(What?) and How are encephalitis and meningitis diagnosed?

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. Encephalitis can also be caused by diseases that cause inflammation of the brain.

What are symptoms of encephalitis?

Symptoms of encephalitis include sudden fever, headache, vomiting, visual sensitivity to light, stiff neck and back, confusion, drowsiness, clumsiness, 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 symptoms of meningitis?

Symptoms of meningitis, which may appear suddenly, often include high fever, severe and persistent headache, stiff neck, nausea, and vomiting. Changes in behavior, such as confusion, sleepiness, and difficulty waking up, are 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 the term used to refer to 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 MRI scan), and spinal 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 (the lower portion of the back). (Less commonly, spinal fluid can also be obtained from other levels of the spine.) 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.



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