How is meningitis diagnosed?
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 diagnose meningitis is the lumbar puncture (commonly called a spinal tap). Lumbar puncture (LP) involves the insertion of a thin needle into a space between the vertebrae in the lower back and the withdrawal of a small amount of CSF. The CSF is then examined under a microscope to look for bacteria or fungi. Normal CSF contains set percentages of glucose and protein. These percentages will vary with bacterial, viral, or other causes of meningitis. For example, bacterial meningitis causes a greatly lower than normal percentage of glucose to be present in CSF, as the bacteria are essentially "eating" the host's glucose, and using it for their own nutrition and energy production. Normal CSF should contain no infection-fighting cells (white blood cells), so the presence of white blood cells in CSF is another indication of meningitis. Some of the withdrawn CSF is also put into special lab dishes to allow growth of the infecting organism, which can then be identified more easily. Special immunologic and serologic tests may also be used to help identify the infectious agent.
In rare instances, CSF from a lumbar puncture cannot be examined because the amount of swelling within the skull is so great that the pressure within the skull (intracranial pressure) is extremely high. This pressure is always measured immediately upon insertion of the LP needle. If it is found to be very high, no fluid is withdrawn because doing so could cause herniation of the brain stem. Herniation of the brain stem occurs when the part of the brain connecting to the spinal cord is thrust through the opening at the base of the skull into the spinal canal. Such herniation will cause compression of those structures within the brain stem that control the most vital functions of the body (breathing, heart beat, consciousness). Death or permanent debilitation follows herniation of the brain stem.
More information on meningitis
What is meningitis? - Meningitis is an inflammation of the meninges, the membrane envelopes that encase the brain and spinal cord. Meningitis can range from mild to life-threatening.
What's viral meningitis? - Viral meningitis, also called aseptic meningitis, is caused by many different viruses. Most viral meningitis is associated with enteroviruses.
What is bacterial meningitis? - Bacterial meningitis may be fatal or cause serious long-term complications. Acute bacterial meningitis is a true medical emergency.
What causes meningitis? - The most common infectious causes of meningitis vary according to an individual's age, habits, living environment, and health status.
What causes bacterial meningitis? - A number of types of bacteria can cause acute bacterial meningitis. They include pneumococcus, meningococcus, haemophilus, and listeria.
What're the risk factors for meningitis? - People who work with domestic animals and pregnant women are at increased risk for meningitis associated with listeriosis.
What're the complications of meningitis? - The complications of meningitis can be severe. Some of these effects are permanent and physically disabling.
How is meningitis diagnosed? - A number of techniques are used to verify the diagnosis. The most important test used to diagnose meningitis is the lumbar puncture.
What's the treatment for meningitis? - Antibiotic medications are the most important element of treatment against bacterial agents of meningitis.
How to prevent meningitis? - Vaccines to protect against S. pneumoniae and H. influenzae type b (Hib) are available and have dramatically reduced the number of meningitis cases.