual analyzer are damaged, central scotoma in both eyes, quadrant hemianopsia, visual hallucinations of various types, as well as visual agnosia can be observed. Neuropsychological research allows us to differentiate violations of visual gnosis that can occur with damage to the occipital lobes. A decrease in visual acuity due to damage to the optic nerve and overlying visual pathways cannot be corrected with glasses, and it should be distinguished from various refractive errors (myopia, farsightedness, etc.).

When the oculomotor (III pair), trochlear (IV pair) and abducens (VI pair) nerves are damaged, strabismus and diplopia occur. Pathology of the third pair is mainly accompanied by drooping of the upper eyelid (ptosis), divergent strabismus and double vision when looking towards the affected nerve, to a lesser extent when looking up and down, pupil dilation (mydriasis). When the IV pair is affected on one side, there is slight strabismus when looking up; a more constant symptom is double vision when looking down to the side. When the abducens nerve is damaged, convergent strabismus and double vision are observed when looking in the direction of the affected nerve, less often when looking directly.

When the sensitive part of the V pair (trigeminal nerve) is damaged, a decrease in sensitivity is detected on the corresponding half of the face, the boundaries of which depend on the level of damage to the trigeminal nerve itself or the ascending projection pathways to the cerebral cortex. When the peripheral branches of the nerve are damaged, sensitivity is lost in the areas of their innervation: the optic nerve - in the forehead, upper eyelid; maxillary nerve - in the area of ​​the temples, cheekbones, lower eyelid, wings of the nose and upper lip (in addition, this branch is involved in the innervation of the mucous membrane of the nose, mouth and pharynx - partly together with the lower branch); mandibular nerve - in the area of ​​the lower cheek, lower lip and chin.

When the middle and lower branches are involved in the pathological process, the sensitivity of the teeth, respectively, of the upper and lower jaws, is impaired. When the trigeminal nerve ganglion is damaged, a severe pain syndrome develops, herpetic eruptions appear on the affected side, vegetative-trophic changes in the form of keratitis, sweating disorders, and vasomotor reactions in the innervation zone. Damage to the sensitive nucleus of the trigeminal nerve, which has a segmental structure, is accompanied by a loss of sensitivity on the face according to a segmental type: in the area of ​​the nose and lips with pathology of the anterior sections of the nucleus and, conversely, in the temporal and parotid regions with pathology of the posterior sections (the so-called segmental Zelder zones). Pain syndrome with trigeminal neuralgia can spread to the entire half of the face, teeth, nasal cavity and mouth, or occur only in the zone of innervation of one of the peripheral branches. To diagnose trigeminal neuralgia, pain points on the face (exit points of the upper, middle and lower branches) are examined.

When the ascending projection pathways are damaged, there is a loss of sensitivity on the entire half of the face on the side opposite to the lesion. Sometimes anesthesia on the face is combined with loss of sensitivity on the body - on the same side (with damage to the common ascending sensory pathways at the level of the midbrain) or on the opposite side (with a combination of damage to the nuclei of the trigeminal nerve and the spinothalamic tract, which carries superficial sensitivity from the opposite half of the body) . Involvement of the motor fibers of the trigeminal nerve in the pathological process causes paralysis and atrophy of the masticatory muscles, as a result of which the act of chewing becomes difficult, the lower jaw deviates towards the affected muscles when opening the mouth, and the mandibular reflex decreases. Neuritis or trigeminal neuralgia can be associated with various processes in the cranial cavity, as well as with inflammatory, vascular and dystrophic lesions in the orbit, nasal cavity, mouth, teeth, etc.

The complexity of the anatomical structure and location of the VII pair (facial nerve), the multiplicity of its anatomical connections determine the variety of pathological manifestations that occur when the nerve is damaged at various levels. Of greatest importance is the syndrome of peripheral lesions of the facial nerve in the cranial cavity, the bone canal or at the site of its exit from the canal of the temporal bone, which can be caused by an acoustic neuroma, arachnoiditis, a tumor or abscess in the posterior cranial fossa, congenital or inflammatory damage to the nucleus of the facial nerve , disorders of cerebral circulation in the vertebrobasilar system, diseases of the inner or middle ear, traumatic brain injury with a fracture of the temporal bone, etc. With this syndrome, sharp asymmetry of the face develops: on the affected side the folds of the forehead and nasolabial fold are smoothed, the palpebral fissure is widened, the eye is not closes, the corner of the mouth is lowered, the superciliary and corneal reflexes disappear, and lacrimation increases.

Depending on the level of damage to the nerve trunk in the canal of the temporal bone, in addition to these symptoms, hyperacusis (an unpleasant sharp increase in the perception of sounds on the affected side), dry eyes instead of lacrimation, as well as a taste disturbance on the anterior two-thirds of the tongue may appear. Vivid external manifestations of peripheral paralysis of the facial muscles are easily recognized; differential diagnosis is more difficult in cases where the pathological process is localized at the level of the nucleus or trunk of the facial nerve. Electromyography can provide some help in such situations: if the nucleus is damaged, a palisade rhythm is recorded, characteristic of the pathology of segmental motor neurons, and if the nerve trunk is damaged on the side of the lesion, the speed of impulse transmission along the nerve decreases. Central paralysis of the facial muscles occurs when the corticonuclear tract is damaged on the side opposite to the paralysis, while only the lower half of the facial muscles suffers, the function of the muscles of the eye and eyebrow is preserved, which determines the differential diagnosis with peripheral damage to the facial nerve.

The VIII pair (vestibular-cochlear nerve) consists of two parts - the auditory and vestibular nerves. When the auditory nerve is damaged from the receptors to the auditory nuclei in the brain stem, hearing on the same side is reduced. The overlying auditory fibers are directed to their own and the opposite side, and therefore unilateral damage to these fibers and the centers to which they are directed is not accompanied by hearing impairment. Damage to the parts of the temporal lobe related to auditory gnosis is accompanied by auditory agnosia. The pathological process in the temporal lobe can also manifest itself as auditory hallucinations. When the vestibular nerve is damaged, dizziness, staggering when walking (vestibular ataxia), nystagmus, vestibular disorders, and muscle tone disorders are observed. Pathology of the vestibulocochlear nerve occurs with acoustic neuroma, as well as other inflammatory, tumor, vascular lesions and injuries in the area of ​​the cerebellopontine angle and the posterior cranial fossa as a whole, as well as with diseases of the inner and middle ear, and temporal bone.

