Meningitis

Inflammation of the meninges is called meningitis.

Meningitis is inflammation of the membranes (meninges) that surround the brain and spinal cord. The term encephalitis refers to inflammation of the brain itself. This may simply be a progression of meningitis or occur at the same time, depending on the cause. Sometimes this is referred to as meningoencephalitis.

Encephalomyelitis is inflammation of both the brain and spinal cord. Encephalomyelitis can be caused by a variety of conditions that lead to irritation of the brain and spinal cord. Among the common causes of encephalomyelitis are viruses that infect the nervous tissues (for example, herpes simplex and varicella-zoster virus). People with encephalomyelitis can exhibit combinations of the various symptoms of either encephalitis or meningitis.

Meningitis may be acute (sudden and short illness) or chronic (slowly starting and long-lasting). Infectious types of meningitis include:

• bacterial meningitis,
• viral meningitis,
• fungal meningitis, and
• parasitic meningitis.

Most infectious meningitis is community-acquired. Very rarely, fungal or bacterial meningitis may be acquired from a hospital or medical procedure. For example, in 2015, over 200 cases of fungal meningitis were reported to the U.S. Centers for Disease Control and Prevention (CDC). The unusual outbreak was linked to tainted steroid medication that was improperly prepared by the New England Compounding Pharmacy.

Viral infection is the most common infectious cause of community-acquired viral meningitis. Most acute viral meningitis (a type of aseptic meningitis) is caused by summer viruses like enterovirus. It is usually not severe. It generally runs its course and goes away without specific treatment. Viral meningitis usually does not cause long-lasting complications or problems. Other community-acquired causes of viral meningitis include influenza, measles, and mumps. Viruses spread by insect bites include the West Nile virus; these viruses often cause meningitis and encephalomyelitis.

Less commonly, herpes simplex viruses, which cause cold sores or genital herpes, can cause viral meningoencephalitis. Hallucinations may be an especially prominent symptom. Varicella zoster virus (the cause of chickenpox, as well as herpes zoster or shingles) may also cause meningoencephalitis. These infections may arise from newly acquired viruses or the reactivation of viruses that infected the body years ago.

Acute bacterial meningitis causes over 4,000 cases and 500 deaths per year in the U.S. A common cause is Streptococcus pneumoniae (pneumococcus), which causes over 50% of cases in the U.S. (about 2,000 per year). It is the leading cause of bacterial meningitis in young children under 5 in the U.S., although immunization with pneumococcal conjugate vaccine has reduced the rate of infection. Pneumococcal meningitis may be complicated by pneumonia (lung infection), bloodstream infection, sepsis, and long-term problems like permanent hearing loss or brain damage. Up to 8% of children and 22% of adults who develop the condition die from it.

Neisseria meningitidis (meningococcus) is known for causing meningococcal disease (bloodstream infection, sepsis) and bacterial meningitis. Meningococcal meningitis is life-threatening and rapidly progressive. Although pneumococcus can do the same, this is the type of meningitis most likely to cause gangrene and amputations of limbs. Up to 15% of people with this infection will die. Up to 19% have long-term complications like permanent deafness or brain damage. It is most likely to occur in children under the age of 1 and youths ages 16 to 23 years, but people of any age may be affected. The most common serogroups (types of the virus that can be identified by antibody testing in the blood) to cause infection in the U.S. are A, C, W, and Y. Serogroup B is more common elsewhere. There is a higher risk of contact with a carrier of serogroup B in areas where groups congregate from many areas, like a college campus or traveling with a group of tourists.

Fortunately, advances in medical care mean that rates of meningococcal disease have been declining for the past few decades. Vaccination of teens added an 80% drop in infections with serogroup C, W, and Y strains. On average in the U.S., there are now 18 cases per thousand people per year. Adolescents are now routinely vaccinated in their early teens, and freshman college students must show proof of meningococcal vaccination before entry.

