Meningitis
Copyright 2010
Definition
Meningitis is a term used for inflammation of the meninges, namely the leptomeninges (the pia mater and arachnoid). It is caused usually by infection, though it can also be chemical and metastatic. In terms of the infectious causes, the agents involved are usually S. pneumoniae, N. meningitidis; E.coli and group B streptococci appear often at childhood.
Bacteria gain access to the meninges by colonizing the mucous membranes, from where they invade and spread hematogeneously. Direct contamination is of course also possibly, whenever there are defects. Both bacteria and virus tend to cause an acute presentation, whereas tuberculosis, cryptococcus and spirochetes cause a chronic meningitis. Regarding the metastatic meningitis, the most common neoplasias primarily originating them are acute leukemias, lymphomas, breast, GI and lung carcinomas. The inflammation may evolve to ventriculitis, empyema, cerebritis, and abscess formation.
For acute settings (that is, infectious), patients present with headache, fevers, neck rigidity, clouding of counsciousness and photophobia.
The CSF is determinant for diagnosis. It can be clear (viral, metastatic), cloudy or purulent. Gram stains, culture and PCR will reveal the etiology in infectious meningitidis.
Neuroimaging studies performed in the setting of acute meningitis may be unremarkable. They are mostly used to detect the complications described above, or, on the other hand, to detect an anatomical abnormality that predisposes to the infection. CT scan has another important role however: to exclude contraindication to lumbar puncture, such as risk of herniation of the cerebellar tonsils. In severe meningitis, MRI has better results, as it is able to demonstrate leptomeningeal enhancement and distention of the subarachnoid space.
Treatment is with antibiotics and corticosteroids to reduce inflammation and brain damage.
Meningitis is a potentially life threatening infection or inflammation of the meninges of the brain caused by viruses, bacteria, drugs and sometimes by metastases clinically resulting in headache, neck pain, nuchal rigidity, fever, and mental status changes.
The diagnosis is best made by evaluation of the CSF with attention to the presence of leukocytes, red cells, or bacteria, and or abnormal levels of sugar and protein.
Early administration of antibiotics is an essential part of the treatment when meningitis is suspected since it is a life threatening disease. Viral meningitis is treated with supportive care.