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Demyelinating diseases of the central nervous system.

Demyelinating diseases of the central nervous system are characterized by the predominant destruction of the myelin (Schwann) membrane with the relative preservation of the axon.

Schwann cells form the Schwann membrane, or neurolemma, surrounding the axons and dendrites of the peripheral nervous system, cell bodies in the sensory ganglia and nerve fibers in the white matter of the central nervous system. With an axon diameter of approximately 2 μm, the plasma membrane of a single Schwann cell cell wraps spirally (in the form of a roll with jam) a section of the axon several hundred microns long. In terms of chemical composition, myelin is a lipoprotein. Based on dry weight, the lipid content in myelin is 70–80%, and the protein is 20–30%. The main functions of myelin: trophic, conduction of a nerve impulse, supporting, barrier.

Myelin diseases are divided into two main groups - myelinopathy and myelinoplasty. Myelinopathies are genetically determined lesions characterized by biochemical defects in the synthesis of myelin. The basis of myelinoklastichesky (or actually demyelinating) diseases is the destruction of normally synthesized myelin under the influence of various influences, both external and internal. These groups are distinguished conditionally, since the manifestations of myelinopathies can be caused by external factors, and a genetic predisposition is probably important in the pathogenesis of myelinclasts.

Multiple sclerosis. The main demyelinating disease is multiple sclerosis (synonyms: multiple sclerosis, lamellar sclerosis, disseminated sclerosis). Clinically, the disease is characterized by a chronic, slowly progressing course. The foci of demyelination are unevenly located in the tissue of the brain and spinal cord, resulting in clinical diversity. The disease most often occurs in young people (20-30 years old), occurs much less frequently at an older age and very rarely in children. As a rule, the disease begins in the midst of full health, but often after the flu, sore throats that accelerate the development of the disease. Sometimes the clinical manifestations of multiple sclerosis provokes pregnancy.

The etiology and pathogenesis of the disease are unknown. A genetic predisposition is confirmed by an increased frequency of detection of HLA antigens: A3, B7, DR2, DR15, etc. In addition, an increased incidence was found in siblings, in particular twins, as well as in the parents of patients. An uneven distribution of the incidence of multiple sclerosis in various regions of the world is noted. An infectious etiology of the disease is suspected, but so far no pathogen has been identified. Confirmations of immune mechanisms in the development of multiple sclerosis have been obtained. So, infiltrates from CD4 + and CD8 + T-lymphocytes, macrophages were revealed in the affected areas of the brain. These cells can cause damage to oligodendrocytes due to the induction of apoptosis of glial cells. In addition to cellular immunity reactions, antibody-dependent mechanisms may also participate in the pathogenesis of multiple sclerosis.

In a macroscopic examination of the brain on unfixed preparations, the affected areas are transparent, especially on transverse or longitudinal sections.
They are in the form of spots or plates of white, gray or pinkish color, depending on their age. The sizes of these plates vary from 1 mm to 1-5 cm or more. The Weigert – Palle and Spielmeyer stain allows us to determine the topography of demyelination. In the study using myelin stains, it was found that a certain predisposition in the localization of the affected areas is noted in relation to the following brain areas: subpial portion of the gray matter of the cerebral cortex, subependymal gray matter of the lateral ventricles, corpus callosum, rhomboid cerebellum, bridge, chiasm, etc. the spinal cord of the plate occupy the lateral or posterior region, sometimes giving a wedge-shaped picture with the base on the periphery, and sometimes they occupy the periependymal region, having in such cases an incorrect ph rmu. In longitudinal sections, the demyelination process can be observed at the level of several segments, which is typical for this disease.

Microscopic manifestations are divided into three options, reflecting the possible stages of the disease.

Acute lesions (active plaques) are manifested by periaxial demyelination with infiltration of lipid-containing macrophages and perivascular accumulations of lymphocytes, monocytes, and plasma cells.

Older lesions (inactive plaques) are characterized by loss of myelin, a decrease in the number of oligodendrocytes, proliferation of astrocytes and the formation of a dense network of glial cells.

Shadow plaques are the transition zone between inactive plaques and unchanged white matter. Chaotically located thin myelin fibers and accumulations of oligodendrocytes are microscopically visible. Shadow plaques are a manifestation of either incomplete demyelination or remyelination.

