Meningitis: Inflammation of the meninges, the three membranes that envelop the brain and the spinal cord. Meningitis can be caused by infection by bacteria, viruses, and protozoa. Other causes include cancer (metastasis to the meninges), inflammatory diseases, and drugs. In some cases the cause of meningitis cannot be determined. The treatment depends on the cause of the meningitis.
Reviewed on 5/13/2016