Diagnostic tests.
I. Ancillary tests
1, peripheral blood leukocyte count is normal or low, sometimes leukocytes can be elevated.
2, brain crest fluid examination brain crest fluid pressure increased, the appearance of more clear, the total number of leukocytes increased, mostly below 300 × 10 ^ 6 / L, mainly lymphocytes. A few children with viral encephalitis may have a normal total leukocyte count in the cerebral crest fluid. Most children with viral encephalitis have mildly elevated or normal brain crest fluid proteins, and no significant changes in sugar and chloride. The smear or bacterial culture is negative.
3. Viral pathogenic diagnosis
The current pathogenic tests concerning viral encephalitis are mainly as follows
① Virus isolation: for different viruses can be isolated from different specimens to provide pathogenic evidence with confirmatory value of viral encephalitis. Such as brain crest fluid (enterovirus, herpes simplex virus, mumps virus), saliva, stool (crest poliomyelitis virus, rotavirus), urine, skin lesions, etc.
②Serological tests: including enzyme-linked immunoassay and immunofluorescence method for virus identification, virus antigen detection, and specific virus antibody (IgM or IgG) detection.
③Molecular biology methods: commonly used are polymerase chain reaction (PCR), real-time PCR and biochip technology, which can detect the viral DNA sequence from the brain tissue and brain crest fluid of the affected children to determine the pathogen.
4.Electroencephalogram
It mainly shows high amplitude slow waves, mostly diffuse distribution, and may have epileptiform discharges, which are of reference value for the diagnosis of viral encephalitis. However, the EEG is not specific and cannot determine the etiology. A normal EEG cannot completely exclude encephalitis.
5. Imaging is mainly used to assess the degree of damage to the central nervous system, and MRI is superior to CT. In severe cases, both CT and MRI can show inflammatory lesions formed by variable size, poorly defined, irregular hypo- or high-density shadows, while mild cases can have no obvious abnormal changes.
II. Diagnosis
The diagnosis of viral encephalitis is based on medical history, clinical manifestations, cerebral crest fluid examination and pathogenic identification.
Differential diagnosis.
Viral encephalitis should be distinguished clinically from the following diseases.
1. septic meningitis
If septic meningitis is not treated properly, its brain crest fluid changes can be similar to viral encephalitis, and should be differentiated by history, treatment and pathogenic examination.
2. Tuberculous meningitis
Tuberculous meningitis in infants and children often has an acute onset, and the total number of cells in the brain crest fluid and the classification are similar to those of viral encephalitis, which requires differentiation. Tuberculous meningitis can be differentiated by a history of tuberculosis exposure, low brain crest fluid sugar and chloride, and the presence of other sites of tuberculosis infection, combined with the tuberculosis pure protein derivative (PPD) test and blood sedimentation.
3.Fungal meningitis
The onset is often slow, the course is long, the intracranial pressure is increased significantly, the headache is severe, and the ink staining of cerebral crest fluid can be distinguished.
4.Other
Must be distinguished from intracranial non-inflammatory diseases (cerebrovascular diseases, tumors, degenerative diseases) and toxic encephalopathy, Reye’s syndrome or brain abscess.