In adults, a severe headache is the most common symptom of meningitis (87% in the bacterial form) followed by nuchal rigidity (neck stiffness). The classic triad of diagnostic signs consists of nuchal rigidity, sudden high fever, and altered mental status ; however, all three features are present in only 44–46% of all cases of bacterial meningitis. If none of the three signs is present, meningitis is extremely unlikely. Other signs commonly associated with meningitis include photophobia (intolerance to bright light), phonophobia (intolerance to loud noises), irritability and delirium (in small children). In infants up to 6 months of age, bulging of the fontanelle (the soft spot on top of a baby's head) may be present. Other features that might distinguish meningitis from less severe illnesses in young children are leg pain, cold extremities, and abnormal skin color.
Nuchal rigidity is the inability to flex the neck forward passively due to increased neck muscle tone. It occurs in 70% of adult cases of bacterial meningitis. Other signs of meningism include the presence of positive Kernig's sign or Brudzinski's sign. Kernig's sign is assessed with the patient lying supine, with the hip and knee flexed to 90 degrees. In a patient with a positive Kernig's sign, pain limits passive extension of the knee. A positive Brudzinski's sign occurs when flexion of the neck causes involuntary flexion of the knee and hip. Although Kernig's and Brudzinski's signs 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 patients reporting fever and headache. The patient is told to rapidly rotate his or her head horizontally; if this does not make the headache worse, meningitis is unlikely.
Meningitis caused by the bacteria 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, conjuctiva, 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. Although this rash is not necessarily present in meningococcal meningitis, it is relatively specific for the disease; it does, however, occasionally occur in meningitis due to other bacteria. Other clues as to the nature of the cause of meningitis may be the skin signs of hand, foot and mouth disease and genital herpes, both of which are associated with various forms of viral meningitis.
In most people with meningitis, the infection has no obvious source. However, recent trauma to the skull gives bacteria in the nasal cavity the potential to enter the meningeal space. Similarly, individuals with a cerebral shunt or related device (such as an extraventricular drain or Ommaya reservoir) are at increased risk of infection through those devices. In a small proportion of people, an infection in the head and neck area, such as otitis media, can lead to meningitis.
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