The extrapyramidal system is the basis for the implementation of complex unconditioned (innate, species) reflexes called instincts (defensive, food, sexual, maternal, etc.). It provides regulation of muscle tone, normal cooperative movements (syncinesia) and unconditioned reflex motor reactions (friendly movements of the hands when walking, gesturing, withdrawing the hand when touching something hot, etc.) and, in particular, stural reflexes (postural reflexes). Recently, the role of the extrapyramidal system in motivational and cognitive activity has been shown.
The main formations of the extrapyramidal system are the lenticular nucleus, caudate nucleus, red nucleus, substantia nigra, subthalamic nucleus, as well as the premotor cortex, which is directly related to both the pyramidal and extrapyramidal systems. They are connected with each other and with other formations of the central nervous system.
Lenticular nucleus
The lenticular nucleus consists of three segments (striatum striatum), two of which - the internal ones - are phylogenetically older formations (paleostriatum), and the external segment, as well as the caudate nucleus, are younger (neostriatum).
In a newborn, the fibers of the neostriatal system are not yet myelinated. As their myelination progresses, postural functions gradually develop: holding the head, sitting, standing.
Extrapyramidal pathways
The main afferent information enters the striatum from the thalamus optica (the collector of all types of sensitivity), as well as from the cerebellum, cerebral cortex, brain stem (rape nucleus, locus coeruleus), and substantia nigra. The main efferent projections of the globus pallidus emerge from its medial part, pass through or near the internal capsule and are directed to a number of thalamic nuclei, as well as to the substantia nigra, limbic gyrus and frontal cortex (Fig. 1.2.3).
Since the basal ganglia closely interact with the thalamus, it is important to note that the efferent pathways of the latter project not only to the striatum, but also to the cerebral cortex - motor, premotor and prefrontal.
It is necessary to point out the significance of cortical projections to the striatum and subsequent ones to the thalamus and again to the cerebral cortex; There is also a two-way connection between the striatum and the substantia nigra. Material from the site
Efferent impulses descending from the extrapyramidal system through the reticulospinal and other pathways (rubrospinal, posterior longitudinal fasciculus, etc.) enter the executive motor unit - the peripheral motor neuron, which generates impulses to the muscles.
This is how impulses circulate through neural circles of varying length and composition. Disruption of normal circulation leads to the development of extrapyramidal disorders. At the same time, neurosurgical destruction of certain groups of cells is used in the treatment of certain extrapyramidal disorders.
Extrapyramidal system – This is a system of cortical, subcortical and stem nuclei of the brain and pathways connecting them to each other, as well as with the motor nuclei of the cranial nerves of the brain stem and anterior columns of the spinal cord, which carries out involuntary automatic regulation and coordination of complex motor acts, regulation of muscle tone, maintenance postures, organization of motor manifestations of emotions.
Composition of the extrapyramidal system:
Cerebral cortex;
Basal ganglia of the telencephalon: caudate and lenticular;
Subthalamic nucleus and thalamic nuclei of the diencephalon;
Red nucleus and substantia nigra, nuclei of the midbrain roof;
Vestibular nuclei;
Inferior olive kernels;
Cerebellum;
Nuclei of the reticular formation;
Conducting pathways.
Functions of the extrapyramidal system:
Providing complex automated movements (crawling, swimming, running, walking, spitting, chewing and others);
Maintaining muscle tone and its redistribution during movement;
Participation in speech articulation and facial expressive movements;
Maintaining the segmental apparatus in readiness for action.
25. Limbic system.
Limbic system– a nonspecific brain system associated with the olfactory analyzer, the main function of which is the organization of holistic behavior and the integration of physiological activity processes.
Functions of the limbic system:
Emotional and motivational behavior and adaptation to external and internal environmental conditions;
Complex forms of behavior: instincts, food, sexual, defensive, changes in phases of sleep and wakefulness;
Regulatory influence on the cortex and subcortical formations to establish the necessary correspondence of activity levels.
Composition of the limbic system:
Cortical structures: limbic lobe (cingulate, parahippocampal, dentate and ribbon gyri) and hippocampus;
Subcortical formations: the basal part of the telencephalon, structures of the diencephalon (papillary bodies, leash nuclei), parts of the midbrain (interpeduncular nucleus, central gray matter) and pathways that provide communication between these structures.
Features of the limbic system– the formation of bilateral connections between the nuclei and many closed circles of different diameters and lengths (large and small).
Greater limbic circle:
Compound: hippocampus - fornix - mammillary bodies of the hypothalamus - mastoid-thalamic fasciculus of Vic-d'Azir - anterior nuclei of the thalamus - thalamic cingulate radiation - cingulate gyrus - parahippocampal gyrus - hippocampus.
Function: ensuring memory and learning processes.
Small limbic circle:
Compound: amygdala – hypothalamus – reticular formation of the midbrain – amygdala.
Function: regulation of aggressive-defensive, eating and sexual behavior.
26. Regularities in the structure of motor pathways .
Descending, Efferent, Motor, Conscious (Tr. Cortico...), Reflexcore (from subcortical formations).
Among the tracts there are Main PyramidPath, which consists of 3 paths. The first passes from neurons of the precentral gyrus to motor neurons concentrated in the nuclei of the brain stem - this corticonuclearpath. Two other paths: corticospinal front and side go from the precentral gyrus to the nuclei of the anterior horns of the spinal cord. The fibers of each tract cross over in different parts of the brain.
Corticonuclear path of conscious movements crosses over the cranial nerve nuclei in the brain stem. It includes two neural reflex arcs.
Lateral and anterior corticospinal tracts also conduct conscious impulses. The lateral tract crosses at the border of the medulla oblongata and spinal cord, forming pyramidal cross. The anterior tract is crossed at the spinal cord.
Corticopontine-cerebellar the path crosses in the pons at the level of the middle cerebellar peduncles. The first motor neurons are located in the cortex of the frontal, temporal, parietal and occipital lobes. They conduct their axons through the internal capsule (knee). The second neurons lie in the motor nuclei of the pons and the cortex of the cerebellar hemispheres. Axons from the cerebellum exit through the middle peduncle to the motor nuclei of the pons, where they switch.
Descending extrapyramidal tracts of unconscious movements belong to the ancient ways, and they always begin in the subcortical structures of the brain. Their reflex arcs have a two-neuron composition and crossovers at different levels of the brain. Some of them run along only one side, without forming crosses.
Red nuclear spinal the pathway regulating and coordinating muscle tone and automatic muscle contractions crosses in the midbrain.
vestibulospinal way of balance and coordination of movements.
Tectospinal tract visual-auditory unconditioned reflexes.
Olive-spinal automatic way muscle tone A.
Posterior longitudinal fasciculus- a way to coordinate the movements of the eyeballs, head and neck.
