VZV encephalitis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Anthony Gallo, B.S. [2]

Synonyms and keywords: Varicella zoster virus encephalitis; Herpes zoster encephalitis; Varicella zoster encephalitis; Varicella encephalitis;

Classification

Based on the duration of symptoms, VZV encephalitis may be classified into either acute or chronic.

Pathophysiology

The exact pathogenesis of VZV encephalitis is not fully understood. It is known that VZV encephalitis is the result of the varicella zoster virus, a double-stranded DNA virus within the Herpesviridae family of viruses. The immune system eliminates the virus from most locations, but it remains latent in the dorsal root ganglion and the trigeminal ganglion near the base of the skull. Initial infection by VZV presents as chickenpox, often in children between 1-9. VZV reactivation, which presents as shingles in adults, is the result of a decline in the frequency of VZV-specific T cells. The molecular basis of reactivation remains unknown. Some histopathologic studies suggest of a postinfectious demyelinating process, while other findings cite direct viral cytopathology.

Causes

VZV encephalitis may be caused by either varicella (chickenpox) or herpes zoster (shingles).

Differentiating VZV Encephalitis from Other Diseases

VZV encephalitis must be differentiated from other diseases that cause fever, headache, vomiting, and altered mental status, such as:

Disease	Findings
Other Viral encephalitis	Presents with acute inflammation of the brain, caused by a viral infection; it may complicate into severe brain damage as the inflamed brain pushes against the skull, potentially leading to mortality. See also: VZV encephalitis, West Nile encephalitis, St. Louis encephalitis, and Japanese encephalitis
Bacterial encephalitis	Presents with acute inflammation of the brain, caused by a bacterial infection; it may complicate into severe brain damage as the inflamed brain pushes against the skull, potentially leading to mortality. See also: Tick-borne encephalitis
Encephalopathy	Presents with steady depression, generalized seizures. Generally absent are fever, headache, leukocytosis, and pleocytosis; MRI often appears normal.
Meningitis	Presents with headache, altered mental status, and inflammation of the meninges, which may develop in the setting of an infection, physical injury, cancer, or certain drugs; it may have an indolent evolution, resolving on its own, or may present as an rapidly evolving inflammation, causing neurologic damage and possible mortality. See also: bacterial meningitis, viral meningitis, and fungal meningitis
Brain abscess	Presents with an abscess in the brain caused by the inflammation and accumulation of infected material from local or remote infectious areas of the body; the infectious agent may also be introduced as a result of head trauma or neurological procedures.
Acute disseminated encephalomyelitis	Presents with scattered foci of demyelination and perivenular inflammation; it can cause focal neurological signs and decreased ability to focus.

Risk Factors

disease arises from various events which depress the immune system, such as aging, severe emotional stress, severe illness, immunosuppression or long-term use of corticosteroids.  The cellular and immunological events that lead to reactivation are poorly understood. There have been recorded cases of outbreaks occurring due to unmanaged stress or other stresses to the skin such as pinching, biting or scratching of  more sensitive areas, such as nipples, ears, and underarms.