When the IX pair (glossopharyngeal nerve) is damaged, sensitivity in the middle ear and pharynx, taste sensitivity in the posterior third of the tongue and palate, swallowing disorders, and cessation of salivation from the parotid gland on the affected side are observed, which causes dry mouth. Isolated unilateral nerve damage is clinically detected mainly during special studies of taste and sensitivity. Of practical importance is mainly the simultaneous damage to the IX and X pairs of nerves.

With unilateral damage to the X pair (vagus nerve), unilateral paralysis of the soft palate (it hangs down on the affected side), paralysis of the vocal fold (hoarse voice), and a decreased pharyngeal reflex on the affected side are noted. With bilateral incomplete damage to the vagus nerves, heart rhythm, breathing, and other autonomic-visceral functions are disrupted; complete bilateral loss of the functions of the vagus nerves is incompatible with life. When sensory branches of the nerve are involved in the process, along with sensitivity disorders, pain syndromes occur in the larynx and ear.

When the XI pair (accessory nerve) is damaged, paralysis and atrophy of the trapezius and sternocleidomastoid muscles develop: the head is turned to the healthy side and slightly thrown back, the shoulder girdle on the side of the paralysis is lowered, raising the arm above the horizontal level is limited. An electromyographic study allows one to study the bioelectrical activity of paralyzed muscles in order to differentiate nuclear and neural lesions, as well as determine the speed of impulse conduction along the accessory nerve (if it is damaged, the conduction speed decreases).

When the X pair (hypoglossal nerve) is affected, limited forward movements of the tongue and its deviation to the affected side, atrophy of the muscles of half the tongue, fibrillary twitching, and less often pain in the root of the tongue are observed. Unilateral damage to the hypoglossal nerve does not cause pronounced functional impairment; bilateral damage is accompanied by speech impairment (dysarthria) and difficulty eating. The speed of impulse conduction along the hypoglossal nerve with neural damage decreases.

Along with isolated syndromes, symptom complexes of combined lesions of Ch. n. are distinguished. caused by congenital dysplasia of their nuclei and intracerebral fibers in the brain stem, as well as various pathological processes at the base of the brain, causing combined pathology of several roots or trunks of the brain, located in anatomical proximity.

Damage to all cranial nerves on one half of the skull base (Garsen syndrome) is associated with the involvement of the cranial nerve roots in the pathological process, the severity and sequence of development of which depends on the initial localization of the process (tumor, vascular malformation, arachnoiditis, etc.), as well as on its further development. distribution. In this case, motor, sensory and autonomic disorders gradually develop in a sequence corresponding to the involvement of nerves in the process. Symptoms of increased intracranial pressure and congestion in the fundus are usually absent.

Superior orbital fissure syndrome is most often caused by tumors of the soft tissues and bones of the orbit. With this syndrome, there is a unilateral combined lesion of the oculomotor, trochlear, abducens nerves and the first branch of the trigeminal nerve, which enter the orbital cavity through the superior orbital fissure. It manifests itself as ptosis and complete paralysis of the muscles that rotate the eyeball, lack of reaction of the pupils to light, pain and decreased sensitivity in the zone of innervation of the first branch.

Anterior cranial fossa syndrome (Kennedy syndrome) is characterized by combined damage to the olfactory and optic nerves and is manifested by a decrease in the sense of smell and vision, and primary atrophy of the optic nerve. Since the syndrome often develops with intracranial tumors at the level of the anterior cranial fossa, symptoms of damage to the frontal lobe are often associated in the form of mental disorders (foolishness, untidiness, etc.), and less often - signs of more extensive damage to the frontal lobe.

Cavernous sinus syndrome is usually caused by tumors, meningioma, gumma and other space-occupying formations in the cavernous sinus area, causing compression and circulatory impairment in the orbital and facial veins, as well as cavernous sinus thrombosis or inflammation. The syndrome is manifested by complete ophthalmoplegia, pain and decreased sensitivity in the zone of innervation of the first branch of the trigeminal nerve, unilateral exophthalmos with swelling of the eyelids, hyperemia and swelling of the conjunctiva of the eye. The involvement of the nerves is due to the fact that they pass in the lateral wall of the sinus - III, IV and VI pairs and the first branch of the V pair.

Cerebellopontine angle syndrome most often occurs due to neuroma of the cochlear root of the vestibulocochlear nerve, cholesteatoma, arachnoiditis, and vascular malformations. The symptom complex includes unilateral damage to the roots of the facial and vestibulocochlear nerves, fibers of the intermediate nerve; with more extensive damage, the V and VI pairs, as well as the cerebellum and pyramidal tracts are involved in the process. It manifests itself as decreased hearing and tinnitus, dizziness, peripheral paralysis of the facial muscles, decreased sensitivity and pain in half of the face, decreased taste sensitivity on the anterior two-thirds of the tongue, convergent strabismus, less commonly, cerebellar disorders on the side of the lesion and pyramidal insufficiency on the side opposite to the lesion.

In childhood, syndromes of combined lesions of Ch. n., associated with malformations of their development, are also important. Marcus Hun synkinesis, caused by the preservation of the embryonic connection between the motor nuclei of the V and III pairs of nerves, is manifested by the association of eyelid movements with movements of the lower jaw, involuntary raising of the eyelid drooping as a result of ptosis when opening, closing the mouth or moving the jaw sideways. Mobius syndrome - congenital aplasia of the nuclei of the abducens and facial nerves is accompanied by peripheral paralysis of facial muscles and convergent strabismus (less often combined with aplasia of nuclei V, VIII, IX, X and XII pairs).

The main components of the peripheral nervous system are the nerves that connect the central nervous system with other parts of the body, and ganglia - groups of nerve cells (nodes) located at different points in the nervous system

A nerve is a bundle of motor (motor) and sensory (sensitive) fibers along with connective tissue and blood vessels. The large nerves (43 of them) actually come from the nervous system: 12 pairs come from the lower part of the brain (cranial nerves) and 31 pairs from the spinal cord (spinal nerves).

Cranial nerves are nerves whose roots are connected to the brain stem. They serve mainly the sense organs and the muscles of the head, although a very important cranial nerve - the vagus (X pair) - serves the digestive organs, the heart and the air passages in the lungs. Some cranial nerves, such as the optic nerve to the eye (II pair), contain only sensory fibers.

