Meningitis

Meningitis is an inflammation of the meninges. These are the membranes that surround the brain and spinal cord.

In some cases, in addition to the meninges, the inflammation also affects the brain. This is then referred to as meningoencephalitis.

Meningitis is caused by bacteria, viruses and other pathogens. Other potential causes include a misguided immune system, cancer or the side-effects of medication.

The typical symptoms include a high temperature, headache, stiff neck and impaired consciousness. People with the condition often appear dazed or confused.

If caused by bacteria, the condition is referred to as purulent meningitis. If no bacteria can be detected, it is referred to as aseptic meningitis. Aseptic meningitis is more common and less dangerous.

The symptoms of meningitis depend on the precise cause of the condition, the age of the person affected and the condition of their immune system.

Typical symptoms are:

• high temperature
• neck stiffness
• headache

In many cases, general symptoms also occur, such as:

• light sensitivity
• nausea and/or vomiting
• diarrhea

Skin rashes can provide important information about the pathogens: meningococci cause bleeding into the skin; pneumococci cause blisters.

The inflamed meninges can lead to an increase in pressure in the cranial cavity. This is the cavity around the brain that is formed by the cranial bones. The heightened pressure can lead to impaired consciousness, the failure of certain cranial nerves and epileptic seizures.

In newborns and small children, the symptoms of meningitis are usually less obvious. They can have either a high or a low temperature. A swollen fontanelle – the soft area between the cranial bones – may indicate inflammation. Furthermore, sick children eat and drink less or have an altered mental status.

In older people, confusion or impaired consciousness can be the main symptom of meningitis.

Meningitis is usually caused by pathogens.

Other triggers such as cancer, autoimmune disorders or taking medication such as non-steroidal anti-inflammatory drugs (NSAIDs) or certain antibiotics are rare.

In most cases, meningitis is caused by viruses. For example:

• enteroviruses: these trigger hand, foot and mouth disease, for instance
• parechoviruses: these cause respiratory and gastrointestinal infections
• Epstein-Barr viruses: pathogens of glandular fever
• herpes simplex viruses: pathogens of oral and genital herpes
• varicella-zoster viruses: pathogens of chickenpox and shingles
• SARS-CoV-2: pathogen of COVID-19
• arboviruses: these include viruses transmitted by mosquitoes or ticks
• flu, measles and mumps viruses

The condition is sometimes caused by bacterial infections. The most common bacterial pathogens include:

• pneumococci
• meningococci
• group b streptococci
• Haemophilus influenzae
• listeria
• in newborns: the intestinal bacterium Escherichia coli

Less common triggers are infections with staphylococci, tuberculosis bacteria or borrelia bacteria.

Meningitis caused by fungal infections, for example with yeast or mold fungi, primarily affects people with a weakened immune system, such as those with HIV/AIDS.

Meningitis caused by infections with parasites such as worms is rare in Germany.

How do the pathogens get to the meninges?

Many pathogens are transmitted via droplet infection, i.e. when speaking, coughing or sneezing. Infection occurs when these pathogen-containing droplets are inhaled.

The pathogens usually start by settling in other areas of the body, then progress to the meninges in several ways. For example, bacteria often colonize the mucous membranes of the nasopharynx, penetrate blood vessels and reach the meninges via the bloodstream.

In the case of inflammation in the vicinity of the meninges, such as in the middle ear or sinuses, the condition can directly spread to the cerebrospinal fluid (liquor) and the meninges. Liquor is the medical term for the fluid that surrounds the brain and spinal cord. Viruses can also travel along the nerves to the meninges.

Some viruses, such as the TBE virus or the West Nile virus, are contracted from mosquitoes or ticks. The viruses enter the bloodstream via a tick or mosquito bite, from where they can get into the meninges.

Infants, small children and very elderly people are particularly susceptible to meningitis.

