Meningitis

Overview

Meningitis is an inflammatory disease of the membranes that surround the brain and spinal cord.

Causes

Meningitis is most often caused by a bacterial or viral infection although 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.

Viral or aseptic meningitis is the most common form of meningitis in North America. 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. 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).

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. It 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.

Meningococcal meningitis which is caused by the bacterium Neisseria meningitides is common in children ages 2-18. Approximately 7 to 10 percent of cases are fatal. 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.

Haemophilus meningitis was at one time the most common form of bacterial meningitis. However the Haemophilus influenzae b vaccine has greatly reduced the number of cases. 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 seniors and newborns and may be transmitted to a baby through the birth canal

Mycobacterium tuberculosis meningitis a rare disease that occurs when the bacterium that causes tuberculosis attacks the meninges.

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 those who have been infected before.

Symptoms

The hallmark signs of meningitis are sudden fever severe headache and a stiff neck. Other symptoms may include nausea and vomiting confusion sleepiness and difficulty waking up. 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.

In infants symptoms of meningitis may include irritability or fatigue lack of appetite and fever.

Viral meningitis usually clears up in 10 days or less but other types of meningitis can be deadly if not treated promptly. Anyone experiencing symptoms of meningitis should see a doctor immediately.

Treatment


Early treatment of bacterial meningitis is important to its outcome. Strong doses of general antibiotics may be prescribed initially 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.

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.

Prevention

Good personal hygiene can reduce the risk of getting the disease from an infected person. Avoid sharing food utensils glasses and other objects with a person who may be exposed to or have the infection. Wash hands often with soap and rinse under running water.

Effective vaccines are available to prevent pneumonia H. influenza pneumococcal meningitis and infection with other bacteria that can cause meningococcal meningitis.

People who live work or go to school with someone who has been diagnosed with bacterial meningitis may be asked to take antibiotics for a few days as a preventive measure.