Thus, a person has 12 pairs of cranial nerves that exit at the base of the brain:

I - olfactory (nervus olfactorii),

II - visual (n. opticus),

III - oculomotor (n. oculomotorius),

IV - block (n. trochlearis),

V - trigeminal (n. trigemenus),

VI - abducens (n. abducens),

VII - facial (n. facialis),

VIII - auditory, or vestibulocochlearis (n. vestibulocochlearis),

IX - glossopharyngeal (n. glossopharyneus),

X - wandering (n. vagus),

XI - additional (n. accesorius),

XII - sublingual (n. hypoglossus).

• three pairs - sensory (sensitive) - I, II, VIII,
• · six pairs - motor (motor) - III, IV, VI, VII, XI, XII,
• · three pairs - mixed - V, IX, X.

All these nerves innervate the muscles of the face, larynx, pharynx, tongue and partly the neck, and the vagus nerve innervates the muscles of the internal organs.

Sensitive fibers of the cranial nerves are the peripheral parts of the olfactory, visual, gustatory, auditory and skin analyzers; when they are damaged, pain and other sensitivity disorders appear. Inflammatory processes, injuries, tumors, strokes and some other pathological processes can cause a variety of symptoms of damage to the cranial nerves - paresis, paralysis, neuropathies and neuralgia, neuritis. cranial nerve lesion

Paresis - weakening, paralysis - complete absence of motor functions with the absence or decrease in muscle strength as a result of various pathological processes in the nervous system, causing disruption of the structure and function of the motor analyzer. Depending on the level of damage, central and peripheral paralysis are distinguished.

Neuropathy (neuropathia) is the general name for damage to peripheral nerves due to intoxication, hypovitaminosis, autoimmune processes, etc.

Neuralgia (neuralgia) is acute pain localized within one, or less often several, peripheral nerves. Neuralgia is caused by various exogenous and endogenous causes: acute and chronic infections (influenza, tonsillitis, malaria, tuberculosis), intoxication with various poisons (lead, arsenic, mercury, alcohol). Neuralgia often appears during chronic intoxication due to gastrointestinal disorders, diabetes; may occur in the presence of chronic toxic-infectious foci (gynecological diseases, tonsillitis), with gout and hypertension. In some cases, they occur due to injury.

The main symptom of neuralgia is subjectively felt and acutely occurring paroxysmal pain (“burning”, “stabbing”, “shooting”), which is accompanied by paresthesia (pins and needles, numbness, cold).

During an objective examination, “pain points” are noted at the exit site of the nerve; Hyperesthesia and vasomotor-secretory disorders in the form of redness or pallor, sweating or dry skin are often observed. If neuralgia progresses to the stage of neuritis or accompanies it, then objective sensitivity disorders appear, which can also be accompanied by reflex-motor disorders. Neuralgia usually occurs in the form of attacks of greater or lesser duration.

Neuritis is inflammation of peripheral nerves. Occurs as a result of infections, intoxications, injuries, as well as nutritional disorders, circulatory disorders, and vitamin deficiencies. Manifested by pain, sensitivity disorders, paralysis, paresis.

Polyneuritis(polyradiculoneuritis) - multiple neuritis, the process of which sometimes involves cranial nerves: IX and III pairs (glossopharyngeal and oculomotor) - for diphtheria, VII pair (facial) - for acute viral polyneuritis, bulbar nerves (motor cranial nerves, located in the medulla oblongata (bulbus), i.e. sublingual (XII pair), vagus (X pair) and glossopharyngeal (IX pair) - in acute ascending Landry's paralysis.The vagus (X pair) and phrenic nerves are often affected.

I pair - olfactory nerve

When affected, hyposmia (decreased sense of smell) or anosmia (lack of smell) is observed. As a rule, they are one-sided. When the temporal cortex is irritated (for example, by a volumetric process), olfactory hallucinations appear - dysosmia and parosmia.

There is also a pathology called olfactory agnosia (failure to recognize familiar odors).

The function of smell is examined using various aromatic substances (mint drops, perfume, ethyl or camphor alcohol), while the nasal passages are closed alternately. You cannot use ammonia and other substances with pungent odors, since the trigeminal nerve (V pair) can react by irritating its branches, i.e., causing pain.

II pair - optic nerve

When the optic nerve is completely interrupted, amaurosis (blindness) occurs. Due to various pathological processes, amblyopia or hemiamblyopia (reduced visual acuity due to toxic damage to the orbital part of the optic nerve; in the second case, visual damage occurs in opposite fields), hemianopsia (loss of visual fields), which is characterized by blindness of the external (temporal) or internal visual fields ( There are several types of hemianopia, differing depending on the degree of nerve damage), scotomas - loss of visual fields in sectors.

When the visual cortex (occipital lobe) is irritated, visual hallucinations occur. With damage to the outer surface of the occipital lobe (on the left - in right-handed people and vice versa), visual agnosia can also be observed - the patient loses the ability to recognize objects by their appearance.

Color blindness (impaired color vision) is detected using multi-color tables.

Visual acuity studies are carried out using Kryukov tables (letters of decreasing size), visual field studies are carried out using the perimeter. Visual fields can be checked by stretching a towel in front of the patient's face, which he must divide in half (if hemianopsia is present, the patient divides the towel into unequal parts) or using a slit lamp. Of no small importance in neurology is the examination of the fundus, the data of which can provide valuable information about the presence of a pathological focus in the brain (volumetric processes).

III pair - oculomotor nerve

This nerve provides movement of the eyeball and innervates the muscle that constricts the pupil and reacts the pupils to light.

When this nerve is damaged, the following symptoms may appear: ptosis (drooping of the upper eyelid), diplopia (double vision) when looking up and in, mydriasis (dilation of the pupil), exophthalmos (protrusion of the eyeballs from the orbits), as well as divergent strabismus and impaired convergence reaction (the ability to bring the eyeballs to the bridge of the nose) and accommodation (the ability to clearly see objects that are closer to the far point of clear vision; accommodation disorders are caused by paralysis of the ciliary muscle).

Symptoms of oculomotor nerve damage may include: anisocoria(difference in pupil size), nystagmus, full immobility pupil, loss of pupillary reactions into the light - friendly constriction of the pupils.

IV pair - trochlear nerve

It innervates the muscle that rotates the eyeball downwards and outwards.

When affected, the following symptoms occur: diplopia (double vision) when looking down, i.e. under your feet, and a convergent squint. It is extremely rarely affected in isolation, most often due to exacerbation of chronic otitis.

VI pair - abducens nerve

It innervates the muscle that abducts the eyeball outward.

When affected, convergent strabismus appears, diplopia (double vision) when looking towards the affected muscle (outward), and the inability to rotate the eyeball outward.

