Meningitis refers to inflammation of the coverings (meninges) of the central nervous system. Meningitis can be caused by bacteria, viruses, or other rarer organisms that gain access to the body, spread to the blood stream, and then seed the meninges, which leads to inflammation/infection. Signs and symptoms of meningitis include photophobia (avoidance of light), fever, stiff neck, and nausea.

In neurosurgical patients, meningitis can also be caused by direct spread of an organism into the cerebrospinal fluid/meninges since these patients have had prior surgery in that area, weakening the body's natural defenses. In either case, meningitis requires prompt diagnosis and treatment, which can entail sampling of the cerebrospinal fluid by lumbar puncture, for example, and administering intravenous antibiotics if bacterial meningitis is suspected.