Meningitis is inflammation of the meninges. The meninges is the collective name for the three membranes that envelope the brain and spinal cord (central nervous system), called the dura mater, the arachnoid mater, and the pia mater. The meninges' main function, alongside the cerebrospinal fluid is to protect the central nervous system.
The word "meningitis" comes from the Modern Latin word meninga and the Greek word Menix meaning "membrane". The suffix "itis" comes from the Greek word itis meaning "pertaining to". In medical English, the suffix "-itis means" "inflammation of".
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Fast facts on meningitis
10-12% of meningitis cases in the industrialized countries are fatal.
20% of meningitis survivors suffer long-term consequences, such as brain damage, kidney disease, hearing loss, or limb amputation.
There are 2,300 cases of meningitis and meningococcal septicemia in the UK each year.
70% of meningitis patients are aged under 5 or over 60.
In the USA bacterial meningitis affects about 3/100,000 people annually.
In the USA viral meningitis affects about 10/100,000 people annually.
Bacterial meningitis caused by Haemophilus influenzae type b has fallen 90% since the Hib vaccine was introduced.
Antibiotic resistance is a major factor in global rising rates of meningitis.
What causes meningitis?
Meningitis is generally caused by infection of viruses, bacteria, fungi, parasites, and certain organisms. Anatomical defects or weak immune systems may be linked to recurrent bacterial meningitis. In the majority of cases the cause is a virus. However, some non-infectious causes of meningitis also exist.
Bacteria mimic human cells to get in and stay in
A study carried out by researchers at the University of Oxford and Imperial College London, England, showed how bacteria that cause bacterial meningitis mimic human cells in order to evade the body's innate immune system.
Although viral meningitis is the most common, it is rarely a serious infection. It can be caused by a number of different viruses, such as mosquito-borne viruses. There is no specific treatment for this type of meningitis. In the vast majority of cases the illness resolves itself within a week without any complications.
Bacterial meningitis is generally a serious infection. It is caused by three types of bacteria: Haemophilus influenzae type b, Neisseria meningitidis, and Streptococcus pneumoniae bacteria. Meningitis caused by Neisseria meningitides is known as meningococcal meningitis, while meningitis caused by Streptococcus pneumoniae is known as pneumococcal meningitis. People become infected when they are in close contact with the discharges from the nose or throat of a person who is infected.
Twenty years ago Hib was the main cause of bacterial meningitis - it is not any more thanks to new vaccines which are routinely administered to children.
The doctor needs to know what type of meningitis has infected the patient. Certain antibiotics can stop some types from infecting others.
Bacterial meningitis in newborns and premature babies
A type of streptococci, called group B streptococci commonly inhabits the vagina and is a common cause of meningitis among premature babies and newborns during the first week of life. Escherichia coli, which inhabit the digestive tract, may also cause meningitis among newborns. Meningitis that occurs during epidemics can affect newborns - Listeria monocytogenes being the most common.
Bacterial meningitis in children under 5
Children under five years of age in countries that do not offer the vaccine are generally infected by Haemophilus influenzae type B.
Bacterial meningitis in older children
Older children generally have meningitis caused by Neisseria meningitides (meningococcus), and Streptococcus pneumoniae (serotypes 6, 9, 14, 18 and 23) .
Bacterial meningitis in adults
About 80% of all adult meningitis are caused by N. meningitidis and S. pneumoniae. People over 50 years of age have an increased risk of meningitis caused by L. monocytogenes.
Bacterial meningitis and people with skull damage implanted devices
People who received a recent trauma to the skull are at increased risk of bacteria in their nasal cavity entering the meningeal space. Patients with a cerebral shunt or related device also run a higher risk of infection with staphylococci and pseudomonas through those devices.
Bacterial meningitis and weak immune systems
People with weak immune systems are also at higher risk of infection with staphylococci and pseudomonas.
Bacterial meningitis and ear infections and procedures
Rarely, otitis media, mastoiditis, or some infection to the head or neck area may lead to meningitis. People who have received a cochlear implant run a higher risk of developing pneumococcal meningitis.
A study published in Otolaryngology-Head and Neck Surgery found that children who are stricken with severe hearing loss are five times more likely to contract meningitis.
In countries where tuberculous meningitis is common, there is a higher incidence of meningitis caused by Mycobacterium tuberculosis.
Anatomical defects or disorders of the immune system
Either congenital or acquired anatomical defects may be linked to recurrent bacterial meningitis. An anatomical defect might allow a way to penetrate into the nervous system from the external environment. The most common anatomical defect which leads to meningitis is skull fracture, especially when the fracture occurs at the base of the brain, or extends towards the sinuses and petrous pyramids.
59% of recurrent meningitis cases are due to anatomical defects, while 36% are due to weakened immune systems.
Symptoms of meningitis
As meningitis and septicemia tend to show similar symptoms and incidences of both tend to rise and fall at the same time in geographical areas, this section refers to both meningitis and septicemia.
Meningitis is not always easy to recognize. In many cases meningitis may be progressing with no symptoms at all. In its early stages, symptoms might be similar to those of flu. However, people with meningitis and septicemia can become seriously ill within hours, so it is important to know the signs and symptoms. Early symptoms of meningitis broadly include:
- Muscle pain
- High temperature (fever)
- Cold hands and feet
- A rash that does not fade under pressure. This rash might start as a few small spots in any part of the body - it may spread rapidly and look like fresh bruises. This happens because blood has leaked into tissue under the skin. The rash or spots may initially fade, and then come back.
In babies, you should look out for at least one of the following symptoms:
- a high-pitched, moaning cry
- a bulging fontenelle
- being difficult to wake
- floppy and listless or stiff with jerky movements
- refusing feeds
- rapid/ unusual/ difficult breathing
- pale or blotchy skin
- red or purple spots that do not fade under pressure
In older children, you should look out for:
- a stiff neck
- severe pains and aches in your back and joints
- sleepiness or confusion
- a very bad headache (alone, not a reason to seek medical help)
- a dislike of bright lights
- very cold hands and feet
- rapid breathing
- red or purple spots that do not fade under pressure
On the next page we look at the glass test (a method of checking meningitis symptoms), treatments and available vaccines.