When affected, isolated paralysis of the rectus muscle of the eye occurs, which leads to convergent strabismus, diplopia (the inability to turn the eye outward), especially when looking towards the affected muscle; sometimes - to dizziness and forced head position.

Nuclear lesions are accompanied by paralysis (or paresis) of the facial muscles and central paralysis of the limbs (Fauville's symptom). Gaze paralysis in the direction of the affected muscle and lesion is also possible.

To study the function of these nerves, a neurological hammer is used, with which the mobility of the eyeballs is checked (they are asked to look up, down, out, in). Pay attention to the width and uniformity of the palpebral fissures and the shape and size of the pupils.

The reaction of the pupils to light is checked with a flashlight or with your palms, first closing your eyes tightly, and then quickly removing one of your hands.

Neuropathies of the III, IV and VI pairs of cranial nerves (oculomotor, trochlear and abducens) are considered together, because normally their functions are interrelated. The nerves are often affected simultaneously or separately with a fracture of the base of the skull, basal arachnoiditis, encephalitis, bone pathology in the orbital area, cavernous sinusitis, diabetes mellitus, mushroom poisoning, and tumors. With joint paralysis of this group of nerves (ophthalmoplegia totalis), eye movement is completely excluded.

V pair - trigeminal nerve

The name of this nerve is due to the fact that it has three branches:

• 1. ocular,
• 2. maxillary And mandibular nerves that supply nerve endings to the skin of the scalp, forehead, nose, upper and lower eyelids, cheeks and lips, as well as teeth, nasal mucosa, gums, tongue and masticatory muscles.

Due to the fact that the trigeminal nerve is mixed, when it is damaged, sensitive ( hypoesthesia, hyperesthesia or pain) and movement disorders ( paralysis of the masticatory muscles). Severe paroxysmal pain occurs in the area of ​​innervation of this nerve - in one or more of its branches. This pathology is called trigeminal neuralgia, which is a common disease. The cause may be pathological processes leading to narrowing of the openings through which nerve branches enter the cranial cavity. These are local diseases (paranasal sinuses, ears, eyes, teeth; purulent processes of the skin and subcutaneous tissue of the face; periostitis, herpetic ganglioneuritis), general infections, facial injuries, and in elderly patients - atherosclerosis of blood vessels in the facial area. Other causes include multiple sclerosis.

Pain in the area of ​​this nerve, simulating neuralgia, can be observed with tumors of the middle cranial fossa, trigeminal neuromas, arachnoiditis of the base of the brain. The process is localized not only in the peripheral part of the nerve, but often in its central segments. The disease occurs as a result of irritation of the nerve itself, and during various processes, in particular, vasospasms in the gasserian node.

Only one of the three branches of the nerve may be affected, but neuralgia of two or all three branches is possible. Pain associated with diseases of the abdominal organs and uterus can sometimes also radiate to the area of ​​innervation of the trigeminal nerve.

The trigeminal nerve is rich in autonomic fibers, and therefore main manifestation of the disease are intense and burning pain paroxysms in the innervation zone of the affected branch (branches) lasting from several seconds to 1-2 minutes, repeated from several to dozens of times a day. They are often accompanied by taste paresthesia, pain tics, vegetative-vascular disorders: facial hyperemia and swelling, increased secretion of saliva, lacrimation, impaired sweating, nasal congestion, pain in the heart, increased blood pressure, and sometimes photophobia.

“Trigger” points are found on the face (in the superior orbital, infraorbital and mental foramina - the exit points of the trigeminal nerve - its I, II and III branches), irritation of which causes an attack of pain. Depending on the localization of the process (neuropathy of the third branch of the nerve), spasms of the facial muscles - paresis of the masticatory muscles - are simultaneously possible.

An attack of pain can be triggered by external influences (touch, wind, loud sound), facial expressions while eating, laughter, coughing, talking, strong emotions. The disease is characterized by a chronic course with increasingly frequent exacerbations, resulting in gradual asthenia of patients.

VII pair - facial nerve

In the facial area, it forms many branches, the so-called “crow's foot”, and innervates all facial muscles, and also gives branches to the anterior third of the tongue and salivary glands.

Damage to the facial nerve causes paralysis of the facial muscles, which, depending on the cause, is called neuropathy (neuritis, paralysis) of the facial nerve.

Facial nerve neuropathy (neuropathy (neuritis) n. facialis) is the most common disease among mononeuropathies. In most cases, against the background of infection and cooling, compression of the nerve occurs in a narrow bone canal, followed by ischemia and degenerative changes. Compression is facilitated by the congenital narrowness of the canal or its outlet. Sometimes the disease is preceded by local infections (mumps, exacerbation of chronic otitis media) or trauma to the parotid region.

Neuropathy itself occurs due to an infection of the inner ear; for syphilitic diseases of the brain (basilar specific meningitis, limited meningitis of the base of the brain). Infections include rheumatism, influenza (as a complication, this disease can be included in the picture of post-influenza encephalitis), viral infections (acute polio). Among organic diseases, one should keep in mind tumors (primarily the cerebellopontine angle), multiple sclerosis. It occurs in children with polio and in cases of birth trauma.

The clinical picture is based on movement disorders in the form of weakness and atrophy of all facial muscles, usually on one side.

Due to the greater strength of the muscles of the undamaged half of the face, its asymmetry occurs: on the side of the paresis, a fold on the forehead does not form, the forehead does not wrinkle, the eyebrow does not rise; the nasolabial fold is smoothed; a wider palpebral fissure, when the eyes are closed, the eyes do not close (lagophthalmos), lacrimation is observed, the eyeball moves upward ( Bell phenomenon). When grinning, the mouth is pulled to the healthy side, the patient cannot whistle, etc., the cheek is swollen, the corner of the mouth is drooping, while eating, solid food gets between the gum and cheek, and liquid food pours out over the edge of the mouth on the affected side. The asymmetry and stiffness of the paretic side intensify with facial movements: smiling, laughing, crying, talking.

On the affected side there is pain, paresthesia, vasomotor-trophic disorders. In most cases, with high nerve damage, hyperacusis (increased perception of sound, especially low tones), impaired taste in the anterior 2/3 of the tongue and dry mouth are observed.

