Inflammation of the meninges, the membranes that cover the brain and spinal cord, due to an infection
- Age and lifestyle as risk factors depend on the cause
- Gender and genetics are not significant factors
In meningitis, the meninges, the membranes that cover the brain and spinal cord, are inflamed. The disease is most often caused by a viral or bacterial infection. The viral form of meningitis is the more common and is usually not as severe as bacterial meningitis. The bacterial form is rarer but can be life-threatening. Although both forms of meningitis can occur at any age, bacterial meningitis occurs predominantly in children and young people between the ages of about 15 and 25 (see Meningitis in children), and viral meningitis is most common in young adults. In rare cases, meningitis may be caused by a fungal infection. This type predominates in people with AIDS (see HIV infection and AIDS) and in those with other disorders that impair the immune system, such as leukaemia.
What are the causes?
Many different viruses can result in meningitis. Among the most common are enteroviruses, such as the coxsackie virus, which can cause sore throats or diarrhoea, and, more rarely, the virus that causes mumps. Viral meningitis tends to occur in small outbreaks, most commonly in summer.
Bacterial meningitis most commonly occurs as a result of infection of the meninges with the bacterium Neisseria meningitidis (meningococcus) in an otherwise healthy child or teenager. This bacterium is the cause of meningococcal meningitis and has three main types: A, B, and C. Type B is the most common in the UK. Although many people carry Neisseria meningitidis bacteria in the back of their throats, only a fraction develop meningitis. Other bacteria that can cause the disease include Haemophilus influenzae (Hib) and Streptococcus pneumoniae, both of which can also cause infections in the lungs and the throat.
Less often, bacterial meningitis is a complication of an infection that has already developed elsewhere in the body. For example, the bacterium that causes tuberculosis can spread from the lungs to the meninges.
Bacterial meningitis usually occurs as single cases only. However, there may be small outbreaks, especially in institutions such as schools and colleges. This form of meningitis is most common during the winter.
People who have a weakened immune system as a result of an existing illness or a particular treatment, such as people with HIV infection or those having chemotherapy, are at increased risk of all types of meningitis.
What are the symptoms?
Initially, meningitis may produce vague flu-like symptoms, such as mild fever and aches and pains. More pronounced symptoms may then develop. Symptoms are the most severe in bacterial meningitis and may develop rapidly, often within a few hours.
The symptoms of viral meningitis may take a few days to develop, while in fungal and tuberculosis meningitis, symptoms develop slowly and may take several weeks to become pronounced. In adults, the main symptoms of meningitis may include the following:
Dislike of bright light.
Nausea and vomiting.
In meningococcal meningitis, a rash of flat, reddish-purple lesions, varying in size from pinheads to large patches, that do not fade when pressed (see Checking a red rash).
What might be done?
If meningitis is suspected, immediate medical attention and admission to hospital is necessary. Intravenous antibiotics are started immediately. A sample of fluid from around the spinal cord is then taken and tested for evidence of infection (see Lumbar puncture). In some cases, CT scanning or MRI of the brain may also be carried out before the lumbar puncture is performed.
If bacterial meningitis is confirmed by the lumbar puncture test, antibiotics are continued for at least a week. If meningitis is found to be caused by tuberculosis bacteria, antituberculous drugs will be given. In cases of bacterial meningitis, continuous monitoring in an intensive therapy unit is often needed. Intravenous fluids, anticonvulsant drugs, and drugs to reduce inflammation in the brain, such as corticosteroids, may be given.
There is no specific treatment for viral meningitis. If bacterial meningitis has been excluded by tests, people with viral meningitis are usually allowed to go home. They may be given drugs to relieve symptoms, such as painkillers for headaches. Fungal meningitis is treated with intravenous antifungal drugs in hospital.
What is the prognosis?
Recovery from viral meningitis is usually complete within 1–2 weeks. It may take weeks or months to make a complete recovery from bacterial meningitis. Occasionally, there may be long-term problems, such as impaired hearing or memory impairment due to damage to a part of the brain. About 1 in 10 people with bacterial meningitis dies despite treatment. Deaths most commonly occur in infants and elderly people.
Can it be prevented?
People in close contact with someone with meningococcal meningitis are usually given antibiotics for 2 days. This treatment kills any meningococcal bacteria that may be present in the back of the throat and prevents their spread to other people. Children are immunized against Haemophilus influenza type b (Hib) and Neisseria meningitidis type C (see Routine immunizations). No vaccine is yet available against type B meningoccal meningitis. People travelling to high-risk areas, such as certain African countries, might be advised to be immunized against several types of meningitis (types A, C, W135, and Y; see Travel immunizations).
From the 2010 revision of the Complete Home Medical Guide © Dorling Kindersley Limited.
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