DEFINITION:
# Meningitis is an infection that causes inflammation of the membranes covering the brain and spinal cord.
# Non-bacterial meningitis is often referred to as "aseptic meningitis."
# Bacterial meningitis may be referred to as "purulent meningitis."




CAUSES, INCIDENCE, RISK FACTORS:
= The most common causes of meningitis are viral infections that usually resolve without treatment.
= However, bacterial infections of the meninges are extremely serious illnesses, and may result in death or brain damage even if treated.
= Meningitis is also caused by fungi, chemical irritation, drug allergies, and tumors.




TYPES:
# Meningitis - cryptococcal
Syphilitic aseptic meningitis
# Meningitis - H. influenza
# Meningitis - meningococcal
# Meningitis - pneumococcal
# Meningitis - staphylococcal
# Meningitis - tuberculous
# Aseptic meningitis
# Meningitis gram negative
# Carcinomatous meningitis (meningitis due to cancer)


= Acute bacterial meningitis is a true medical emergency, and requires immediate hospital-based treatment.
= Bacterial strains that cause meningitis include Streptococcus pneumoniae, Haemophilus influenzae, Neisseria meningitidis (meningococcus), Listeria monocytogenes, and many other types of bacteria.
= In the U.S. about 17,500 cases of bacterial meningitis occur each year.


= Viral meningitis is milder and occurs more often than bacterial meningitis.
= It usually develops in the late summer and early fall, often affects children and adults under 30.
= Seventy percent of the infections occur in children under the age of 5.
= Most viral meningitis is associated with enteroviruses, which are viruses that commonly cause intestinal illness.
= However, many other types of viruses can also cause meningitis.
= For example, viral meningitis may occur as a complication in people with genital herpes. =Recently, West Nile virus spread by mosquito bites has become a cause of viral meningitis in most of the U.S.
= In addition to causing viral meningitis, West Nile virus may cause encephalitis in some patients and a polio-like syndrome in others.




SYMPTOMS:
# Fever and chills
# Severe headache
# Nausea and vomiting
# Stiff neck (meningismus)
Sensitivity to light (photophobia)
# Mental status changes
= Additional symptoms that may be associated with this disease:
# Decreased consciousness
# Rapid breathing
# Agitation
Opisthotonos (severe neck stiffness, ultimately resulting in a characteristic arched posture-seen in infants or small children)
# Bulging fontanelles (the soft spots in a baby's skull may bulge)
# Poor feeding or irritability in children
# Meningitis is an important cause of fever in newborn children.
# For this reason, a lumbar puncture is often done on newborns who have a fever of uncertain origin.




SIGNS AND TESTS:
= Lumbar puncture with CSF glucose measurement and CSF cell count
= Gram-stain and culture of CSF (cerebral spinal fluid)
= Chest x-ray to look for other sites of infection
= Head CT scan looking for hydrocephalus, abscess or deep swelling




TREATMENT:
# Antibiotics will be prescribed for bacterial meningitis; the type will vary depending on the infecting organism.
# Antibiotics are not effective in viral meningitis.
# Treatment of secondary symptoms including brain swelling, shock, and seizures will require other medications and intravenous fluids.
# Hospitalization may be required depending on the severity of the illness and the needed treatment.



PROGNOSIS:
= Early diagnosis and treatment of bacterial meningitis is essential to prevent permanent neurological damage.
= Viral meningitis is usually not serious, and symptoms should disappear within 2 weeks with no residual complications.



COMPLICATIONS:
Hearing loss or deafness
Brain damage
Loss of vision
Hydrocephalus




PREVENTION:
# Haemophilus vaccine (HiB vaccine) in children will help prevent one type of meningitis.
# The pneumococcal conjugate vaccine is now a routine childhood immunization and is very effective at preventing pneumococcal meningitis.
# It is highly recommended that household contacts and people with close contact with individuals with meningococcal meningitis receive preventative antibiotics to avoid becoming infected themselves.
# Some communities conduct vaccination campaigns following an outbreak of meningococcal meningitis.
# Military recruits are routinely vaccinated against this form of meningitis because of its high rate of occurrence.
# The American Academy of Pediatrics and the American College Health Association encourage college students (particularly freshmen living in dormitories) to consider being vaccinated with the meningococcal vaccine.