Basic Overview
Viral encephalitis is a primary encephalitis caused by direct viral invasion of the brain parenchyma. The disease occurs throughout the year and is therefore also known as sporadic encephalitis. The common viruses that cause encephalitis are enterovirus, cytomegalovirus, mucovirus and some other viruses. The main clinical manifestations are symptoms of brain parenchymal damage and signs of intracranial hypertension, such as fever, headache, vomiting, convulsions, and in severe cases, coma. However, the severity of the disease can vary depending on the location and extent of virus invasion.
Many viruses can cause encephalitis, the most common of which are coxsackieviruses and echoviruses, and others are herpes simplex virus, varicella-virus, mumps virus, rubella virus, measles virus, and EBV. Most of the megaviruses are intrauterine infections and acquired only in immunocompetent children. Enteroviruses replicate in local lymphoid tissues, and herpesviruses, measles and rubella viruses invade the blood stream after mucosal reactions and spread to multiple organs. Replication in organ tissues is massive and re-enters causing a second viraemia. The varicella-zoster virus, on the other hand, can follow the neurons directly to the nervous system. Viral invasion of brain tissue with massive replication and proliferation can directly disrupt the main mechanisms of neurological injury, which can also stimulate host responses that damage the nervous system, such as perivasculitis, avascular necrosis, and endothelial hyperplasia.
Pathology
The disease is endemic worldwide, and the types of viral encephalitis occurring and prevalent in different countries and regions vary. China, Japan and Southeast Asia are thought to be the most prevalent regions. In the United States, St. Louis encephalitis, eastern equine encephalitis, western equine encephalitis, and California encephalitis are prevalent. The clinical manifestations, disease and prognosis of viral encephalitis caused by different viruses also differ. Epidemic B encephalitis and herpes virus encephalitis are dangerous, have a high mortality rate, and are prone to sequelae. In contrast, enteroviruses such as ECHO virus and Coxsackie virus cause encephalitis and encephalitis, which are mild, have a low mortality rate, and generally do not leave sequelae.
Types
There are many types, which can be divided into 3 categories: acute viral encephalitis, lentiviral encephalitis and post-infectious encephalitis.
1, acute viral encephalitis: is a variety of viral invasion of brain tissue caused by acute inflammation. Commonly, herpes viral encephalitis, enteroviral encephalitis and encephalitis caused by other viruses (mumps encephalitis, AIDS encephalitis, adenoviral encephalitis, etc.).
2. Lentiviral encephalitis: It is caused by a lentivirus, and the lesions are chronic and progressive. Eventually, the patient is disabled or dies due to loss of brain function, such as Kulu disease (chills-like tremor disease) and Crohn’s Felt-Jacob II disease.
3. Post-infectious encephalitis: It is the clinical manifestation of encephalitis that does not appear at that time after infection with the virus or vaccination, but only after a period of time. It may be due to the virus first latent in the brain tissue, and only later cause lesions. It may also be related to demyelinating lesions of the nerves caused by a metamorphic reaction after infection with a virus or vaccination. Commonly, encephalitis is caused by measles, chickenpox, rubella, and vaccination against rabies.
Clinical manifestations
The clinical manifestations of acute viral encephalitis caused by various viruses vary widely and are determined by
1, the site of neurological involvement.
2, the intensity of viral pathogenesis.
3. the immune response of the affected child, etc. Therefore, even if the infection is caused by the same virus, the clinical manifestations may vary.
(I) Prodromal symptoms
Symptoms of the upper respiratory tract or gastrointestinal tract, such as fever, headache, sore throat, vomiting, diarrhea, loss of appetite, etc.
(II) Neuropsychiatric symptoms
1.Disorders of consciousness: the lighter ones are indifferent, sluggish or irritable to the outside world, drowsy; the heavier ones appear delirium and coma.
2, increased intracranial pressure: headache, vomiting, dizziness and even brain herniation, the infant’s fontanelle is full.
3, convulsions: can be limited, generalized or continuous.
