Meningitis in Adults

Meningitis in Adults Overview

Meningitis is a potentially life-threatening infection of the meninges—the tough layer of tissue that surrounds the brain and the spinal cord. If not treated, meningitis can lead to brain swelling and cause further disability, including coma and even death.

Meningitis can be caused by a variety of things, including bacteria (the most serious), viruses, fungi, reactions to medications, and environmental toxins such as heavy metals. Although bacterial and fungal meningitis require extended hospitalization, meningitis caused by viruses can often be treated at home and has a much better outcome.

• Bacterial meningitis
  
  
  • The most serious form of meningitis, bacterial meningitis, occurs in about 5,000-7,000 people in the United States every year.
    
    
  • Approximately 20% of the time, even with treatment, bacterial meningitis can be fatal. If bacterial meningitis progresses rapidly, in 24 hours or less, death may occur in more than half of those who develop it, even with proper medical treatment.
  
  
• Viral meningitis
  
  
  • Determining how many people get viral meningitis is difficult because it often remains undiagnosed and is easily confused with the flu.
    
    
  • The prognosis for viral meningitis is much better than that for bacterial meningitis, with most people recovering completely with simple treatment of the symptoms. Because antibiotics do not help viral infections, they are not useful in the treatment of viral meningitis.

Adult Meningitis Causes

Usually, the brain is protected naturally from the body’s immune system by the barrier the meninges creates between the bloodstream and the brain itself. Normally, this helps prevent the body from attacking itself. In meningitis, however, this can become a problem.

Once bacteria or other organisms have found their way to the brain, they are somewhat isolated from the immune system and can spread. However, when the body eventually begins to fight the infection, the problem can worsen.

As the body tries to fight the infection, blood vessels become leaky and allow fluid, white blood cells, and other infection-fighting particles to enter the meninges and the brain. This causes brain swelling and can eventually lead to decreased blood flow to parts of the brain, worsening the symptoms of infection.

• Meningitis is usually caused by one of a number of bacteria. The most common is Streptococcus pneumoniae. Neisseria meningitidis can cause outbreaks in crowded conditions, such as college dormitories or military barracks. Haemophilus influenzae type B (Hib) can also cause meningitis in adults and children, but it is becoming less common because children now receive the Hib vaccine in infancy.

• Bacterial meningitis can occur for a number of reasons. Often, it is the result of an infection by bacteria that already live in the nose and mouth. The bacteria enter the blood and become lodged in the brain’s outer covering, the meninges.

• Meningitis can also be caused by the spread of an infection occurring near the brain, such as from the ears or the sinuses. It is also an occasional complication of brain, head, or neck surgery.

• The average age for meningitis is 25 years, and meningitis affects both men and women equally. For unclear reasons, African Americans seem to develop meningitis more frequently than do people of other races.

• Those people at greater risk for meningitis than the rest of the population include the following:
  
  
  • Adults older than 65 years
    
    
  • Children younger than 5 years
    
    
  • Persons with alcoholism
    
    
  • People with cancer, especially those receiving chemotherapy
    
    
  • People who have received transplants and are taking drugs that suppress the immune system
    
    
  • People with diabetes
    
    
  • Those recently exposed to meningitis at home
    
    
  • IV drug users
    
    
  • People with shunts for hydrocephalus