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Noninfectious meningitis is inflammation of the layers of tissue that cover the brain and spinal cord (meninges) and of the fluid-filled space between the meninges (subarachnoid space) and is caused by disorders that are not infections or by drugs.
The subarachnoid space is located between the middle layer and the inner layer of the meninges (see Figure: Viewing the Brain). This space contains the cerebrospinal fluid.
Noninfectious meningitis is a type of aseptic meningitis (meningitis caused by something other than the bacteria that typically cause acute meningitis).
Disorders and drugs are uncommon causes of meningitis. Disorders that most commonly cause meningitis include disorders that cause inflammation, including the inflammation that occurs when the body's immune system malfunctions and attacks the body's own tissues (autoimmune disorders). Such disorders include rheumatoid arthritis and systemic lupus erythematosus (lupus).
Drugs that can cause meningitis include nonsteroidal anti-inflammatory drugs (NSAIDs) and certain antibiotics.
Noninfectious meningitis may also develop after fluid leaks from a brain cyst into the subarachnoid space. Such cysts may be caused by a tapeworm infection called cysticercosis (see Cysticercosis).
Some Causes of Noninfectious Meningitis
Usually, noninfectious meningitis causes symptoms that are similar to those of bacterial meningitis but are milder and may develop more slowly. Symptoms include headache, a stiff neck, and often fever. When the neck becomes stiff, lowering the chin to chest becomes painful.
Most people recover in 1 to 2 weeks.
Doctors suspect meningitis when people have a headache and stiff neck, particularly with fever. They then try to determine whether meningitis is bacterial (requiring immediate treatment) or not. If the symptoms are less severe, the cause is less likely to be bacteria.
A spinal tap (lumbar puncture—see Tests for Brain, Spinal Cord, and Nerve Disorders : Spinal Tap) is done to obtain a sample of cerebrospinal fluid, which is sent to a laboratory to be examined and analyzed. Sugar and protein levels and the number and type of white blood cells in the fluid are determined. The fluid is cultured to check for bacteria and thus rule out or confirm bacterial meningitis. Noninfectious meningitis is possible when the fluid contains excess white blood cells (indicating inflammation) and does not contain any bacteria that could be the cause. Then other tests are done to identify infectious organisms other than bacteria, such as viruses and fungi. Noninfectious meningitis is likely If a noninfectious cause (such as a disorder that is not an infection, a drug, or recent vaccination) is possible and the person's symptoms and test results do not suggest that the cause is an infection.
If doctors suspect that a brain cyst is the cause, they do magnetic resonance imaging (MRI) of the brain or, if MRI is unavailable, computed tomography (CT).
If people appear very ill, doctors start treatment right away without waiting for test results to identify the cause. Treatment includes antibiotics, which are given until doctors are sure that these people do not have bacterial meningitis, which, if untreated, can quickly cause permanent brain damage or death (see Acute Bacterial Meningitis). They are also given acyclovir (an antiviral drug) in case the infection is due to herpes simplex virus.
After the cause is identified, doctors treat the cause accordingly—for example, by treating a disorder or stopping a drug. Symptoms are treated as needed.
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