Encephalitis and Meningitis

Encephalitis and meningitis facts

• Encephalitis is an inflammation of the brain.
• Meningitis is an inflammation of the membranes (called meninges) that surround the brain and spinal cord.
• Anyone experiencing symptoms of encephalitis or meningitis should see a doctor immediately.

What is encephalitis?

Encephalitis is an inflammation of the brain. There are many types of encephalitis, most of which are caused by infections. Most often these infections are caused by viruses. In addition to infections, encephalitis can also be caused by certain diseases that result in an inflammation of the brain.

What are encephalitis symptoms and signs?

The signs and symptoms of encephalitis can range from very mild symptoms to potentially life-threatening. Signs and symptoms of encephalitis include sudden fever, headache, vomiting, visual sensitivity to light, stiff neck and back, confusion, drowsiness, unsteady gait, and irritability. Loss of consciousness, poor responsiveness, seizures, muscle weakness, sudden severe dementia and memory loss can also be found in patients with encephalitis.
Anyone experiencing symptoms of encephalitis should see a doctor immediately.

What is meningitis?

Meningitis is an inflammation of the membranes (called meninges) that surround the brain and spinal cord. Meningitis may be caused by many different viruses and bacteria. It can also be caused by diseases that can trigger inflammation of tissues of the body without infection (such as systemic lupus erythematosus and Behcet's disease).

What are meningitis symptoms and signs?

The classic signs and symptoms of meningitis are headache, fever, and stiff neck (in adults and older children). Symptoms of meningitis may appear suddenly and can also include nausea and vomiting. Changes in behavior, such as confusion, sleepiness, and difficulty waking up, are other important symptoms. In infants, symptoms of meningitis are often much less specific and may include irritability or tiredness, poor feeding, and fever.
Some types of meningitis can be deadly if not treated promptly. Anyone experiencing symptoms of meningitis should see a doctor immediately.

What is encephalomyelitis?

Encephalomyelitis is inflammation of both the brain and spinal cord. Encephalomyelitis can be caused by a variety of conditions that lead to irritation of the brain and spinal cord. Among the common causes of encephalomyelitis are viruses which infect the nervous tissues (for example, herpes zoster virus). People with encephalomyelitis can exhibit combinations of the various symptoms of either encephalitis or meningitis.

How are encephalitis and meningitis diagnosed?

Encephalitis or meningitis is suggested when the symptoms described above are present. The doctor diagnoses encephalitis or meningitis after a completing a thorough history (asking the patient questions) and examination. The examination includes special maneuvers to detect signs of inflammation of the membranes that surround the brain and spinal cord (meninges). Based on the history and examination, the doctor suggests specific tests to further help in determining the diagnosis.
Tests that are used in the evaluation of individuals suspected of having encephalitis or meningitis include evaluation of the blood for signs of infection and possible presence of bacteria, brain scanning (such as CT scanning or MRI scan), and cerebrospinal fluid analysis.
A lumbar puncture is the most common method of obtaining a sample of the fluid in the spinal canal (the cerebrospinal fluid or CSF) for examination. A lumbar puncture (an LP) is the insertion of a needle into the fluid within the spinal canal. It is termed a "lumbar puncture" because the needle goes into the lumbar portion of the back (the lower portion of the back). The needle passes between the bony parts of the spine until it reaches the cerebral spinal fluid. A small amount of fluid is then collected and sent to the laboratory for examination. The evaluation of the spinal fluid is usually necessary for the definite diagnosis and to help make optimal treatment decisions (such as the appropriate choice of antibiotics).
The diagnosis is confirmed by abnormal spinal fluid results and, in the case of an infection, by identifying the organism causing the infection. In patients with meningitis, the CSF fluid often has a low glucose (sugar) level and increased white blood cell count. In addition, the fluid can be used to identify some viral causes of meningitis (PCR or polymerase chain reaction) or be used to culture bacterial organisms causing the meningitis.

What is the treatment of encephalitis and meningitis?

