This type of meningitis is usually caused by viruses but it may be due to bacterial infection that has already been partially treated, when bacteria disappear from the meninges, or pathogens infect a space adjacent to the meninges (e.g. sinusitis). Endocarditis (an infection of the heart valves which spreads small clusters of bacteria through the bloodstream) may cause aseptic meningitis. Aseptic meningitis may also result from infection with spirochetes, a group of bacteria that includes Treponema pallidum (the cause of syphilis) and Borrelia burgdorferi (known for causing Lyme disease). Meningitis may be encountered in cerebral malaria (malaria infecting the brain) or amoebic meningitis, meningitis due to infection with amoebae such as Naegleria fowleri, contracted from freshwater sources. Bacterial
The types of bacteria that cause bacterial meningitis vary according to the infected individuals age group. In premature babies and newborns up to three months old, common causes are group B streptococci (subtypes III which normally inhabit the vagina and are mainly a cause during the first week of life) and bacteria that normally inhabit the digestive tract such as Escherichia coli (carrying the K1 antigen). Listeria monocytogenes (serotype IVb) can be contracted when consuming improperly prepared food such as dairy products, produce and deli meats, and may cause meningitis in the newborn. Older children are more commonly affected by Neisseria meningitidis (meningococcus) and Streptococcus pneumoniae (serotypes 6, 9, 14, 18 and 23) and those under five by Haemophilus influenzae type B (in countries that do not offer vaccination).
Other signs include the presence of positive Kernigs sign or Brudziński sign. Kernigs sign is assessed with the person lying supine, with the hip and knee flexed to 90 degrees. In a person with a positive Kernigs sign, pain limits passive extension of the knee. A positive Brudzinskis sign occurs when flexion of the neck causes involuntary flexion of the knee and hip. Although Kernigs sign and Brudzinskis sign are both commonly used to screen for meningitis, the sensitivity of these tests is limited. They do, however, have very good specificity for meningitis: the signs rarely occur in other diseases. Another test, known as the "jolt accentuation maneuver" helps determine whether meningitis is present in those reporting fever and headache. A person is asked to rapidly rotate the head horizontally; if this does not make the headache worse, meningitis is unlikely.Other problems can produce symptoms similar to those above, but from non-meningitic causes. This is called meningism or pseudomeningitis.Meningitis caused by the bacterium Neisseria meningitidis (known as "meningococcal meningitis") can be differentiated from meningitis with other causes by a rapidly spreading petechial rash, which may precede other symptoms. The rash consists of numerous small, irregular purple or red spots ("petechiae") on the trunk, lower extremities, mucous membranes, conjunctiva, and (occasionally) the palms of the hands or soles of the feet. The rash is typically non-blanching; the redness does not disappear when pressed with a finger or a glass tumbler.