Neuroinfections are a group of infectious pathologies that are caused by bacteria, viruses, fungi or protozoa, characterized by the predominant localization of the pathogen in the central nervous system and signs of damage to its departments. Clinical manifestations are represented by meningeal, intoxication, liquorodynamic syndromes, vegetative-vascular disorders. In the process of diagnosis, anamnestic data, the results of a physical, general clinical laboratory, serological, bacteriological or virological examination are used. During treatment, antibiotics or antiviral drugs, pathogenetic and symptomatic agents are prescribed.
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Neuroinfections are a relatively common group of pathologies. According to statistics, infectious lesions of the central nervous system reach 40% in the structure of neurological morbidity. The main part consists of bacterial and viral meningitis, the prevalence of which in various geographical regions is in the range of 5-12 cases per 100,000 population per year. Most of the diseases included in this group are characterized by autumn-winter seasonality. They can occur among all age groups of the population, but the majority of patients are children under 10-12 years old and people who have not received vaccines according to the vaccination calendar.
The etiology of infectious damage to the structures of the central nervous system depends on the type of disease. In most episodes, a sick or healthy carrier person becomes the source of infection. Contributing factors are constant contact with a large number of people, TBI, immunodeficiency conditions, chronic somatic pathologies, promiscuous sex life. The following mechanisms of infection are distinguished:
- Airborne. It is realized when coughing, sneezing, talking. It is characteristic of pathogens of bacterial and viral meningitis, encephalitis, polio, herpes infection.
- Contact and household. It implies the transmission of an infectious agent in direct contact with a patient, carrier or infected household items. This is one of the ways of spreading herpes viruses, polio, syphilis.
- Fecal-oral. The type of transmission in which the pathogen is excreted together with feces, enters the body with food or water. It can be realized with herpes infection, ESNO and Coxsackie viruses, botulism, polio.
- Sexual. In this variant, infection occurs during sexual intercourse through the mucous membranes of the genital tract. In this way, HIV infection, syphilis spreads, less often – viruses that cause meningitis, encephalitis.
Each form of neuroinfection has its own pathogenetic features, but the mechanisms of development of most syndromes and symptoms are usually similar in all variants of this group of diseases. Infectious syndrome is caused by antigen-antibody complexes and pathogen toxins that have a destructive effect on the central nervous system, provoking vascular tone disorders, metabolism and hemodynamics in general. Meningeal syndrome develops with inflammatory lesions of the meninges and increased intracranial pressure. Vegetative disorders are caused both by direct contact of infectious agents with the centers of the autonomic nervous system, and by indirect exposure through intracranial hypertension. Cerebrospinal fluid changes are potentiated by increased production of cerebrospinal fluid against the background of irritation of vascular plexuses and blockade of pachyonic granulations, complicating the process of its resorption.
The use of systematization is due to the need to combine a large number of heterogeneous infectious pathologies with the involvement of the nervous system. Depending on the nature of morphological changes, clinical features and a specific pathogen, several groups of CNS lesions of infectious origin are distinguished in neurology. The main variants of neuroinfections are:
1. Encephalitis. Diseases with inflammation of brain tissue. Tick-borne, herpetic, chickenpox and rubella encephalitis are considered the most common. Manifestations depend on the type of pathogen, may include cerebral, focal symptoms, systemic intoxication of varying severity.
2. Meningitis. Diseases in which there is a lesion of the meninges. Characterized by the presence of meningeal and intoxication syndromes, taking into account the peculiarities of the inflammatory process, they are divided into:
- Purulent. They are provoked by bacteria, protozoa or fungi, can be primary or secondary. The primary ones include meningitis caused by meningococcus, pneumococci, Hemophilus bacillus. Secondary lesions are a complication of purulent processes of other localizations – paranasal sinuses, middle ear, etc.
- Serous. They are accompanied mainly by lymphocytic pleocytosis. Tuberculosis bacillus, mumps virus, enteroviruses Coxsackie and ESNO act as pathogens.
3. Polio. CNS lesion caused by RNA-containing polio virus. It can occur in two forms: nonparalytic (meningeal, abortive, inapparant) and paralytic (spinal, bridge, bulbar, encephalitic).
4. Brain abscess. It is a capsule-limited accumulation of purulent masses in brain tissues. It may have otogenic, rhinogenic, metastatic or post-traumatic origin. It is manifested by systemic intoxication, focal neurological symptoms, less often by epileptic and hypertensive syndromes.
5. Shingles. A variant of chronic neuroinfection caused by human type III herpesvirus is Varicella-Zoster. There is a persistence of the pathogen in the spinal ganglia with activation with a decrease in immunity or injury. The main symptoms include acute pain, herpetic rashes in the area of 1-2 dermatomes.
6. Neurosyphilis. Infectious pathology provoked by pale treponema. At an early stage of CNS lesion, there are general infectious, cerebral and focal symptoms with impaired functions of II, III, VI, VIII pairs of cranial nerves. In the later stages, progressive dementia develops, mental disorders, stroke-like symptoms are revealed.
7. Botulism. An infectious disease caused by Clostridium botulinum and accompanied by an interruption in the transmission of nerve impulses in cholinergic synapses. There are signs of damage to the motor nuclei of the brain stem, the anterior horns.
8. Neurospeed. It is caused by infection with the human immunodeficiency virus. It is often represented by primary lesions of the central nervous system: encephalopathies, recurrent HIV meningitis, vacuolar myelopathy. Manifestations are diverse, including paresis, aphasia, ataxia, mnestic disorders, psychopathological disorders.