The fibers of the bundle connect the motor nuclei with each other III, IV, VI pairs of cranial nerves and the nuclei of the anterior horns of the spinal cord of the cervical and thoracic regions.
Characteristics of pyramidal tracts.
Pyramid – Tractuspyramidalis(volitional, conscious) conduct impulses from the cortex to the motor nuclei and further to the muscles. They are divided into: fibrae corticospinales And fibrae corticonucleares
Fibrae (tractus) corticospinalis
1 neuron – giant pyramidal cell (Betsa) – neuron of the fifth layer of the cortex of the precentral gyrus
The pathways pass through the internal capsule in its posterior limb just behind the knee.
In the midbrain, the fibers of the pathway are located in the cerebral peduncles, in their middle part.
In the pons area - fibers pass in the ventral part of the pons
In the medulla oblongata - in the pyramids.
At the border with the spinal cord, 85% of the tracts cross (decussatio pyramidum), the remaining 15% go into the spinal cord without crossing and pass to the opposite side in the corresponding segment of the spinal cord.
2 neuron – cell of the motor nucleus of the anterior horn of the spinal cord.
The axon of the second neuron passes as part of the anterior root, cord and branches of the spinal nerve to the skeletal muscle.
Fibrae (tractus) corticonuclearis (corticobulbaris)
1 neuron - giant pyramidal cell (Betz) of the fifth layer of the cortex in the precentral gyrus
The path passes through the knee of the internal capsule
2 neuron – cells of the somatic motor nuclei of cranial nerves
The axon of the second neuron passes as part of the cranial nerve to the muscle
The path gives branches to its own and the opposite side, with the exception of the nuclei of X11 and V11 pairs of cranial nerves
Characteristics of motor extrapyramidal pathways.
Extrapyramidal The pathways carry impulses to the muscles from the subcortical centers: the basal nuclei of the hemispheres, the dorsal (optic) tubercle, the red nucleus, the substantia nigra, the olive nuclei, the nuclei of the vestibular nerve, the reticular formation. The extrapyramidal system automatically maintains the tone of skeletal muscles and ensures the work of antagonist muscles. The extrapyramidal tracts include: tractus rubrospinalis, tractus tectospinalis, tractus reticulospinalis, tractus olivospinalis, tractus vestibulispinalis. The tracts begin in the corresponding subcortical nuclei (1 neuron). The axons of the first neurons, having previously made the transition to the opposite side, switch to the motor cells of the anterior horns of the spinal cord, the processes of which end in the skeletal muscles. The extrapyramidal system also includes the cortical-cerebellar correlation pathways (tractus cortico-ponto - cerebello - dentato - rubro - spinalis.
Fundamental morphological differences between central and peripheral paralysis.
PARALYSIS - complete loss of motor functions with lack of muscle strength.
Paresis– weakening of motor functions with a decrease in muscle strength.
Paralysis and paresis develop as a result of various pathological processes (trauma, hemorrhage, etc.) in the central or peripheral part of the nervous system.
Central paralysis
1.Muscle groups are diffusely affected; there is no damage to individual muscles. Moderate atrophy
2. Spasticity with increased tendon reflexes
3. Extensor plantar reflex, Babinski's symptom
4. There are no fascicular twitches
Peripheral paralysis
1.Individual muscles may be affected
2. Severe atrophy, 70-80% of the total mass
3. Lethargy and hypotonia of the affected muscles with loss of tendon reflexes. Plantar reflex, if evoked, is of the normal, flexion type.
4. There may be fasciculations; Electromyography reveals a decrease in the number of motor units and fibrillation
Regularities in the structure of sensitive pathways.
Ascending, Centripetal, Afferent, Sensitive (...), Conscious (to the cortex), reflex.
Characteristics of conscious afferent pathways.
Proprioceptive pathways of cortical direction
Fasciculus gracilis (Goll) and fasciculus cuneatus (Burdach).
1 neuron
The axon as part of the dorsal root goes to the spinal cord, without entering the gray matter of the dorsal horn, lies in the dorsal funiculi and goes to the medulla oblongata (tractus gangliobulbaris)
2 neuron - nucleus gracilis et nucleus cuneati lies in the same-named tubercles of the medulla oblongata
The axons of the second neurons bend ventrally and move to the opposite side, giving rise to the formation of the medial loop
(Lemniscus medialis – tractus bulbothalamicus)
3 neuron – cells of the lateral nucleus of the dorsal (optic) thalamus
The processes of the third neurons (tractus thalamocorticalis) pass through the posterior leg of the internal capsule and reach the precentral and postcentral gyri (cells of the fourth layer of the cortex).
Characteristics of reflex afferent pathways.
Proprioceptivewayscerebellardirections
Tractus spinocerebellaris anterior (Gowers) et spinocerebellaris posterior (Flechsig)
1 neuron – pseudounipolar cell of the spinal ganglion
The dendrite of the first neuron ends with a receptor in muscles, tendons, ligaments, joints
The axon as part of the dorsal root enters the gray matter of the spinal cord and switches to the body of the second neuron
2 neuron: for Gowersa – nucleus intermediomedialis
for Flechsiga - nucleus thoracicus
The axons of the second neuron of the Gowersa pathway through the anterior white commissure are directed to the lateral funiculus of the opposite side, ascend to the medulla oblongata, the pons, and in the superior medullary velum pass to the opposite side and reach the vermis cortex through the superior cerebellar peduncle. The axons of the second neuron of the Flechsiga pathway are directed to the lateral cord of the same side, ascend into the medulla oblongata and reach the vermis cortex through the inferior cerebellar peduncle.
Medial loop.
A bundle of white matter fibers formed by the axons of the gracilis and cuneate nuclei conducts the conscious proprioceptive pathways and the pathways of general sensitivity, because the spinothalamic tracts join it.
Commissural nerve fibers of the brain, their structure.
Commissural nerve fibers connect similar areas of the two hemispheres. The nerve fibers of the brain are divided into associative, commissural and projection - they all form pathways for nerve impulses. Association fibers connect cells within one hemisphere, and in the spinal cord - at the level of one half. Commissural fibers connect the right and left hemispheres, the right and left halves of the spinal cord. Projection fibers connect higher and lower brain structures: cortical cells with nuclear cells and organs. They are divided into ascending (sensory) and descending (motor) pathways or tracts.
Commissural fibers, which are part of the so-called cerebral commissures, or commissures, connect the symmetrical parts of both hemispheres. The largest cerebral commissure is the corpus callosum, corpus callosum , connects the parts of both hemispheres related to neencephalon .
Two brain adhesions comissura anterior And comissura inferior , much smaller in size, belong to rhinencephalon and connect: comissura anterior - olfactory lobes and both parahippocampal gyri, comissura fornicis - hippocampi.
