Encephalitis: causes and classification

Encephalitis is an inflammation of the brain tissue. Currently, encephalitis is used to refer not only to infectious, but also to infectious-allergic, allergic and toxic brain damage.

The classification of encephalitis reflects the etiological factors, associated clinical manifestations and course characteristics.

By time of occurrence

• Primary - independent diseases caused mainly by neurotropic viruses:
  • viral:
    • viral (polyseasonal): herpes, enterovirus, influenza, cytomegalovirus, rabies, etc.;
    • arbovirus (vector-borne): tick-borne, mosquito-borne (Japanese), Australian Murray Valley, American St. Louis;
    • caused by an unknown virus: epidemic (Economo);
• microbial and rickettsial:
  • for syphilis;
  • borreliosis;
  • typhus, etc.
• Secondary - diseases that arise against the background of the main disease:
  • postexanthematic:
    • measles;
    • rubella;
    • chickenpox;
  • post-vaccination:
    • after DPT;
    • after measles, rubella, mumps vaccination;
  • bacterial and parasitic:
    • staphylococcal;
    • streptococcal;
    • tuberculous;
    • toxoplasmosis;
    • chlamydial;
    • malarial, etc.;
  • demyelinating:
    • acute encephalomyelitis;
    • multiple sclerosis.

By the rate of development and flow:

• super sharp;
• sharp;
• subacute;
• chronic;
• recurrent.

By localization:

• cortical;
• subcortical;
• stem;
• cerebellar damage.

By prevalence:

• leukoencephalitis (white matter disorder);
• polioencephalitis (gray matter damage);
• panencephalitis.

By morphology:

• necrotic;
• hemorrhagic.

By severity:

• moderate severity;
• heavy;
• extremely heavy.

Complications:

• edema-swelling of the brain;
• dislocation;
• cerebral coma;
• epileptic syndrome;
• cystic.

Outcomes:

• recovery;
• vegetative state;
• gross focal symptoms.

Encephalitis caused by neurotropic viruses is characterized by epidemicity, contagiousness, seasonality and climatic and geographical features of distribution. Depending on the predominant localization, encephalitis is divided into brainstem, cerebellar, mesencephalic, and diencephalic. Often, along with the brain matter, some parts of the spinal cord are affected; in such cases, they speak of encephalomyelitis. Encephalitis can be diffuse and focal, and by the nature of the exudate - purulent and serous.

Primary polyseasonal encephalitis

This group includes encephalitis of various etiologies, including those caused by enteroviruses Coxsackie (A9, B3, B6), ECHO (2, 11, 24) and many unknown viruses.

Clinical picture

In the clinical picture of enteroviral encephalitis, several syndromes are distinguished: stem, cerebellar, hemispheric. Focal neurological symptoms develop against the background of moderately expressed general infectious and general cerebral symptoms on the 2nd-5th day of the disease. The etiologic factor is identified by virological and serological studies. Lymphocytosis is usually detected in the cerebrospinal fluid.

The course is favorable, with complete regression of neurological symptoms. Mild lesions of the III, VI, VII pairs of cranial nerves, hemi- and monoparesis, aphasic disorders rarely persist. The cerebellar form is the most favorable, recovery with it is always complete.

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