A severe inflammation of the brain, encephalitis is usually caused by a mosquito-borne or (in some areas) a tick-borne virus. The virus may also be transmitted through ingestion of infected goat’s milk and accidental injection or inhalation of the virus. In encephalitis, intense lymphocytic infiltration of brain tissues and the leptomeninges causes cerebral edema, degeneration of the brain’s ganglion cells, and diffuse nerve cell destruction. Eastern equine encephalitis may produce permanent neurologic damage and is often fatal.
Encephalitis can be divided into two forms, primary and secondary encephalitis. Primary encephalitis occurs when a virus directly invades the brain and spinal cord. Secondary, or post-infectious encephalitis occurs when a virus first infects another organ and secondarily enters the brain. Symptoms include fever, headache, and altered mental status, often accompanied by seizures or focal neurologic deficits. Diagnosis requires CSF analysis and neuroimaging. Treatment is supportive and, for certain causes, includes antiviral drugs.
Meningitis and encephalitis are inflammatory diseases of the membranes that surround the brain and spinal cord and are caused by bacterial or viral infections. It’s a rare disease that only occurs in approximately 0.5 per 100,000 individuals most commonly in children, the elderly, and people with weakened immune systems (i.e., those with HIV/AIDS or cancer).
Encephalitis can cause brain damage, which may result in or exacerbate the symptoms of a developmental disorder or mental illness. The form called encephalitis lethargica results in a set of Parkinson’s disease like symptoms called postencephalitic parkinsonianism. In some cases encephalitis causes death. Treatment of encephalitis must begin as early as possible to avoid potentially serious and life-long effects. Depending on the cause of the inflammation, this may include antibiotics, anti-viral medications, and anti-inflammatory drugs. If brain damage results from encephalitis, therapy may help patients regain lost functions.
The viruses responsible are often common viruses. They include measles, chicken pox, influenza, enteroviruses (tummy bugs) and herpes simplex I (the cold sore virus). In most cases the virus involved is not identified. Arthropod-borne viruses, which are usually transmitted by mosquitoes, cause arboviral encephalitis. People who live in warm, moist climates are at higher risk for this type. Other causes include herpesvirus,mumps virus, human immunodeficiency virus, adenoviruses, and demyelinating diseases following measles, varicella, rubella, or vaccination.
The most common symptoms of encephalitis are fever, severe headache, and confusion. Symptoms that require emergency treatment include loss of consciousness, poor responsiveness, seizures, muscle weakness, sudden severe dementia, memory loss, withdrawal from social interaction, and impaired judgement. Anyone experiencing symptoms of encephalitis should see a doctor immediately.
Antiviral medications may be prescribed for encephalitis caused by the herpes virus or other severe viral infections. Antibiotics are prescribed for bacterial infections. Anticonvulsants are used to prevent or treat seizures. Corticosteroids are used to reduce brain swelling and inflammation. Sedatives may be needed for irritability or restlessness. Over-the-counter medications may be used for fever and headache. Individuals with bacterial meningitis are usually hospitalized and treated with antibiotics intravenously. Antiviral drugs may also be prescribed.
