Aseptic meningitis, or sterile meningitis, is a condition in which the layers lining the brain, meninges, become inflamed and a pyogenic bacterial source is not to blame. Meningitis is diagnosed on a history of characteristic symptoms and certain examination findings (e.g., Kernig's sign). Investigations should show an increase in the number of leukocytes present in the cerebrospinal fluid (CSF), obtained via lumbar puncture, (normal being fewer than five visible per microscopic High Power Field). The term aseptic is frequently a misnomer, implying a lack of infection. On the contrary, many cases of aseptic meningitis represent infection with viruses or mycobacteria that cannot be detected with routine methods. While the advent of polymerase chain reaction has increased the ability of clinicians to detect viruses such as enterovirus, cytomegalovirus, and herpes virus in the CSF, many viruses can still escape detection.
Contributions by NCurse, Arcadian, and Joncomelately.