Less common causes of acute bacterial meningitis include Hemophilus influenzae, which is now prevented very effectively by the Hib vaccine. Group B Streptococcus (GBS) causes life-threatening newborn meningitis and bloodstream infections. It may be spread to the baby during birth. Fortunately, women are screened for this bacterium at 35 to 37 weeks of pregnancy as part of routine maternal care. Those who have it will get antibiotics during delivery to prevent GBS disease and bacterial meningitis in the newborn.

A rarer cause but serious cause of bacterial meningitis, Listeria monocytogenes, may cause meningitis in pregnant women, people over 50, and those with immune problems. It may cause mild illness in a pregnant woman only to cause a severe infection of the fetus, with premature delivery and fetal death. It is acquired from unpasteurized, unaged soft cheeses, and deli meats.

Fungal causes of meningitis are usually limited to people with very weak immunity from medications, immune disorders, or advanced HIV disease. An exception is Coccidioides immitis, which commonly causes valley fever in the American Southwest and can cause meningitis even if immunity is normal. Cryptococcus is a more common cause of fungal meningitis in people with weak immunity.

Rarer still are the parasitic causes of meningitis. Parasites often cause elevation of eosinophils, a specific type of inflammatory cell, in the blood or spinal fluid. Eosinophilic meningitis is caused by parasites that usually infect animals. Humans are accidental hosts for parasites such as:

• Angiostrongylus cantonensis (by eating raw or undercooked snails or slugs, often by accident, on leafy greens);
• Bayliscaris procyonis (by accidentally eating soil contaminated with raccoon feces);
• Gnathostoma spinigerum (by eating raw or undercooked freshwater fish, eels, frogs, chicken, or snakes);
• Toxoplasma gondii (by eating raw or undercooked pork, lamb, deer, or shellfish, or accidental ingestion of eggs from cat feces); and
• free-living amoebae like Naegleria fowleri, Acanthamoeba, and Balamuthia mandrillaris (through contact with warm water or soil).

Angiostrongylus meningitis has been reported in Asia and the Pacific, including Hawaii, but infected snails have been reported in Florida, as well. Baylisascaris is most often diagnosed in the U.S. in children who play in areas frequented by raccoons and put their hands in their mouths. Gnathostoma meningitis is most commonly reported in Thailand.

Primary amoebic meningitis (Naegleria fowleri) and granulomatous meningoencephalitis (Acanthamoeba species, Balamuthia mandrillaris) are caused by amoeba found in water and soil. The organisms are forced up the nose in water (primary amoebic meningitis) or inhaled or enter via a break in the skin (granulomatous meningoencephalitis). All are highly fatal even with aggressive and prolonged treatment. Primary amoebic meningitis mimics acute bacterial meningitis in its symptoms and is often fatal within days; swimming in warm freshwater is the clue for appropriate diagnosis and treatment. Granulomatous meningoencephalitis is often chronic.

Chronic meningitis lasts four weeks or longer and is fairly uncommon in the U.S. and developed countries. Most bacterial infection causes acute meningitis, but worldwide the most common cause of chronic meningitis is tuberculosis (Mycobacterium tuberculosis). Other causes include spirochete bacteria like syphilis and Lyme disease, fungi like Cryptococcus, insect-borne viruses like West Nile virus, herpes simplex virus, and varicella zoster virus.

Meningitis may be caused by infectious or non-infectious conditions:

• Many different viruses, bacteria, fungi, and parasites can cause meningitis.
• Diseases that can trigger inflammation of tissues of the body without infection (such as systemic lupus erythematosus and Behçet's disease) may cause aseptic (non-bacterial) meningitis.
• Certain drugs may cause aseptic meningitis, most commonly nonsteroidal anti-inflammatory drugs (NSAIDS, for example, ibuprofen) or the antibiotic trimethoprim-sulfamethoxazole.

This depends on the type of meningitis and the specific organism.

