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Meningitis: Infection of the Central nervous system

Meningitis is an infection of the central nervous system. Neurological infections are one of the most serious medical problems, because the survival of the patient depends on fundamentally that it detected early way to proceed immediately to specific treatment.
The significance of different infections of the nervous system is highly variable. While it is true that there are some that only require bed rest, the most important are those in which the patient's life is in real danger, or may leave important sequelae which renders the patient forever.

Central nervous system

The central nervous system consists of the brain, the cerebellum, brain stem and spinal cord. The first three structures form the brain. All of this is protected by bone, in particular by the skull and spine. In addition, the nervous system is covered by three membranes called meninges, which are located directly over it and provide additional protection to the bone. On the inside of these membranes is the cerebrospinal fluid, which works as a cushion from injury.
Meningitis is defined as inflammation of the meninges, with consequent alteration of the cerebrospinal fluid. This liquid is very important for the diagnosis of meningitis, because its appearance will change, or not, depending on the type of microorganism that produces the box.
Meningitis is accompanied, at times, a process of inflammation of the brain that can lead to a decrease in the level of consciousness and other symptoms that suggest a more severe. When it happens this is known as meningoencephalitis.

Causes of meningitis

The best-known form of meningitis, its intense gravity, is the cause bacterial. But there is another type of infections that can also reach the nervous system and cause meningitis. In this way, other possible causes of meningitis are viral infections (caused by viruses), which are the most common and most benign; and fungal oirgen (caused by fungi such as candida or cryptococcus, and which are much more uncommon).
There are other types of meningitis which are non-infectious cause; i.e., are microorganisms that cause inflammation, but certain diseases, tumors, parasites, or reactions to drugs that do not usually found in the cerebrospinal fluid. This group of meningitis is very rare, and much less important than the infectious type.
The meningitis of viral origin, the most common, are due mostly to enterovirus (intestinal infections cause), although it can also occur by viruses herpes, HIV, mumps, or even West Nile virus. Many people have viral meningitis in the course of their lives and are not aware of it.

Types of meningitis

One of the most important points when it comes to diagnosing meningitis is to distinguish whether the cause is bacterial or viral, because the survival of the patient is not the same in both cases and, therefore, the therapeutic approach will be different depending on one way or another. Existing types of meningitis are:

Viral meningitis

This form of the disease usually involve much less risk to the patient's life. This type also is known as aseptic meningitis because studies responsible for demonstrating the presence of micro-organisms in samples generally tend to give negative.
There are several types of viruses that are capable of causing a meningitis box. The most common are the so-called enterovirus, but herpes simplex virus is also important.
The viral form of meningitis usually presents a more mild than the bacterial clinic. They usually present with fever, headache and, sometimes, present any symptom that is closer to the clinic of the bacterial form, but less intense. This box is usually disappear in a few days. In general, they are benign processes attending without complications, and treatment is limited to relieve the symptoms of the patient. However, be to highlight that meningitis caused by the herpes simplex virus should receive special attention, as it is more frequent that it complicated with encephalitis, where inflammation reaches the brain and causes major neurological alterations, which can incapacitate the patient's lifetime. That is why, at the slightest suspicion concerned of a herpes simplex virus he is added to the normal treatment specific for this virus, and submits the patient to a strict observation.

Bacterial meningitis

This is the best known form of the disease. Different microorganisms that can cause this type of infection depend on the age of the patient and other factors as, for example, the State of the immune system of the patient. This system is responsible for protecting the human body from external aggressions such as infections; malfunctioning implies a greater predisposition to allergies.
Among all the bacteria responsible for meningitis include:
  • The Streptococcus pneumoniae or Pneumococcus. It is the most common cause of meningitis. This bacteria often colonizes the pharynx of the people without giving any kind of disease. It can be found in 5-10% of healthy adults and 20-40% of healthy children. However, sometimes the immune system is not able to control its growth and reach the meninges through blood, or directly by contiguity when there is an infection of the sinuses for nose (sinusitis) or the middle ear (otitis media), or a skull fracture after trauma. The pneumococcus can also be the cause of pneumonia (pneumonias), which occasionally may be associated with meningitis. Pneumococcal meningitis can occur at any age. It is more frequent to be given in people with some deficiencies of the immune system (e.g. treatment with immunosuppressant drugs,) or people with disorders of the spleen, in diabetics, alcoholics, people with kidney or liver failure, people malnourished, or after a trauma in which skull fractures occur. Its mortality rate is very high. There is a vaccine that covers some serotypes of pneumococcus, which has lowered the incidence of meningitis pneumococcal in children.
  • The Neisseria meningitidis or meningococcus, which is responsible for many of the epidemics of meningitis, especially in children and young people. The meningococcus can colonize the pharynx of many people without disease. Meningitis can occur in people with a disorder of the immune system, but frequently also occurs in healthy people. There is an effective vaccine against meningococcus, but unfortunately does not cover all the serotypes that are of this bacterium.
  • In the newborn and elderly bacteria causing this disease can be totally different from those of the rest of the population. For example, in newborn babies can be meningitis by a bacteria called Streptococcus agalactiae (also called Group B Streptococcus). This is a bacterium that colonizes the female genital tract and can infect to the newborn during childbirth. Fortunately, the study and eradication of this bacterium in pregnant women has decreased the incidence of this complication. In children under five years was common meningitis by a bacterium that is found in the respiratory tract call Haemophilus influenzae type b. Childhood vaccination has greatly diminished this disease. Children, the elderly, pregnant women, and some immunocompromised, may suffer a meningitis by a bacteria called Listeria monocytogenes. It is often associated with the consumption of dairy products and some raw vegetables and has a poor prognosis.
As we see, it is very important to take into account the age and State of health of the patient to begin managing the treatment for a suspected meningitis.
From this point, the information that follows will refer mainly to cause bacterial meningitis.

