Postvaccinal encephalitis is inflammatory changes in cerebral tissues that occur in connection with vaccination. Develops acutely on the 3-30 th day after vaccination. It begins with fever, vomiting, headache, convulsive attack, loss of consciousness; then focal symptoms occur: paresis, sensitive disorders, hyperkinesis, cerebellar syndrome. Diagnostic value has anamnesis data, assessment of neurological status, analysis of cerebrospinal fluid, EEG, Echo-EG, bacteriological, virological, serological studies and diagnosis by PCR. Treatment is divided into 2 stages: correction of vital functions and symptomatic therapy in the acute period, subsequent rehabilitation.
General information
Postvaccinal encephalitis develops as a postvaccinal complication. It is rarely observed, mainly after the introduction of vaccines against rabies, measles, APDT (adsorbed pertussis-diphtheria-tetanus). Previously, post-vaccination encephalitis occurred as a complication of immunization against smallpox (mass preventive vaccinations were canceled in 1975) and the use of CDD vaccines (the predecessor of modern APDT). For the first time, the connection of encephalitis with vaccination was proved by isolating the vaccine virus from the cerebral tissues of the patient.
There are no exact data on the prevalence of this post-vaccination complication, since it is difficult to determine whether the occurrence of encephalitis is directly related to vaccination or is a consequence of an external infection of a child that coincided with the post-vaccination period. According to American statistics, post-vaccination encephalitis occurred on average in 1 child per 1.5 million vaccinated. In most cases, postvaccinal encephalitis is observed after primary vaccination and extremely rarely after revaccination. The ratio is approximately 40:1. Available statistical data indicate that the frequency of encephalitis increases with increasing age of primary vaccination.
Causes
The issues of etiopathogenesis of postvaccinal encephalitis are not completely clear. There is an assumption that brain damage occurs as a result of reactivation and reproduction of the vaccine virus. Another hypothesis suggests that under the influence of the vaccine, activation of some unknown infectious agent may occur. However, most researchers are of the opinion that post-vaccination encephalitis has an infectious and allergic mechanism of development. According to this theory, the antigens coming with the vaccine sensitize the body, resulting in a cross—autoimmune reaction to the vaccine’s antigens and the antigens of its own cerebral tissues – autoimmune inflammation develops.
The process proceeds with the defeat of cerebral vessels: the development of perivascular inflammation, increased permeability of the vascular wall, diapedesis hemorrhages. Cerebral edema and the formation of foci of demyelination are characteristic. Predominantly white cerebral matter is affected, and therefore postvaccinal encephalitis refers to leukoencephalitis.
Symptoms
The clinical picture may occur in the period from 3 to 30 days from the moment of vaccination, but most often post-vaccination encephalitis manifests on 7-12 days. It is characterized by an acute debut with a high rise in temperature, vomiting, headache. Often there are disorders of consciousness with psychomotor agitation, darkening of consciousness, sometimes its complete loss. In many cases, postvaccinal encephalitis proceeds according to the type of meningoencephalitis with involvement of the cerebral membranes in the inflammatory process, while meningeal symptoms are pronounced in the clinical picture (tension of the occipital muscles, positive symptoms of Brudzinsky and Kernig). In the first days of the onset of encephalitis, convulsive paroxysms often occur, usually clonic-tonic generalized, less often focal. In some cases, the epileptic status is noted.
Against the background of pronounced cerebral and meningeal symptom complexes, focal symptoms appear and rapidly progress. It can be represented by hyperkinesis, spastic mono- and hemiparesis, pelvic disorders, cranial nerve dysfunction, mental disorders, cerebellar ataxia, loss of sensitivity. In some cases, paresis appears after focal epiprimes. Sometimes the inflammatory process spreads to the tissues of the spinal cord with the development of peripheral paresis with muscular hypotension. In such cases, they talk about encephalomyelitis. The most dangerous is postvaccinal encephalitis with the development of bulbar syndrome, with damage to the respiratory and cardiovascular centers of the medulla oblongata. At the same time, severe bulbar crises with respiratory and cardiac disorders are observed, which can lead to a fatal outcome.
Diagnostics
The characteristic clinical picture allows to establish post-vaccination encephalitis (the debut with hyperthermia and general cerebral symptoms, certain disorders of consciousness), neurological status data (detection of focal symptoms), anamnestic information (the fact of vaccination that took place no earlier than a month before the onset of the disease), the results of additional examinations. During the diagnosis, the neurologist needs to differentiate post-vaccination encephalitis from other diseases of the central nervous system (manifestations of a brain tumor, viral meningitis, toxic encephalopathy, stroke, etc. P.), as well as from other bacterial and viral encephalitis.
There may be no changes in the blood test, in some patients there is a slightly increased ESR and a small leukocytosis. During the Echo-EG, intracranial hypertension is detected. With electroencephalography, diffuse rhythm changes with a predominance of delta waves are noted, epileptiform activity can be recorded. When performing a lumbar puncture, an increased pressure of the cerebrospinal fluid is detected. Analysis of the latter can reveal moderate cytosis due to an increase in the fraction of lymphocytes, sometimes a slight increase in protein concentration. In order to clarify the etiology of encephalitis, cerebrospinal fluid and blood bacposage, blood and liquor examination by PCR, serological reactions are carried out.
Treatment
Therapy is carried out in a hospital, has a pathogenetic and symptomatic character. First of all, the correction of cardiac, hemodynamic and respiratory disorders is carried out. In order to reduce brain edema, dehydration measures are carried out — depending on the degree of cerebrospinal hypertension, the introduction of mannitol, furosemide or other diuretics. The patient’s serious condition is an indication for glucocorticosteroid therapy. In the presence of seizures, anticonvulsants are prescribed, in case of mental disorders — antipsychotics. To prevent bacterial complications (pneumonia, pyelonephritis), broad-spectrum antibiotic therapy is performed.
Rehabilitation treatment aimed at a faster and more complete restoration of lost nervous functions begins when the acute period of encephalitis has passed. Its medicinal component includes neurometabolites (gamma-aminobutyric acid, thiamine, piracetam, pyridoxine, etc.), pharmaceuticals for improving the metabolism of muscle tissue (ATP) and neuromuscular transmission (neostigmine). At the same time, physical therapy, physiotherapy (electrophoresis, electromyostimulation, reflexotherapy), massage of paretic limbs are carried out.
Prognosis and prevention
The most variable outcome of the disease is possible: from complete recovery to the death of the patient. Often, timely intensive therapy can achieve a favorable outcome. Even after a deep coma, there may be a recovery of consciousness and a complete regression of symptoms. However, in a number of patients after encephalitis, residual phenomena persist: paresis and hyperkinesis of varying severity, mental retardation, epilepsy, cerebrospinal hypertension syndrome.
The best preventive measure is compliance with the terms, indications and rules of vaccination. Children who have contraindications to the introduction of vaccines should be carefully identified. If there is a tendency to allergic reactions, vaccination is better carried out against the background of desensitization of the body. It is advisable to avoid the introduction of vaccines to children who are not completely healthy, and even more so feverish. To reduce the load on the immune system, according to indications, the vaccination of APDT can be replaced by the introduction of a more weakened vaccine without the pertussis component of ADS-M.