If you’ve ever knocked your head into an overhead lamp or doorway, you have the meninges to thank for protecting your brain. This three-layer membrane surrounds the brain and spinal cord. But when the meninges and the cerebrospinal fluid that cushions the brain become infected and inflamed, it can trigger a potentially life-threatening condition called meningitis.

Although viruses, fungi, and protozoa can all cause the infection that brings on meningitis, bacterial meningitis is the most dangerous. Because these cases are contagious and are easily spread in close quarters, such as college dormitories, they often grab newspaper headlines and other media attention. The most common culprits are strains called Streptococcus pneumoniae (pneumococcus) and Neisseria meningitidis (meningococcus).

One reason why bacterial meningitis is such a threat is because symptoms often come on rapidly—and can be lethal within a few hours. As the bacteria begin to multiply in the bloodstream, the earliest signs are a fever and possibly a rash. When bacteria infect the meninges, inflammation and pus thicken the cerebrospinal fluid, leading to vomiting, severe headache, and a stiffening of the neck. If the fluid blocks a ventricle, it can pool and create harmful pressure in the brain. This can result in coma or even death.

Most forms of viral meningitis, on the other hand, are rarely fatal and usually clear up in about 2 weeks. Symptoms include a rash, a sore throat, joint aches and pains, and a splitting headache. Physicians test for meningitis with a throat culture, chest x-ray, and spinal tap to analyze the cerebrospinal fluid. If a case of bacterial meningitis is diagnosed, it is treated with antibiotics or, rarely, by procedures to drain any accumulation of fluid in the brain.

ADDITIONAL FACTS

  1. Before antibiotics were invented, half of bacterial meningitis cases were deadly.
  2. The word meninges is derived from the Greek word meninx, which means “membrane.”
  3. Although meningitis can develop at any time, bacterial types are more likely to occur during the winter, and viral cases are more common in summer.