Meningitis

Meningitis is the inflammation of the meninges¹, most commonly due to infection with a bacterium or virus – bacterial meningitis tends to be potentially life-threatening, whereas viral meningitis is usually relatively benign. The classic triad of symptoms seen in meningitis is headache, neck stiffness and photophobia², with other symptoms depending upon the microbe involved and the severity of the disease. Meningitis may also occur together with encephalitis³ – this is known as meningo-encephalitis. Meningitis is a notifiable disease in the UK, meaning that public health authorities are notified of all cases.

Causes

The cause of bacterial meningitis depends upon age. Children less than one year old – newborns in particular – are vulnerable to a specific set of bacteria such as Escherichia coli⁴, Listeria monocytogenes⁵ and Group B streptococcus⁶. On the other hand, bacterial meningitis in adults has two common causes:

• Neisseria meningitidis, also known as meningococcus, is found in the nasal passages of 10% of the population and is spread via droplets in coughs and sneezes, and by direct contact such as kissing⁷. The meningococcus can also cause meningococcal septicaemia, a life-threatening bacterial infection of the blood. In the UK, a vaccine against the C serotype⁸ is given to all infants as part of the national immunisation scheme. A vaccine also exists that covers serotypes A, C, W135 and Y, and is recommended to individuals visiting high-risk areas such as pilgrims travelling on the Hajj to Saudi Arabia. Unfortunately, no vaccine exists for the B serotype, which continues to be a common cause of meningitis.

• Streptococcus pneumoniae, also known as pneumococcus, is also found in the upper airways, and is a common cause of pneumonia. It may cause meningitis by spreading directly to the meninges through a skull fracture, or by spreading via the blood following pneumonia. Those at risk of pneumococcal meningitis include children under the age of two years, the elderly, individuals with no spleen and, of course, those who have suffered a skull fracture. In the UK, the elderly are offered a vaccination at age 65 against pneumococcal infection, and since September 2006 a separate vaccination has been given to all infants as part of the national immunisation scheme.

Since the introduction of a vaccine in the 1980s, meningitis due to Haemophilus influenzae type b has become rare. Spirochaete bacteria may also rarely cause a meningo-encephalitis, and include Leptospira (Weil's disease), Borrelia burgdorferi (tick-borne Lyme disease) and Treponema pallidum (syphilis).

Mycobacterium tuberculosis, the organism responsible for TB, may rarely produce a sub-acute form of meningitis in which the individual slowly becomes unwell. M. tuberculosis is spread via droplets from the respiratory tract and usually causes tuberculosis in the lungs, but can cause infection anywhere in the body.

Viral meningitis is most commonly caused by the enteroviruses such as the poliovirus, coxsackie viruses A and B and the echoviruses. All of these are found in the human gut, and are spread both through faecal contamination of food and in the droplets of coughs and sneezes from those suffering from an infection. Viral meningitis may also be caused by various other organisms such as herpes simplex, the varicella zoster virus, the Epstein-Barr virus, or the paramyxovirus⁹.

In individuals with an impaired immune system, such as those with HIV, other organisms may also cause meningitis. These include Mycobacterium tuberculosis (see above), which causes widespread infection in such individuals, the fungus Cryptococcus neoformans, and Listeria monocytogenes (see above). It is worth noting that HIV itself may also cause meningitis.

Occasionally, meningitis may be caused by an amoeba contracted by drinking unsterilised water, or by Toxoplasma gondii, a parasite found in cat litter. Also, meningitis can occur as the result of a non-infectious condition such as cancer, sarcoidosis or systemic lupus.

Symptoms in Adults and Children

For a pictorial reference for the symptoms of meningitis, see the Meningitis Trust website. The symptoms listed on that website are highlighted here in bold type. Any individual with symptoms suggestive of meningitis should seek medical attention immediately.

As mentioned above, meningitis can cause headache, neck stiffness and photophobia, all of which are a result of the irritation of the meninges. Individuals with bacterial meningitis tend to become unwell rapidly, whereas viral meningitis tends to be relatively mild and may be preceded by a flu-like illness. Vomiting may also occur in severe meningitis.

A non-fading, purple rash may occur and is a sign of meningococcal septicaemia, which is a separate condition and may occur with or without meningococcal meningitis. Meningococcal septicaemia may also produce stomach cramps, diarrhoea, fever, drowsiness, and confusion. As the rash does not occur in all cases, any individual with suspected meningitis should seek medical attention immediately rather than waiting for a rash. A morbilliform (measles-like) rash may occur in some cases of viral meningitis – unlike the rash of meningococcal septicaemia, a morbilliform rash will fade when a glass is pressed against it, but this differentiation is best left to a doctor.

