Generality
Meningitis is the term by which doctors identify an inflammatory process affecting the meninges .
Meninges are the lining membranes of the central nervous system (CNS), with protective functions against encephalon and spinal cord.
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The main causes of meningitis are viral, bacterial and fungal infections. Among the infectious meningitis, bacterial meningitis is the most dangerous: it can have permanent consequences, if not even cause death.
The symptoms are very broad and include: high fever, vomiting, confusion, irritability, neck stiffness, headache, etc.
Although it is not always easy, the diagnosis must be immediate, because the treatment must start as early as possible.
The therapy varies according to the triggering causes.
Brief review of the central nervous system (CNS)
In vertebrates, the most important part of the entire nervous system is the central nervous system ( CNS ).
The CNS has two main components: the brain and the spinal cord .
Thanks to its enormous network of neurons (ie nerve cells), the central nervous system is responsible for analyzing the information coming from the internal or external environment to the organism and for processing the most appropriate responses (to the aforementioned information).
What is meningitis?
Meningitis is the inflammation of the membranes that cover and protect the brain and spinal cord (called meninges ).
BRAINS
In number of three, the meninges are comparable to overlapping sheets. Their precise location is between the encephalic matter (in the case of the encephalon) or medullary (in the case of the spinal cord) and the bone covering that protects the main structures of the central nervous system (skull for the encephalon and spinal column for the marrow spinal).
Proceeding from the outside towards the inside, the three meninges are:
- The dura mater . Very thick membrane, it contains an intricate network of venous vessels, which, through the venous sinuses, operate the drainage of the blood that circulates in the CNS.
The dura mater of the brain is slightly different from the spinal dura mater. The first has two laminae, one that acts as a periosteum and one that passes over the circumference of the brain. The second has the shape of a hollow cylinder and is separated from the vertebrae by an area rich in adipose tissue and venous blood vessels; this area is called a perdural space or epidural space.
- The arachnoid . It owes its name to the fact that it has a fabric similar to a spider's web.
To separate it from the innermost meninge is a space known as the subarachnoid space. In the subarachnoid space lies part of the cerebrospinal fluid (which is the substance taken at the time of the lumbar punctures).
- The pious mother . Very thin and in direct contact with the brain and spinal cord, it contains the arteries that supply the central nervous system.
Causes
Generally, meningitis is the result of a viral, bacterial or fungal infection .
However, occasionally, it may be due to irritative factors, such as certain particular drugs, certain physical injuries, certain brain tumors and some systemic diseases.
In this article, infectious meningitis is of particular interest, since it is the one that from the epidemiological point of view affects the greatest number of individuals.
VIRUS MENINGITE
Meningitis with viral origin (or aseptic meningitis ) is the most common form of meningitis and usually the one with less serious consequences.
Today, the viruses that can cause it most frequently are enteroviruses and herpes viruses.
- Enterovirus . They represent a group of viruses that cause mild intestinal infections and that can spread through coughing, sneezing and contact (direct or indirect) with contaminated surfaces.
Epidemiological studies have shown that enteroviruses are the viruses that cause most viral meningitis.
- Herpes virus . They are a very heterogeneous category of viruses, with a feature that unites them: they no longer abandon the infected host and hide in some cell (latent infection) to protect themselves from the immune reaction.
Among the herpes viruses, the one most associated with meningitis is the so-called herpes simplex virus, known for its ability to cause cold sores and genital herpes.
Warning : measles virus, rubella virus and mumps virus have been an important cause of viral meningitis until the advent of mass vaccination against these same viruses.
From that moment on, the number of cases of meningitis associated with measles, rubella or mumps suffered a drastic reduction.
BACTERIAL MENINGITIS
Meningitis with bacterial origin (or bacterial meningitis ) is uncommon but particularly dangerous, as it can have permanent consequences if not even cause the death of the patient.
Today, the main bacteria that can cause it are three:
- Neisseria meningitidis (or meningococcus ). It is the bacterial agent responsible for the most feared form of meningitis.
There are many subtypes of meningococcus, but only a few are dangerous due to the consequences they can cause. In this case, the subtypes that can produce inflammation at the level of the meninges, even with lethal outcomes, are: meningococcus A, meningococcus B, meningococcus C, meningococcus W135 and meningococcus Y.
- Streptococcus pneumoniae (or pneumococcus ). Generally, this bacterial agent causes infections in the upper respiratory tract, ear infections and pneumonia.
