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Viral encephalitis

Description

An in-depth report on the causes, diagnosis, treatment, and prevention of viral encephalitis.

Alternative Names

West Nile virus

Treatment

With the exception of herpes simplex and varicella-zoster encephalitis, the viral forms of encephalitis are not treatable. The primary objective is to diagnose the patient as soon as possible so they receive the right medicines to treat the symptoms. It is very important to lower fever and ease the pressure caused by swelling of the brain.

Patients with very severe encephalitis are at risk for body-wide (systemic) complications including shock, low oxygen, low blood pressure, and low sodium levels. Any potentially life-threatening complication should be addressed immediately with the appropriate treatments.

Treating Probable Causes of Encephalitis

Since it is difficult to determine the cause of encephalitis and rapid treatment is essential, it is common to give the patient medication for the symptoms that respond to therapy without waiting to determine the cause of the illness.

• Some experts advise immediately administering intravenous acyclovir, the standard treatment for herpes simplex encephalitis, to all patients whose symptoms indicate encephalitis.
• Corticosteroids, which reduce inflammation, may also be administered immediately.
• Antibiotics, which attack bacteria but not viruses, are used in case the cause of the symptoms is bacterial meningitis.

Additional Treatments

All encephalitis treatments are aimed at reducing symptoms.

• Seizures may be prevented by using fosphenytoin (Cerebyx).
• Seizures may be treated with intravenous lorazepam (Ativan).
• Sedatives may be prescribed for irritability or restlessness.
• Simple pain relievers may be used for fever and headache.
• In patients who are otherwise stable, the only other treatment measures are to keep the head elevated and monitor the patient's status.

Treatments for Herpes Virus Encephalitis

Intravenous acyclovir is the treatment of choice for encephalitis caused by herpes simplex virus or varicella-zoster virus. Treatment must be initiated within 2 days of symptoms for the best outcome. In nearly all cases, the virus clears within 2 weeks of treatment. If it does not, medications are continued for another 2 weeks. In rare cases, surgical measures may be needed to relieve the buildup of pressure in the brain.

Acyclovir is usually administered in the hospital. However, some patients may be safely treated with intravenous medications at home after the first few days with close monitoring by a health professional.

About 25% of patients who have been successfully treated for herpes encephalitis have a relapse. Early diagnosis and treatment may help reduce this risk. Doctors are investigating if a 3-month course of oral valacyclovir will improve remission rates after a patient completes treatment with intravenous acyclovir. Foscarnet (Foscavir), another powerful antiviral drug known as a pyrophosphate analogue, may be useful for herpes simplex viral strains that have become resistant to acyclovir.

Investigational Treatments for West Nile Virus and Other Arboviruses

There are no drugs that have been effective for treating arboviruses, including West Nile virus. A number of drugs used to treat other virus infections are being investigated. They include ribavirin (an antiviral drug used to treat influenza), interferon alfa 2a (Roferon-A) and other interferons, immunoglobulin G, and glycyrrhizin (a compound in licorice root with anti-viral activity). Researchers with the U.S. National Institutes of Health are investigating Omr-IgG-am, a blood-derived product that contains WNV antibodies, which can be given intravenously.

Treatment for Acute Disseminated Encephalomyelitis (ADEM)

ADEM is usually treated with high-dose intravenous methylprednisolone, a powerful anti-inflammatory drug known as a corticosteroid. Intravenous immunoglobulin (IVIG), alone or in combination with methylprednisolone, is also showing promise in certain patients, including children with severe ADEM.

Recombinant erythropoietin epoetin alfa (Epogen, Procrit, AraNESP), a genetically engineered drug that stimulates the production of red blood cells, may also help protect the brain. Experimental work suggests it may be helpful for patients with ADEM.

• Review Date: 1/18/2007
• Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital

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