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 response | Arthropod: 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 features | Arthropod: 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 studies | Arthropod 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 |
| Treatment | Arthropod: 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 complications | Seizures, 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.