Under the corpus callosum is the so-called fornix, forniх , representing two arched white cords, which, in their middle part, corporis fornicis , are connected to each other, and diverge in front and behind, forming pillars of the vault in front, columnae fornicis , behind are the legs of the arch, crura fornicis . Crura fornicis , heading back, descend into the lower horns of the lateral ventricles and pass there into fimbria hippocampi . Between crura fornicis under splenium corporis callosi transverse bundles of nerve fibers extend, forming commissura fornicis . The anterior ends of the arch columnae fornicis , continue down to the base of the brain, where they end in corpora mamillaria passing through gray matter hypothalamus . Columnae fornicis limit the interventricular foramina lying behind them, connecting the third ventricle with the lateral ventricles. In front of the columns of the arch is the anterior commissure, commissura anterior , having the appearance of a white transverse crossbar consisting of nerve fibers. Between the front of the arch and genu corporis callosi a thin vertical plate of brain tissue is stretched - a transparent septum, septum pellucidum , in the thickness of which there is a small slit-like cavity, cavum septi pellucidi .
Morphological basis of alternating syndrome.
Alternating syndromes- syndromes that combine damage to the craniocerebral nerves on the side of the lesion with conduction disorders of motor and sensory functions on the opposite side.
They occur when the anatomical components of the brain stem are damaged: the cerebral peduncles - pedincular crossed syndromes, the pons - pontine syndrome, the medulla oblongata - bulbar. These also include crossed hemiplegia - damage to the pyramidal pathway that crosses at different levels of the brain. Therefore, for example, paralysis or paresis of the right arm and left leg occurs with lesions below the brain stem. With opposite hemianesthesia, the ascending pathways are damaged: spinothalamic and bulbothalamic rhythms, fibers of the medial lemniscus.
(21 Votes)The normal functioning of the extrapyramidal system and the cerebellum in humans is the basis on which the formation of a voluntary motor act is based. Damage to the extrapyramidal system or cerebellum causes a variety of motor disorders, knowledge of which is an indispensable condition in the training of a neurologist.
Anatomy and physiology of the cerebellum.
The cerebellum lies in the posterior cranial fossa. The weight of the cerebellum is 120–150 g. The middle part of the cerebellum is called the vermis. On either side of it lie the cerebellar hemispheres - right and left. The cerebellum is divided into convolutions by parallel arcuate grooves. Phylo- and ontogenetically, the cerebellum is divided into ancient (treg, nodule), old (worm) and new (hemispheres). The cerebellum has three pairs of peduncles. The upper pair of legs connects the cerebellum with the midbrain, the middle one with the pons, and the lower one with the medulla oblongata. The peduncles consist of nerve fibers that carry impulses to or away from the cerebellum. In the depths of the cerebellum, the gray matter forms nuclei: dentate, cork-shaped, spherical, and also the tent nucleus.
The cerebellum performs the function of automatic coordination of movements, participates in the regulation of muscle tone and body balance. In the implementation of voluntary movement, the main role of the cerebellum is to coordinate the fast (phasic) and slow (tonic) components of the motor act. This becomes possible thanks to the bilateral connections of the cerebellum with the muscles and cerebral cortex. The cerebellum receives afferent impulses from all receptors that are stimulated during movement (from proprioceptors, vestibular, visual, auditory, etc.). Receiving information about the state of the motor system, the cerebellum influences the red nuclei and reticular formation, which sends impulses to the gamma motor neurons of the spinal cord, which regulate muscle tone. In addition, part of the afferent impulses enters the motor zone of the cerebral cortex through the cerebellum.
However, the main function of the cerebellum appears to occur at the subcortical level (brain stem, spinal cord). Efferent impulses from the cerebellar nuclei regulate proprioceptive stretch reflexes. Many symptoms of cerebellar dysfunction are associated with impaired reciprocal innervation of antagonists.
The main afferent and efferent connections of the cerebellum: Flexig's pathway (posterior spinocerebellar), uncrossed; Govers' pathway (anterior spinocerebellar), crossing twice; frontopontocerebellar tract; occipito-temporo-cerebellar tract.
The existing crossovers of the cerebellar afferent and efferent systems lead to a homolateral connection of one hemisphere of the cerebellum and the limbs. Therefore, when the cerebellar hemisphere or the lateral columns of the spinal cord are damaged, cerebellar disorders are observed on their half of the body.
The cerebral hemispheres are connected to the opposite hemispheres of the cerebellum. In this regard, when the brain or red nuclei are affected, cerebellar disorders are observed on the opposite half of the body.
There is a certain somatotopy in the cerebellum. It is believed that the cerebellar vermis is involved in the regulation of the muscles of the trunk, and the cerebral cortex - the distal parts of the limbs. As a result, a distinction is made between static and dynamic ataxia.
Symptoms of defeat.
A) Static ataxia.
Mostly standing and walking are upset. The patient stands with his legs wide apart and sways. The gait resembles that of a drunk. Turning is especially difficult. In the Romberg position, the patient sways or cannot stand at all with his feet together. This is observed both with open and closed eyes. When a patient tries to lean back while standing, there is no flexion in the knee joints and in the lumbar spine observed in healthy people. Asynergia appears (Babinsky test, Stewart-Holmes “reverse push” absence syndrome).
B) Dynamic ataxia.
The performance of various voluntary movements of the limbs is impaired. This type of ataxia depends mainly on damage to the cerebellar hemispheres. When performing the finger-nose test, overshooting and intention tremor are observed. During the heel-knee test, the patient does not hit the knee with the heel; the heel slides to the side when passed along the shin. Missing, slipping of the heel from the shin occurs in the patient both with open and closed eyes. Adiadochokinesis and hypermetria are observed.
In addition to impaired movement in the limbs, when the cerebellar systems are damaged, other simple and complex motor acts are also disrupted: speech (bradylalia, scanned speech), handwriting (megalography), nystagmus. In patients with cerebellar damage, muscle hypotonia is also observed.
Coordination of movements is impaired when the frontal and temporal lobes and their conductors are affected. In such cases, walking and standing are disrupted, the torso deviates back and in the direction opposite to the lesion (astasia-abasia). Missing in the arm and leg is detected - hemiataxia.
Research methodology.
Study of walking, stability in the Romberg position, Babinski test, Stewart-Holmes test, coordination tests, diadochokinesis, speech impairment, the presence of nystagmus, changes in muscle tone.
Extrapyramidal system, symptoms of damage.