4.Motor dysfunction: Depending on the site of damage, it can be central or peripheral paralysis of one side or one limb; it can also be extrapyramidal movement disorders such as choreiform movements and muscle ankylosis; it can also have strabismus, facial paralysis or swallowing disorder due to cerebral nerve paralysis.
5. Mental disorders: such as memory loss, disorientation, hallucinations, hallucinations, mood changes, irritability, and sometimes suspicion, which are often mistaken for psychosis or frontal lobe tumor.
Accompanying symptoms
Viral infections are systemic diseases, but each virus has its own unique clinical manifestations. For example, Echovirus and Coxsackie virus infections often have a small measles-like rash or are accompanied by myocarditis or pericarditis. In mumps, the parotid glands are enlarged (and may be preceded by encephalitis). In herpes simplex virus infection, a herpes rash appears around the mouth and lips. The duration of the disease is usually about 2 weeks, and most cases recover completely, with only a few cases having sequelae of epilepsy, visual and hearing impairment, limb paralysis, and varying degrees of mental retardation.
Epidemiological history of viral encephalitis
The epidemiological history of viral encephalitis includes the epidemic season, exposure history, symptoms associated with the virus infection, and vaccination history.
1. Children in the prodromal phase have fever, headache, myalgia, vomiting, diarrhea, etc.
2. The symptoms of encephalitis vary in severity, mainly manifesting as neuropsychiatric abnormalities. Neurological abnormalities include fever, headache, vomiting, drowsiness, coma, and convulsions, etc. In severe cases, symptoms of the brain, subthalamic, basal ganglia, brainstem, cerebellum, and spinal cord may be abnormal. Mental abnormalities may include excitement, irritability, crying and laughing, insomnia, abnormal behavior, hallucinations, fantasies, or indifferent expression, silence, reduced activity, not eating, poor orientation, memory loss, incontinence, etc.
3. Concomitant symptoms precede the onset of encephalitis or are accompanied by symptoms of the corresponding viral infection.
Clinical diagnosis
It is mainly based on clinical manifestations and laboratory tests.
(I) Clinical manifestations
As mentioned above, if the lesion involves the meninges (meningoencephalitis), meningeal irritation, such as cervical ankylosis, positive Kernig’s sign and Brookinski’s sign, may occur.
(II) Laboratory tests
1, cerebrospinal fluid examination When the above clinical manifestations and suspected acute viral encephalitis should be made lumbar puncture, cerebrospinal fluid sent for laboratory tests. It may show typical viral encephalitis changes. (In special cases, even if the cerebrospinal fluid does not change can not be ruled out)
2. Pathogenetic diagnosis
①Cerebrospinal fluid is sent for virus isolation;
②Cerebrospinal fluid cells for immunofluorescence antibody test;
③Serological examination, the antibody titer is more than 4 times higher in the recovery period than in the acute period for diagnosis. Antibodies in the cerebrospinal fluid can also be measured.
Although the above changes are not specific, they are still of some value for diagnosis and prognosis estimation when combined with the clinical situation.
Differential diagnosis
The disease needs to be differentiated from septic meningitis (including those not thoroughly treated), tuberculous meningitis, fungal meningitis and brain abscess.
Treatment measures
(A) Strengthen nursing care
Care should be strengthened during the course of the disease to prevent the occurrence of bedsores. Supply certain amount of water, nutrition and electrolytes. Prevent accidents in sick children with psychiatric symptoms. Observe for precursors of brain herniation.
(B) Anti-viral treatment
Although there are no effective antiviral drugs, the following drugs can be used: iodoside (herpes net), triazolyl nucleoside (virazol), aprotinin, others such as transfer factor, interferon can improve the body’s resistance to the virus, can be applied.
(C) Symptomatic treatment.
1, antipyretic, antispasmodic. High fever can cause convulsions. Use physical cooling or Chinese and Western drugs to reduce fever. Phenobarbital or Valium can prevent or control convulsions.
2, reduce cerebral edema. 20% mannitol. Hydrocortisone or diazepam may also be used.