This is an old revision of this page, as edited by Vogon77 (talk | contribs) at 05:52, 30 October 2004 (→Causative organisms). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.
Revision as of 05:52, 30 October 2004 by Vogon77 (talk | contribs) (→Causative organisms)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)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.
Causative organisms
Major bacteria that cause meningitis are Streptococcus pneumoniae, Haemophilus influenzae, staphylococcus and meningococcus. Meningitis caused by Haemophilus influenzae is known to occur in outbreaks, examples include outbreaks in dorms and military outbreaks. Community acquired cases of meningitis are usually caused by Streptococcus pneumoniae, seen in elderly patients. Listeria monocytogenes and Neisseria meningitis are also other causes of community acquired meningitis. On the other hand, viruses are the most common cause of aspetic meningitis.
Incidence
20,000 to 25,000 cases of bacterial meningitis are seen in 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 children.
Symptoms
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.
treatment
Meningitis is a medical emergency, being a condition with a high mortality rate if untreated. The cause is most commonly a bacterial infection sensitive to antibiotics. 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 (likely due to edema or concomitant brain abscess), a broad spectrum intravenous antibiotic should be started immediately (this is often a third generation cephalosporin). 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 (but not in adults) 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 (which include the sinuses and mastoid cells of ear). These should be investigated when diagnosis of meningitis is confirmed or suspected.
Complications
Convulsions are a known complication of meningitis and are treated with appropriate anti-seizure drugs such as phenytoin.
Categories: