Meningitis is inflammation
of the membranes (meninges) covering the brain and the spinal cord. Although
the most common causes are infection (either bacterial or viral),
chemical agents and even tumor cells may cause meningitis. Encephalitis
and brain abscess can complicate infective meningitis.
Viruses are the most common
cause of meningitis.
Major bacteria that cause
meningitis are Neisseria meningitidis (meningococcus), Streptococcus
pneumoniae (pneumococcus), and Haemophilus influenzae. Less common
bacterial causes include Listeria monocytogenes, Staphylococcus and Escherichia
coli. In developing countries, Mycobacterium tuberculosis is a common
cause of bacterial meningitis.
In immunocompromised patients,
fungal meningitis may occur, typically caused by Cryptococcus neoformans.
- Brain tumors
- Brain metastasis
- Intrathecal drugs
- Lead poisoning
20,000 to 25,000 cases of
bacterial meningitis are seen in the United States every year. Mostly
adults are infected, where it can be community acquired or nosocomial.
Vaccination against Haemophilus influenzae has reduced the incidence in
Meningitis may occur in
outbreaks in communities who have close contact with each other, such as
in dorms or military establishments.
The classical symptoms of
meningitis are headache, neck stiffness and photophobia (the trio are
called "meningism"). An altered level of consciousness or other
neurological deficits may be present depending on the severity of the
disease. A lumbar puncture to obtain cerebrospinal fluid (CSF) is usually
indicated to determine the cause and direct appropriate treatment.
Meningitis is a medical
emergency, being a condition with a high mortality rate if untreated.
Patients with suspected meningitis should optimally initially have a CT
scan to help determine if there is a raised intracranial pressure that
might cause a serious or fatal brain herniation during lumbar puncture.
If there are no signs of elevated central nervous system pressure
demonstrated on the CT scan, a lumbar puncture procedure is performed to
obtain cerebrospinal fluid for microscopic examination, chemical
analysis, and bacterial cultures. Broad spectrum antibiotics should be
urgently started before the culture results are available. If lumbar
puncture can not be performed because of raised intracranial pressure, a
broad spectrum intravenous antibiotic should be started immediately. When
cerebrospinal fluid gram stain, or blood or CSF culture and sensitivity
results, are available, the empiric treatment can be refined by switching
to more specific antibiotics. In children, the administration of steroids
helps reduce the incidence of deafness following meningitis.
Infection of the meninges
usually originates through spread from infection of the neighbouring
structures. These should be investigated when diagnosis of meningitis is
confirmed or suspected.
If the patient is commonly
in contact with many others, people in the surroundings may be commenced
on prophylactic treatment; this is generally done with the antibiotic
rifampicin, which is otherwise mainly used in tuberculosis.
Haemophilus influenzae (Hib) have decreased neonatal meningitis
Vaccines against type A and
C Neisseria meningitidis, the kind that causes most disease in preschool
children and teenagers in the United States have also been around for a
A trial of type B vaccine
(MeNZB), the strain of meningitis prevalent in Norway, New Zealand and
Cuba, is underway in New Zealand, and being given to high-risk children
in South Auckland.
Convulsions are a known
complication of meningitis and are treated with appropriate anti-seizure
drugs such as phenytoin.