A special variant of multiple sclerosis was described by Davis in 1894 and was called Davis opticomyelitis. The most common cases of Davis disease are found in indigenous women in Southeast Asia. The disease is characterized by damage to the spinal cord (transverse myelitis) and optic nerves from one or two sides, as well as the periventricular white matter, rarely the brain stem and cerebellum. At the same time, in addition to the foci of demyelination typical for multiple sclerosis, peculiar diffuse inflammatory changes with severe cerebral edema, sometimes with hemorrhages, are observed. Pathogenesis is based on the formation of autoantibodies against various antigens of nervous tissue. The course of Davis disease is often malignant.

Another malignant variant of multiple sclerosis is Marburg disease. In this progressive and fatal disease, multiple foci of demyelination develop in the optic nerves and cervical spinal cord, as well as axon degeneration and necrosis.

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Demyelinating diseases of the central nervous system.

  1. Classification of demyelinating diseases of the nervous system
    I Demyelinating diseases with a primary lesion of the central nervous system. 1. Acute forms. • Primary (acute disseminated encephalomyelitis; clinical forms - encephalomyelopoliradiculoneuritis, opticoencephalomyelitis, opticomyelitis, polioencephalitis, disseminated myelitis); • Secondary (parainfection - encephalomyelitis with measles, whooping cough, chickenpox,
  2. Demyelinating diseases of the nervous system
    Demyelinating Nervous Disease
  3. Degenerative diseases of the central nervous system.
    Degenerative diseases of the central nervous system is a heterogeneous group of diseases characterized by progressive loss of neurons with secondary changes in white matter and the concomitant glial-proliferative reaction. Most neurodegenerative diseases occur in the 5-6th decades of life and at a later age. Macroscopically determined atrophy of certain
  4. Metabolic diseases of the central nervous system
    Many metabolic diseases are inherited in an autosomal recessive manner, and some of them in an X-linked, recessive manner (see chapter 8). Hereditary metabolic defects disrupt the metabolism of many substances: lipids, carbohydrates, glycosaminoglycans (mucopolysaccharides), amino acids and trace elements. In some metabolic diseases, pathological changes begin with
  5. Viral diseases of the central nervous system.
    Viral meningitis is more benign than bacterial meningitis. Enteroviruses detect more than 70% of cases of viral meningitis. All representatives of enteroviruses cause meningitis, but most often Coxsackie viruses, ECHO and nonparalytic polio. In the study of cerebrospinal fluid, a lymphocytic composition is noted, and the level of protein and sugar does not significantly change. Macroscopic picture
  6. Systemic diseases of the central nervous system
    This is a group of diseases, many of which are family in nature and are accompanied by progressive degeneration of neurons and their processes of the central nervous system in certain areas. Patients are affected by sensory or motor (motor) systems with cerebellar ataxia and involuntary movements or dementia. Parkinson's syndrome (parkinsonism, trembling paralysis,
  7. Infectious diseases of the central nervous system.
    The classification of infectious diseases of the central nervous system takes into account the etiology, localization, nature of morphological changes, especially the clinical course of the lesion. By etiology, bacterial, viral, fungal, prion, and parasitic diseases are distinguished; according to the localization of inflammatory changes, meningitis (arachnoiditis, leptomeningitis, pachymeningitis); encephalitis; myelitis; encephalomyelitis; meningomyelitis;
    The group of students to be transferred to special schools in most cases includes children who have undergone meningitis, encephalitis, meningoencephalitis and other forms of neuroinfection. In some cases, there are children with some form of damage to the nervous system as a result of syphilis, tuberculosis, and rheumatism. The causative agents of diseases are various types of microbes and
    There is a striking similarity between the central nervous system and the cardiovascular. In the latter, one subsystem (venous) returns blood to the heart, and the other (arterial) drives blood through the vessels from the heart. Similarly, the central nervous system (CNS) has two distinctly different types of nerves that are connected to the brain, and the brain, in turn, plays a paramount role in the central nervous system.
  10. Infectious diseases of the central nervous system
    Infectious diseases of the central nervous system
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