Symptoms in Infants

Babies with meningitis tend to be irritable, cry when picked up, and have a fever. Other symptoms include drowsiness, paleness, floppiness, rapid breathing or grunting, unusual crying or moaning, refusal of food or vomiting, and a rash in cases of septicaemia. Parents with a baby in such a state will hardly need telling to take their baby to a doctor immediately.

Diagnosis and Treatment

Diagnosis of meningitis is based on a history of the above symptoms and examination for rash, neck stiffness, neurological symptoms and signs of serious infection. Provided that the patient does not have signs of raised intracranial pressure, a lumbar puncture can be performed¹⁰; otherwise, a CT scan of the brain must first be performed. A lumbar puncture involves inserting a needle into the layers surrounding the spinal cord in order to remove some of the cerebrospinal fluid (CSF). In bacterial meningitis, the CSF becomes cloudy and bacteria may be detected by PCR testing or culture of the fluid¹¹. Blood cultures are taken before antibiotics are started to help identify the bacteria responsible, and a throat swab may also be taken. In viral meningitis, the CSF remains clear and no bacteria can be detected, leading to the use of the confusing term 'aseptic meningitis' for such CSF samples – an 'aseptic meningitis' may also be due to a spirochaete, TB, fungus or amoeba.

When bacterial meningitis or meningococcal septicaemia is suspected, antibiotics are started as soon as blood samples have been taken for culture. Out of hospital, suspected meningitis can be treated with benzyl penicillin. Treatment is usually with a third-generation cephalosporin antibiotic such as cefotaxime, ceftriaxone or ceftazidime, with adjustments being made once tests reveal the bacterium responsible and the antibiotics to which it is sensitive. Steroids are sometimes given alongside antibiotics in order to treat swelling around the brain and reduce the risk of long-term consequences such as deafness. Ampicillin is given to pregnant women and individuals with an impaired immune system to cover the possibility of listeria. In order to target the appropriate range of bacteria, newborns are treated with the antibiotics penicillin and gentamicin.

In viral meningitis due to herpes simplex, treatment is with the antiviral acyclovir. There is no specific treatment for meningitis due to other viruses, though drugs may be given to reduce swelling of the brain.

Prognosis

Without treatment, bacterial meningitis is typically fatal. With treatment, the prognosis varies with age: the death rate is around 10% on average, with adults and newborns having a 20% chance of dying and children having only a 2% chance. However, 15% of the children who survive suffer from hearing loss, epilepsy or learning difficulties, and around a third of adults suffer from either hearing loss or some form of cognitive impairment¹².

Viral meningitis is rarely fatal and tends not to have long-term effects. However, this does not mean viral infections never cause harm – viral encephalitis has a death rate of 20% and is associated with a risk of severe long-term brain damage.

Treatment of Contacts

Individuals who have been in close contact with an individual with bacterial meningitis are usually followed up by a public health team and given antibiotic treatment to prevent them falling ill (chemoprophylaxis). This usually consists of rifampicin, ciprofloxacin or a cephalosporin. However, no follow-up is required for pneumococcal meningitis.

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¹ The meninges are three layers of tissue that cover the brain.
² Excessive sensitivity to light.
³ Inflammation of the brain tissue itself.
⁴ E. coli is found in the gut and generally only causes meningitis in newborns.
⁵ Listeria is a food-borne bacteria found in soft cheeses, cold meats and unwashed fruit and vegetables. Pregnant women are usually advised to avoid these foods.
⁶ Group B streptococcus is the most common cause of meningitis in newborns as it can spread from the mother to the baby at birth, and can also spread amongst babies in intensive care wards. The risk of Group B streptococcal infection is currently being tackled by such measures as screening pregnant women and treating them before they give birth.
⁷ We're talking about more than a peck on the cheek here.
⁸ A serotype is a subdivision of a species of bacteria based upon the different proteins found in the different types.
⁹ The paramyxovirus causes mumps, and was the most common cause of viral meningitis until the MMR vaccine was introduced.
¹⁰ Signs such as reduced conscious level, a drop in pulse rate, rising blood pressure, neurological signs and swelling of the optic disc all suggest that an individual has an increased degree of pressure inside their brain and spinal cord. This can be caused by meningitis or encephalitis, and makes taking a lumbar puncture dangerous.
¹¹ Polymerase chain reaction (PCR) testing detects an organism's DNA by multiplying it to a detectable level, whereas a culture involves growing it on a plate.
¹² Cognitive impairment refers to an impairment of brain function, and includes problems with memory, intelligence, learning, speech and other aspects of higher function.