Numerous reflex mechanisms that operate automatically play a significant role in ensuring voluntary human motor skills. This large complex of nerve structures is called the extrapyramidal system. The extrapyramidal system includes: the globus pallidus and the striatum, consisting of the putamen and the caudate nucleus. The caudate nucleus and putamen together constitute the neostriatum, while the globus pallidus is the paleostriatum. The division into two different nuclei is based both on the different times in which these formations appeared in phylogenesis and their inclusion in action in ontogenesis, and on the differences in their histological structure. In addition, the extrapyramidal system includes the subthalamic nuclei of Lewis, the substantia nigra, the red nuclei, the optic thalamus, the reticular formation, the vestibular nuclei of Deiters, the dentate nucleus of the cerebellum, the inferior olives, and the nuclei of Darkshevich. Currently, the extrapyramidal system includes large areas of the cerebral cortex (especially the frontal lobes), which are closely connected with the above formations. The listed components of the extrapyramidal system have numerous connections. The latter form closed neural circles that unite numerous extrapyramidal formations of the brain stem and cerebral hemispheres into single functional systems. From the cortex of the lateral, medial and inferior surfaces of the frontal lobe, fibers are sent to the homolateral ganglia and nuclei of the brain stem.
The caudate nucleus, putamen, and globus pallidus are connected to the underlying cells of the brain stem, in particular, to the reticular formation. From the nuclei of the brain stem, bundles of fibers originate, representing a collection of axons of the corresponding nerve cells. These bundles pass in the cords of the spinal cord and end in synapses with the cells of the anterior horns of the spinal cord at different levels. These include: the reticulospinal tract, olivospinal, rubrospinal, tectospinal fascicles, as well as the medial longitudinal fasciculus. It must be assumed that descending impulses from the substantia nigra are sent to the motor neurons of the spinal cord, probably through the reticulospinal tract.
Thus, the extrapyramidal system is a long column of cells with many nerve fibers throughout the brain and spinal cord. This column in some places sharply increases in volume (subcortical nodes, at some levels a dense interweaving of fibers with cell bodies is formed (globus pallidus, reticular substance)).
The discovery of the functional significance of the extrapyramidal system was facilitated by clinical and anatomical observations. The clinical picture of hyperkinesis, hypokinesis, and muscle tone disorders was described. Previously, the concept was put forward that hypokinesia depends on damage to the globus pallidus, and hyperkinesis is associated with damage to the caudate nucleus and putamen. However, recently, such a mechanism for the occurrence of hypo- and hyperkinesis has been rejected. It has been found that extrapyramidal disorders can occur both with damage to the cerebral cortex and with damage to the brainstem.
The principle of a neural ring, which is closed using a feedback channel, is currently recognized as the main one in organizing the activity of the central nervous system.
The extrapyramidal system is involved in the formation of muscle tone and posture, as if preparing the skeletal muscles to perceive excitatory and inhibitory impulses at every moment. A disruption in one of the links regulating the activity of the extrapyramidal system can lead to rigidity and the development of hypo- or hyperkinesis.
A topical diagnosis must be established based on an analysis of a complex of disorders of various functions of the extrapyramidal system.
Syndromes of damage to the extrapyramidal system.
1. Parkinsonism (hypertensive hypokinetic syndrome). This syndrome is characterized by:
- low motor activity of the patient - oligokinesia (the face has a mask-like appearance, the gaze is motionless, poor gesticulation). The torso is tilted forward, the arms are slightly bent at the elbow joints, pressed to the body. There is a tendency to freeze in one, even uncomfortable, position;
- active movements are performed very slowly - bradykinesia (the patient walks in small steps, there are no friendly movements of the arms when walking);
- propulsions are observed;
- muscle rigidity (cogwheel symptom);
- the presence of hyperkinesis in the form of trembling (rhythmic tremor in the fingers, reminiscent of counting coins or rolling pills).
In a more pronounced form, the above symptoms occur with lesions in the upper parts of the brain stem (involvement of the substantia nigra).
Muscle rigidity is caused by insufficient levels of dopamine in the caudate nucleus, where it comes from the substantia nigra. As a result, the facilitating influences coming from the premotor cortex and globus pallidus to the motor neurons of the spinal cord are enhanced, which is accompanied by an increase in the tonic reflex.
Other symptoms of parkinsonism include autonomic disorders and mental disorders.
2. Extrapyramidal hyperkinesis.
A) Chorea (hypotonic hyperkinetic syndrome) is characterized by erratic involuntary movements with a pronounced locomotor effect; it occurs in various parts of the body both at rest and during voluntary motor acts. The movements resemble expedient, although exaggerated, actions. They are compared to dancing, clowning around. With this hyperkinesis, a decrease in muscle tone is often observed.
B) Athetosis (unstable) - this hyperkinesis is characterized by slow tonic muscle contractions, which outwardly resemble worm-like movements of a slow rhythm. They arise at rest and intensify under the influence of emotions. These periodically occurring muscle spasms are most often localized in the distal parts of the arms. Athetosis can be bilateral. Athetosis differs from chorea by slower movements and usually less widespread. Sometimes difficulty arises in distinguishing these hyperkinesis, then they speak of choreoathetosis. Athetosis can be observed with damage to various parts of the extrapyramidal system.
B) Torsion dystonia. In patients, especially during active movements, there is an incorrect distribution of muscle tone in the trunk and limbs. Outwardly, this is expressed by the fact that when walking, corkscrew-like violent movements appear in the torso and limbs. Torsion-dystonic hyperkinesis may be limited to any part of the muscular system, for example, with spastic torticollis. Torsion dystonia occurs when various parts of the extrapyramidal system (basal ganglia, brain stem cells) are affected.
D) Hemiballism. This rare type of hyperkinesis is localized on one side of the body, the arm suffers more. In single cases, both sides are captured, then they talk about paraballism. Hyperkinesis manifests itself through fast, sweeping movements of large volume, reminiscent of throwing or pushing a ball. This clinical picture is described with damage to the Lewis nucleus.
D) Myoclonus - fast paced, usually random contractions of various muscles or their parts. A small amplitude and simultaneous contraction of antagonistic muscle groups do not lead to a pronounced locomotor effect.
E) Tic – rapid involuntary muscle contractions. Unlike functional (neurotic) tics, tics of extrapyramidal origin are distinguished by their consistency and stereotypy.
G) Other hyperkinesis: facial spasm, tonic gaze convulsion, myoclonus-epilepsy.
The term “extrapyramidal system” refers to subcortical and brainstem extrapyramidal formations and motor pathways that do not pass through the pyramids of the medulla oblongata. Part of this system are also those bundles that connect the cerebral cortex with the extrapyramidal gray structures: the striatum, the red nucleus, the substantia nigra, the cerebellum, the reticular formation and the tegmental nuclei of the trunk. In these structures, impulses are transmitted to intercalary nerve cells and then descend as tegmental, red-nuclear spinal, reticular and vestibular spinal and other pathways to the motor neurons of the anterior horns of the spinal cord. Through these pathways, the extrapyramidal system influences spinal motor activity. The extrapyramidal system, consisting of projection efferent nerve pathways starting in the cerebral cortex, including the nuclei of the striatum, some nuclei of the brain stem and the cerebellum, regulates movements and muscle tone. It complements the cortical system of voluntary movements; voluntary movements become prepared, finely tuned for execution.