It is necessary to distinguish the peripheral nature of the lesion from the central one. At peripheral(extracranial) lesions are characterized by unilateral nerve palsy and the entire half of the face is affected. At central(intracranial, basal) paralysis affects only the lower branch - from the cerebral cortex to the nerve nucleus (unilateral damage to the region of the central part of the cortical analyzer or pathways accompanying, for example, hemiplegia). The nucleus or fibers of the facial nerve can be involved in a pathological process in the brain stem (vascular, infectious, oncological), while the innervation of only the lower part of the face is disrupted and paresis of the lower half of one side of the face occurs, while the patient is able to close his eyes and wrinkle his forehead on the affected side.

The disease begins suddenly: paresis develops over several hours or days. Partial restoration of nerve function occurs during the first week, complete restoration within 2 months in 2/3 of cases. In 1/3 of patients, after 4-6 weeks, a complicated form of the disease develops with contracture and increased tone of some facial muscles and involuntary movements on the affected side that occur when eating, smiling, laughing and other facial actions.

Contracture is accompanied by unpleasant sensations of tightness and tension, aggravated by excitement, physical stress, and cold.

During a neurological examination, even during an external examination, attention is drawn to the symmetry of the face. For a more detailed test of the functions of the facial nerve, the patient is asked to collect folds on the forehead (“surprised”), frown his eyebrows (“angry”), close his eyes (“tightly, as if soap was in contact”), puff out his cheeks, bare his teeth, smile and whistle ( or “blow out the match”).

Classical electrodiagnostics with measurement of the excitability of nerve branches and facial muscles to different types of current and electromyography help clarify the diagnosis of neuropathy and identify the prognosis for recovery.

It is necessary to carefully examine the ear and nasal cavities; conduct an epidemiological analysis, since the disease often occurs due to infections.

VIII pair - auditory, or vestibulocochlear, nerve

This pair of nerves combines two functionally different sensory nerves, one of which - the cochlear (auditory) - provides the perception of sounds, and the other - the vestibular - regulates balance and orientation of the head and body in space. Thus, the nerve has two branches: the true auditory and vestibular parts of the nerve.

Violation cochlear(auditory ) parts leads to hearing disorders: hypacusia (decreased hearing), anakusia (deafness - hearing loss), or hyperacusis (increased perception of sounds).

For pathology vestibular part of the nerve, vestibular ataxia occurs: body balance is upset (bending and falling towards the affected side) and coordination of movements, dizziness, vomiting and nystagmus appear (involuntary rhythmic twitching of the eyeballs, especially when they are abducted, in the horizontal, vertical or rotational plane).

Neuropathy of the VIII nerve occurs as a result of intoxication with various substances (for example, a number of antibiotics), as a complication of influenza infection, skull trauma, with a vascular process in the vertebrobasilar region and neuroma of the nerve trunk.

The function of the auditory nerve is examined by otolaryngologists, but in neurology, if necessary, whispered speech is checked (on both sides in turn) at a distance of 6 meters. In this case, words are called that contain loud consonants (“forty-six”, “artillery”, etc.). If the patient cannot hear from 6 meters, then the distance must be reduced until the patient hears the words called.

The presence of nystagmus is determined by studying the movements of the eyeballs: when they are abducted to the sides (horizontal nystagmus) and upward (vertical nystagmus).

When the temporal lobe cortex is irritated, auditory hallucinations occur, even complex ones (patients hear music, various voices).

IX pair - glossopharyngeal nerve

It supplies innervation to the posterior third of the tongue, palate, middle ear, pharynx and vocal cords.

Dysfunction of this nerve leads to a variety of disorders: taste disturbance in the posterior third of the tongue or on the side of the affected nerve, anesthesia (loss of sensitivity) of the mucous membrane of the pharynx and tongue, dysphagia (impaired swallowing) - since the vagus nerve is also involved in the innervation of the pharynx.

At unilaterally If the function of the parotid salivary gland is impaired, dry mouth may be absent or insignificant, since this function is compensated by the work of the remaining salivary glands.

Neuropathy of the glossopharyngeal nerve is a rare disease, usually manifested by a neuralgia syndrome with severe paroxysms of pain lasting from a few seconds to 1-3 minutes - in the pharynx, tonsils and posterior third of the tongue with irradiation to the ear.

Painful attacks can be provoked by swallowing, hot or cold food, coughing, laughing, talking, accidental touching the back third of the tongue and be accompanied by bradycardia, arrhythmia, drop in blood pressure, and fainting.

X pair - vagus nerve

This is the largest autonomic nerve. It provides fiber to the muscles and blood vessels of all internal organs, as well as the pharynx, soft palate, larynx and epiglottis.

At unilaterally In cases of damage, there is a drooping of the soft palate, deviation of the uvula (to the healthy side), dysphonia (hoarseness of the voice), dysphagia (impaired swallowing).

At bilateral If affected, aphonia occurs (the voice becomes whispery, silent), choking and coughing occurs when eating, and liquid food falls out through the nose. Cardiovascular and respiratory activity is impaired, which can result in the death of the patient.

The technique for studying the IX and X pairs of cranial nerves includes examining the condition of the soft palate: normally it is located symmetrically and when pronouncing the letter “a-a-a” it rises equally on both sides; tongue location: normally it is located in the midline. The patient is asked to drink a few sips of water or swallow saliva - swallowing should be free, without choking.

XI pair - accessory nerve

It innervates the sternocleidomastoid muscle (turns the head to the sides - opposite to the nerve) and the trapezius muscle (movements of the scapula and clavicle when they are lifted and pulled back).

Damage to the nerve leads to paresis or paralysis of these muscles, which is expressed in their atrophy: it is difficult to turn the head in the healthy direction (possible formation of torticollis), shrugging the shoulders, abducting the shoulder blades to the spine, and limiting the raising of the arms above the horizontal line.

During the examination, the patient should normally perform all these movements without difficulty.

Occasionally, spasms of muscles innervated by the XI nerve are observed; they are more often unilateral or the result of cortical or subcortical irritations. Tonic the spasm gives the picture of “torticollis”; clonic- twitching of the head in the opposite direction, sometimes with simultaneous raising of the shoulder. Bilateral clonic spasms result in nodding movements of the head (Salaam's spasm).

XII pair - hypoglossal nerve

It is the motor nerve of the tongue, providing articulation when speaking and moving food forward for swallowing when eating.

Damage to this nerve leads to paresis or paralysis of the corresponding half of the tongue and is accompanied by atrophy and thinning of the muscles of the tongue, its deviation towards the lesion and dysarthria (impaired speech: it becomes slurred and slurred - “mess in the mouth”). To check the function of the hypoglossal nerve, the patient is asked to stick out his tongue. Normally it should be located in the midline.

