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The term meninges refers to 3 membranes that surround the brain and spinal cord: the dura
mater, the arachnoid mater, and the pia mater.
The meninges protect and provide structural support for the brain as well as contain cerebrospinal
Meningitis is an inflammation of the meninges.
This inflammation is typically caused by an infection, although there are non-infectious
causes of meningitis as well.
A variety of pathogens can cause meningitis, but the most severe cases tend to involve
bacterial infections.
Although the central nervous system is separated from the bloodstream by barriers like the
blood-brain barrier and blood-cerebrospinal fluid barrier, meningitis can occur when pathogens
evade these types of barriers and enter the meninges.
When a pathogen enters the cerebrospinal fluid, an immune response causes the inflammation
that characterizes meningitis.
As a consequence of the immune response, the blood-brain barrier is made more permeable.
This causes an influx of white blood cells and constituents of blood plasma into the
cerebrospinal fluid, which contributes to inflammation and increases the volume and
viscosity of the cerebrospinal fluid.
These changes contribute to the development of cerebral edema, or the accumulation of
fluid in the brain, as well as to the build-up of the pressure inside the skull, known as
intracranial pressure.
The increased intracranial pressure can disrupt cerebral blood flow and result in damage to
brain tissue.
Common symptoms of meningitis include headache, neck stiffness, fever, and altered mental
status, but the disease can cause serious long-term complications or death.
A lumbar puncture, or spinal tap, is typically done to diagnose meningitis.
Although treatment will vary depending on the cause of the disease, antibiotics are
often started before a diagnosis is made if bacterial meningitis is suspected, as bacterial
meningitis is typically fatal if left untreated.