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1、Viral Encephalitis,Zhang Xinqing,Xuanwu Hospital The Capital University of Medical Sciences,Epidemiology,Viral encephalitis occurs in all seasons but peaks in summer and early fall. Viral encephalitis can occur at any age but the elderly and infants tend to have more severe encephalitis,Clinical man
2、ifestations,The onset is usually abrupt clinical course progress rapidly over 1 to 3 days the strain of encephalitic virus determines the severity of the signs and symptom the table lists the most common signs and symptoms,Clinical manifestations,Clinical manifestations,Laboratory findings,The blood
3、 leukocyte count is often elevated lumbar puncture findings a lumbar puncture shows a normal or elevated opening pressure the CSF contains 5 to 300WBC/mm3;50 to 200 mg/dl of protein; and normal glucose; bacterial cultures are sterile,Laboratory findings,the EEG is always abnormal and shows diffuse b
4、ackground slowing with occasional epileptiform or electrographic seizure activity MRI studies often show areas of increased signal intensity on T2-weighted images. The CT scan may appear normal early, and later may show cerebral edema, necrosis or hemorrhage,Diagnosis,The clinical diagnosis is made
5、on: acute onset of fever progressive mental status deterioration focal neurological signs and seizures(generalized or focal) CSF containing lymphocytic pleocytosis, normal glucose and elevated protein abnormal MRI abnormal EEG,Diagnosis,The specific etiology of the viral encephalitis is made by: PCR
6、 assay of CSF CSF IgM antibodies to some but not all viruses virus is isolation from throat or stool for some viruses acute and convalescent serum antibody titre rise brain biopsy with virus culture ;virus is seldom isolated from CSF,Mortality rate and frequency of neurologic sequelae,Herpes simplex
7、 encephalitis (HSE),Etiology,HSV type 1 encephalitis is the most common type in adults, the virus migrates along nerve axons to trigeminal ganglia, where it persists in a latent form and may be subsequently reactivated HSV type 2 encephalitis causes neonatal HSE by passage through the birth canal of
8、 a mother with active genital lesions,Pathology,HSE type 1 encephalitis is an acute, necrotizing, asymmetric hemorrhagic process with lymphocytic and plasma cell reaction. It usually involves the medial temporal and frontal lobes. Inclusions may be seen in neurons and glia,Clinical findings,Acute on
9、set Rapid progression over several days Headache, fever, vomiting, fatigue, behavioral disorders, memory loss, aphasia, hemiparesis Focal or generalized seizures Coma, even death,CSF,Increased pressure and lymphocytic cell mild protein elevation, normal glucose red blood cells may be seen in some ca
10、ses viral antibody may be detected by ELISA,EEG,diffuse slow wave activities periodic slow-wave complexes arising from one or both temporal lobes,CT or MRI,MRI: may show hyperintensity in temporal lobe, frontal lobes, insular cortex, or cerebral convexity on T2-weighted images CT: is less sensitive
11、and may be normal during early phase and become abnormal later similar to the MRI,T2-weighted MRI demonstrated hyperintense lesion in the mesial temporal lobe,HSE: MRI T1-weighted demonstrated middling intense and hyper intense in T2-weight,T1-weighted MRI demonstrates hypointense and T2-weighted de
12、monstrates hyperintense lesion in the mesial temporal lobe,Diagnosis,HSE should be clinically suspected if the Acute onset, clinical symptoms Neurological signs EEG shows a characteristic pattern of high-voltage, periodic, lateralizing epileptiform discharges(PLEDS) at a rate of 2-3Hz originating fr
13、om the temporal lobe. MRI shows focal medial temporal lobe abnormality,Diagnosis,The diagnosis of HSE is conformed by detection of fragments of HSV DNA in CSF or brain biopsy showing diffuse inflammation with intranuclear inclusion bodies identification of HSV particles by electron microscopy viral
14、antigen identification by immunohistochemistry herpes simplex DNA fragments by PCR isolation of HSV from the tissue,Treatment and prognosis,treatment Acyclovir given intravenously at a dosage of 10mg/kg every 8 hours, continued for 14 days symptomatic and supportive therapy prognosis up to 50% untre
15、ated cases dieearly treatment with acyclovir can reduce the mortality rate to 20% to 30%,Differential diagnosis,Bacterial meningitis: signs of systemic infection CSF: pressure is elevated appearance ranges from slightly turbid to grossly purulent CSF white cell counts of 1000-10000/ml may be seen pr
16、otein concentration is elevated glucose is decreased Gram-stained smears of CSF can identify the causative organism,Differential diagnosis,Tumor subacute or chronic onset slowly progressive course CT scan or MRI may be helpful Acute demyelinated encephalopathy acute or subacute onset upper respirato
17、ry tract infection and fever may be present MRI shows lesion in white matter,Varicella-zoster encephalitis,Etiology,After infection of varicella-zoster virus(VZV), the virus migrates to ganglia(latent infection) In condition of lower immunity, the virus is reactivated and causes encephalitis or meningitis,