Classic community-acquired acute bacterial meningitis spreads from person to person, usually from respiratory droplets or saliva (spit). Meningococcus, pneumococcus, and H. influenzae are spread this way. Community-acquired acute viral meningitis usually spreads from person to person in saliva, respiratory droplets, or diarrhea.

Group B Streptococcus spreads from mother to baby during vaginal delivery. People acquire Listeria monocytogenes from contaminated food.

Herpes and varicella are acquired from person to person and can reactivate several years after infection. Several encephalitis viruses are transmitted by mosquitoes.

Fungal meningitis is usually acquired from breathing fungal spores in the air.

Some forms of viral and bacterial meningitis are contagious. The organisms are spread through the exchange of respiratory and throat secretions (for example, coughing, kissing, sharing of utensils), as well as diarrhea in the case of viruses. Sometimes meningitis can spread to other people who have had close or prolonged contact with a patient with meningitis.

This depends on the type of meningitis. People with normal immunity but exposure to crowding, certain age groups, or certain activities may be at higher risk for certain types of meningitis. Patients with a suppressed immune system, either because of medications (organ transplant recipients, etc.) or from a disease that suppresses the immune system (HIV, for example), are at increased risk for less common bacteria, tuberculosis, as well as fungal meningitis.

Certain people are at higher risk of pneumococcal meningitis and should receive pneumococcal vaccines, including people who:

• Smoke tobacco
• Have immune disorders like HIV
• Are taking medications that suppress immunity
• Have a spleen that is not working or has been removed (hyposplenia, asplenia, sickle cell disease)
• Have had skull or facial fractures with leakage of cerebrospinal fluid (CSF)
• Have a cochlear implant
• Have chronic lung, heart, or kidney conditions

Teens and young adults are at higher risk for invasive meningococcal disease, and routine vaccination of this age group is recommended with meningococcal conjugate vaccine, which covers the commonest serogroups in the U.S. (A, C, W, and Y). Certain people with immune problems are at higher risk for meningococcal disease and should also receive serogroup B meningococcal vaccine. These include people:

• Whose spleen is not working or had it removed (hyposplenia, asplenia, sickle cell disease);
• With specific immune disorders like deficiencies of complement, properdin, factor H, or factor D;
• Living with HIV disease; and
• Take eculizumab (Soliris) for paroxysmal nocturnal hemoglobinuria.

Certain groups of people are more likely to be exposed to meningococcal disease. They can also benefit from vaccination with serogroup B meningococcal vaccines:

• People living in close and household contact with someone who has meningococcal meningitis
• People who may have been exposed during an outbreak of meningococcal meningitis
• Freshman college students living in on-campus group housing
• Military recruits living in group housing
• Travelers to areas where meningococcal meningitis is common (endemic). Sub-Saharan Africa during the dry season is known as the meningitis belt, and risk is high during the crowded annual Islamic pilgrimage (Hajj) to Mecca in Saudi Arabia.
• People who may be exposed to meningococcus in a laboratory

Pregnant women and people over 50 years of age are at increased risk of meningitis from Listeria monocytogenes. Other types of meningitis have risk factors due to specific exposure to soil, water, foods, and insect bites.

The classic signs and symptoms of meningitis include:

• headache,
• fever (usually high, but can also be low-grade),
• stiff neck (in adults and older children), and
• painful sensitivity to light (photophobia).

Signs a health professional will look for during an examination for meningitis include Kernig and Brudzinski signs:

• Kernig's sign: With the patient lying flat on the back, the leg is bent 90 degrees at the hip and the knee bent 90 degrees. From this position, the examiner straightens the leg at the knee. If there is strong resistance to straightening the bent knee with the hip bent at 90 degrees, it suggests meningitis.
• Brudzinski's sign: With the patient lying flat on the back and legs flat on the bed, the examiner bends the head forward at the neck. If this makes the legs pull up and bend at the knee, it suggests meningitis.