Antibiotic and/or antiviral medications need to be considered urgently when the diagnosis of encephalitis or meningitis is suggested. In some situations, anticonvulsants are used to prevent or treat seizures. Sometimes corticosteroids are administered to reduce brain swelling and inflammation. Sedatives may be needed for irritability or restlessness. Additional medications might be used to decrease the fever or treat headaches. The need for hospitalization usually depends on the type of meningitis the patient has and the severity of symptoms.

What is the outlook (prognosis) for patients with encephalitis or meningitis?

The prognosis for encephalitis or meningitis varies. Some cases are mild, short, and relatively benign and patients have full recovery. Other cases are severe, and permanent impairment or death is possible. This is usually determined by the type of infection present and how quickly treatment can be started. Meningitis can lead to permanent damage to the nervous system and can cause hydrocephalus. The acute phase of encephalitis may last for one to two weeks, with gradual or sudden resolution of fever and neurological symptoms. Neurological symptoms may require many months before full recovery occurs. Some patients will not fully recover.
With early diagnosis and prompt treatment, many patients recover from meningitis. Viral meningitis can be self-limiting to 10 days or less, however, in some cases, the disease progresses so rapidly that death occurs during the first 48 hours, despite early treatment.

Is meningitis contagious?

Yes. Especially some forms of bacterial meningitis are contagious. The bacteria are spread through the exchange of respiratory and throat secretions (for example, coughing, kissing). Fortunately, none of the bacteria that cause meningitis are as contagious as conditions like the common cold or flu, and they are not spread by casual contact or by simply breathing the air where a person with meningitis has been. However, sometimes the bacteria that cause meningitis can spread to other people who have had close or prolonged contact with a patient with meningitis. Meningitis caused by Neisseria meningitidis (also called meningococcal meningitis) is the most important example. People in the same household, dormitory, or day-care center, or anyone with direct contact with a patient's oral secretions (such as a boyfriend or girlfriend) would be considered at increased risk of acquiring the infection. This also holds true for health-care professionals involved in direct, prolonged contact, especially during procedures such as intubations (placing a breathing tube). People who qualify as close contacts of a person with meningitis caused by N. meningitidis should receive antibiotics to prevent them from getting the disease.

Can meningitis be prevented?

Basic steps to avoid spread of organisms, such a hand washing and covering your mouth when coughing, will also help in decreasing the risk of spreading meningitis. There are vaccines against Hib (Haemophilus influenzae type B) and against some strains of N. meningitidis and many types of Streptococcus pneumoniae.
The vaccines against Hib are considered very safe and highly effective. By 6 months of age, every infant should receive at least three doses of an Hib vaccine. A fourth dose ("booster") should be given to children between 12 and 18 months of age.
There is also a vaccine that protects against four strains of N. meningitidis, but it is not routinely used in the United States. It is not effective in children under 18 months of age. It is sometimes used to control outbreaks of some types of meningococcal meningitis in the United States. College students are typically given the vaccine prior to residence at college.
Although large epidemics of meningococcal meningitis do not occur in the United States, some countries experience large, periodic epidemics. Overseas travelers should check to see if meningococcal vaccine is recommended for their destination. Travelers should receive the vaccine at least one week before departure if possible.
A vaccine to prevent meningitis due to S. pneumoniae (also called pneumococcal meningitis) can also prevent other forms of infection due to S. pneumoniae. The pneumococcal vaccine is not effective in children under 2 years of age, but it is recommended for all people over 65 years of age and younger people with certain chronic medical problems.

REFERENCE:

United States. National Institute of Neurological Disorders and Stroke, National Institutes of Health. "Meningitis and Encephalitis Fact Sheet." Dec. 18, 2009. <http://www.ninds.nih.gov/disorders/encephalitis_meningitis/detail_encephalitis_meningitis.htm>.

Medical Author:

Jerry R. Balentine, DO, FACEP

Medical Editor:

William C. Shiel Jr., MD, FACP, FACR

Source:Medicinenet.com.