The pyramidal tract (via interneurons) and fibers of the extrapyramidal system ultimately meet on the anterior horn motor neurons, alpha and gamma cells, and influence them through both activation and inhibition.
The extrapyramidal system is phylogenetically more ancient (especially its pallidal part) compared to the pyramidal system. With the development of the pyramidal system, the extrapyramidal system moves into a subordinate position.
The extrapyramidal system consists of the following main structures: the caudate nucleus, the putamen, the lentiform nucleus, the globus pallidus, the subthalamic nucleus, the substantia nigra and the red nucleus. The lower order level of this system is the reticular formation of the tegmentum of the brain stem and the spinal cord. With the further development of the animal world, the paleostriatum (globus pallidus) began to dominate these structures. Then, in higher mammals, the neostriatum (caudate nucleus and putamen) takes on a leading role. As a rule, phylogenetically later centers dominate over earlier ones. This means that in lower animals the innervation of movements belongs to the extrapyramidal system. A classic example of "pallidar" creatures is fish. In birds, a fairly developed neostriatum appears. In higher animals, the role of the extrapyramidal system remains very important, despite the fact that as the cerebral cortex develops, phylogenetically older motor centers (paleostriatum and neostriatum) are increasingly controlled by a new motor system, the pyramidal system.
The striatum is the leading center among the structures that make up the extrapyramidal system. It receives impulses from various areas of the cerebral cortex, especially from the frontal motor cortex, which includes fields 4 and 6. These afferent fibers are organized in a somatotopic projection, run ipsilaterally and are inhibitory in their action. Another system of afferent fibers coming from the thalamus also reaches the striatum. From the caudate nucleus and the putamen of the lentiform nucleus, the main afferent fibers are directed to the lateral and medial segments of the globus pallidus, which are separated from each other by the internal medullary plate. There are connections going from the ipsilateral cerebral cortex to the substantia nigra, red nucleus, subthalamic nucleus, and reticular formation.
The caudate nucleus and the shell of the lentiform nucleus have two “channels” of connections with the substantia nigra. On the one hand, nigrostriatal afferents are described as dopaminergic and reducing the inhibitory function of the striatum. On the other hand, the strionigral pathway is GABAergic and has an inhibitory effect on dopaminergic nigrostriatal neurons. These are closed feedback loops. GABAergic neurons, via gamma neurons in the spinal cord, control muscle tone.
All other efferent fibers of the striatum pass through the medial segment of the globus pallidus. They form rather thick bundles of fibers. One of these bundles is called the lenticular loop. Its fibers begin in the ventral part of the medial segment of the pallidum and run ventromedially around the posterior limb of the internal capsule to the thalamus and hypothalamus, and also reciprocally to the subthalamic nucleus. After crossing, they connect to the reticular formation of the midbrain, from which a chain of neurons forms the reticular spinal tract (descending reticular system), ending in the cells of the anterior horns of the spinal cord.
The main part of the efferent fibers of the globus pallidus goes to the thalamus. This is the pallidothalamic fascicle, or Trout area H1. Most of its fibers end in the anterior nucleus of the thalamus, which projects to cortical area 6. Fibers starting in the dentate nucleus of the cerebellum end in the posterior nucleus of the thalamus, which projects to cortical area 4. All these thalamocortical connections transmit impulses in both directions. In the cortex, thalamocortical pathways synapse with corticostriatal neurons and form feedback rings. Reciprocal (coupled) thalamocortical connections facilitate or inhibit the activity of cortical motor fields.
The fibers of the basal ganglia that descend to the spinal cord are relatively few in number and reach the spinal cord only through a chain of neurons. This pattern of connections suggests that the main function of the basal ganglia is to control and regulate the activity of motor and premotor cortical fields, so that voluntary movements can be performed smoothly, continuously.
The pyramidal tract begins in the sensorimotor area of the cerebral cortex (fields 4, 1,2, 3). These are at the same time the fields in which the extrapyramidal motor pathways begin, which include corticostriatal, corticorubral, corticonigral and corticoreticular fibers going to the motor nuclei of the cranial nerves and to the spinal motor nerve cells through descending chains of neurons.
Most of these cortical connections pass through the internal capsule. Consequently, damage to the internal capsule interrupts not only the fibers of the pyramidal tract, but also the extrapyramidal fibers. This break is the cause of muscle spasticity.
Semiotics of extrapyramidal disorders. The main signs of extrapyramidal disorders are disorders of muscle tone (dystonia) and involuntary movements (hyperkinesis, hypokinesis, akinesis), which are absent during sleep. Two clinical syndromes can be distinguished. One of them is characterized by a combination of hyperkinesis (automatic violent movements due to involuntary muscle contractions) and muscle hypotonia and is caused by damage to the neostriatum. The other is a combination of hypokinesis and muscle hypertension or rigidity and is observed when the medial part of the globus pallidus and substantia nigra are affected.
Akinetic-rigid syndrome (syn.: amyostatic, hypokinetic hypertonic, pallidonigral). This syndrome in its classical form is found in shaking palsy, or Parkinson's disease. The pathological process in this disease is degenerative, leading to the loss of melanin-containing neurons of the substantia nigra. The lesions in Parkinson's disease are usually bilateral. With unilateral cell loss, clinical signs are observed on the opposite side of the body. In Parkinson's disease, the degenerative process is hereditary. Similar loss of substantia nigra neurons may be due to other causes. In such cases, shaking palsy is referred to as Parkinson's syndrome or parkinsonism. If it is a consequence of encephalitis lethargica, it is called postencephalitic parkinsonism. Other conditions (cerebral atherosclerosis, typhus, cerebral syphilis, primary or secondary involvement of the midbrain due to tumor or injury, intoxication with carbon monoxide, manganese and other substances, long-term use of phenothiazine or reserpine) can also cause parkinsonism.
Clinical manifestations of akinetic-rigid syndrome are characterized by three main signs: hypokinesia (akinesis), rigidity and tremor. With hypokinesia, the patient's mobility slowly decreases. All facial and expressive movements gradually disappear or slow down sharply. Starting movement, such as walking, is very difficult. The patient first takes several short steps. Having started moving, he cannot suddenly stop and takes a few extra steps. This continued activity is called propulsion. The facial expression becomes mask-like (hypomimia, amymia). Speech becomes monotonous and dysarthric, which is partly caused by tongue rigidity and tremor. The body is in a fixed flexion position of anteflexion, all movements are extremely slow and incomplete. Hands are not involved in the act of walking (acheirokinesis). All facial and friendly expressive movements characteristic of the individual are absent.
In contrast to spastic increases in muscle tone, rigidity can be felt in the extensors as a “waxy” resistance to all passive movements. The muscles cannot be relaxed. With passive movements, you can feel that the muscle tone of the antagonists decreases stepwise, inconsistently (gear wheel symptom). The raised head of a lying patient does not fall if suddenly released, but gradually falls back onto the pillow (head fall test). In contrast to the spastic state, proprioceptive reflexes are not increased, and pathological reflexes and paresis are absent. It is difficult to evoke reflexes and impossible to strengthen the knee reflex with the Jendrasik maneuver.