A meningitis diagnosis

Bacterial meningitis is a medical emergency. The more time has elapsed since the onset of the disease until the establishment of the treatment, the bigger the risk of permanent neurological damage. The seriousness of this infection is much higher in infants and the elderly. Suspected meningitis should the necessary antibiotics promptly and collect blood samples for crops. A crop is a diagnostic method that favours the growth of micro-organisms for the identification of the bacteria that cause the disease. In the diagnosis of meningitis more relevant data is going to get with the lumbar puncture. This will be as soon as possible, except that its realization is not indicated.
Physical examination
Before a clinical picture compatible with meningeal infection, is to perform a thorough scan of the patient looking for signs of infection, especially at the level of the head, neck, ears, and skin. A neurological examination that study the level of consciousness of the patient and the existence of intracranial hypertension (increased pressure inside the head) is conducted. The same appropriate maneuvers will be carried out to detect the presence of nuchal rigidity and meningeal signs.
Imaging tests
As diagnostic tests, x-rays of the chest, sinuses, can be made to look for an infection to that level (sinusitis) that has spread to the nervous system, and a CT scan (computed axial tomography), which is not always indicated. However, definitive diagnosis will probably require an analysis of cerebrospinal fluid obtained by lumbar puncture.
Lumbar puncture
Examination of the cerebrospinal fluid is the pivotal study. In normal conditions it is a liquid clear and transparent. In the case of bacterial meningitis, its appearance is cloudy and their analysis shows a significant increase of leukocytes (white blood cells). It can be cultivated part of the liquid to determine the type of disease causing microorganism.
When there is suspicion of intracranial hypertension do a spinal tap, because it can lead to severe complications. In these cases, is previously a cranial CT scan to rule out hypertension and, if any, appropriate measures shall be taken.

Treatment of meningitis

Bacterial meningitis is a medical emergency. Given that the defenses of the patient are little or nothing effective to control the infection, the Elimination of microorganisms will exclusively depend on antibiotic treatment. For this reason, acute bacterial meningitis should institute immediate antibiotic treatment.
The type of antibiotic that is chosen to treat meningitis depends on the bacteria that causes the infection. As this disease is very serious, not to expect the results of the culture of the cerebrospinal fluid, which can take days. Why is usually to establish antibiotic treatment depending on the bacteria that most likely is causing the box, based on the age of the patient. The antibiotics most used in bacterial meningitis are third generation cephalosporins, since they cover the majority of microorganisms that cause this picture. Once the bacteria that caused the infection is known, is a more specific antibiotic administration.
In many cases, in addition to antibiotics, it is necessary to administer treatments for cerebral edema that occurs, to seizures or dehydration. Corticosteroids are useful to reduce brain swelling and it has been shown that, especially in children, they reduced the number of complications.
If a liquid between the meninges has accumulated, it may be necessary to drain it or remove it surgically.

Prognosis of meningitis

Mortality from bacterial meningitis, or the possibility of sequels, depends largely on the pathogen causing and the age of the patient. Mortality is very high in children under one year, decreases in adulthood, and again increase in elderly. The mortality estimated according to the pathogens are as follows:
• Pneumococcal meningitis: 20-30% in adults and 10% in children.
• Meningococcal meningitis: 3-13%.
• Meningitis by Haemophilus influenzae: 3-6%.
• Meningitis by Listeria monocytogenes: 15-29%.
In the forecast also influences the clinical condition of the patient before the meningitis, the severity of the clinical picture and the early establishment of an appropriate treatment. Bacterial meningitis that receives no treatment is lethal in nearly all cases. However, if it is early and properly, mortality is generally less than 10%.
After meningitis cure, between 5 and 20% of the patients presented some type of neurological sequel. Neurological sequelae are more common in young children, elderly, and pneumococcal meningitis. In childhood, the most frequent sequelae are deafness, mental retardation and epilepsy.
On the other hand, the meningitis caused by viruses, encephalitis, prognosis is very good. Usually heal without sequelae in the vast majority of cases. The outcome can be worse if occurs in people with any underlying disease or any immunodeficiency, or if it occurs in elderly or small children.

Preventing meningitis

Today many children are vaccinated against meningitis-producing bacteria most.
In this way, there are vaccines against pneumococcus, meningococcus and Haemophilus influenzae. However, the meningococcal vaccine is not fully effective, because it does not cover all strains of the bacteria that causes meningitis.
In the meningitis meningococcal should be given antibiotic treatment to persons who were in close contact with the patient: the family and workforce exposed, the closest companions of daycare or school (according to the age of the patient).
In case of an outbreak caused by a type of meningitis for which there is a vaccine, vaccination is also recommended to people who have had close contact with the sick and who are not properly vaccinated.
Also be treated with an antibiotic to the family and colleagues of care of patients affected by meningitis caused by Haemophilus influenzae.
Published for educational purposes
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