The motor pyramidal path. Symptoms of defeat of the pyramidal pathway

Our brain is a unique multicomplex system that controls simultaneously sensory, vestibular apparatus, movement, thinking, speech, sight and much more.

In this article, let's talk about how the brain controls involuntary and involuntary movement. And about what kind of neurological abnormalities are associated with damage to the pyramidal system of the brain.

Pyramid and extrapyramidal path

The pyramidal system consists of pyramidal and extrapyramidal pathways. What is their difference? The pyramidal path, or tractus pyramidalis, is the path that connects neurons of the cortex responsible for motor activity, with nuclei of the spinal cord and cranial nerves. His job is to control arbitrary muscular movements, transmitting CNS signals to the body. But extrapyramidal, it controls the unconscious conditioned reflexes of our body. This is an older and deeper structure of the brain, and its signals are not displayed in consciousness.

Extrapyramidal and pyramidal - descending. And the ascending main ways are responsible for transmitting information from the senses to the brain. They include: a lateral dorsal-thalamic path, anterior spinal-cerebellar and posterior spinal-cerebellar.

Pyramidal ways of the brain. Structure

They are divided into 2 types: cortical-spinal and cortical-nuclear. Cork-spinal cord is responsible for the movement of the trunk, the cortical-nuclear controls the mimic and swallowing muscles.

What is the structure of the cortical and spinal pyramidal pathway? This electric path begins with the cortex of the brain, the region that is responsible for higher mental activity, for consciousness. The whole bark consists of interconnected neural networks. More than 14 billion neurons are concentrated in the cortex.

In the hemispheres, information is redistributed in this way: everything that concerns the operation of the lower extremities is in the upper divisions, and that, as for the upper ones, on the contrary, in the lower structures.

All signals from the upper and lower parts of the cortex are collected and transferred to the inner capsule. Then, through the middle brain and through the middle part of the bridge, a bundle of nerve fibers enters the pyramids of the medulla oblongata.

Here branching occurs: most of the fibers (80%) pass to the other side of the body and form a lateral spinal path. These branches "run" motoneurons, which then transmit the signals to contract or relax directly to the muscles. The smaller part of the fiber bundle (20%) innervates the motoneurons of its "own" side.

The cork-nuclear pyramid path first passes through the same brain structures as its "partner," but it crosses already in the middle brain and goes to the facial neurons.

Anatomical features important for diagnosis

The pyramidal pathway has some features of its structure that can not be overlooked when it is necessary to find out the localization of pathology. Which features do you need to know?

1. Part of the nerve fibers of the cortical and spinal cord, in addition to the lateral intersection, cross over in the region of the white spike of the segment of the spinal cord, where they end.
2. Most muscles of the trunk are controlled by both hemispheres of the brain. This is an important defense. In the case of a stroke or stroke, those patients who are diagnosed with hemiplegia can support the body vertically.
3. In the region of the brain bridge, the fibers of the cortical and spinal cord are separated by other fibers-the cerebellar pathway. Separate bundles emerge from the bridge. In this regard, motor disorders are often scattered. Whereas the pathological focus can be one.

The symptoms of the defeat of the pyramidal path are sometimes quite distinct, as in the case of paralysis of the lower extremities, for example. But it happens that it is difficult to establish the cause. It is important to notice small violations in motor skills on time and to see a doctor.

Symptoms of defeat. Levels

The clinical manifestations of the disturbance of the conductive pyramidal path depend on which department the nerve fibers are damaged. There are several levels of damage to motor activity: from complete paralysis to relatively favorable disorders.

So, neurology distinguishes the following levels of defeat of the pyramidal path:

1. Central monoparesis (paralysis). Disturbances are localized in the cerebral cortex (left or right).
2. Central hemiparesis. The inner capsule is damaged.
3. Various alternating syndromes-the area of the brainstem is affected.
4. Paralysis of the extremities. One of the lateral cord in the region of the spinal cord.

Central paralysis with damage to the capsule of the brain and the cerebral hemispheres is characterized by the fact that the work of the muscles is broken on the opposite side of the body relative to the area of the lesion. After all, the crossroad of the pyramidal path works in the nervous system. That is, the fibers pass to the lateral or lateral spinal path. A simplified diagram shows how the pyramid path, the anatomy of which was considered above, crosses and moves further.

If the lateral cord is damaged in the spinal cord, the muscles work on the same side as the damage.

Neuropathology. Peripheral and central Pallas

Nerve fibers under the microscope look like cords. Their work is extremely important for the body. If conductivity is impaired at some part of the nervous circuit, the muscles in some parts of the body will not be able to receive signals. This will cause paralysis. Paralysis is divided into 2 types: central and peripheral.

If one of the central motor nerves is broken in the "network", then there is a central paralysis. And with a problem with the peripheral motor nerve, paralysis will be peripheral.

With peripheral paralysis, the doctor observes a decrease in muscle tone and a strong decrease in muscle mass. Tendon reflexes will also be reduced or disappear altogether.

