Viral Encephalitis

Viral encephalitis involves viral infection of the central nervous system (CNS). It often presents with altered mental status, motor or sensory deficits, behavioral and personality changes, speech and movement disorders. Viral encephalitis can be primary or post-infectious and is caused by various viruses, including herpes simplex virus type 1, St. Louis encephalitis, Japanese encephalitis, enterovirus type 71, West Nile virus, cytomegalovirus (CMV), varicella zoster virus, Epstein-Barr virus, HIV, human herpes virus-6, and Zika virus.

Introduction to Viral Encephalitis

Viral encephalitis refers to viral infection of the central nervous system (CNS). Patients often present with altered mental status, motor or sensory deficits, altered behavior, personality changes, speech and movement disorders. Viral encephalitis can be either primary or post-infectious. A common cause of viral encephalitis is herpes simplex virus (HSV) type 1.

Common Viral Pathogens

Other viral pathogens include St. Louis encephalitis in North America and Japanese encephalitis in Asia, enterovirus type 71 in Colorado, West Nile virus in some parts of Africa, cytomegalovirus (CMV), varicella zoster virus, Epstein-Barr virus, HIV, human herpes virus-6, and Zika virus.

Diagnostic Procedures

Brain CT/ MRI scanning is useful to rule out space-occupying lesions. Temporal lobe involvement is strongly suggestive of HSV encephalitis. Also, cerebrospinal fluid (CSF) analysis and PCR are required as an initial diagnostic step in patients with suspected viral encephalitis. Mortality and morbidity may be high and long term sequelae are known among survivors.

Treatment Options for Viral Encephalitis

There are no specific therapies for most viral encephalitis with the exception of herpes simplex virus (HSV) -1 infection with acyclovir (10 mg/kg intravenously every eight hours for 14-21 days) which should be initiated as soon as possible if the patient has encephalitis without apparent explanation. Acyclovir should also be considered if varicella zoster virus encephalitis is likely. CMV encephalitis does not respond to aciclovir. The use of ganciclovir (5 mg/kg intravenously twice daily) and/or foscarnet (60 mg/kg every eight hours or 90 mg/kg every 12 hours) is currently recommened in CMV encephalitis.

Managing Increased Intracranial Pressure

Increased intracranial pressure, manifesting as headache, vomiting, blurred vision, should be treated with steroids (dexamethasone 4mg twice daily), or mannitol (an initial bolus of 0.5 to 1 g/kg, followed by repeated infusions of 0.25 to 0.5 g/kg, generally every twelve hours as needed).

Seizure Management in Viral Encephalitis

Seizures should be treated aggressively with antiseizure medications during the acute illness. This includes lorazepam (0.1 mg/kg intravenously (IV) up to a maximum of 4 mg), diazepam (0.2 mg/kg IV; maximum dose 8 mg), levetiracetam 40 mg/kg IV, or fosphenytoin (20 mg/kg IV)

References

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