Unilateral damage to the IX, X and XII pairs of nerves (glossopharyngeal, vagus and hypoglossal) leads to the so-called bulbar palsy, which is characterized by the presence of “three Ds”:

• 1. Dysphonia (nasal, nasal tone of voice or hoarseness);
• 2. Dysarthria (articulation disorder - slurred speech, characterized by difficulty pronouncing certain letters - “l”, “s”, “b”, “p”);
• 3. Dysphagia (disorder of chewing and swallowing - choking when eating, liquid food getting into the nose).

There is atrophy of the tongue muscles with fibrillary twitching and paresis of the soft palate. Sensitivity is not upset. Usually the facial (VII pair) and trigeminal (V pair) nerves are also affected, as a result of which the patient’s face is amicable, the mouth is open, and saliva flows from it.

At bilateral In case of damage, all of the above pathology occurs in full (“three A”):

• 1. Aphonia (almost silent, whispered speech);
• 2. Anarthria (serious articulation disorder up to the inability to speak);
• 3. Aphagia (serious swallowing disorder up to the inability to swallow).

As an independent disease, bulbar palsy is rare; it is usually associated with amyotrophic lateral sclerosis and syringomyelia, when the disease process also affects the bulbar part of the brain. This must be kept in mind when recognizing, like tumors of the medulla oblongata, syphilis, pseudobulbar palsy due to bilateral damage to the corticonuclear tracts in the brain. Infectious diseases of the brain, poliomyelitis and encephalitis, also accompanied by bulbar paralytic disorders, always develop very acutely.

Each light-sensitive cell in the retina is connected by a nerve to the brain, where all information about images, color and shape is collected and processed. All of these nerve fibers come together at the back of the eye and form one main "cable" known as the optic nerve. It exits the eyeball through a bony tunnel in the skull and re-emerges just below the brain in the area of ​​the pituitary gland to join the second optic nerve. The nerves on both sides then cross so that some of the information from the left eye goes to the right side of the brain and vice versa. The nerves of the temporal side of each retina do not cross and remain on the same side of the brain, while fibers from the same part of the eye, which does the main work of vision, go to different sides of the brain. The optic nerve is nothing more than a bundle of nerve fibers carrying tiny electrical impulses along tiny cables, each of which is isolated from the next by a layer of myelin. In the center of the main cable there is a large artery running along its entire length. It is called the central retinal artery. This artery arises in the central part of the eye, and its capillaries cover the entire surface of the retina. There is a corresponding vein that runs in the opposite direction along the optic nerve next to the central retinal artery and carries blood away from the retina. The nerves coming from the retina are sensory nerves; Unlike motor nerves, which have only one connection on their route to the brain, optic nerves connect several times. The first meeting occurs just behind that point, the sensory information from different eyes switches places. This point is called the optic chiasm and is located close to the pituitary gland. Directly beyond this junction is the first junction, called the lateral geniculate body. Here the information from the left eye and the right eye is swapped once again. The function of this connection is related to the reflexes of the pupils. From the lateral geniculate body, the nerves fan out on both sides around the temporal part of the brain, forming the optic radiation. They then turn slightly and come together to pass through the main "switchboard" - the internal capsule where all the motor and sensory information supplying the body is concentrated. From here, the nerves travel to the back of the brain to the visual cortex. Myopia The most common cause of myopia is an eyeball that is too "long" so that light rays form an image in front of the retina.

Myopia is corrected with concave lenses.

Olfactory nerve (n. olfactorius).

Olfactory receptor cells are scattered in the epithelium of the mucous membrane of the olfactory region of the nasal cavity. The thin central processes of these cells are collected into olfactory filaments, which are the olfactory nerve itself. From the nasal cavity, the nerve enters the cranial cavity through the openings of the ethmoid bone and ends in the olfactory bulb. From the cells of the olfactory bulb, the central olfactory pathways begin to the cortical zone of the olfactory analyzer in the temporal lobe of the brain.

Bilateral complete loss of smell (anosmia) or its decrease (hyposmia) is often the result of a disease of the nose or is congenital (sometimes in this case combined with certain endocrine disorders). Unilateral disturbances of smell are mainly associated with a pathological process in the anterior cranial fossa (tumor, hematoma, traumatic brain injury, etc.). Unusual paroxysmal olfactory sensations (parosmia), often some vague unpleasant odor, are harbingers of an epileptic seizure caused by irritation of the temporal lobe of the brain. Irritation of the temporal lobe of the brain can cause a variety of olfactory hallucinations.

Research methodology. The study of smell is carried out using a special set of aromatic substances (camphor, mint, valerian, pine extract, eucalyptus oil). The subject, with his eyes closed and one half of his nose pinched, is presented with odorous substances and asked to say what smell he smells and whether he perceives the smells equally well in each nostril separately. Do not use substances with strong odors (ammonia, acetic acid), because in this case, irritation of the endings of the trigeminal nerve occurs, so the results of the study will be inaccurate.

Symptoms of the lesion. They vary depending on the level of damage to the olfactory nerve. The main ones are loss of smell - anosmia, decreased sense of smell - hyposmia, increased sense of smell - hyperosmia, perversion of smell - dysosmia, olfactory hallucinations. For the clinic, a unilateral decrease or loss of smell is mainly important, because bilateral hypo- or anosmia is caused by symptoms of acute or chronic rhinitis.

Hypoosmia or anosmia occurs when the olfactory pathways up to the olfactory triangle are affected, i.e. at the level of the first and second neurons. Due to the fact that third neurons have cortical representation on both their own and the opposite side, damage to the cortex in the olfactory projection field does not cause loss of smell. However, in cases of irritation of the cortex of this area, sensations of non-existent odors may occur.

The proximity of the olfactory filaments, olfactory bulb and olfactory tract to the base of the skull leads to the fact that during pathological processes at the base of the skull and brain, the sense of smell is also impaired.

Optic nerve (n. opticus).

It is formed by the axons of neurons of the ganglion layer of the retina, which, through the cribriform plate of the sclera, exit the eyeball through a single trunk of the optic nerve into the cranial cavity. At the base of the brain in the area of ​​the sella turcica, the fibers of the optic nerves converge on both sides, forming the optic chiasm and optic tracts. The latter continue to the external geniculate body and the thalamic cushion, then the central visual pathway goes to the cerebral cortex (occipital lobe). Incomplete decussation of the fibers of the optic nerves causes the presence in the right optic tract of fibers from the right halves, and in the left optic tract - from the left halves of the retinas of both eyes.

Symptoms of the lesion .