Symptoms of meningitis may appear suddenly and also include:

• nausea,
• vomiting, and
• changes in behavior, such as confusion, sleepiness, and difficulty waking up.

In infants, symptoms of meningitis are often much less specific and may include:

• irritability or tiredness,
• poor feeding, and
• fever.

Especially early in the disease, meningitis can have symptoms similar to the flu. Some types of meningitis can be deadly if not treated promptly. Anyone experiencing symptoms of meningitis should see a doctor immediately.

Specialists who may be part of the team caring for someone with meningitis include: pediatricians, family practice or general internal medicine specialists, hospitalists or critical care (intensive care) specialists, neurologists, neurosurgeons, and infectious disease specialists.

Meningitis is suspected when fever, headache, and neck stiffness are present. The doctor diagnoses meningitis after completing a thorough history (asking the patient questions) and examination. The examination includes Brudzinski's and Kernig's maneuvers to detect signs of inflammation of the membranes that surround the brain and spinal cord (meninges). Based on the history and examination, the doctor suggests specific tests to further help in determining the diagnosis.

Tests that are used in the evaluation of individuals suspected of having meningitis include evaluation of the blood for signs of infection and the possible presence of bacteria, brain scanning (such as CT scan or MRI scan), and cerebrospinal fluid analysis.

A lumbar puncture is the most common method of obtaining a sample of the fluid in the spinal canal (the cerebrospinal fluid or CSF) for examination. A lumbar puncture (LP) is the insertion of a needle into the fluid within the spinal canal. It is termed a "lumbar puncture" because the needle goes into the lumbar portion of the back (the lower portion of the back). The needle passes between the bony parts of the spine until it reaches the cerebral spinal fluid. A small amount of fluid is then collected and sent to the laboratory for examination. The evaluation of the spinal fluid is usually necessary for the definitive diagnosis and to help make optimal treatment decisions (such as the appropriate choice of antibiotics in the case of bacterial meningitis).

The diagnosis is confirmed by abnormal spinal fluid results and, in the case of an infection, by identifying the organism causing the infection. In patients with meningitis, the CSF fluid often has a low glucose (sugar) level and an increased white blood cell count. In addition, the fluid can be used to identify some viral causes of meningitis (PCR or polymerase chain reaction) or be used to culture bacterial organisms causing meningitis.

There is no over-the-counter treatment or home remedy for meningitis. It is a medical emergency and requires immediate medical evaluation at an emergency department or hospital to determine the type of treatment:

• Antibiotic and/or antiviral medications need to be considered urgently when the diagnosis of acute meningitis is suspected.
• In the case of suspected amoebic meningitis with warm water exposure, an infectious disease specialist and CDC consultation must be urgently considered.
• In some situations, anticonvulsants are used to prevent or treat seizures (a possible side effect of inflammation of the brain).
• Sometimes doctors administer corticosteroids to reduce brain swelling and inflammation.
• Sedatives may be needed for irritability or restlessness. Additional medications might be used to decrease the fever or treat headaches.
• With severe meningitis that is causing high CSF pressure, a neurosurgeon may be called to insert a tube (CSF shunt) to measure and relieve the pressure.

The duration of hospitalization and the need for other tests and treatments usually depend on the type of meningitis the patient has and the severity of the symptoms.

The prognosis for meningitis varies. Some cases, like aseptic meningitis, are mild, short, and relatively benign and patients have full recovery. Other cases are severe, and permanent impairment, brain damage, or death is possible. This is usually determined by the type of infection present and how quickly treatment can be started. Meningitis can lead to permanent damage to the nervous system and can cause hydrocephalus (increased CSF, or water on the brain).

With early diagnosis and prompt treatment, many patients recover from meningitis. Viral meningitis can be self-limited to 10 days or less. However, in some cases, the disease progresses so rapidly that death occurs during the first 48 hours, despite early treatment.