The clinical picture depends on the form of an infectious lesion of the central nervous system. Combinations of various common clinical manifestations of neuroinfections are usually observed: intoxication, meningeal, vegetative-vascular and cerebrospinal fluid syndromes. The general infectious syndrome is formed a few days or hours before the appearance of signs of an acute stage of damage to the nervous system, it can be represented by moderate headache, malaise, weakness, catarrhal phenomena, an increase in body temperature to 38-39.5 ° C, stool disorders such as diarrhea or constipation, fluctuations in blood pressure, tachycardia, less often – convulsive readiness, mental disorders.
Meningal syndrome occurs when the meninges are involved in the pathological process, consists of general cerebral symptoms, musculotonic and radicular symptoms. The first group includes intense diffuse bursting headache; photophobia, hypersensitivity to sounds and light, vomiting without nausea, which does not bring relief. Often there is a violation of consciousness by the type of hallucinations, delirium, stun, sopor. Children may have febrile seizures. Musculotonic and radicular manifestations include rigidity of the occipital muscles, symptoms of Kernig, Brudzinsky, Lessage, Gordon, Mendel, Bekhterev, etc.
Vegetative-vascular disorders in neuroinfections can be sympathoadrenal, vagoinsular or mixed in nature. In the first case, increased heart rate, increased blood pressure, excessive sweating and thirst are detected, in the second – bradycardia, arterial hypotension, copious urination. With a mixed variant, symptoms from different groups are combined with each other. Violation of the normal circulation of the cerebrospinal fluid can occur in the hypertensive and hypotensive type. More characteristic of neuroinfections is intracranial hypertension, accompanied by depression of consciousness, convulsive and dislocation syndromes.
The diagnostic program for CNS infections is based on anamnesis, physical examination, general clinical and specific laboratory tests. Radiation diagnostic methods are rarely used, often for the purpose of differentiation with volumetric lesions of the nervous system. The patient’s examination program may include the following procedures:
- Finding out the anamnesis. When communicating with a patient or his relatives, the treating infectious disease specialist or neurologist details the existing complaints, finds out the dynamics of their development. An important role is played by an epidemiological history – contact with infectious patients or travel abroad over the past 21 days.
- General and neurological status. During the examination, the doctor determines the level of consciousness, examines the skin and mucous membranes in order to search for rashes, determines the heart rate and blood pressure. When establishing the neurological status, the specialist evaluates the tone of the occipital muscles, identifies specific symptoms characteristic of various neurological syndromes.
- Laboratory tests. In the general blood test, in addition to an increase in ESR, the following changes are noted: with bacterial infection – high neutrophil leukocytosis, with viral leukocytosis with a shift of the leukocyte formula to the right, with HIV infection and severe immunodeficiency – leukopenia. Indicators of biochemical blood analysis depend on concomitant lesions of internal organs.
- Spinal puncture. In neuroinfections, there are two main variants of changes in the cerebrospinal fluid (protein-cell dissociations) – by purulent and serous type. With the first type of CSF, it is cloudy, has a certain color (white, yellowish), neutrophil pleocytosis from 1,000 is observed, protein levels increase from 1.0 g/l. In the serous form, the cerebrospinal fluid is transparent, opalescent, cytological examination reveals lymphocytic pleocytosis of more than 100, the protein level is above 0.4 g / l.
- Serological examination. It consists in determining the elevated level of antibodies in the blood by means of hemagglutination suppression reactions, complement binding or neutralization. ELISA is used, during which a specific IgM to the pathogen is detected. PCR is performed to clarify the DNA or RNA of the infectious agent.
- Virological or bacteriological diagnostics. It involves the determination of the causative agent of the disease in the blood or cerebrospinal fluid of the patient by seeding samples on specific nutrient media. After identification of the pathogenic agent, it is advisable to clarify the sensitivity to the main antibacterial drugs.
All neuroinfections are indications for hospitalization of a patient in an infectious or neurological hospital. In a serious condition, the need for continuous monitoring of vital functions (breathing, heartbeat), the patient is transported to the ICU department. The treatment program includes the following activities:
- Etiotropic therapy. The main goal is to eliminate the pathogen from the patient’s body. Initially, broad-spectrum drugs are used. After receiving the results of serological and bacteriological studies, medicines are replaced with antibacterial or antiviral agents, to which the identified pathogen showed the greatest sensitivity.
- Pathogenetic drugs. They are used to combat systemic intoxication, cerebral edema and homeostasis disorders, to correct the water-electrolyte balance, desensitization and stimulation of immunity. Plasma substitutes, diuretics, glucocorticosteroids, antihistamines, interferons, donor and artificial immunoglobulins, anticoagulants are prescribed.
- Symptomatic remedies. This category includes medications that relieve individual symptoms and improve the general condition of the patient: analgesics, antipyretics, antiemetic medications, anticonvulsants, neuroleptics.
- Surgical treatment. The nature of the surgical intervention depends on the detected changes. Surgery may be required in the case of abscess, tuberculoma of the brain, spinal cord compression with tuberculous spondylitis, large areas of necrosis with shingles.
Prognosis and prevention
The outcome of neuroinfection is determined by the type of disease, the general condition of the patient, the timeliness and usefulness of treatment. In most cases, timely diagnosis and adequate therapy can save the patient’s life, minimize the risk of complications. In some forms of neuroinfections, for example, encephalitis, mortality reaches 50-80%. Specific prevention is represented by vaccines against specific pathogens: herpes viruses, botulism, tick-borne encephalitis, measles, polio, meningococcus, etc. Non-specific preventive measures are aimed at strengthening immunity, timely treatment of immunodeficiency conditions and prevention of contact with potential carriers of infectious diseases.