It can cause meningitis in children and in immunosuppressed subjects, as they are two categories of people who, for different reasons, have reduced immune defenses.
- Haemophilus influenzae type B. It is a bacterium that generally causes otitis, sinusitis, pneumonia and bronchitis.
It can cause the appearance of meningitis only in the presence of certain immune conditions.
For further information: Meningococcus Meningitis and Sepsis
FUNGIN MENINGITIS
Fungal meningitis is very uncommon and generally affects immunosuppressed subjects .
The fungus responsible for most clinical cases is the so-called Cryptococcus neoformans .
The latter can be found everywhere, both in the animal world and in the vegetable world.
TRANSMISSION OF INFECTIOUS MENINGITIS
By coughing, sneezing, kissing and speaking, people expel millions of small volatile droplets.
Volatile droplets from people with infectious meningitis contain the infectious agent that caused it. Therefore, their inhalation, by people who are nearby (within two meters), may involve the transmission of the bacterium, virus or fungus responsible for the infection.
Once it has been inhaled, the infectious agent can simply cause a local infection in the upper respiratory tract (nose-pharynx), but it can also spread in the blood and reach the meninges through the bloodstream. Only if it reaches the meninges, it has the possibility of causing meningitis.
Do your meninges lack any kind of protection?
Not always and not all infectious agents that reach encephalic meninges cause inflammation, causing meningitis. This is explained by the fact that the brain has a very efficient protection system, known as a blood-brain barrier .
The blood-brain barrier acts as a filter against the substances contained in the blood, which is about to reach the brain. Among the filtered impurities, there are also numerous infectious agents.
For various reasons (immunodepression, strong viral or bacterial charge, etc.), this natural encephalon protection system can work inadequately and not be up to the task.
The passage of impurities through the blood-brain barrier is the event underlying infective meningitis.
WHAT IS THE FAVOR OF THE INFECTION?
To facilitate the transmission of meningitis (or, better, of the infectious agents that cause it), is the coexistence of many people in closed environments . It is for this reason that schoolchildren, university students, the military and, in general, all the frequent visitors of very crowded meeting places are particularly at risk of getting sick.
That said, readers are reminded that two other important risk factors, favoring the transmission of infective meningitis, are: young age (children aged 0-5 are the most at risk) and the state of immunodepression .
Epidemiology
- Bacterial meningitis mainly affects subjects under the age of 5 years (in particular children one year); however, their spread among individuals between the ages of 15 and 19 is not negligible either.
An epidemiological study dating back to the two-year period 2011-2012 concerning the United Kingdom reports that the number of cases of meningitis with bacterial origin was approximately 2, 350.
The meningococcal that causes most infections (at least in the UK) is subtype B.
From the point of view of transmission capacity, experts have found that the pneumococcus spreads with coughs and sneezes much more easily than meningococcus.
- Like bacterial ones, viral meningitis affects children most of all. Summer is the time of year when it is easier to contract the viruses.
- Fungal meningitis is particularly common among adults living in Africa.
Symptoms and Complications
To learn more: Symptoms Meningitis
The symptomatic picture of an infective meningitis is independent of the fact that it was caused by a virus, a bacterium or a fungus. In other words, the symptoms do not allow even the most experienced doctor to distinguish bacterial meningitis from viral or fungal meningitis.
After this necessary premise, the actual description of clinical manifestations in newborns and in subjects of more mature age can begin.
SYMPTOMS IN NEWBORN AND VERY SMALL CHILDREN
In infants and very young children, infectious meningitis causes:
- High fever, characterized by cold hands and feet
- Vomiting and poor appetite
- Irritability
- Continuous and particularly acute crying
- Drowsiness, softness and poor reactivity
- Neck stiffness and photophobia (abnormal intolerance to light).
- Apathetic look
- Enlarged head with bowing of the fountains towards the outside
- Convulsions or seizures of epilepsy
- Skin pallor
It is important to stress that these symptoms and signs do not appear with a specific order; however, drowsiness and lack of appetite are usually characterized by the onset of meningeal inflammation in infants and very young children.
SYMPTOMS IN THE BIGGEST CHILDREN, IN TEENAGERS AND ADULTS
In older children, adolescents and adults, infectious meningitis almost always begins with headache (headache), lack of appetite and drowsiness .
Therefore, after 2-3 days, it determines an evident worsening of the health conditions, determining the appearance of:
- Very high fever, characterized by cold hands and feet
- Nausea and vomit
- Confusion and irritability
- Intense muscle pain
- Stiffening of the neck or, better, of the nape (the patient cannot bend his head forward)
- Pallor
- Fotofobia
- Convulsions or seizures of epilepsy
- Lethargy
As in the case of infants and very young children, this series of slightly later symptoms does not follow a specific order of appearance.
INCUBATION TIMES
The incubation period depends on the infectious agent that caused the inflammation of the meninges.
Bacterial meningitis usually appears in the 2-10 days following infection ; viral meningitis almost always occurs 3-6 days after infection ; finally, fungal meningitis can appear after a few days, but also after more than a month .
COMPLICATIONS
The most dangerous meningitis and the high probability of a poor prognosis is bacterial meningitis.
Its high danger is linked to the high capacity of the infecting bacteria to stabilize in the blood and / or spread in the nervous tissues, giving rise to:
- Septicemia . Septicemia (or sepsis ) is a serious clinical condition, of an inflammatory type, characterized by the persistent presence of bacteria in the bloodstream. (NB: it should not be confused with bacteremia, which always consists of the presence of bacteria in the blood, but in this case it is transitory).
To indicate the onset of a condition of sepsis, in an individual with bacterial meningitis, is the appearance of a skin rash (or skin rash or skin rash), marked by red spots that do not disappear with the so-called glass test *.
Septicemia is a typical consequence of bacterial meningitis and is often the clinical event that causes the death of patients (especially very small ones).
- Encephalitis or myelitis . The term encephalitis indicates an inflammatory process against the elements that make up the brain; the word myelitis, on the other hand, indicates an inflammation against the spinal cord.
Encephalitis and myelitis can have numerous consequences, both temporary and permanent, including: hearing loss, memory loss, recurrent lack of concentration, balance disorders and coordination, learning difficulties, behavioral disorders, epilepsy, cerebral palsy (in children very small), language difficulties and loss of vision.
Viral meningitis and fungal meningitis are less dangerous than bacterial meningitis for at least two reasons: they do not cause septicemia and more rarely (generally if not treated properly) cause encephalitis or myelitis.
In essence, therefore, the risk of developing complications in the event of non-bacterial meningitis is decidedly lower than when bacterial meningitis is underway.
In general, hearing loss is one of the most common complications of meningitis, especially in young patients.
To understand if meningitis may have caused a certain degree of deafness in a very young child, doctors use a test specifically designed for measuring acoustic abilities. Usually, the best time to perform this test is 4-6 weeks after discharge from the hospital.
WHEN TO REFER TO THE DOCTOR?
In the presence of any symptom or sign that may suggest meningitis (NB: it is not possible to determine the type of meningitis from the symptoms), it is advisable to contact your doctor immediately or go to the nearest hospital for a detailed examination of the situation .
In fact, meningitis is always a medical emergency, that is a condition that, in the absence of a diagnosis and timely treatment, can have serious consequences.
Diagnosis
Diagnosing meningitis is quite difficult, certainly not immediate.
The difficulties are mainly due to the fact that, at least in the initial phase, the symptoms and signs are reminiscent of those of an influenza. This similarity is dangerous, because it can lead to a loss of useful time that would be devoted to treatment.
In general, for the recognition of a meningitis are essential: a thorough physical examination, blood tests, a lumbar puncture and some instrumental radiological tests.
Important note : the doctors dealing with a case of meningitis (in particular the bacterial one) must immediately communicate with the health authorities of the area and provide for the isolation of the patient. The danger is that of a spread of the pathogen that triggered inflammation against the meninges.
EXAMINATION OBJECTIVE
A thorough physical examination requires the doctor to visit the patient, looking for any external clinical signs on it and asking him about the symptoms (if the patient is a child, the people questioned are the parents or adults who spend more time with him).
The most common questions - because they are more important for a correct diagnostic analysis - are:
- What are the symptoms?
- When did the first disturbances appear?
- Do you remember attending people with similar symptoms?
- Do you spend a lot of time in crowded meeting places (schools, universities, etc.)?
BLOOD TESTS
Thanks to the collection and analysis of a blood sample from the patient, a doctor can trace the type of infectious agent that triggered the infection on the meninges, as it is possible to find their presence in the blood.
