Encephalitis Health Article

When to call the doctor

A physician should be called whenever a headache does not respond to medication or when a person experiences a fever over 104°F (40.0°C), nausea and vomiting, visual disturbances, a stiff neck, or seizures.

A doctor should be called when an infant's temperature rises above 100°F (37.8°C) and cannot be brought down within a few minutes. Infants whose temperatures exceed 102°F (38.9°C) should be sponge-bathed in cool water while waiting for emergency help to arrive.

Diagnosis

Diagnosis of encephalitis includes careful questioning to determine possible exposure to viral sources. Tests that can help confirm the diagnosis and rule out other disorders include:

• blood tests (to detect antibodies to viral antigens and foreign proteins)
• cerebrospinal fluid analysis, or spinal tap (to detect viral antigens and provide culture specimens for the virus or bacteria that may be present in the cerebrospinal fluid)
• electroencephalogram (EEG)
• CT and MRI scans

A brain biopsy (surgical gathering of a small tissue sample) may be recommended in some cases in which treatment has thus far been ineffective and the cause of the encephalitis is unclear. Definite diagnosis by biopsy may allow specific treatment that would otherwise be too risky.

Treatment

Choice of treatment for encephalitis depends on the cause. Bacterial encephalitis is treated with antibiotics. Viral encephalitis is usually treated with antiviral drugs, including acyclovir, ganciclovir, foscarnet, ribavirin, and AZT. Viruses that respond to acyclovir include herpes simplex, the most common cause of sporadic (non-epidemic) encephalitis in the United States.

The symptoms of encephalitis may be treated with a number of different drugs. Corticosteroids, including prednisone and dexamethasone, are sometimes prescribed to reduce inflammation and brain swelling. Anticonvulsant drugs, including phenytoin, are used to control seizures. Fever may be reduced with acetaminophen or other fever-reducing drugs.

A person with encephalitis must be monitored carefully, since symptoms may change rapidly. Blood tests may be required regularly to track levels of fluids and salts in the blood.

Prognosis

Encephalitis symptoms may last several weeks. Most cases of encephalitis are mild, and recovery is usually quick. Mild encephalitis usually leaves no residual neurological problems. Overall, approximately 10 percent of those with encephalitis die from their infections or complications such as secondary infection. Some forms of encephalitis have more severe courses, including herpes encephalitis, in which mortality is 15 to 20 percent with treatment, and 70 to 80 percent without. Antiviral treatment is ineffective for eastern equine encephalitis, and mortality is approximately 30 percent.

Permanent neurological consequences may follow recovery in some cases. Consequences may include personality changes, memory loss, language difficulties, seizures, and partial paralysis.

Prevention

Because encephalitis is caused by infection, it may be prevented by avoiding the infection. Minimizing contact with others who have any of the viral illnesses listed above may reduce one's chances of becoming infected. Most infections are spread by hand-to-hand or hand-to-mouth contact; frequent hand washing may reduce the likelihood of infection if contact cannot be avoided.

Mosquito-borne viruses may be avoided by preventing mosquito bites. Mosquitoes are most active at dawn and dusk and are most common in moist areas with standing water. Covering skin and using mosquito repellents on exposed skin can reduce the chances of being bitten.

Vaccines are available against some viruses, including polio, herpes B, Japanese encephalitis, and equine encephalitis. Rabies vaccine is available for animals; it is also given to people after exposure. Japanese encephalitis vaccine is recommended for those traveling to Asia and staying in affected rural areas during transmission season.