Meningitis is a potentially fatal inflammation of the meninges, the thin, membranous covering of the brain and the spinal cord. Meningitis is most commonly caused by infection (by bacteria, viruses, or fungi), although it can also be caused by bleeding into the meninges, cancer, or diseases of the immune system.
The meninges are three separate membranes, layered together, which serve to encase the brain and spinal cord. The dura is the toughest, outermost layer, and is closely attached to the inside of the skull. The middle layer, the arachnoid, is important in the normal flow of the cerebrospinal fluid (CSF), a lubricating fluid which bathes both the brain and the spinal cord. The innermost layer, the pi…
The most common infectious causes of meningitis vary according to an individual host's age, habits and living environment, and health status. In newborns, the most common agents of meningitis are those which are contracted from the newborn's mother, including Group B streptococci (becoming an increasingly common infecting organism in the newborn period), Escherichia coli, and Listeri…
The majority of meningitis infections are acquired by blood-borne spread. An individual may have another type of infection (of the lungs, throat, or tissues of the heart) caused by an organism which can also cause meningitis. The organism multiplies, finds its way into the blood stream, and is delivered in sufficient quantities to invade past the blood-brain barrier. Direct spread occurs when an a…
A number of techniques are used when examining a patient suspected of having meningitis to verify the diagnosis. Certain manipulations of the head (lowering the head, chin towards chest, for example) are difficult to perform and painful for a patient with meningitis. The most important test used to diagnosis meningitis is the lumbar puncture (commonly called a spinal tap). Lumbar puncture (LP) inv…
A series of vaccines against Haemophilus influenzae, started at two months of age, has greatly reduced the incidence of that form of meningitis. Vaccines also exist against Neisseria meningitidis and Streptococcus pneumoniae bacteria, but these vaccines are only recommended for those people who have particular susceptibility to those organisms, due to certain immune deficiencies, lack of a spleen,…
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