Most patients exhibit passive tremor of low frequency (4–8 movements per second). Passive tremor is rhythmic and results from the interaction of agonists and antagonists (antagonistic tremor). In contrast to intention tremor, antagonistic tremor stops during goal-directed movements. Rolling pills or counting coins are signs characteristic of parkinsonian tremor.
The mechanism that causes the appearance of the three listed signs is not fully understood. Akinesis may be associated with loss of dopaminergic transmission of impulses to the striatum. Akinesis can be explained as follows: damage to the neurons of the substantia nigra causes the loss of the influence of inhibitory descending nigroreticulospinal impulses on Renshaw cells. Renshaw cells having a connection with large ones? motor neurons, their inhibitory effect reduces the activity of the latter, which makes the onset of voluntary movement more difficult.
Rigidity may also be explained by loss of substantia nigra neurons. Normally, these neurons have an inhibitory effect on the impulses of the striatum, which in turn inhibit the globus pallidus. Their loss means that efferent pallidal impulses are not inhibited. The descending tract of the globus pallidus forms synapses with reticulospinal neurons; which facilitate the action of interneurons in the circuit of the tonic stretch reflex. In addition, impulses emanating from the medial part of the globus pallidus reach through the thalamic nuclei of area 6a and, through corticospinal fibers, also have a facilitating effect on interneurons in the circuit of the tonic stretch reflex. There is a disturbance in muscle tone called rigidity.
If the efferent cells and fibers of the globus pallidus are destroyed by stereotactic surgery in its medial part or the region of the lenticular loop, or the thalamic nucleus, rigidity decreases.
Stereotactic coagulation operations of the medial part of the globus pallidus, pallidothalamic fibers or dentatothalamic fibers and their terminal thalamic nucleus are indicated in some patients.
Hyperkinetic hypotonic syndrome. Develops when the striatum is damaged. Hyperkinesis is caused by damage to the inhibitory neurons of the neostriatum, the fibers of which go to the globus pallidus and the substantia nigra. In other words, there is a violation of higher-order neuronal systems, which leads to excessive excitation of neurons in lower-lying systems. As a result, hyperkinesis of various types occurs: athetosis, chorea, spastic torticollis, torsion dystonia, ballism, etc.
Athetosis is usually caused by perinatal damage to the striatum. It is characterized by involuntary slow and worm-like movements with a tendency to hyperextension of the distal parts of the limbs. In addition, there is an irregular, spastic increase in muscle tension in agonists and antagonists. As a result, the postures and movements are quite eccentric. Voluntary movements are significantly impaired due to the spontaneous occurrence of hyperkinetic movements, which can involve the face, tongue and thus cause grimaces with abnormal movements of the tongue. Spastic bursts of laughter or crying are possible. Athetosis can be combined with contralateral paresis. It can also be double-sided.
Facial paraspasm is a tonic symmetrical contraction of the facial muscles of the mouth, cheeks, neck, tongue, eyes. Sometimes blepharospasm is observed - an isolated contraction of the circular muscles of the eyes, which can be combined with clonic spasms of the muscles of the tongue and mouth. Paraspasm sometimes occurs during conversation, eating, or smiling. Intensifies with excitement and bright lighting. Disappears in sleep.
Choreic hyperkinesis is characterized by short, fast, involuntary twitches, randomly developing in the muscles and causing various types of movements, sometimes resembling voluntary ones. The distal parts of the limbs are involved first, then the proximal ones. Involuntary twitching of the facial muscles causes grimaces. In addition to hyperkinesis, a decrease in muscle tone is characteristic. Choreic movements with slow development can be a pathognomonic sign in Huntington's chorea and chorea minor, secondary to other brain diseases (encephalitis, carbon monoxide poisoning, vascular diseases). The striatum is affected.
Spasmodic torticollis and torsion dystonia are the most important dystonia syndromes. In both diseases, the putamen and centromedian nucleus of the thalamus, as well as other extrapyramidal nuclei (globus pallidus, substantia nigra, etc.) are usually affected. Spasmodic torticollis is a tonic disorder expressed in spastic contractions of the muscles of the cervical region, leading to slow, involuntary turns and tilts of the head. Patients often use compensatory techniques to reduce hyperkinesis, in particular supporting their head with their hands. In addition to other neck muscles, the sternocleidomastoid and trapezius muscles are especially often involved in the process.
Spasmodic torticollis may represent an abortive form of torsion dystonia or an early symptom of another extrapyramidal disease (encephalitis, Huntington's chorea, hepatocerebral dystrophy).
Torsion dystonia is characterized by passive rotational movements of the trunk and proximal limb segments. They can be so severe that the patient cannot stand or walk without support. The disease may be symptomatic or idiopathic. In the first case, birth trauma, jaundice, encephalitis, early Huntington's chorea, Hallerwarden-Spatz disease, hepatocerebral dystrophy (Wilson-Westphal-Strumpel disease) are possible.
Ballistic syndrome usually occurs in the form of hemiballismus. Manifested by rapid contractions of the proximal muscles of the extremities of a rotating nature. With hemiballismus, the movement is very powerful, strong (“throwing”, sweeping), since very large muscles contract. It occurs due to damage to the subthalamic nucleus of Lewis and its connections with the lateral segment of the globus pallidus. Hemiballismus develops on the side contralateral to the lesion.
Myoclonic jerks usually indicate damage to the area of the Guillen-Mollare triangle: red nucleus, inferior olive, dentate nucleus of the cerebellum. These are rapid, usually erratic contractions of various muscle groups.
Tics are rapid involuntary contractions of muscles (most often the orbicularis oculi muscle and other facial muscles).
Hyperkinesis presumably develops as a result of the loss of the inhibitory effect of the striatum on the underlying neuronal systems (globus pallidus, substantia nigra).
Pathological impulses go to the thalamus, to the motor cortex and then along efferent cortical neurons.
In elderly patients with cerebral atherosclerosis, one can often find signs of Parkinson-like disorders or hyperkinesis, especially tremor, a tendency to repeat words and phrases, final syllables of words (logoclonia) and movements (polykinesia). There may be a tendency toward pseudospontaneous movements, but true choreiform or athetoid movements are relatively rare. In most cases, symptoms are due to miliary and somewhat large necrotic lesions of the striatum and globus pallidus, which are found in the form of scars and very small cysts. This condition is known as lacunar status. The tendency to repetition and logoclonus is considered to be due to similar lesions of the caudate nucleus, and tremor - to the putamen.
Automated actions are complex motor acts and other sequential actions that occur without conscious control. Occurs with hemispheric lesions that destroy the connections of the cortex with the basal ganglia while their connection with the brain stem is preserved; appear in the limbs of the same name as the lesion.
