Knowing Meningitis

DEFINITIONMeningitis (pronounced meh-nen-JI-tiss) is an inflammation of the meninges (pronounced meh-NIN-jeez). The meninges are the thin layers of tissue that cover the brain and the spinal cord. Meningitis is most commonly caused by infection (by bacteria, viruses, or fungi). It can also be caused by bleeding into the meninges, cancer (see cancer entry), diseases of the immune system, and other factors. The most dangerous forms of meningitis are those caused by bacteria. The disease is very serious and can be fatal.Meningitis: Words to KnowBlood-brain barrier:Cells within the blood vessels of the brain that prevent the passage of toxic substances from the blood into the brain.Cerebrospinal fluid (CSF):Fluid made in chambers of the brain that flows over the surface of the brain and the spinal cord. CSF provides nutrients to cells of the nervous system and provides a cushion for the structures of the nervous system.Meninges:The three-layer membranous covering of the brain and spinal cord.DESCRIPTIONAny time a part of the body is infected, it is likely to become inflamed and swollen. These symptoms are especially serious in the brain. The brain is enclosed in the skull, a bony structure that cannot change size. If the brain swells, it pushes outward against the skull. Brain cells may become squeezed and begin to die. Brain cells are some of the only kinds of cells in the body that do not regenerate (renew) themselves. Once they die, they cannot be replaced.An infection in the brain can cause damage in a second way. Brain cells are very delicate.
They require just the right balance of chemicals, including sugar, sodium, calcium, potassium, and oxygen. An infection can change the balance of chemicals in the brain. Brain cells may receive too much of one chemical or too little of another. This loss of chemical balance can also kill brain cells.Meningitis is a serious medical problem because it is difficult to treat. Blood flows into the brain from the neck through a network of blood vessels. This network contains special cells that prevent many chemicals from passing into the brain. This system is known as the blood-brain barrier.The blood-brain barrier prevents harmful substances from getting into the brain. The blood-brain barrier "knows" which substances the brain needs and which will damage brain cells.Brain tissue covered with thick white exudate (pus) from acute meningitis. (© 1994Joseph R. Siebert, Ph.D.Reproduced by permission ofCustom Medical Stock Photo.)The problem is that the blood-brain barrier usually does not recognize drugs as "good" chemicals. It prevents them from passing into the brain, where they could help clear up an infection. Doctors often have to find other ways to treat the kinds of infection that cause meningitis.CAUSESMeningitis may be caused by bacteria, viruses, fungi, head injuries, infections in other parts of the body, and other factors. The type of meningitis a person is most likely to contract depends on his or her age, habits, living environment, and health status.Bacteria are not the most common cause of meningitis. But they produce the most serious and most life-threatening forms of the disease. The most common kinds of meningitis in newborns are those caused by streptococci (pronounced STREP-tuh-KOK-see) bacteria. These bacteria pass from the mother to the child through the blood system they share before birth. The highest incidence (rate) of meningitis occurs in babies under the age of one month. Children up to the age of two years are also at relatively high risk for the disease.Adults are usually infected by a different kind of bacterium. This bacterium produces a form of meningitis that has some symptoms like those of pneumonia (see pneumonia entry).One type of bacterium causes a contagious form of meningitis. A person with this form of meningitis can pass it to others with whom he or she comes into contact. Epidemics (mass infections) of meningitis have been known to occur in crowded day-care centers and military training camps.Meningitis is often caused by a virus. The virus is usually the same one that causes other viral infections such as mumps (see mumps entry), measles (see measles entry), chickenpox (see chickenpox entry), rabies (see rabies entry), and herpes infections (like cold sores; see herpes infections entry).A person's general health can also increase his or her risk of developing meningitis. For example, a person with a weakened immune system is at greater risk for meningitis than one who has a healthy immune system. People with AIDS (see AIDS entry) have damaged immune systems and are less able to fight off fungal infections. These fungal infections can lead to infections of the brain and meningitis.People who have had their spleens removed are also at higher risk for meningitis. Spleen removal may be necessary to solve some other medical problem, such as cancer of the spleen. But it may also expose the patient to greater risk for meningitis.The most common cause of meningitis is blood-borne spread. This term means that a person already has an infection in some other part of his or her body. If that infection is not treated properly, it can become more serious and start to spread through the body by way of the bloodstream. Normally, the blood-brain barrier would keep the infectious agents out of the brain. But if huge numbers of infectious agents accumulate in the blood, some of them may get through the blood-brain barrier. They will then be able to infect the meninges and cause meningitis. Infections that occur close to the brain, such as an ear or sinus infection, pose an especially high risk for meningitis.Meningitis can also develop because of openings in the skull. These openings can occur because of a skull fracture or a surgical procedure. These openings provide a way for infectious agents to get into the brain because the blood-brain barrier cannot prevent the infection.SYMPTOMSThe classic symptoms of meningitis include fever, headache, vomiting, sensitivity to light, irritability, severe fatigue, stiff neck, and a reddish-purple rash on the