Introduction, Cause, Symptoms and Diagnosis, Treatment and Prevention
I. Introduction
Meningitis, inflammation of the meninges, the membranes that surround the brain and spinal cord. Meningitis may be caused by a physical injury, a reaction to certain drugs, or more commonly, infection by certain viruses, bacteria, fungi, or parasites. This article focuses on meningitis caused by viral or bacterial infection. In the United States viral meningitis is the most common form of the disease, while bacterial meningitis, which affects an estimated 17,500 people each year, is the most serious form of the disease. Most cases of both viral and bacterial meningitis occur in the first five years of life.
II. CausePrint section
The most common causes of viral meningitis are coxsackie viruses and echoviruses, although herpesviruses, the mumps virus, and many other viruses can also cause the disease. Viral meningitis is rarely fatal, and most patients recover from the disease completely.
Many of the microorganisms that cause meningitis are quite common in the environment and are usually harmless. The microorganisms typically enter the body through the respiratory system or, sometimes, through the middle ear or nasal sinuses. Many people carry these bacteria or viruses without having any symptoms at all, while others experience minor, coldlike symptoms. Meningitis only develops if these microorganisms enter a patient's bloodstream and then the cerebrospinal fluid (CSF), which surrounds the brain and spinal cord. The CSF contains no protective white blood cells to fight infection, so once the microorganisms enter the CSF, they multiply rapidly and make a person sick.
Although the viruses and bacteria that cause meningitis are contagious, not everyone who comes in contact with someone with meningitis will develop the disease. In fact, meningitis typically occurs in isolated cases. Occasionally outbreaks of meningitis caused by Neisseria meningitidis, also known as meningococcal meningitis, occur in group living situations, such as day-care centers, college dormitories, or military barracks. A child whose immune system is weakenedâdue to a disease or genetic disorder, for instanceâis at increased risk for developing meningitis. In general, however, scientists do not know why microorganisms that are usually harmless are able to cross into the CSF and cause meningitis in some people but not others.
III. Symptoms and DiagnosisPrint section
No matter what the cause, the symptoms of meningitis are always similar and usually develop rapidly, often over the course of a few hours.
Nearly all patients with meningitis experience vomiting, high fever, and a stiff neck. Meningitis may also cause severe headache, back pain, muscle aches, sensitivity of the eyes to light, drowsiness, confusion, and even loss of consciousness. Some children have convulsions. In infants, the symptoms of meningitis are often more difficult to detect and may include irritability, lethargy, and loss of appetite. Most patients with meningococcal meningitis develop a rash of red, pinprick spots on the skin. The spots do not turn white when pressed, and they quickly grow to look like purple bruises.
Meningitis is diagnosed by a lumbar puncture, or spinal tap, in which a doctor inserts a needle into the lower back to obtain a sample of CSF. The fluid is then tested for the presence of bacteria and other cells, as well as certain chemical changes that are characteristic of meningitis
