|Also Listed As:
|| Brain Inflammation, Viral
Encephalitis is an inflammation of the brain caused, most often, by a viral
infection. The specific viruses that cause encephalitis vary. Exposure to
viruses that cause encephalitis occur mostly through insect bites. The virus
enters through the blood stream and spreads to the brain, causing inflammation
of the nerve cells (encephalitis) and/or surrounding membranes (meningitis).
Encephalitis is different than meningitis, but these two brain infections often
occur together. Although the vast majority of individuals with encephalitis
recover after a long period of time, inflammation may cause irreparable damage
to the brain, bleeding within the brain, and even death. An estimated 10,000 to
20,000 cases of encephalitis are reported annually in the United
|Signs and Symptoms|
- 90% of people with encephalitis experience flu-like symptoms such as
fever, sore throat, cough, and malaise
- If meningitis accompanies encephalitis, an individual may experience
headache, stiff neck, intolerance to light, and/or vomiting
- A change in the level of consciousness, ranging from mild confusion to
coma, develops in virtually all people with encephalitis; often includes
disorientation and delusion with possible hallucinations, agitation, and
- Seizures occur in up to 50% of individuals with
- Other signs and symptoms of encephalitis depend on which area of the
brain is most affected; these may include an impaired ability to use or
comprehend words or coordinate voluntary muscle movements, muscle weakness or
partial paralysis on one side of the body, uncontrollable tremors or involuntary
movements, and an inability to regulate body
Arboviruses, or viruses carried by insects, are among the most common causes
of viral encephalitis. Some of the major arboviruses include:
- Eastern equine encephalitis - transmitted by
mosquito; primarily affects individuals along the eastern seaboard of the United
States; one-third of infected individuals die of the condition and many others
suffer permanent brain damage
- European and Far Eastern (Russian) encephalitis
- transmitted by ticks; although vaccine against this
type of encephalitis is available in Europe, there is speculation that it may
cause serious side effects
- Japanese encephalitis - transmitted by
mosquito; widespread in Asia; between 10% and 30% of infected individuals,
primarily children, die of the condition
- La Crosse encephalitis - transmitted by
mosquito; primarily affects children under 16 years of age in the upper
Midwestern United States; approximately 1% of infected individuals die of the
- St. Louis encephalitis - transmitted by
mosquito; primarily affects individuals in rural Midwestern and southern United
States; 7% of infected children and 30% of infected elderly die of the condition
- Venezuelan equine encephalitis - transmitted
by mosquito; primarily affects individuals in Central and South America;
fatalities rare in humans but common in horses; epidemics in people occasionally
occur after an outbreak in horses
- West Nile encephalitis - transmitted by
mosquito; primarily affects individuals in Africa and the Middle East, but
outbreaks have also been recently recorded in the United States (New York City
area and parts of New England); infections are most common in children and the
elderly; as many as 10% of infected individuals die of the
- Western Equine encephalitis - transmitted by
mosquito; primarily affects individuals in western United States and Canada;
usually causes a mild infection in people, except in children under 1 year of
age, who often suffer permanent complications; 3% of infected individuals die of
Other viruses that commonly cause viral encephalitis include:
- Herpes simplex virus type 1 (HSV1)
- Enteroviruses (viruses that typically occur in the gastrointestinal
Less common causes include:
- Epstein-Barr virus (EBV)
- Human immunodeficiency virus (HIV)
- Varicella-zoster virus (VZV)
- Rabies virus
Not all cases of encephalitis are caused by viruses. Some nonviral causes of
- Bacterial infection
- Fungal infection
- Parasitic infection
- Noninfectious causes, such as allergic reactions or
The following factors may increase an individual's risk for becoming infected
with viral encephalitis:
- Very young or very old age
- Exposure to mosquitoes or ticks
- Compromised immune system
- Not being immunized against measles, mumps, and rubella
- Traveling to areas where viral encephalitis is prevalent
- Handling potentially infected
Encephalitis is a serious condition, so diagnosis and initial treatment
usually take place in a hospital setting. After performing a physical exam, a
physician may take the following steps to diagnose the
- Blood test - detects viruses in the
- Spinal tap - detects viruses in the
- MRI and CT scan - determines whether bleeding
is present in the brain
- Electroencephalogram (EEG) - detects abnormal
The most effective way for an individual to prevent encephalitis is to avoid
contracting viruses that lead to encephalitis:
- Take protective measures when working or playing outside, such as
using insect repellant and wearing long pants and long sleeves
- Immunize against viruses that lead to encephalitis with vaccines such
as the measles, mumps, rubella (MMR), and rabies
- Maintain a balanced diet to keep the immune system healthy
- An infectious disease specialist may recommend a particular Japanese
encephalitis vaccine for those traveling to Asia during the summer, but serious
allergic reactions have been reported with its
Because encephalitis is a serious condition that can cause severe
complications, treatment usually occurs in the hospital and sometimes requires
intensive care. Generally, there are no specific medications to treat the
viruses causing encephalitis. HSV1, VZV, and EBV are exceptions to this rule,
acyclovir is an excellent treatment.