Basic steps to avoid the spread of organisms, such as hand washing and covering one's mouth when coughing, will also help in decreasing the risk of spreading meningitis.

There are vaccines against Hib (Haemophilus influenzae type B) and against some strains of N. meningitidis and many types of Streptococcus pneumoniae. Prior to routine vaccination, H. influenzae type B was one of the most common causes of acute meningitis and invasive infections in children. These conditions are now uncommon. The vaccines against Hib are very safe and highly effective. By 6 months of age, every infant should receive at least three doses of a Hib vaccine, the earliest at 8 weeks of age. A fourth dose ("booster") should be given to children between 12 and 18 months of age. Hemophilus influenzae can cause severe infections in adults, who can spread an invasive strain to a newborn or unvaccinated older child. Close contact with a person with invasive H. influenzae disease may be considered for preventive antibiotics (called prophylaxis or chemoprophylaxis).

There are two types of vaccines available to prevent N. meningitides (meningococcal) infections in the U.S. Protection lasts about five years, so they are given during the highest risk age periods:

• Meningococcal conjugate vaccines (Menactra and Menveo)
  • Prevents infection with serogroups A, C, W, and Y
  • Recommended for all preteens and teens at age 11 to 12 years of age, plus a booster dose at 16.
• Serogroup B meningococcal vaccines (Bexsero and Trumenba)
  • Prevents infection with serogroup B
  • Recommended for all those at high risk, including immune defects and travel to high-risk areas
  • All those aged 16-23 should consider this vaccine, especially before college entry.

Because meningococcal disease causes lasting disability or death, it is highly contagious, and travelers are bringing it home from endemic areas, the CDC recommends two doses of meningococcal conjugate vaccine during the preteen and teen years of greatest risk. Those aged 16 through 23 may also want to be vaccinated with a serogroup B meningococcal vaccine. This is especially important for those intending to attend college, as living in a large college environment is a risk factor for developing meningococcal meningitis.

Although large epidemics of meningococcal meningitis do not occur in the United States, some countries experience large, periodic epidemics. Overseas travelers should check to see if meningococcal vaccine is recommended for their destination. Travelers should receive the vaccine at least one week before departure if possible.

Chemoprophylaxis for Neisseria meningitidis is very effective in preventing infections of close contact with people with meningococcal disease and helps prevent or stop epidemics while protection from vaccines kicks in. People in the same household, dormitory, daycare center, or anyone with direct contact with a patient's oral secretions would be considered at increased risk of acquiring the infection. This also holds true for healthcare professionals involved in direct, prolonged contact, especially during procedures such as intubations (placing a breathing tube). People who qualify as close contacts of a person with meningitis caused by N. meningitidis should receive antibiotics (prophylaxis or chemoprophylaxis) to prevent them from getting the disease.

Vaccines to prevent meningitis due to S. pneumoniae (also called pneumococcal meningitis) can also prevent other forms of infection due to S. pneumoniae. The two types of pneumococcal vaccine are available in the U.S.:

• Pneumococcal conjugate vaccine (PCV13, or Prevnar 13)
  • Recommended routinely between 8 weeks and 2 years
  • Recommended routinely at 65 years of age and over
  • Recommended between ages 2 and 64 for higher-risk groups
• Pneumococcal polysaccharide vaccine (PPSV23, or Pneumovax23)
  • Recommended routinely at 65 years of age and over
  • Recommended between ages 19 and 64 for cigarette smokers
  • Recommended between ages 2 and 64 for higher-risk groups

The side effects of the vaccines available for preventing acute bacterial meningitis are generally mild, and the vaccines are highly effective. The following are possible symptoms that have been reported with the pneumococcal, meningococcal, and Hib vaccines.

Interestingly, bacterial meningitis from pneumococcus does not commonly spread or cause outbreaks from people with meningitis but from people who are carrying it in their throat without symptoms. Therefore, prophylaxis of close contact is not generally recommended for those with pneumococcal meningitis.