In addition to age, there are also several other factors that increase the risk of meningitis, including:

• chronic underlying conditions such as diabetes mellitus
• immunodeficiency as a result of conditions such as HIV/AIDS or the use of medication that weakens the immune system, for example after an organ transplant
• alcohol abuse
• removal of the spleen
• a middle ear infection or sinusitis
• bacterial endocarditis (inflammation of the lining of the heart)

Meningitis is most commonly caused by viruses: in western countries up to 17 in 100,000 people contract viral meningitis each year. About half of all meningitis cases are caused by enteroviruses.

One to two of every 100,000 people in western Europe contract bacterial meningitis each year. The most common bacterial pathogens are pneumococci and meningococci. Meningococcal infections primarily affect infants and one-year-olds.

In countries with a moderate climate like Germany, meningococci infections usually peak at the beginning of the year. On the other hand, viral meningitis is most common in the summer and autumn months.

The outlook for meningitis depends on the cause and the age of the person affected, as well as the condition of their immune system.

Inflammation triggered by viruses or taking medication usually results in mild cases that go away of their own accord within 2 to 3 weeks without any special treatment.

On the other hand, cases of bacterial meningitis can sometimes start very suddenly, rapidly deteriorate and quickly result in fatality. Serious complications such as blood poisoning (sepsis), increased pressure on the brain and water excretion issues are also possible.

Serious cases of meningitis can lead to long-term effects such as the loss of individual nerve functions, hearing loss or thought disorders. Behavioral disorders, movement disorders and seizures are also possible long-term effects.

Vaccinations that prevent meningitis exist against several of its pathogens. These include vaccinations against pneumococci, Haemophilus influenzae, meningococci, measles, mumps and chickenpox. In Germany, these are part of the childhood vaccinations recommended by the Standing Committee on Vaccination (Ständige Impfkommission – STIKO). 

Meningococcal meningitis can be caused by various bacterial subtypes (serogroups). In Germany, most conditions are caused by serogroups B and C. The vaccine recommended for children protects against meningococcal serotype C. People with an increased risk of the condition can also be vaccinated against serogroups A, C, W and Y.

Close contacts of people with meningococcal meningitis should take preventative antibiotics.

The quickest possible diagnosis is important for preventing serious cases of meningitis.

As there are many different causes, doctors use targeted questions to try and isolate possible triggers. These include questions about:

• living conditions: for example, whether people live in shared accommodation
• vaccinations that have been received
• indications of immune deficiency due to a chronic condition or taking medication
• alcohol consumption
• sex life
• contact with animals
• recent travel and operations

In most cases, a blood sample is then taken. The blood can provide evidence of the inflammation and, in the case of bacteria, often also the pathogen.

A lumbar puncture is key for the diagnosis. This involves inserting a special needle into the lower back and taking a liquor sample, i.e. the cerebrospinal fluid that surrounds the brain and spinal cord, from the spinal canal. In the event of impaired consciousness, the doctor must arrange a computed tomography (CT) or magnetic resonance imaging (MRI) scan of the brain prior to the lumbar puncture.

Depending on the outlook, other tests and investigations are also required, such as:

• throat swabs and stool specimens
• an electroencephalography (EEG) to measure the electrical activity of the brain
• imaging of the blood vessels in the brain (angiography)

Bacterial meningitis needs to be treated with effective antibiotics as quickly as possible. Otherwise, it risks developing into a serious or even fatal case. The antibiotics are administered intravenously in a hospital.

If bacterial meningitis is suspected, doctors will start treatment with several antibiotics immediately, even if the results of the laboratory tests are not yet available.

If the condition has been caused by pneumococci, anti-inflammatory cortisone can prevent complications. No benefits of this have been proven to date with other bacterial pathogens.

If a viral infection is suspected, medication is administered that combats herpes viruses – unless these can be ruled out as the cause.

With milder cases, doctors wait for the test results and then specifically treat the causes.

If no bacteria or herpes viruses have been detected, only the symptoms can be treated. In such cases, patients are generally administered painkillers and medication that regulate the fluid balance in the body.