WHAT IS IT?
Encephalitis is an acute inflammatory disease of the brain, usually caused by a virus. It is usually a serious medical condition but may be so mild that it is barely noticeable. The primary disorder is due to a direct viral invasion of the central nervous system. Sporadic encephalitis is most commonly due to the herpes simplex virus. Epidemic varieties of encephalitis are usually due to mosquito-borne viruses (arboviruses) that occur only in warm weather. An increasing number of cases are caused by infection with the human immunodeficiency virus (HIV). Encephalitis can also occur as a secondary complication following viral infections such as measles,
chickenpox, rubella, mumps and other less well-known viruses.
HOW IS IT DIAGNOSED?
History: In adults, the initial symptoms of malaise (vague feeling of discomfort or illness), fever, headache, loss of appetite (anorexia), and nausea progress to a subtle change of personality and confusion. In later stages, mental disturbances become more apparent and may include difficulty in talking (dysphasia), weakness, seizures, severe disorientation, and coma. In secondary viral encephalitis, the disease may develop five to ten days after onset of the initial viral infection.
Physical exam may show evidence of fever, as well as stiff neck, signs of meningeal irritation, tremors, convulsions, cranial nerve palsies, paralysis of extremities, and abnormal reflex reactions.
Tests: Lumbar puncture to collect spinal fluid for analysis may reveal increased pressure of the cerebrospinal fluid, as well as an increased protein content and cell count (usually lymphocytes).
A CT scan or MRI of the brain may detect temporal lobe lesions caused by a herpes virus infection. Measuring the electrical activity of the brain by electroencephalography (EEG) is also useful in diagnosing a herpes virus encephalitis, but a brain biopsy (sample of brain tissue collected for microscopic examination) is usually necessary to confirm a diagnosis of herpes encephalitis while excluding other treatable diseases. Occasionally, specific diagnosis of a viral infection can only be made by comparing a sample of the individual's blood taken during the disease with a sample taken after the disease has resolved (acute and convalescent antibody titers).
HOW IS IT TREATED?
Supportive measures are used to maintain the individual's hydration, electrolyte balance, and nutritional needs. Medication may be needed to reduce fever, reduce intracranial pressure, and prevent seizures. Antiviral agents are available for the treatment of some forms of encephalitis. For other viral infections, there is no known effective treatment. Physical and speech therapies may be necessary for individuals with mental impairment.
WHAT MIGHT COMPLICATE IT?
Possible complications include
seizures, demyelinating conditions (causing loss of sensation, coordination, and power in specific areas of the body), and death. The meninges (membranes that cover and enclose the brain) may also be involved, causing meningoencephalitis.
PREDICTED OUTCOME
Overall, ten percent of individuals with encephalitis will die. Encephalitis caused by eastern equine and
herpes simplex viruses is associated with severe disease and high mortality rates. Severe cases usually require hospitalization and leave significant mental impairment including loss of memory, the inability to speak coherently, lack of muscle coordination, paralysis, and hearing or vision defects. Individuals under the age of 30 and those who are only lethargic at the onset of treatment, are more likely to survive than are older or comatose individuals. In mild cases, full recovery occurs within two to three weeks.
ALTERNATIVES
Conditions with similar symptoms include
meningitis, cerebral abscess, septic emboli, cortical septic thrombophlebitis, toxic encephalopathies, subdural and subarachnoid hemorrhage, porphyria, and
multiple sclerosis.
REHABILITATION
Physical therapy and/or occupational therapy, three to five times a week, for a period of six to twelve weeks.
APPROPRIATE SPECIALISTS
Neurologist, infectious disease specialist, physical therapist, and speech therapist.