Viral encephalitis medical therapy

Template:Encephalitis Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

Encephalitis is an acute inflammation of the brain, commonly caused by a viral infection. Sometimes, encephalitis can result from a bacterial infection, such as bacterial meningitis, or it may be a complication of other infectious diseases like rabies (viral) or syphilis (bacterial). Certain parasitic or protozoal infestations, such as toxoplasmosis, malaria, or primary amoebic meningoencephalitis, can also cause encephalitis in people with compromised immune systems. Treatment with acyclovir with or without steroids and antibiotics should be initiated as soon as possible. Antiviral agent like acyclovir has been useful in treatment of encephalitis due to herpes simplex virus and varicella zoster. Treatment for other causative agents of encephalitis is mostly supportive.

Medical therapy

General considerations

• Reliably tested specific antiviral agents are available only for a few viral agents (e.g. acyclovir for herpes simplex virus and varicella-zoster encephalitis). Administer the first dose of acyclovir as soon as possible (in the emergency department itself). Acyclovir can be initiated with or without antibiotics or steroids.The advantages of an early antiviral drug administration are:
  • Decreases disease duration
  • Decreases development of latency
  • Decreases development of complications
  • Decreases recurrence
  • Decreases transmission from infected person
• Treatment for Toxoplasma gondii and cytomegalovirus encephalitis are available but are used with limited succes
• Treatment is usually symptomatic. In patients who are very sick, supportive treatment, such as mechanical ventilation, is equally important.
• Systemic complications like hypotension, shock, hypoxemia, electrolyte imbalances (hyponatremia, SIADH should be treated promptly.
• Neuroimaging with MRI or CT scan should be done before lumbar puncture especially if raised intracranial pressure is suspected.
• Lab tests like blood samples should be taken before initiation of therapy.

Empirical treatment regimen

• Adult & Pediatrics- Acyclovir, 10 mg/kg body weight, 8h, intravenously, for 2-3 weeks.
• Neonatal HSV- Give acyclovir 10-15 mg/kg IV q8h for neonatal HSV
• HIV positive - Foscarnet is generally the treatment of choice given the high incidence of acyclovir resistance in these patients.

Treatment for increased intracranial pressure

General

• Elevation of head
• Hyperventilation may be used to decrease intra-cranial pressure on emergency basis
• Constant monitoring of neurological status
• Avoid increase in intra cranial pressure i.e. control of straining and coughing
• Antipyretics and analgesic for fever and pain.
• Monitoring and preventing seizures and hypotension.

Drug therapy

• Furosemide 20 mg iv and mannitol 1 gm/kg intravenously for diuresis (blood pressure and CVP should be monitored while administrating these drugs)
• Dexamethasone 10mg intravenously 6 hourly to decrease cerebral edema.

Encephalitis drug summary

Acyclovir

• It is effective for HSV1, HSV2 and varicella zoster.
• It is selectively taken up by the body cells infected with HSV and varicella zoster
• Prompt treatment with acyclovir is useful in decreasing complications, latency and communicability

Foscarnet

• It is effective against HSV 1, HSV 2 and CMV
• It is useful in patients who have developed resistance or are non-responders against acyclovir for e.g. HIV positive patients
• Drug dosage depends on the renal function of the patient as Foscarnet is excreted through kidneys.

Dexamethasone

• It is used in post-infectious and disseminated encephalitis.
• It may be used as an adjunct with the antiviral agents