Overview of meningitis

[Kai]

Meningitis is inflammation of the meninges and subarachnoid space. It may result from infections, other disorders, or reactions to drugs. Severity and acuity vary. Findings typically include headache, fever, and nuchal rigidity, Diagnosis is by cerebrospinal fluid (CSF) analysis. Treatment includes antimicrobial drugs as indicated plus adjunctive measures.
(See also Introduction to Brain Infections and Neonatal Bacterial Meningitis.)
Meningitis may be classified as acute, subacute, chronic, or recurrent. It may also be classified by its cause: bacteria, viruses, fungi, protozoa, or, occasionally, noninfectious conditions. But the most clinically useful categories of meningitis are

Acute bacterial meningitis
Viral meningitis
Noninfectious meningitis
Recurrent meningitis
Subacute and chronic meningitis
Meningeal inflammation as an atypical reaction to anti-inflammatory, immunosuppressive, or other drugs

Acute bacterial meningitis is particularly serious and rapidly progressive. Viral and noninfectious meningitides are usually self-limited. Subacute and chronic meningitides usually follow a more indolent course than other meningitides, but determining the cause can be difficult.
Aseptic meningitis, an older term, is sometimes used synonymously with viral meningitis; however, it usually refers to acute meningitis caused by anything other than the bacteria that typically cause acute bacterial meningitis. Thus, aseptic meningitis can be caused by

Viruses
Noninfectious conditions (eg, drugs, disorders)
Occasionally, other organisms (eg, Borrelia burgdorferi in Lyme disease, Treponema pallidum in syphilis)