Conscious muscle contraction is ensured by the pyramidal system. However, when performing one or another voluntary movement, a person does not think about which muscles need to be contracted at the moment. Ordinary movements, carried out thanks to the coordinated action of many muscles, are performed automatically, imperceptibly for attention, and the change in some muscle contractions by others is involuntary. The most advanced are automated movements. They are energetically stingy, optimal in volume, time, and energy consumption. The consistency, duration of muscle contractions, and perfection of movements are ensured by the extrapyramidal system, which, compared to the pyramidal system, is a phylogenetically more ancient motor-tonic apparatus. The extrapyramidal system creates the prerequisites for the performance of motor reactions, the background against which fast, precise, differentiated movements are carried out, prepares the muscles for action, and ensures the appropriate distribution of tone between different muscle groups. The extrapyramidal system is directly involved in the formation of a certain human posture, motor manifestations of emotions, and creates an individual expression of human movements. It ensures the execution of automated, learned motor stereotypes, as well as unconditional reflex protective movements.
1 - cerebral cortex; 2 - caudate nucleus; 3 - shell; 4 - globus pallidus; 5 - thalamus; 6 - lateral vestibular nucleus; 7 - reticular formation; 8 - roof of the midbrain; 9 - Darkshevich nucleus (medial longitudinal fasciculus); 10 - black substance; 11 - red core; 12 - subthalamic nucleus (Luysi); 13 - descending stem-spinal cord.
The extrapyramidal system includes numerous cellular structures located in the brain and spinal cord, as well as their afferent and efferent pathways.
The extrapyramidal system can be divided into four levels:
- cortical formations - premotor zones of the cerebral hemispheres;
- subcortical (basal) nuclei: caudate nucleus and lentiform nucleus, consisting of the putamen, medial and lateral globus pallidus;
- main stem structures: substantia nigra, red nuclei, reticular formation, subthalamic nucleus, nucleus of the medial longitudinal fasciculus (Darkshevich), vestibular nuclei, roof of the midbrain;
- the spinal level is represented by descending pathways ending near the cells of the anterior horns of the spinal cord. Next, extrapyramidal influences are sent to the muscles through the system of alpha and gamma motor neurons.
In evolutionary terms, according to morphological and functional features, the extrapyramidal system is divided into two parts - neostriate and palleostriatal (or pallidonigral). The neostriatal system (neostriatum) includes cortical structures, the caudate nucleus and the putamen. The palleostriatal system consists of the lateral and medial globus pallidus, substantia nigra, subthalamic nucleus, nucleus of the medial longitudinal fasciculus, vestibular nuclei, roof of the midbrain and some other structures. The neostriate and palleostriatal systems, functioning in concert and balancing each other, are conventionally combined into the striopallidal system. The neostriate system is younger than the palleostriatal system, both phylogenetically and ontogenetically. It is considered the highest subcortical regulatory and coordination center for organizing movements, a powerful inhibitory regulator of the motor system. It inhibits the palleostriatal system, which activates motor function.
The basal ganglia are the main structures of the extrapyramidal system. They have a large number of connections with other parts of the nervous system, ensuring the inclusion of extrapyramidal apparatuses in the system of voluntary movements. Afferent fibers carry information from the thalamus, cerebellum, and reticular formation. The neostriatal system receives afferent connections from many parts of the cerebral cortex, especially from the motor areas of the frontal lobe. Descending impulses from the extrapyramidal system through the structures of the midbrain and medulla oblongata (red nuclei, vestibular nuclei, reticular formation, quadrigeminal plate, motor nuclei of the cranial nerves) arrive at the segmental apparatuses, coordinating muscle tone and motor activity.
The functions of the extrapyramidal system are carried out due to the presence of neurotransmitters in its structures. The substantia nigra contains neurons that produce dopamine, which is formed into granules here. Dopamine travels through the dopaminergic nigrostriatal pathway to the caudate nucleus, where it is released in the synaptic apparatus. Dopamine inhibits the function of the caudate nucleus, blocking the production of the excitatory mediator acetylcholine by striatal cholinergic neurons. Thus, dopamine reduces the inhibitory effect of the caudate nucleus on motor skills. Dopamine also enters the limbic structures, hypothalamus, and frontal lobe of the brain, providing control over mood, behavior, and the onset of motor acts. A decrease in its content in these structures leads to an increase in the inhibitory effects of the caudate nucleus on motor activity with the occurrence of hypo- or akinesia, and emotional disorders. In addition, the caudate nucleus produces the inhibitory transmitter gamma-aminobutyric acid (GABA), which is transmitted through the gamkergic strionigral pathway to the substantia nigra and controls the synthesis of dopamine. There are other neurotransmitters in the structures of the extrapyramidal system - norepinephrine, serotonin, glutamic acid, neuropeptides. The function of all mediator systems is normally balanced; there is an equilibrium between them. When it is violated, various pathological clinical syndromes arise.
Damage to the substantia nigra and degeneration of the nigrostriatal pathway lead to a decrease in the synthesis and amount of dopamine, which is clinically manifested by the picture of hypertensive-hypokinetic syndrome, or parkinsonism. The syndrome received this name on behalf of the English physician James Parkinson (J. Parkinson, 1755-1824), who in 1817 described a hereditary disease with muscle rigidity, akinesia and tremor, which later became known as Parkinson's disease. Similar symptoms also occur after traumatic brain injury, carbon monoxide poisoning, manganese poisoning, after suffering from lethargic encephalitis and for other reasons. In such cases, it is called parkinsonism, indicating the etiology (toxic, postencephalitic, posttraumatic, etc.). With the development of parkinsonism, the effect of dopamine on the caudate nucleus decreases, which, as a result of an increase in cholinergic activity, is disinhibited and increases its inhibitory effect on motor activity. Hypokinesia, muscle rigidity and static trembling (tremor) occur. Hypokinesia or akinesia (poverty of movements) is manifested by a combination of symptoms - hypomimia, rare blinking, monotony of speech (bradylalia), micrographia, disappearance of friendly movements, especially in the hands while walking (acheirokinesis), a decrease in general motor activity, movement initiative, disruption of the process of inclusion in movement. In such cases, patients seem to freeze during movements, cannot immediately start walking, and mark time. When walking, they cannot stop immediately. The gait is slow, with small steps, shuffling, with a tendency to accelerate. While walking forward, the patient cannot suddenly stop; the torso seems to be ahead of the lower limbs, balance is disturbed and the patient may fall. This phenomenon is called propulsion. Also, the patient cannot suddenly stop while walking backwards (retropulsion) or to the side (lateropulsion).
