Encephalitis
Inflammation of the brain usually caused by a viral infection. Often, the meninges (membranes covering the brain) are affected. An attack may be very mild, but in most cases it is a serious condition.
The most common strains of encephalitis in North America include St. Louis encephalitis (SLE), eastern equine encephalitis (EEE), California encephalitis (CE), western equine encephalitis, La Crosse encephalitis, Venezuelan equine encephalitis, WEST NILE VIRUS encephalitis, and Powassan encephalitis (spread by ticks, not mosquitoes). Japanese encephalitis is not found in the United States, but it is very common throughout Asia and poses a risk to international travelers.
Cause
Most of the time, the virus responsible is the HERPES simplex virus type I, which also causes COLD SORES. In the United States it may also be caused by a virus transmitted to humans via mosquito bite, causing St. Louis encephalitis. More and more cases are related to infection with HIV, the organism responsible for AIDS. Occasionally, encephalitis is a complication of other viral infections such as MEASLES or MUMPS.
Symptoms
Usually, symptoms begin with headache, fever, and prostration, leading to hallucinations, confusion, paralysis of one side of the body, and disturbed behavior, speech memory, and eye movement. There is a gradual loss of consciousness and sometimes a coma; epileptic seizures may develop. If the meninges are affected, the neck is usually stiff and the eyes are unusually sensitive to light.
Central nervous system symptoms include some (not all) of these:
- abnormal reflexes
- changes in consciousness
- confusion
- disorientation
- dizziness
- inability to speak
- irritability
- listlessness
- loss of balance
- odor hallucinations
- seizure
- sleepiness
- spasticity
- tremor
- weakness
Diagnosis
Symptoms, signs, and the results of CT scans, EEG, and a spinal tap will help diagnose the disease.
Treatment
The antiviral drug ACYCLOVIR administered intravenously is an effective treatment for encephalitis caused by the herpes virus. If the disease is related to other viral infections, there is no known effective treatment. Depending on the virus causing the problem, some patients will die and some who recover will have brain damage, with mental impairment, behavioral disturbances, and epilepsy. Supportive care is the treatment of choice in these cases.
Tags: Encephalitis, Inflammation of the brain, meninges are affected, usually caused by a viral infection
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