skin. If the infection is not treated quickly, more serious symptoms develop, including seizures, confusion, and coma.SARA ELIZABETH BRANHAMBefore the discovery of antibiotics, meningitis was a dreaded diseases. There was no way to stop its progress. Those who survived an attack of the disease were likely to be left blind, deaf, or mentally retarded. The disease was also feared because of the ease with which it spread. During World War I (1914–18), for example, meningitis often swept through groups of soldiers who lived and fought together. The only way to stop its spread was to isolate infected soldiers from others who were still healthy.Important breakthroughs in the treatment of meningitis came as the result of the work of Dr. Sara Elizabeth Branham (1888–1962). Dr. Branham worked for many years at the National Institutes of Health. Initially, she was interested primarily in food poisoning caused by bacteria. But the tragedies of World War I encouraged her to focus on ways of treating meningitis.When she began her research, the only treatment available for meningitis was antiserum obtained from horses. Horse antiserum is a chemical produced in horses when they have been exposed to meningitis bacteria. As horse antiserum lost its effectiveness, Dr. Branham developed another form of antiserum, produced in rabbits.Finally, in 1937, Dr. Branham decided to try the newly discovered sulfonamide drugs on meningitis. The sulfonamides were the first antibiotics to be widely used. Dr. Branham found that they could be used effectively against the bacteria that cause meningitis. Largely as a result of her research, meningitis was kept under control during World War II (1939–45).These symptoms may not be present in very young babies or the elderly. The immune system of babies is usually not developed enough to fight off an infection of the meninges. So symptoms that accompany an immune response, such as fever, are not observed. Seizures may be the only symptom of meningitis in young children. The same is true of older people who have other kinds of medical disorders that leave them in a weakened state.DIAGNOSISThe first clues that a person may have meningitis can be obtained from a simple physical examination. The doctor may try to move the patient's head in various directions. For a person with meningitis, these movements can be difficult and painful.The standard test for diagnosing meningitis is called a lumbar puncture (LP), or spinal tap. An LP involves the insertion of a thin needle into the space between the vertebrae that make up the spine. A small sample of cerebrospinal fluid is removed. Cerebrospinal fluid (CSF) is a clear liquid present in the space between cells in the brain and the spinal cord. It serves a number of important functions. It provides a cushion for the brain and spinal cord, brings nutrients to these structures, and carries away waste products.CSF normally contains certain fixed amounts of various chemicals, such as sugar, sodium, potassium, and calcium. An infection in the meninges will cause a change in these amounts. For example, bacteria "eat" sugar, so the presence of bacteria in the meninges causes a reduction in the amount of sugar in the CSF.The presence of white blood cells in the CSF is also a clue to the presence of meningitis. The immune system produces white blood cells to fight off infections. A healthy body would normally not have white blood cells in the CSF. If they are present, the immune system is probably fighting an infection in the brain or spinal cord, such as meningitis.TREATMENTMeningitis infections caused by bacteria can be treated with antibiotics. Penicillin and cephalosporins (pronounced seff-a-lo-SPORE-inz) are commonly used. Special methods are necessary for giving these drugs, however, because of the blood-brain barrier. The usual procedure is to inject large quantities of an antibiotic directly into a person's bloodstream. If the concentration of drugs is high enough, some will get through the blood-brain barrier and into the meninges.Antiviral and antifungal medications can be used similarly. Antiviral drugs usually do not kill viruses, but they can lessen some of the effects of the viruses.Steroids may also be used to treat meningitis. Steroids tend to reduce inflammation and swelling, lessening possible harm to brain cells. The balance of sugar, sodium, potassium, calcium, and other substances in the CSF must also be carefully monitored. It may be necessary to inject one or more of these chemicals into the patient's body to maintain a proper balance.PROGNOSISViral meningitis is the least severe type of the disease. Patients usually recover with no long-term effects. Bacterial infections are far more serious and progress quickly. Very rapid treatment with antibiotics is necessary. If the infection is not halted, the patient may fall into a coma and die in less than a day.Death rates for meningitis vary depending on the cause of the infection. Overall, the death rate from the disease is just less than 20 percent.Long-term effects of meningitis are not unusual. For example, damage to cells in certain parts of the brain can cause deafness and/or blindness. Some patients develop permanent seizure disorders. These disorders may require lifelong treatment with antiseizure medications. Scarring of brain tissue can block normal flow of CSF. This condition may be serious enough to require the installation of shunt tubes, surgically implanted devices that help to restore normal circulation of CSF.PREVENTIONThere are no specific recommendations for avoiding meningitis. People should try to avoid developing any kind of infection that might spread to the meninges, especially those of the ear and sinus.Some preventive treatments are available for specific types of meningitis. For example, there is a vaccine for individuals who have to be in areas where contagious meningitis exists. These individuals may also take antibiotics to protect them from infection by the bacterium that causes this form of the disease. A vaccine is available for one of the forms of meningitis that occurs in young children.