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) when it is caused by disorders that are not infections or by drugs or vaccines.
(See also Introduction to Meningitis.)
The brain and spinal cord are covered by three layers of tissue called meninges. The subarachnoid space is located between the middle layer and the inner layer of the meninges. This space contains the cerebrospinal fluid, which flows through the meninges, fills the spaces within the brain, and helps cushion the brain and spinal cord.
Noninfectious meningitis is a type of aseptic meningitis (meningitis caused by something other than the bacteria that typically cause acute meningitis).
Tissues Covering the Brain
Within the skull, the brain is covered by three layers of tissue called the meninges. |
Causes of Noninfectious Meningitis
Noninfectious meningitis is caused by disorders that are not infections or by drugs or vaccines. Overall, these conditions are uncommon causes of meningitis.
Disorders that most commonly cause noninfectious meningitis include disorders that cause inflammation, such as 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 noninfectious meningitis include nonsteroidal anti-inflammatory drugs (NSAIDs) and certain antibiotics. Noninfectious meningitis due to NSAIDs may occur in people who have autoimmune disorders such as rheumatoid arthritis or systemic lupus erythematosus (lupus).
Noninfectious meningitis may also develop after a brain cyst ruptures and the fluid in it leaks into the subarachnoid space. Such cysts may be present at birth or be caused by a tapeworm infection called cysticercosis.
Symptoms 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.
Diagnosis of Noninfectious Meningitis
Spinal tap and analysis of cerebrospinal fluid
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) is done to obtain a sample of cerebrospinal fluid. Computed tomography (CT) or magnetic resonance imaging (MRI) is done first if doctors suspect that pressure within the skull is increased or that a brain cyst or other mass in the brain is the cause. In such cases, doing a spinal tap may cause a life-threatening disorder called brain herniation. After pressure within the skull is lowered or if no mass is detected, the spinal tap is done.
The sample of cerebrospinal fluid 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 in the cerebrospinal fluid.
Noninfectious meningitis is likely if people have a disorder or take a drug that can cause meningitis and the person's symptoms and test results do not suggest that the cause is an infection.
Treatment of Noninfectious Meningitis
Treatment of the cause
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
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.
