Herpesvirus encephalitis
- Lesion
Herpes simplex type 1 is the most common cause of serious sporadic encephalitis; zoster and CMV attack the nervous system in other ways.
What it is
Herpesviruses persist in the body for life and can damage the CNS at first infection or on reactivation. HSV-1 causes a hemorrhagic necrotising encephalitis of the temporal and frontal lobes in children and adults. HSV-2 causes generalised encephalitis in newborns infected at birth. Varicella-zoster reactivates in sensory ganglia to cause shingles and can inflame cerebral arteries. CMV damages the developing brain in utero and the periventricular region in people with AIDS.
Step by step
- HSV-1 infects the mouth in childhood and becomes latent in the trigeminal ganglion.
- Primary infection or reactivation sends the virus along olfactory or trigeminal pathways to the base of the brain.
- Virus multiplies in neurons and glia of the temporal and orbitofrontal cortex.
- Infected cells die; vessels bleed, causing hemorrhagic necrosis.
- Healing leaves cystic temporal lobes with memory loss and epilepsy.
Herpesviruses and the nervous system
| Virus | Who | Lesion | Inclusion |
|---|---|---|---|
| HSV-1 | Children and adults | Hemorrhagic necrosis of temporal and orbitofrontal lobes | Cowdry type A, intranuclear |
| HSV-2 | Newborns; adults with recurrent meningitis | Diffuse encephalitis; aseptic meningitis | Intranuclear |
| Varicella-zoster | Older or immunosuppressed adults | Ganglionitis, shingles, vasculopathy, encephalitis | Intranuclear in ganglion cells and glia |
| Cytomegalovirus | Fetus; adults with AIDS | Periventricular necrosis and calcification; ventriculitis | Large owl-eye nuclear and cytoplasmic inclusions |
Clinical notes
- HSV encephalitis: fever, confusion, personality change, seizures, aphasia; MRI shows temporal lobe changes and CSF PCR is diagnostic.
- Herpes zoster is common in Latin America in older adults and people with HIV; vaccination lowers its risk.
Test yourself
Think of the answer, then tap the question to see it.
Which brain regions does HSV-1 encephalitis typically destroy?
The inferior and medial temporal lobes and the orbital gyri of the frontal lobes, with hemorrhagic necrosis.
Where does varicella-zoster virus remain latent?
In the sensory neurons of dorsal root and cranial nerve ganglia.
What does congenital CMV do to the developing brain?
It causes periventricular necrosis and calcification, with microcephaly, seizures and sensorineural hearing loss.
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Encephalitis | MedlinePlus (MedlinePlus, US National Library of Medicine, 2026); Herpes Zoster (StatPearls (NCBI Bookshelf), 2026).
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Representative model, for educational purposes only.