It is different with central paralysis. Then there is hyperreflexia, muscle tone is elevated, sometimes there are contractures.

Pyramidal insufficiency in newborns. Causes

Symptoms of impellent insufficiency in the child are strange twitchings, or it can walk differently than other children - on tiptoes; Or the stop is incorrect. The reasons for this condition in a child can be:

• Underdevelopment of the brain (spinal or head);
• Birth trauma, if the parietal lobe of the brain or the brain stem is damaged, the pyramidal pathway will be unambiguously broken;
• Hereditary diseases of the nervous system.
• Hypoxia;
• Cerebral hemorrhage after childbirth;
• An infection such as meningitis or arachnoiditis.

Treatment for adults is more often medicamentous. But for children it is much better to use methods such as exercise therapy, massage and vitamin intake. If there are no abscesses in the brain, no other serious injuries, by the first year of life the condition is improving.

Paresthesia and myoclonus

Violation in the cervical spine leads to paresthesia. This is neuropathy, which is characterized by a violation of sensitivity. A person can either lose touch sensitiveness of the skin, or feel tingling in the body. Paresthesia is treated with reflexology, manual therapy or physiotherapy. And, of course, you need to remove the underlying cause of neuropathy.

Another defeat of the pyramidal pathways and, consequently, motor activity is myoclonia - involuntary twitching.

Myoclonia are of several types:

• Rhythmic myoclonic contractions of a particular muscle group;
• Velopatamine contractions - sudden non-rhythmical contractions of the tongue or throat;
• Postural myoclonia;
• Cortical;
• Myoclonia in response to motor activity (in athletes).

Myoclonus or cortical myoclonia are diseases of the conduction pathway, the cause of which is a disorder in the motor centers of the brain. That is, at the very beginning of the pyramid path. If there is a "crash" in the cortex, the signals to the muscles are already distorted.

However, the causes of violations of the motor pyramidal path may be a lack of magnesium, and psycho-emotional or physical fatigue, and many other reasons. Therefore, the diagnosis should be made by a doctor after an MRI scan.

Diagnosis of violations

The descending pyramidal path is a projection, the ascendant path is the one that transmits the body signals through the spinal cord to the central nervous system. The descending, on the contrary, transmits brain signals to the neurons.

To determine which system is affected and how much, the neurologist examines a variety of parameters relating to muscles, joints, and nervous reflexes.

The doctor-neurologist carries out such diagnostic procedures:

• Explores the volume of movements of all joints;
• Checks deep reflexes, looks, whether there are pathological reflexes ;
• Checks the work of all facial nerves;
• Measures the electrical conductivity of muscles, their biopotentials;
• Examines muscular strength;
• And also is obliged to check whether pathological clonic contractions are present.

When a neurologist checks the volume of movements, he begins to examine the larger joints first, and then investigates the smaller ones. That is, first examines the shoulder joint, then the ulnar and wrist.

The defeat of the cortical-nuclear pathway

The pyramidal path is the basis of all the movements not only of the muscles of the body, but also of the face. Axons of various facial motoneurons transmit signals to the muscles. Let's consider more in detail Motoneurons of the double nucleus innervate the muscles of the pharynx, larynx, soft palate and even the upper esophagus muscle. Motoneurons of the trigeminal nerve are responsible for the work of some chewing muscles and those that give the signal to shrink the eardrum. Individual motoneurons shorten the muscles of the face when we smile or frown. These are mimic neurons. Another group of muscles is responsible for the movements of the eyes and eyelids.

The defeat of the leading neuron is reflected in the work of the muscles "subordinate" to it. This principle is based on the entire pyramid path. Neurology of the facial nerve leads to very unpleasant consequences. However, the movements of the eyeballs and swallowing are usually preserved.

It should be noted that the complete disconnection of the facial muscles from the controlling segment of the brain occurs only if both the right and left hemispheres are affected. Most facial neurons are controlled bilaterally, as well as the muscles of the trunk. One-sided crossed fibers go only to the lower part of the face, namely to the muscles of the tongue and lower jaw.

Defeat of motor cortex

When as a result of an injury motor zones in the cortex of one of the hemispheres are damaged, a person paralyzes one side. When both hemispheres are damaged, the paralysis is bilateral. If these centers experience overexcitation, local or centralized convulsions are caused. Frequent convulsions may indicate the development of epilepsy.

Symptoms of defeat of the pyramidal path at the level of the brainstem

Since at the level of the brainstem (oblong and variolic bridge) a fiber cross occurs, then in the defeat of these structures, the hemiplasia occurs already on the other half of the body. This symptom is called alternating paralysis.

The pyramid path is the basis of fine motor skills. Even if the trunk of the brain is slightly damaged, small movements of the fingers are severely affected.

There are many different syndromes that clearly and in detail characterize the disturbances affecting the work performed by the pyramidal path: the syndromes of Avellis, Schmidt, Wallenberg-Zakharchenko and others. According to the symptoms of these syndromes, the doctor can often determine the exact location of the disturbance of the pathway to the tests.