Encephalitis

Encephalitis means inflammation of the brain. It can be caused by bacterial infections and, most often, viral infections.Several thousand cases of encephalitis are reported each year, but many more may actually occur, since the symptoms may be mild to non-existent in most patients

Types of Encephalitis

There are two types of the condition:

• Primary encephalitis (also called acute viral encephalitis) is caused by a direct viral infection of the spinal cord and brain. The infection may be focal (located in only one area) or diffuse (located in many different areas).
• Secondary encephalitis (also known as post-infective encephalitis) can result from complications of a current viral infection. When this type results from an immunization or earlier viral infection, it is known as acute disseminated encephalitis. This illness often occurs two to three weeks following the initial infection.

Causes

Most cases of encephalitis in the United States are caused by:

• Enteroviruses
• Herpes simplex virus types 1 and 2
• A bite from a rabid animal (rabies virus)
• Arboviruses, which are transmitted from infected animals to humans through the bite of an infected tick, mosquito, or other blood-sucking insect.

Lyme disease, a bacterial infection spread by tick bite, can also cause it.

Who Is at Risk?

Anyone can get it. People with weakened immune systems, including those with HIV or those taking immunosuppressant drugs, are at the highest risk of contracting encephalitis.

Symptoms

The brain inflammation caused by encephalitis can produce a wide range of symptoms, including:

• Sudden fever
• Headache
• Vomiting
• Heightened sensitivity to light
• Confusion and impaired judgment
• Drowsiness
• Weak muscles
• Clumsy and unsteady gait
• Irritability.

Symptoms that might require emergency treatment include:

• Loss of consciousness
• Seizures
• Muscle weakness
• Sudden severe dementia.

Encephalitis Diagnosis

In order to make an encephalitis diagnosis, the doctor will ask a number of questions to review activities of the past several days (such as recent exposure to insects or animals, any contact with ill people, or recent travel), perform a physical exam, and may order various tests.

Early encephalitis diagnosis is vital, as encephalitis symptoms can appear suddenly and escalate to brain damage, hearing and/or speech loss, blindness, or even death.

Using Neurological Exams to Make an Encephalitis Diagnosis

A neurological examination involves a series of tests designed to assess:

• Motor and sensory function
• Nerve function
• Hearing and speech
• Vision
• Coordination and balance
• Mental status
• Changes in mood or behavior.

Doctors may test the function of the nervous system through tests of strength and sensation with the aid of items including a tuning fork, small light, reflex hammer, and pins.

Laboratory Screening as a Means of Making an Encephalitis Diagnosis

Laboratory screening of blood, urine, and body secretions can help detect and identify brain and/or spinal cord infection and determine the presence of antibodies and foreign proteins. Such tests can also rule out metabolic conditions that have similar symptoms.

For example, a throat culture may be taken to check for viral or bacterial organisms that cause meningitis or encephalitis. In this procedure, the back of the throat is wiped with a sterile cotton swab, which is then placed on a culture medium. Viruses and bacteria are then allowed to grow on the medium. Samples are usually taken in the physician's office or in a laboratory setting and sent out for analysis to state laboratories or to the U.S. Centers for Disease Control and Prevention. Results are usually available in two to three days.

Encephalitis Diagnosis: Analysis of Cerebrospinal Fluid

Analysis of the cerebrospinal fluid that surrounds and protects the brain and spinal cord can detect infections in the brain and/or spinal cord, acute and chronic inflammation, and other diseases.

In a procedure known as a spinal tap (or lumbar puncture), a small amount of cerebrospinal fluid is removed by a special needle that is inserted into the lower back. The skin is anesthetized with a local anesthetic prior to the sampling. The fluid, which is completely clear in healthy people, is tested to detect the presence of bacteria or blood, as well as to measure glucose levels (a low glucose level is a sign of bacterial or fungal meningitis) and white blood cells (elevated white blood cell counts are also a sign of infection). The procedure is usually done in a hospital and takes about 45 minutes.

Encephalitis Diagnosis: CT Scan and MRI

Computer-assisted imaging can reveal signs of brain inflammation, internal bleeding or hemorrhage, or other brain abnormalities. Two painless, noninvasive imaging procedures routinely used to make an encephalitis diagnosis are CT scans and MRI.

Encephalitis Treatment

People who are suspected of having encephalitis should receive immediate, aggressive encephalitis treatment. Encephalitis can progress quickly and has the potential to cause severe, irreversible neurological damage.

Medications for Encephalitis Treatment

Treatment for very mild cases of encephalitis may include being monitored at home by the physician and a caregiver.

Supportive care as part of encephalitis treatment includes:

• Fluids
• Bed rest
• Over-the-counter analgesics to reduce fever and headache.

Antiviral drugs (including either acyclovir or ganciclovir) may be used for viral encephalitis treatment.

For more severe cases, encephalitis treatment may involve hospitalization. Anticonvulsants may be prescribed to stop or prevent seizures, and sedatives may be used to calm more severely infected people. Certain drugs may be used to counter nausea and vomiting. Corticosteroids and intravenous administration of carbohydrate solutions can reduce brain swelling. Patients with breathing difficulties may require artificial respiration.

Complementary Therapy and Encephalitis Treatment

For patients who experience severe brain inflammation, encephalitis treatment may involve physical, speech, and occupational therapy once the acute illness is under control.

The outcome of encephalitis treatment generally depends on the particular infectious agent involved, the severity of the illness, and how quickly treatment is given. In most cases, people with very mild encephalitis can make a full recovery, although the process may be slow.

Patients receiving treatment for viral encephalitis usually see some relief in 24 to 48 hours and recover in about a month.

In more serious cases, encephalitis can cause:

• Hearing and/or speech loss
• Blindness
• Permanent brain and nerve damage
• Behavioral changes
• Cognitive disabilities
• Lack of muscle control
• Seizures
• Memory loss.

These patients may need long-term therapy, medication, and supportive care.

Encephalitis Treatment: Prevention

There are ways to reduce the chance of getting encephalitis so that encephalitis treatment is not needed.

Good personal hygiene can reduce the risk of getting encephalitis from an infected person. Avoid sharing food, utensils, glasses, and other objects with a person who may be exposed to or have the infection. Wash hands often with soap and rinse under running water.

To lessen the risk of being bitten by an infected mosquito or other insect, people should:

• Limit outdoor activities at night
• Wear long-sleeved clothing when outdoors
• Use insect repellents that are most effective for that particular region of the country
• Rid lawn and outdoor areas of free-standing pools of water, in which mosquitoes breed.

Do not over-apply repellants, particularly on young children and especially infants, as chemicals may be absorbed through the skin.

Encephalitis Research

Current research efforts include gaining a better understanding of how the central nervous system responds to inflammation and the role of T cells (blood cells involved in immune system response) in suppressing infection in the brain.

Scientists hope to better understand the molecular mechanisms involved in the protection and disruption of the blood-brain barrier, which could lead to the development of new treatments for several neuroinflammatory diseases such as meningitis and encephalitis.

Other scientists hope to define, at a molecular level, how certain viruses overcome the body's defense mechanism and interact with target host cells.

A possible treatment under investigation involves testing neuroprotective compounds that block the damage that accumulates after the inflammation of encephalitis. (This damage can lead to potential complications including dementia and loss of cognitive function.)