Meningitis (pl. meningitides) is acute or chronic inflammation of the protective membranes covering the brain and spinal cord, collectively called the meninges. The most common symptoms are fever, intense headache, vomiting, neck stiffness, and occasionally photophobia. Other symptoms include confusion or altered consciousness, nausea, and an inability to tolerate loud noises. Young children often exhibit only nonspecific symptoms, such as irritability, drowsiness, or poor feeding. A non-blanching rash (a rash that does not fade when a glass is rolled over it) may also be present. The inflammation may be caused by infection with viruses, bacteria, fungi or parasites. Non-infectious causes include malignancy (cancer), subarachnoid hemorrhage, chronic inflammatory disease (sarcoidosis) and certain drugs. Meningitis can be life-threatening because of the inflammation's proximity to the brain and spinal cord; therefore, the condition is classified as a medical emergency. A lumbar puncture, in which a needle is inserted into the spinal canal to collect a sample of cerebrospinal fluid (CSF), can diagnose or exclude meningitis. Some forms of meningitis are preventable by immunization with the meningococcal, mumps, pneumococcal, and Hib vaccines. Giving antibiotics to people with significant exposure to certain types of meningitis may also be useful for preventing transmission. The first treatment in acute meningitis consists of promptly giving antibiotics and sometimes antiviral drugs. Corticosteroids can be used to prevent complications from excessive inflammation. Meningitis can lead to serious long-term consequences such as deafness, epilepsy, hydrocephalus, or cognitive deficits, especially if not treated quickly. In 2019, meningitis was diagnosed in about 7.7 million people worldwide, of whom 236,000 died, down from 433,000 deaths in 1990. With appropriate treatment, the risk of death in bacterial meningitis is less than 15%. Outbreaks of bacterial meningitis occur between December and June each year in an area of sub-Saharan Africa known as the meningitis belt. Smaller outbreaks may also occur in other areas of the world. The word meningitis comes from the Greek μῆνιγξ (meninx, 'membrane') and the medical suffix -itis ('inflammation').
Signs and symptoms
Clinical features
In adults, the most common symptom of meningitis is a severe headache, occurring in almost 90% of cases of bacterial meningitis, followed by neck stiffness (the inability to flex the neck forward passively due to increased neck muscle tone and stiffness). The classic triad of diagnostic signs consists of neck stiffness, sudden high fever, and altered mental status; however, all three features are present in only 44–46% of bacterial meningitis cases. If none of the three signs are present, acute meningitis is extremely unlikely. Other signs commonly associated with meningitis include photophobia (intolerance to bright light) and phonophobia (intolerance to loud noises). Small children often do not exhibit the aforementioned symptoms and may only be irritable and look unwell. The fontanelle (the soft spot on the top of a baby's head) can bulge in infants aged up to 6 months. Other features that distinguish meningitis from less severe illnesses in young children are leg pain, cold extremities, and an abnormal skin color. Neck stiffness occurs in 70% of adults with bacterial meningitis. Other signs include the presence of positive Kernig's sign or Brudziński sign. Kernig's sign is assessed with the person lying in the supine position, with the hip and knee flexed to 90 degrees. In a person with a positive Kernig's sign, pain limits passive knee extension. A positive Brudzinski's sign occurs when neck flexion causes involuntary flexion of the knee and hip. Although Kernig's sign and Brudzinski's sign are both commonly used to screen for meningitis, the test sensitivity is limited. They do, however, have excellent specificity for meningitis: the signs rarely occur in other diseases. Another test, known as the "jolt accentuation maneuver" (aka the "jolt test") 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. 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 on 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.
Early complications
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