1.50. Diseases of the Nervous System http://www.ck12.org
Encephalitis
Encephalitisis a brain infection (Figure1.97). If you have encephalitis, you are likely to have a fever and headache
or feel drowsy and confused. The disease is most often caused by viruses. The immune system tries to fight off a
brain infection, just as it tries to fight off other infections. But sometimes this can do more harm than good. The
immune system’s response may cause swelling in the brain. With no room to expand, the brain pushes against the
skull. This may injure the brain and even cause death. Medicines can help fight some viral infections of the brain,
but not all infections.
FIGURE 1.97
This scan shows a person with encephali-
tis.Meningitis
Meningitisis an infection of the membranes that cover the brain and spinal cord. If you have meningitis, you are
likely to have a fever and a headache. Another telltale symptom is a stiff neck. Meningitis can be caused by viruses
or bacteria. Viral meningitis often clears up on its own after a few days. Bacterial meningitis is much more serious
(Figure1.98). It may cause brain damage and death. People with bacterial meningitis need emergency medical
treatment. They are usually given antibiotics to kill the bacteria.
A vaccine to prevent meningitis recently became available. It can be given to children as young as two years old.
Many doctors recommend that children receive the vaccine no later than age 12 or 13, or before they begin high
school.