Infections of the central nervous system

The general name of a group of infectious diseases with localization of the pathogen in various departments of the CNS - neuroinfections. The cause of neuroinfection can be viruses, bacteria, fungi, protozoa and prions. Excrete inflammation of the membranes of the brain and spinal cord (meningitis), damage to the brain substance (encephalitis) and the spinal cord (myelitis). In the presence of signs of meningitis and encephalitis, meningoencephalitis is diagnosed.

All these diseases are polyethiologic in nature, accompanied by general intoxication of the body and inflammatory changes in CSF, differing in clinical manifestations depending on the type of pathogen, localization of the process and the extent of infection.

Depending on the features of the CSF cellular composition in the patient - neutrophilic or lymphomonocytic pleocytosis, - neuroinfections are divided into purulent or serous meningitis (encephalitis), respectively. An approximately equal ratio of neutrophilic leukocytes and lymphocytes in CSF indicates a mixed character of pleocytosis, which can be determined at an early stage of the disease in bacterial meningitis of any etiology. Purulent cerebrospinal fluid most often implies the bacterial nature of the infection, predominance of lymphocytes in the cerebrospinal fluid indicates a predominantly viral etiology of the disease. Therefore, obtaining the results of CSF puncture in the patient during the first hours of admission to the hospital allows to determine the spectrum of possible pathogens (bacteria or viruses) and to prescribe adequate treatment. At the same time, it must be remembered that a number of bacterial meningitis (tuberculosis, syphilitic, Yersiniosis, etc.) can have both a purulent and serous nature.

The most common cause of purulent bacterial meningitis (encephalitis) is meningococci (Neisseria meningitidis), pneumococci (Streptococcus pneumoniae), Haemophilus influenzae b Haemophilus influenzae b, Staphylococcus aureus, other pathogens (genus Streptococcus, Staphylococcus, Listeria, Pseudomonas , Family Enterobacteriaceae, etc.) are much less common. According to the primary lesions of the membranes and (or) brain substance, these diseases are divided into primary, characterized by the development of the disease without the previous focal or septic damage to the organism by the microbial agent and secondary, complicating the localized acute or chronic infection as a result of generalization of the process or injury. Primary bacterial meningitis primarily causes meningococci (Neisseria meningitidis), to a lesser degree hemophilic rods of type b (Haemophilus influenzae b) and pneumococci (Streptococcus pneumoniae), the remaining pathogens tend to cause secondary meningitis.

Serous bacterial meningitis, in addition to the already mentioned meningitis with mixed pleocytosis (yersiniosis, syphilitic, etc.), includes diseases of mycoplasma (genus Mycoplasma), leptospirosis (genus Leptospira) and Borrelia (genus Borrelia) etiology. Serous protozoal meningitis (meningoencephalitis) is most often caused by Toxoplasma gondii. Fungal meningitis causes cryptococci (Cryptococcus neofomans), fungi of the genus Candida, fungi of coccidoidosis (Coccidoides immitis). In addition, serous meningitis can be caused by the Mycobacterium tuberculosis complex.

Primary viral meningitis is predominantly represented by the meningoencephalic form of tick-borne viral encephalitis (caused by the virus belonging to the Arbovirus group, the Flavivirus genus), the meningeal form of acute poliomyelitis (the causative agent belongs to the genus Enterovirus, Poliovirus hominis) and some others.

The most common cause of secondary viral meningitis (encephalitis) is the causative agents of enterovirus infections (the family Picornaviridae genus Enterovirus), the mumps virus (the family Paramyxoviridae, the genus Rubulavirus), herpes viruses (the Herpesviridae family), significantly less often measles and rubella viruses.

The indications for examination for the purpose of detecting neuroinfection are signs of general infectious intoxication of the patient, accompanied by a syndrome of increased intracranial pressure, a syndrome of edema and swelling of the brain, a syndrome of affecting the meninges or an encephalic syndrome, and inflammatory changes in the cerebrospinal fluid. At the same time, a comprehensive assessment of the patient's condition is needed, careful collection of anamnestic data, especially those related to the epidemiological component (cases of similar diseases in the patient's environment, tick bites, presence of domestic animals, previous infectious pathology, belonging to risk groups, etc.).

Given the similarity of symptoms in the infectious lesion of the CNS by different pathogens, the definition of the etiology of the disease should occur only with the use of laboratory diagnostic methods. For this, first of all, the liquor and blood of patients using direct ones (visual detection of the pathogen using microscopy, isolation of the pathogen in the cell culture, detection of its AG or fragments of genetic material) and indirect methods of laboratory diagnostics (determination of AT) are primarily studied.