Agyhártyagyulladás

Meningitis by origin can be bacterial, viral, fungal, parasitic and non-infectious. The viral infection can reach the level of an outbreak or epidemic.

Bacterial meningitis is usually severe. While most people with meningitis recover, it can cause serious complications, such as brain damage, hearing loss, or learning disabilities.

There are several pathogens (types of germs) that can cause bacterial meningitis. Some of the leading causes of bacterial meningitis in the United States include Haemophilus influenzae (most often caused by type b, Hib), Streptococcus pneumoniae, group B Streptococcus, Listeria monocytogenes, and Neisseria meningitidis.

Signs and symptoms

Meningitis infection may show up in a person by a sudden onset of fever, headache, and stiff neck. It will often have other symptoms, such as

• Nausea
• Vomiting
• Increased sensitivity to light (photophobia)
• Altered mental status (confusion)

The symptoms of bacterial meningitis can appear quickly or over several days. Typically they develop within 3–7 days after exposure.

Babies younger than one month old are at a higher risk for severe infections, like meningitis, than older children. In newborns and infants, the classic symptoms of fever, headache, and neck stiffness may be absent or difficult to notice. The infant may appear to be slow or inactive (lack of alertness), irritable, vomiting or feeding poorly. In young infants, doctors may look for a bulging fontanelle (soft spot on infant’s head) or abnormal reflexes, which can also be signs of meningitis. If you think your infant has any of these symptoms, call the doctor or clinic right away.

Later symptoms of bacterial meningitis can be very severe (e.g., seizures, coma). For this reason, anyone who thinks they may have meningitis should see a doctor as soon as possible.

Diagnosis

If meningitis is suspected, samples of blood or cerebrospinal fluid (near the spinal cord) are collected and sent to the laboratory for testing. It is important to know the specific cause of meningitis because that helps doctors understand how to treat the disease, and possibly how bad it will get. In the case of bacterial meningitis, antibiotics can help prevent severe illness and reduce the spread of infection from person to person.

If bacteria are present, they can often be grown (cultured). Growing the bacteria in the laboratory is important for confirming the presence of bacteria, identifying the specific type of bacteria that is causing the infection, and deciding which antibiotic will work best. Other tests can sometimes find and identify the bacteria if the cultures do not.

Treatment

Bacterial meningitis can be treated effectively with antibiotics. It is important that treatment be started as soon as possible. Appropriate antibiotic treatment of the most common types of bacterial meningitis should reduce the risk of dying from meningitis to below 15%, although the risk remains higher among young infants and the elderly.

Prevention is possible by applying vaccines. There are vaccines for three types of bacteria that can cause meningitis: Neisseria meningitidis (meningococcus), Streptococcus pneumoniae (pneumococcus), and Haemophilus influenzae type b (Hib).

Viral meningitis is generally less severe and resolves without specific treatment. Most viral meningitis cases occur especially during the summer months, and are caused by enteroviruses; however, only a small number of people with enterovirus infections actually develop meningitis.

Other viral infections that canlead to meningitis include

• Mumps
• Herpesvirus, including Epstein-Barr virus, herpes simplex viruses, varicella-zoster virus (which also causes chicken pox and shingles), measles, and influenza
• Viruses spread through mosquitoes and other insects (arboviruses)
• In rare cases LCMV (lymphocytic choriomeningitis virus), which is spread by rodents, can cause viral meningitis.

Enteroviruses, the most common cause of viral meningitis, are most often spread from person to person through fecal contamination (which can occur when changing a diaper or using the toilet and not properly washing hands afterwards). Enteroviruses can also be spread through respiratory secretions (saliva, sputum, or nasal mucus) of an infected person. Other viruses, such as mumps and varicella-zoster virus, may also be spread through direct or indirect contact with saliva, sputum, or mucus of an infected person. Contact with an infected person may increase your chance of becoming infected with the virus that made them sick; however you will have a small chance of developing meningitis as a complication of the illness.

Signs & Symptoms

Meningitis infection is characterized by a sudden onset of fever, headache, and stiff neck. It is often accompanied by other symptoms, such as

• Nausea
• Vomiting
• Photophobia (sensitivity to light)
• Altered mental status

Viral meningitis is an infection of the meninges (the covering of the brain and spinal cord) that is caused by a virus. Enteroviruses, the most common cause of viral meningitis, appear most often during the summer and fall in temperate climates.

Viral meningitis can affect babies, children, and adults. It is usually less severe than bacterial meningitis and normally clears up without specific treatment. The symptoms of viral meningitis are similar to those for bacterial meningitis, which can be fatal. Because of this, it is important to see a healthcare provider right away if you think you or your child might have meningitis.

Diagnosis

If meningitis is suspected, samples of blood or cerebrospinal fluid (near the spinal cord) are collected and sent to the laboratory for testing. It is important to know the specific cause of meningitis because the severity of illness and the treatment will differ depending on the cause.

The specific causes of meningitis may be determined by tests used to identify the virus in samples collected from the patient.

Treatment

There is no specific treatment for viral meningitis. Antibiotics do not help viral infections, so they are not useful in the treatment of viral meningitis. Most patients completely recover on their own within 7 to 10 days. A hospital stay may be necessary in more severe cases or for people with weak immune systems.

Fungal meningitis is rare and usually the result of spread of a fungus through blood to the spinal cord. Although anyone can get fungal meningitis, people with weak immune systems, like those with AIDS or cancer, are at higher risk.

The most common cause of fungal meningitis for people with weak immune systems is Cryptococcus. This disease is one of the most common causes of adult meningitis in Africa.

Parasitic meningitis, primary amebic meningoencephalitis (PAM) is a very rare form of parasitic meningitis that causes a fatal brain infection.  The parasite enters the body through the nose and is caused by the microscopic ameba (a single-celled living organism) Naegleria fowleri.

Naegleria fowleri infects people by entering the body through the nose. This typically occurs when people go swimming or diving in warm freshwater places, like lakes and rivers. The Naegleria fowleri ameba travels up the nose to the brain where it destroys the brain tissue.