Meningitis
What is Meningitis?
Infections in the brain and spinal cord can cause dangerous inflammation. This inflammation can produce a wide range of symptoms, including fever, headache, or confusion and, in extreme cases, can cause brain damage, stroke, seizures, or even death. Infection of the meninges, the membranes that surround the brain and spinal cord, is called meningitis.
What causes Meningitis?
Meningitis are usually caused by viruses or bacteria. Most often, the body’s immune system is able to contain and defeat an infection. But if the infection passes into the blood stream and then into the cerebrospinal fluid that surrounds the brain and spinal cord, it can affect the nerves and travel to the brain and/or surrounding membranes, causing inflammation. This swelling can harm or destroy nerve cells and cause bleeding in the brain.
Meningitis
Meningitis is most often caused by a bacterial or viral infection. It also may be caused by a fungal infection, a reaction to certain medications or medical treatments, an inflammatory disease such as lupus, some types of cancer, or a traumatic injury to the head or spine.
Bacterial meningitis is a rare but potentially fatal disease. It can be caused by several types of bacteria that first cause an upper respiratory tract infection and then travel through the blood stream to the brain. The disease can also occur when certain bacteria invade the meninges directly. The disease can block blood vessels in the brain, causing stroke and permanent brain damage.
Pneumococcal meningitis is the most common form of meningitis and is the most serious form of bacterial meningitis. Some 6,000 cases of pneumococcal meningitis are reported in the United States each year. The disease is caused by the bacterium Streptococcus pneumoniae, which also causes pneumonia, blood poisoning (septicemia), and ear and sinus infections. At particular risk are children under age 2 and adults with a weakened or depressed immune system. Persons who have had pneumococcal meningitis often suffer neurological damage ranging from deafness to severe brain damage.
Meningococcal meningitis, which is caused by the bacterium Neisseria meningitides, is common in children ages 2-18. Each year in the United States about 2,600 people get this highly contagious disease. High-risk groups include infants under the age of 1 year, people with suppressed immune systems, travelers to foreign countries where the disease is endemic, and college students (freshmen in particular) who reside in dormitories. Between 10 and 15 percent of cases are fatal, with another 10-15 percent causing brain damage and other serious side effects.
Haemophilus meningitis was at one time the most common form of bacterial meningitis. Fortunately, the Haemophilus influenzae b vaccine has greatly reduced the number of cases in the United States. Those most at risk of getting this disease are children in child-care settings and children who do not have access to the vaccine.
Other forms of bacterial meningitis include Listeria monocytogenes meningitis, which can cross the placental barrier and cause a baby to be stillborn or die shortly after birth; Escherichia coli meningitis, which is most common in elderly adults and newborns and may be transmitted to a baby through the birth canal, and Mycobacterium tuberculosis meningitis, a rare disease that occurs when the bacterium that causes tuberculosis attacks the meninges.
Viral, or aseptic, meningitis is the most common form of meningitis in the United States. This typically mild and non-lethal disease is usually caused by enteroviruses—common viruses that enter the body through the mouth and travel to the brain and surrounding tissues where they multiply. Enteroviruses are present in mucus, saliva, and feces and can be transmitted through direct contact with an infected person or an infected object or surface. Other viruses that cause meningitis include varicella zoster (the virus that causes chicken pox and can appear decades later as shingles), influenza, mumps, HIV, and herpes simplex type 2 (genital herpes).
Many fungal infections can affect the brain. The most common form of fungal meningitis is caused by the fungus cryptococcus neoformans (found mainly in dirt and bird droppings). Cryptococcal meningitis is common in AIDS patients. Although treatable, fungal meningitis often recurs in nearly half of affected persons.
Who is at risk for meningitis?
Anyone can get meningitis. People with weakened immune systems, including those persons with HIV or those taking immunosuppressant drugs, are at the highest risk of contracting the diseases.
What are the signs and symptoms?
The hallmark signs of meningitis are sudden fever, severe headache, and a stiff neck; encephalitis is characterized by seizures, stupor, coma, and related neurological signs. In more severe cases, neurological symptoms may include nausea and vomiting, confusion and disorientation, drowsiness, sensitivity to bright light, and poor appetite.
Meningitis often appears with flu-like symptoms that develop over 1-2 days. Distinctive rashes are typically seen in some forms of the disease. Meningococcal meningitis may be associated with kidney and adrenal gland failure and shock.
Patients with encephalitis often show mild flu-like symptoms. In more severe cases, patients may experience problems with speech or hearing, double vision, hallucinations, personality changes, loss of consciousness, loss of sensation in some parts of the body, muscle weakness, partial paralysis in the arms and legs, sudden severe dementia, impaired judgment, seizures, and memory loss.
Important signs of encephalitis to watch for in an infant include vomiting, body stiffness, constant crying that may become worse when the child is picked up, and a full or bulging fontanel (the soft spot on the top of the head).
How are these infections treated?
Persons who are suspected of having meningitis should receive immediate, aggressive medical treatment. Both diseases can progress quickly and have the potential to cause severe, irreversible neurological damage.
Meningitis
Early treatment of bacterial meningitis is important to its outcome. Strong doses of general antibiotics may be prescribed first, followed by intravenous antibiotics in more severe cases. Antibiotics may also be given to prevent other bacterial infections. Appropriate antibiotic treatment for most types of meningitis can reduce the risk of dying from the disease to below 15 percent.
Infected sinuses may need to be drained. Corticosteroids such as prednisone may be ordered to relieve brain pressure and swelling and to prevent hearing loss that is common in patients with Haemophilus influenza meningitis. Pain medicine and sedatives may be given to make patients more comfortable. Lyme disease is treated with intravenous antibiotics.
Unlike bacteria, viruses cannot be killed by antibiotics (an exception is the herpes virus, which can be treated with the antiviral drug acyclovir). Patients with mild viral meningitis may be allowed to stay at home, while those who have a more serious infection may be hospitalized for supportive care. Patients with mild cases, which often cause only flu-like symptoms, may be treated with fluids, bed rest (preferably in a quiet, dark room), and analgesics for pain and fever. The physician may prescribe anticonvulsants such as dilantin or phenytoin to prevent seizures and corticosteroids to reduce brain inflammation. If inflammation is severe, pain medicine and sedatives may be prescribed to make the patient more comfortable.
Acute disseminated encephalomyelitis is treated with steroids. Fungal meningitis is treated with intravenous antifungal medications.
Credit: National Institute of Health.