Encephalitis

Encephalitis is irritation and swelling (inflammation) of the brain, most often due to infections.

Causes Symptoms Exams and Tests Treatment Outlook

Encephalitis is a rare condition. It occurs more often in the first year of life and decreases with age. The very young and older adults are more likely to have a severe case.

Encephalitis is most often caused by a virus. Many types of viruses may cause it. Exposure can occur through:

Breathing in droplets from the nose, mouth, or throat from an infected person
Contaminated food or drink
Mosquito, tick, and other insect bites
Skin contact

Different viruses occur in different geographic locations. Many cases occur during a certain season.

Encephalitis caused by the herpes simplex virus is the leading cause of more severe cases in all ages, including newborns.

Routine vaccination has greatly reduced encephalitis due to some viruses, including:

Measles
Mumps
Polio
Rabies
Rubella
Varicella (chickenpox)

Other viruses that cause encephalitis include:

Adenovirus
Coxsackievirus
Cytomegalovirus
Eastern equine encephalitis virus
Echovirus
Japanese encephalitis, which occurs in Asia
West Nile virus

After the virus enters the body, the brain tissue swells. This swelling may destroy nerve cells, and cause bleeding in the brain and brain damage.

Other causes of encephalitis may include:

An allergic reaction to vaccinations
Autoimmune disease
Bacterial infections such as Lyme disease, syphilis, and tuberculosis
Parasites such as roundworms, cysticercosis, and toxoplasmosis in people with HIV/AIDS and other people who have a weakened immune system
The effects of cancer

Some people may have symptoms of a cold or stomach infection before encephalitis symptoms begin.

When this infection is not very severe, the symptoms may be similar to those of other illnesses:

Fever that is not very high
Mild headache
Low energy and a poor appetite

Other symptoms include:

Clumsiness, unsteady gait
Confusion, disorientation
Drowsiness
Irritability or poor temper control
Light sensitivity
Stiff neck and back (sometimes)
Vomiting

Symptoms in newborns and younger infants may not be as easy to recognize:

Body stiffness
Irritability and crying more often (these symptoms may get worse when the baby is picked up)
Poor feeding
Soft spot on the top of the head may bulge out more
Vomiting

Emergency symptoms:

Loss of consciousness, poor responsiveness, stupor, coma
Muscle weakness or paralysis
Seizures
Severe headache
Sudden change in mental functions, such as flat mood, impaired judgment, memory loss, or a lack of interest in daily activities

Your health care provider will perform a physical exam and ask about symptoms.

Tests that may be done include:

Brain MRI
CT scan of the head
Single-photon emission computed tomography (SPECT)
Culture of cerebrospinal fluid (CSF), blood, or urine (however, this test is rarely useful)
Electroencephalogram (EEG)
Lumbar puncture and CSF examination
Tests that detect antibodies to a virus (serology tests)
Test that detects tiny amounts of bacteria or virus DNA (nucleic acid amplification)

The goals of treatment are to provide supportive care (rest, nutrition, fluids) to help the body fight the infection, and to relieve symptoms.

Medicines may include:

Antiviral medicines, if a virus caused the infection
Antibiotics, if bacteria are the cause
Antiseizure medicines to prevent seizures
Steroids to reduce brain swelling
Sedatives for irritability or restlessness
Acetaminophen for fever and headache

If brain function is severely affected, physical therapy and speech therapy may be needed after the infection is controlled.

Setting Up Your Home
Watching Your Skin
Treating Pain
Treating Other Symptoms

Remove loose wires and rugs from areas where you walk.
Do not keep small pets in your home.
Fix uneven flooring in doorways.
Have good lighting.
Put handrails in the bathtub or shower and next to the toilet. Place a slip-proof mat in the bathtub or shower.

Wear shoes at all times to protect your feet from injury. Before you put them on, always check inside your shoes for stones or rough areas that may hurt your feet.

Check your feet every day. Look at the top, sides, soles, heels, and between the toes. Wash your feet every day with lukewarm water and mild soap. Use lotion, petroleum jelly, lanolin, or oil on dry skin.

Check bathwater temperature with your elbow before putting your feet in the water.

Avoid putting pressure on areas with nerve damage for too long.

Medicines may help reduce pain in the feet, legs, and arms. They usually do not bring back loss of feeling. Your provider may prescribe:

Pain pills
Topical agents that relieve pain
Medicines that treat seizures or depression, which can also manage pain

Your provider may refer you to a pain specialist. Talk therapy may help you better understand how your pain is affecting your life. It can also help you learn ways to better cope with pain.

Taking medicine, sleeping with your head raised, and wearing elastic stockings may help with low blood pressure and fainting. Your provider may give you medicines to help with bowel movement problems. Eating small, frequent meals may help. To help bladder problems, your provider may suggest that you:

Do Kegel exercises to strengthen your pelvic floor muscles.
Use a urinary catheter, a thin tube inserted into your bladder to drain urine.
Take medicines.

Medicines can often help with erection problems.

The outcome varies. Some cases are mild and short, and the person fully recovers. Other cases are severe, and permanent problems or death is possible.

The acute phase normally lasts for 1 to 2 weeks. Fever and symptoms gradually or suddenly disappear. Some people may take several months to fully recover.

Symptoms are often worst during the teenage years and then improve in early adulthood. In some people, symptoms go away entirely for a few years and then return. In a few people, symptoms do not return at all.

Possible Complications Prevention When to Contact a
Medical Professional

Permanent brain damage may occur in severe cases of encephalitis. It can affect:

Hearing
Memory
Muscle control
Sensation
Speech
Vision

Children and adults should avoid contact with anyone who has encephalitis.

Controlling mosquitoes (a mosquito bite can transmit some viruses) may reduce the chance of some infections that can lead to encephalitis.

Apply an insect repellant containing the chemical DEET when you go outside (but do not use DEET products on infants younger than 2 months).
Remove any sources of standing water (such as old tires, cans, gutters, and wading pools).
Wear long-sleeved shirts and pants when outside, especially at dusk.

Children and adults should get routine vaccinations for viruses that can cause encephalitis. People should receive specific vaccines if they are traveling to places such as parts of Asia, where Japanese encephalitis is found.

Vaccinate animals to prevent encephalitis caused by the rabies virus.

Go to the emergency room or call 911 or the local emergency number if you have:

Sudden fever
Other symptoms of encephalitis

References

Beckham JD, Tyler KL. Encephalitis. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett’s Principles and Practice of Infectious Diseases. 9th ed. Philadelphia, PA: Elsevier; 2020:chap 89.

Bronstein DE, Glaser CA. Encephalitis and meningoencephalitis. In: Cherry JD, Harrison GJ, Kaplan SL, Steinbach WJ, Hotez PJ, eds. Feigin and Cherry’s Textbook of Pediatric Infectious Diseases. 8th ed. Philadelphia, PA: Elsevier; 2019:chap 36.