LUMBAR PUNCTURE
The lumbar puncture consists in taking a sample of cerebrospinal fluid (or liquor) and in its laboratory analysis. To take liquor, the doctor uses a needle that inserts between the lumbar vertebrae L3-L4 or L4-L5.
Like blood tests, the lumbar puncture supports the identification of the triggering causes. In fact, it provides useful information about the infectious agent that triggered inflammation of the meninges.
INSTRUMENTAL TESTS
The instrumental tests serve, above all, to clarify the consequences of meningitis up to that moment and to have a further confirmation on the infective agent triggering the inflammation.
Among the instrumental tests usually performed, there are the cerebral CT and the Rx-thorax .
The brain CT scan shows any signs of damage to brain structures, which can be the consequence of encephalitis.
The Rx-thorax, on the other hand, allows the detection of possible infections at the lung level, as, as readers will remember, one of the causes of bacterial meningitis is pneumococcal infection (a bacterium that causes pneumonia).
Treatment
While bacterial meningitis and fungal meningitis always require hospitalization, viral meningitis can also be treated at home, provided the infection and the consequent inflammatory state are minor.
BACTERIAL MENINGITIS
Once transported to the intensive care unit, patients with bacterial meningitis need a treatment based on intravenous antibiotics. The choice of the most suitable antibiotic is up to the doctor and depends on the bacterial agent that triggered the inflammation of the meninges.
Very often, to these drugs, it is appropriate to add:
- Administration of corticosteroid drugs.
Corticosteroids are powerful anti-inflammatory medicines, therefore, with their use, doctors intend to reduce the inflammatory state present at the meningeal level.
- The administration of analgesics, ie pain medications.
- Liquids for rehydration .
- Oxygen to rebalance any deficiencies.
If antibiotic treatment is effective immediately, the expected hospitalization is generally at least a week.
If the antibiotic treatment is not effective, then the stay in the hospital can last several weeks (if not even months).
VIRUS MENINGITE
Most viral meningitis requires a fairly simple treatment, based on an absolute rest period and on the use of analgesics (against headache) and anti-emetics (against vomiting). Generally, healing occurs within 5-14 days and the inflammation leaves no trace of its passage.
If viral meningitis is severe ...
In these situations, the doctors could admit the patient and monitor him closely, offering him all the assistance he needs and also giving him some antiviral drugs.
FUNGIN MENINGITIS
Fungal meningitis requires the administration of antifungal drugs at high doses. The medicines usually used include: flucytosine, fluconazole and amphotericin B.
Generally, therapy takes place in the hospital, as the aforementioned drugs must be taken intravenously.
It should be remembered that patients with fungal meningitis are generally immunosuppressed and therefore very fragile from an immune point of view.
Prognosis
The prognosis depends, first of all, on the triggering causes and, secondly, on the timeliness of the diagnosis.
The causes have already been widely discussed: bacterial meningitis is more likely to lead to unpleasant consequences and cause the patient to die; viral and fungal meningitis, on the other hand, can be treated with good results and only in the most serious cases have permanent consequences.
As for the timeliness of the diagnosis, this is important because it affects the timing of therapy planning: an early diagnosis allows to establish the most appropriate treatment first; a timely treatment adapted to the circumstances significantly improves the prognosis of the inflammatory state, present at the level of the meninges.
Prevention
To learn more: Vaccine Meningitis
In Italy, for all newborns, some vaccines are available that prevent certain forms of meningitis: the MMR vaccine (ie against measles, mumps and rubella), the vaccine against meningococcus type C, the vaccine against Haemophilus influenzae and the pneumococcal vaccine.
In order to increase the level of protection, in many countries of the world, doctors and pathologists are collaborating assiduously in the creation of new vaccines against forms of meningitis that are not yet preventable.
What changes since 2017
With the decree-law on vaccination prevention for minors from zero to 16 years, approved on 07/28/2017 the vaccine against meningitis has become mandatory for those born since 2001 .
As far as vaccinations against meningococcus C and meningococcus B are concerned, although they are not mandatory, they are offered by the Regions and Autonomous Provinces, based on the indications of the vaccination calendar for the year of birth:
- those born between 2012 and 2016 are offered free antimeningococcal vaccinations C
- those born in 2017 are offered free antimeningococcal B, anti-meningococcal C and pneumococcal vaccinations
For more information on mandatory vaccines in children, see this article.