When the conduction of the optic nerve is completely interrupted, blindness occurs on the side of the damage with the loss of the direct reaction of the pupil to light. When only part of the optic nerve fibers are damaged, focal loss of the visual field (scotomy) occurs. When the chiasm is completely destroyed, bilateral blindness develops. However, in many intracranial processes, damage to the chiasm can be partial - loss of the outer or inner halves of the visual fields develops (heteronymous hemianopsia). With unilateral damage to the optic tracts and overlying visual pathways, unilateral loss of visual fields on the opposite side occurs (homonymous hemianopsia).

Damage to the optic nerve can be inflammatory, congestive and dystrophic in nature; detected by ophthalmoscopy. The causes of optic neuritis can be meningitis, encephalitis, arachnoiditis, multiple sclerosis, influenza, inflammation of the paranasal sinuses, etc. They are manifested by a decrease in acuity and a narrowing of the field of vision, which is not corrected by the use of glasses. A congested optic nerve papilla is a symptom of increased intracranial pressure or impaired venous outflow from the orbit. As congestion progresses, visual acuity decreases and blindness may occur. Optic nerve atrophy can be primary (with tabes dorsalis, multiple sclerosis, optic nerve injury) or secondary (as a result of neuritis or congestive nipple); There is a sharp decrease in visual acuity up to complete blindness, and a narrowing of the field of vision.

Ocular fundus– part of the inner surface of the eyeball visible during ophthalmoscopic examination (optic disc, retina and choroid). The optic disc stands out against the red background of the fundus as a rounded formation with clear boundaries and a pale pink color. In the posterior pole of the eye there is the most sensitive area of ​​the retina - the so-called macula macula, which has the shape of a horizontal oval of a yellowish tint. The macula consists of cones, which provide daytime vision and are involved in the accurate perception of the shape, color and details of an object. As you move away from the macula, the number of cones decreases and the number of rods increases. The rods have very high light sensitivity and provide the perception of objects at dusk or at night.

Research methodology. Find out whether there are complaints about decreased visual acuity, loss of the visual field, the appearance of sparks, dark spots, flies, etc. before the eyes.

Visual acuity is examined using special tables on which letters are depicted in rows. Moreover, each bottom row is smaller than the previous one. On the side of each row there is a number indicating from what distance the letters of this row should be read with normal visual acuity.

Visual fields are examined using the perimeter. It is often necessary to use an approximate method for measuring visual fields. To do this, a person sits with his back to the light source, closes one eye, but without pressing on the eyeball. The examiner sits in front of the patient, asks the patient to fix the gaze on some point in front of him, moves the hammer from the patient’s ear in a circle to the bridge of the nose, and asks the patient to tell him when he sees him. The external field of view is usually 90 degrees. The internal, upper and lower visual fields are examined in a similar way and are 60, 60, 70 deg. respectively.

Color perception is studied using special polychromatic tables, on which numbers, figures, etc. are depicted in spots of different colors.

The fundus is examined using an ophthalmoscope and a photo-ophthalmoscope, which allows obtaining both black-and-white and color photographs of the fundus.

Oculomotor nerve. ( n. oculomotorius).

Innervates the external muscles of the eye (with the exception of the external rectus and superior oblique), the muscle that lifts the upper eyelid, the muscle that constricts the pupil, the ciliary muscle, which regulates the configuration of the lens, which allows the eye to adapt to near and far vision.

System III pair consists of two neurons. The central one is represented by the cells of the cortex of the precentral gyrus, the axons of which, as part of the corticonuclear tract, approach the nuclei of the oculomotor nerve on both its own and the opposite side.

A wide variety of functions performed by the third pair is carried out using 5 nuclei for the innervation of the right and left eyes. They are located in the cerebral peduncles at the level of the superior colliculi of the midbrain roof and are peripheral neurons of the oculomotor nerve. From the two magnocellular nuclei, the fibers go to the external muscles of the eye on their own and partially the opposite side. The fibers innervating the muscle that lifts the upper eyelid come from the nucleus of the same and opposite side. From two small cell accessory nuclei, parasympathetic fibers are directed to the muscle constrictor pupil, on its own and the opposite side. This ensures a friendly reaction of the pupils to light, as well as a reaction to convergence: constriction of the pupil while simultaneously contracting the rectus intrinsic muscles of both eyes. From the posterior central unpaired nucleus, which is also parasympathetic, the fibers are directed to the ciliary muscle, which regulates the degree of convexity of the lens. When looking at objects located near the eye, the convexity of the lens increases and at the same time the pupil narrows, which ensures a clear image on the retina. If accommodation is impaired, a person loses the ability to see clear outlines of objects at different distances from the eye.

The fibers of the peripheral motor neuron of the oculomotor nerve begin from the cells of the above nuclei and emerge from the cerebral peduncles on their medial surface, then pierce the dura mater and then follow in the outer wall of the cavernous sinus. From the skull, the oculomotor nerve exits through the superior orbital fissure and enters the orbit.

Symptoms of defeat.

Disruption of the innervation of individual external muscles of the eye is caused by damage to one or another part of the magnocellular nucleus; paralysis of all muscles of the eye is associated with damage to the nerve trunk itself. An important clinical sign that helps to distinguish between damage to the nucleus and the nerve itself is the state of innervation of the muscle that lifts the upper eyelid and the internal rectus muscle of the eye. The cells from which the fibers go to the muscle that lifts the upper eyelid are located deeper than the rest of the cells of the nucleus, and the fibers going to this muscle in the nerve itself are located most superficially. The fibers innervating the internal rectus muscle of the eye run in the trunk of the opposite nerve. Therefore, when the trunk of the oculomotor nerve is damaged, the first to be affected are the fibers innervating the muscle that lifts the upper eyelid. Weakness of this muscle or complete paralysis develops, and the patient can either only partially open the eye or not open it at all. With a nuclear lesion, the muscle that lifts the upper eyelid is one of the last to be affected. When the core is hit, “the drama ends with the curtain falling.” In the case of a nuclear lesion, all external muscles on the affected side are affected, with the exception of the internal rectus muscle, which is isolated in isolation on the opposite side. As a result of this, the eyeball on the opposite side will be turned outward due to the external rectus muscle of the eye - divergent strabismus. If only the magnocellular nucleus is affected, the external muscles of the eye are affected - external ophthalmoplegia. Because when the nucleus is damaged, the process is localized in the cerebral peduncle, then the pyramidal tract and fibers of the spinothalamic tract are often involved in the pathological process, alternating Weber syndrome occurs, i.e. lesion of the third pair on one side and hemiplegia on the opposite side.