Often, people with symptoms of encephalitis are treated with this medication
until the virus causing the condition is identified.
Behavioral techniques, such as those used
to treat individuals with traumatic brain injury, have been recently explored in
the treatment of individuals recovering from the condition. Although
complementary and alternative therapies have not been extensively studied for
the treatment of encephalitis, some studies indicate that
scalp acupuncture, combined with proper
medication, may aid in the healing process. Careful observation and supportive
care, including rest, proper nutrition, and fluids are a mainstay of treatment
for encephalitis and allow the body to fight the infection.
Medications used to treat viral encephalitis include:
- Acyclovir - treats encephalitis caused by
HSV, VZV, and EBV
- Ganciclovir or foscarnet - treats
encephalitis caused by cytomegalovirus and HSV1
- Anticonvulsant medications - prevent and
treat seizures associated with
|Nutrition and Dietary Supplements|
Although nutrition and dietary supplements have not been scientifically
evaluated for use in treating encephalitis in humans, some studies suggest that
melatonin may protect animals from serious complications associated with the
condition and even increase their survival rates. In one study of mice that had
been infected with Venezuelan equine encephalitis virus, melatonin supplements
significantly reduced the presence of viruses in the blood and decreased the
rate of death by more than 80%. More studies are needed, however, to determine
whether similar treatment may offer the same protection to humans with viral
Astragalus (Astragalus membranaceus)
Animal studies suggest that Astragalus (Astragalus membranaceus), an
herb used in Asia to improve weakness and to enhance immune function, may also
protect humans from contracting viral encephalitis. In one study, mice that were
given astragalus extracts before being infected with Japanese encephalitis
virus, had a 60% to 80% chance of survival. Mice that did not receive astragalus
extracts before being infected with the virus only had a 10% chance of survival.
More studies are needed, however, to determine whether similar treatment may
offer the same protection to humans with viral encephalitis.
Professional herbalists may also use a combination of herbs to relieve the
symptoms associated with viral encephalitis, such as cognitive impairment,
visual and speech disturbances, and difficulty performing routine functions.
This herbal mixture includes:
- Ginkgo (Ginkgo biloba)
- St. John's wort (Hypericum perforatum)
- Rosemary (Rosmarinus
A study of a small number of individuals with complications associated with
encephalitis suggests that acupuncture delivered to the scalp may lessen the
severity of such complications and reduce the symptoms associated with the
condition. Some researchers theorize that scalp acupuncture is effective for
individuals with encephalitis because all meridians converge at the head, and
the method can stimulate and regulate qi throughout the entire body. More
research is necessary, however, to conclusively determine whether scalp
acupuncture is safe and effective for individuals with encephalitis.
|Massage and Physical Therapy|
Behavioral and Physical Training
Recently, behavioral and physical training techniques have been explored in
the treatment of individuals recovering from encephalitis. In one case, a woman
experiencing poor short-term memory and decreased muscle coordination as a
result of viral encephalitis began to improve significantly after participating
in a behavioral rehabilitation training program. As a result of the program, she
gained a high level of independence and was able to return home from the
hospital with only minimal assistance by a caregiver. More studies are needed to
determine whether behavioral training is safe and effective for other
individuals recovering from encephalitis.
The most common cause of encephalitis in newborns is vaginal delivery from a
mother who is infected with herpes simplex virus 2 (HSV 2). This infection in
newborns is often severe and fatal. For this reason, cesarean section may be
advised for pregnant women with a history of HSV 2, even if there is no sign of
an active infection.
|Prognosis and Complications|
Full recovery from encephalitis can take weeks or months, during which time
many individuals experience complications ranging from fatigue and difficulty
concentrating to tremors and personality changes. The most severe complications
associated with encephalitis result from the destruction of nerve cells in the
brain that do not regenerate. The severity of complications depends on the
condition of the immune system (whether it is healthy or weak) and the infection
causing the encephalitis. For example, 80% of those infected with Eastern equine
encephalitis, St. Louis encephalitis, and Japanese encephalitis, have permanent
neurologic impairments (such as memory, speech, vision, hearing, muscle control,
and sensation) and a very low survival rate, while those infected with EBV or
Venezuelan equine encephalitis rarely experience any serious complications. The
long-term outlook for those with HSV encephalitis depends primarily on how
quickly the condition is treated.
Between 80% and 95% of individuals infected with viral encephalitis will
survive the condition, but 20% will experience debilitating side effects or
complications, such as memory loss or severe personality changes. The survival
rate for those with HSV encephalitis increases dramatically from 30% to 70% when
the condition is detected early and treated with antiviral
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|Review Date: March 2001|
|Reviewed By: Participants in the review process include: Jacqueline A. Hart, MD,
Department of Internal Medicine, Newton-Wellesley Hospital, Harvard University
and Senior Medical Editor Integrative Medicine, Boston, MA; David Winston,
Herbalist, Herbalist and Alchemist, Inc., Washington,
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