Meningitis is inflammation of the protective membranes covering the brain and spinal cord, known collectively as the meninges.

The most common symptoms of meningitis are headache and neck stiffness. There can also be fever, altered consciousness and inability to tolerate bright light (photophobia) or loud noises (phonophobia). In meningococcal meningitis (caused by a type of bacteria called meningococcus) there is a typical petechial rash consisting of small purple or red spots that do not blanch when compressed (which can be checked using a transparent object such as a glass). While some forms of meningitis are mild and resolve on their own, meningitis is a potentially life-threatening condition due to the proximity of the inflammation to the brain and spinal cord. The potential for serious neurological damage or even death necessitates prompt medical evaluation.

The inflammation is usually caused by an infection of the fluid surrounding the brain and spinal cord. Meningitis may develop in response to a number of causes, usually bacteria, viruses and other microbes, but also physical injury, cancer or certain drugs.

Meningitis is treated promptly with antibiotics or antiviral drugs. To prevent complications from overactive inflammation, corticosteroid drugs are given in some situations. Some forms of meningitis (such as those associated with meningococcus, mumps virus or pneumococcus infections) are contagious, but may be prevented with immunization. Meningitis can also lead to long-term complications such as deafness, epilepsy or hydrocephalus.

Signs and symptoms

Severe headache is the most common symptom of meningitis (87 percent) followed by nuchal rigidity ("neck stiffness", found in 83%). The classic triad of diagnostic signs consists of nuchal rigidity, sudden high fever and altered mental status. All three features are present in only 44% of all cases of infectious meningitis. Other signs commonly associated with meningitis are photophobia (inability to tolerate bright light), phonophobia (inability to tolerate loud noises), irritability and delirium (in small children) and seizures (in 20-40% of cases). In infants (0-6 months), swelling of the fontanelle (soft spot) may be present.

Nuchal rigidity is the inability to flex the neck forward passively due to increased tone in the neck muscles. Other signs of meningism include Kernig's sign and Brudzinski's sign. Kernig's sign is typically assessed with the patient lying supine, with both 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 knee and hip flexion. Although commonly tested, the sensitivity and specificity of Kernig's and Brudzinski's tests are limited.