A person has 12 pairs of cranial nerves(see diagrams below). Scheme of localization of cranial nerve nuclei: anteroposterior (a) and lateral (b) projections
Red indicates the nuclei of the motor nerves, blue indicates the sensory nerves, and green indicates the nuclei of the vestibulocochlear nerve.

Olfactory, visual, vestibulocochlear are nerves of highly organized specific sensitivity, which in their morphological characteristics represent, as it were, peripheral parts of the central nervous system.

The article below will list all 12 pairs of cranial nerves, information about which will be accompanied by tables, diagrams and figures.

For more convenient navigation through the article, there is a picture with clickable links above: just click on the name of the pair of CNs you are interested in and you will immediately be taken to information about it.

12 pairs of cranial nerves

Motor nuclei and nerves are indicated in red, sensory in blue, parasympathetic in yellow, preocochlear nerve in green.

1 pair of cranial nerves - olfactory (nn. olfactorii)

NN. olfactorii (scheme)

2 pair of cranial nerves - optic (n. opticus)

N. opticus (diagram)

When the 2nd pair of cranial nerves is damaged, various types of visual impairment can be observed, shown in the figure below.

amaurosis (1);
hemianopsia - bitemporal (2); binasal (3); eponymous (4); square (5); cortical (6).

Any pathology of the optic nerve requires a mandatory examination of the fundus, the possible results of which are shown in the figure below.

Fundus examination

Primary optic nerve atrophy. The color of the disk is gray, its boundaries are clear.

Secondary optic nerve atrophy. The color of the disc is white, the contours are unclear.

3rd pair of cranial nerves - oculomotor (n. oculomotorius)

N. oculomotorius (diagram)

Innervation of the eye muscles

Scheme of innervation of the muscles of the eyeball by the oculomotor nerve

The 3rd pair of cranial nerves is involved in the innervation of the muscles involved in eye movement.

Schematic representation of the path

- this is a complex reflex act in which not only the 3rd pair, but also the 2nd pair of cranial nerves are involved. The diagram of this reflex is shown in the figure above.

4th pair of cranial nerves - trochlear (n. trochlearis)

5th pair of cranial nerves - trigeminal (n. trigeminus)

Nuclei and central pathways n. trigeminus

The dendrites of sensory cells along their course form three nerves (see the figure below for innervation zones):

• orbital— (zone 1 in the figure),
• maxillary— (zone 2 in the figure),
• mandibular— (zone 3 in the figure).

Zones of skin innervation by branches n. trigeminus

From skull n. ophthalmicus exits through fissura orbitalis superior, n. maxillaris - through foramen rotundum, n. mandibularis - through foramen ovale. As part of one of the branches n. mandibularis, which is called n. lingualis, and chorda tympani, taste fibers are suitable for the sublingual and mandibular glands.

When the trigeminal ganglion is involved in the process, all types of sensitivity suffer. Usually this is characterized by excruciating pain and the appearance of herpes zoster on the face.

When the nucleus n. is involved in the pathological process. trigeminus, located in the spinal tract, the clinic is accompanied by dissociated anesthesia or hypoesthesia. In case of partial damage, segmental annular zones of anesthesia are noted, known in medicine under the name of the scientist who discovered them “ Zelder zones"(see diagram). When the upper parts of the nucleus are affected, sensation around the mouth and nose is impaired; lower - outer areas of the face. Processes in the nucleus are usually not accompanied by pain.

6th pair of cranial nerves - abducens (n. abducens)

Abducens nerve (n. abducens) - motor. The nerve nucleus is located in the inferior part of the pons, under the floor of the fourth ventricle, lateral and dorsal to the dorsal longitudinal fasciculus.

Damage to the 3rd, 4th and 6th pairs of cranial nerves causes total ophthalmoplegia. When all the muscles of the eye are paralyzed, external ophthalmoplegia.

The defeat of the above pairs, as a rule, is peripheral.

Innervation of gaze

Without the cooperative functioning of several components of the muscular system of the eye, it would be impossible to carry out movements of the eyeballs. The main formation, thanks to which the eye can move, is the dorsal longitudinal fasciculus longitudinalis, which is a system that connects the 3rd, 4th and 6th cranial nerves with each other and with other analyzers. The cells of the nucleus of the dorsal longitudinal fasciculus (Darkshevich) are located in the cerebral peduncles lateral to the cerebral aqueduct, on the dorsal surface in the region of the posterior commissure of the brain and frenulum. The fibers are directed down along the cerebral aqueduct to the rhomboid fossa and on their way approach the cells of the nuclei of 3, 4 and 6 pairs, communicating between them and the coordinated function of the eye muscles. The dorsal bundle includes fibers from the cells of the vestibular nucleus (Deiters), which form the ascending and descending pathways. The first ones contact the cells of the nuclei of 3, 4 and 6 pairs, the descending branches stretch down, pass in the composition, which end at the cells of the anterior horns, forming the tractus vestibulospinalis. The cortical center that regulates voluntary gaze movements is located in the middle frontal gyrus. The exact course of the conductors from the cortex is unknown; apparently, they go to the opposite side to the nuclei of the dorsal longitudinal fasciculus, then along the dorsal fasciculus to the nuclei of the named nerves.

Through the vestibular nuclei, the dorsal longitudinal fasciculus is connected with the vestibular apparatus and the cerebellum, as well as with the extrapyramidal part of the nervous system, and through the tractus vestibulospinalis with the spinal cord.

7th pair of cranial nerves - facial (n. facialis)

N. facialis

A diagram of the topography of the facial nerve is presented above.

Intermediate nerve (n. intermedius)

Paralysis of facial muscles:
a - central;
b - peripheral.

The intermediate nerve is inherently part of the facial nerve.

When the facial nerve, or more precisely its motor roots, is damaged, peripheral paralysis of the facial muscles is noted. The central type of paralysis is a rare phenomenon and is observed when the pathological focus is localized in, in particular in the precentral gyrus. The differences between the two types of facial muscle paralysis are presented in the figure above.

8th pair of cranial nerves - vestibulocochlearis (n. vestibulocochlearis)

The vestibulocochlear nerve anatomically has two roots with completely different functional abilities (this is reflected in the name of the 8th pair):

1. pars cochlearis, performing an auditory function;
2. pars vestibularis, performing the function of a static feeling.

Pars cochlearis

Other names for the root: “inferior cochlear” or “cochlear part”.