Muscle rigidity that occurs with parkinsonism is characterized by an increase in muscle tone evenly in all muscle groups, similar to waxy or plastic rigidity. When performing passive movements in the limbs, a kind of intermittency, a stepwise stretching of the muscles, called the “gear wheel” symptom, is sometimes observed. General stiffness and increased muscle tone determine the patient’s characteristic posture: the head is tilted forward, the torso is bent, the arms are bent at the elbow joints (supplicant pose).
Trembling is small-rhythmic in nature, with a frequency of 4-5 vibrations per 1 s, occurs at rest, increases with excitement, decreases or disappears during sleep and voluntary movements. First, trembling appears in the hand of one hand (such as “counting coins” or “rolling pills”, “flexion-extension” of the fingers). As the disease progresses, it spreads along the hemitype, covers the head (like “yes-yes”) or becomes generalized. Autonomic disorders often occur in the form of increased salivation, greasiness of the skin, excessive sweating, and delayed bowel movements. Most patients with Parkinsonism experience mental disorders such as lack of initiative, lethargy, a characteristic peculiar viscosity, importunity, a tendency to repeat the same questions, depression, and in the later stages of the disease dementia (dementia) may occur.
Sometimes patients with parkinsonism experience paradoxical kinesia, when they can temporarily, due to a short decrease in muscle tone, quickly perform voluntary movements (dance, skate, etc.). This phenomenon, which has not yet found a definitive explanation, can be observed after waking up, during stressful situations. Patients with parkinsonism are characterized by the occurrence of so-called fixation rigidity, which leads to increased tonic postural reflexes (position reflexes). Their essence lies in the fact that the return to the starting position of a body part after a movement is disrupted. Thus, as a result of an increase in plastic tone in the muscles of the neck and proximal parts of the upper extremities, the head of a patient lying on his back, raised by the doctor, seems to freeze in this position, and then slowly lowers (the “air cushion” symptom). The leg of the patient lying on his stomach, passively bent at the knee joint, remains in this position even after the irritation stops, and slowly lowers. After sharp passive dorsiflexion of the foot, it maintains this position for some time.
To identify hidden extrapyramidal muscular hypertension, the Noika-Ganev test is used. When checking muscle tone in the upper limb by passive movements in the elbow joint, the patient is asked to raise his leg. Simultaneous raising of the lower limb leads to increased tone in the muscles of the arm.
Correction of neurotransmitter shifts in parkinsonism is carried out using anticholinergic drugs (cyclodol, parkopan, amizil) and drugs that stimulate dopaminergic transmission (L-Dopa, sinemet, nacom, madopar, parlodel, umex, midantan, simetrel, etc.).
The symptom complex of damage to the neostriatal system and its connections leads to excessive “facilitation” of movements, resulting in a hyperkinetic-hypotonic syndrome. The main manifestations of this syndrome are extrapyramidal hyperkinesis - a variety of involuntary, violent movements, diffuse or in a specific area of the body, which are combined with hypotension or muscle atony.
Varieties of extrapyramidal hyperkinesis are chorea, athetosis, torsion dystonia, hemiballismus, myoclonus, tic. Chorea is characterized by polymorphic, fast, irregular, erratic violent movements in various muscle groups, which intensify with excitement and disappear during sleep. Twitching of the facial muscles leads to grimaces, and the limbs lead to gesticulation. There is a disturbance in gait (the patient seems to be dancing), speech, and writing. The patient cannot keep his tongue out due to hyperkinesis of the tongue, sometimes he bites it, especially while simultaneously closing his eyes tightly. With significant muscle hypotonia (chorea mollis), reflexes are not evoked and pseudoparesis occurs. If muscle tone in the limbs is slightly reduced, tendon reflexes are preserved. Can be observed Gordon's sign-2. When the knee reflex is evoked, due to tonic tension of the quadriceps femoris muscle, the extended lower leg seems to freeze for a moment in an extended position, and can also perform several pendulum-like, gradually fading movements (pendulum symptom). Choreic hyperkinesis is observed with Huntington's chorea, minor chorea (Sydenham's chorea), and chorea of pregnant women.
Athetosis occurs as a result of tonic muscle spasms and is characterized by violent slow, worm-like movements in the distal limbs with a tendency to hyperextend them, as well as in the muscles of the face and tongue. Typical athetosis of the fingers, when each finger makes slow, elaborate movements independently, independently of the others. Athetosis in the facial muscles leads to the appearance of various grimaces, in the tongue - to unintelligible speech. Athetosis occurs as a result of a neuroinfection suffered in the prenatal period, with fetal asphyxia or a discrepancy between the Rh factor of the mother and the fetus.
Torsion dystopia is tonic spasms of various muscle groups, mainly the torso, which manifest themselves while walking. Hyperkinesis is elaborate, often rotating around the longitudinal axis of the body (corkscrew-shaped). In such patients, due to uneven muscle tension, curvature of the spine occurs. The onset of torsion dystonia can manifest itself in the form of torticollis, since the neck muscles are the first to be affected.
Hemiballismus is, as a rule, non-rhythmic, one-sided, rough, large-swinging movements of the limbs, usually the upper. Reminiscent of the flapping of a bird's wing. Occurs more often with vascular pathology in the subthalamic nucleus (Lewis body).
Myoclonus is short lightning-fast clonic twitching of individual muscles or their groups, so fast that there may be no movement of the limbs in space. Sometimes patients with myoclonus experience generalized seizures accompanied by dementia (myoclonus-epilepsy). Myoclonus occurs due to pathology of the cerebellar-red nuclear connections of the inferior olive and neostriatum. If myoclonus is constant, stereotypical, and has a clear localization, it is called myorhythmia. More often it occurs in the muscles of the face, tongue, pharynx, soft palate, and diaphragm.
Tic is a rapid contraction of individual muscle groups, creating various, usually stereotypical movements. The muscles of the neck and face suffer. The patient twitches his neck, as if adjusting his collar; throws his head back, as if straightening his hair, raises his shoulder, makes blinking movements, wrinkles his forehead, raises and lowers his eyebrows. In contrast to the neurotic, functional, unstable tic, the extrapyramidal tic is distinguished by its consistency and stereotyping.
Most hyperkinesis caused by damage to the extrapyramidal system disappear during sleep, and intensify with excitement and voluntary movements.
Clinically, hyperkinetic-hypotonic syndrome seems to be the opposite of parkinsonism syndrome. This antagonism is the result of the occurrence of opposite mediator shifts. Thus, with a hereditary disease - Huntington's chorea - a decrease in the amount of acetylcholine and GAM K, as well as enzymes responsible for their synthesis, was detected in the neostriatal system. The amount of dopamine is increased. Therefore, to treat patients with Huntington's chorea, drugs that suppress dopaminergic transmission are used - reserpine, aminazine, haloperidol, lithium preparations.
When studying the functions of the extrapyramidal system, the patient’s movements and posture, facial expressions, expressiveness of speech are assessed, muscle tone is checked, hyperkinesis, psycho-emotional disorders and autonomic disorders are identified.