Features of viral encephalitis

Features of viral encephalitis

Pathogenesis, clinical features, diagnostic approach, treatment, and common complications of viral encephalitis

Pathogenesis: direct CNS invasion by virus or immune-mediated responseArthropod: inoculation from mosquito → local replication → viremia → infection of cerebral capillary endothelial cells → neurons OR choroid plexus → intraventricular CSF → ventricular ependymal cells → periventricular cerebral tissue (prefer basal ganglia and thalami)
HSV: retrograde axoplasmic flow of virus in the axons of a division of trigeminal nerve → latent infection in the ganglion and reactivation (prefer inferior and medial temporal lobes)
Clinical featuresArthropod: nonspecific, increased lethargy and behavioral changes, or brief single seizures, rashes in WNV, parkinsonian features, poliomyelitis-like syndrome
HSV: subacute fever, headache, behavioral changes, focal seizure activity, and neurologic deficits
VZV: subacute small and large vessel ischemic and hemorrhagic infarctions
Diagnosis, CSF studiesArthropod
CSF: antibody titer or immunoassay
MRI: hyperintense lesions on FLAIR in subcortical areas, basal ganglia
HSV
CSF: +HSV PCR
MRI: hyperintensity on T2 FLAIR sequence in medial and inferior temporal lobe up to insula with CSF correlation, at times hemorrhagic
EEG: PLEDS over temporal lobes
VZV
CSF: antibody titer more sensitive than PCR
MRI: large- and small-vessel ischemic and hemorrhagic infarctions and spherical subcortical white matter lesions
TreatmentArthropod: supportive care and management of neurologic complications; ribavirin for La Crosse virus
HSV: acyclovir 10 mg/kg q 8h × 3 weeks
VZV: acyclovir 10 mg/kg q 8h × 3 weeks
CMV: foscarnet and gancyclovir
Common complicationsSeizures, increased ICP, multifocal neurologic deficits, cognitive impairment, myelitis, death

 View full sizeWNV , West Nile virus; HSV , herpes simplex virus-1; VZV , varicella zoster virus; CNS , central nervous system; CSF , cerebrospinal fluid; VZV , varicella zoster virus; MRI , magnetic resonance imaging; EEG , electroencephalogram; PCR , polymer chain reaction; FLAIR , fluid attenuation inversion recovery; CMV , cytomegalovirus; ICP , intracranial pressure.

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