brain, spinal cord, and nerve disorders
Subacute and Chronic Meningitis
Diagnosis of Subacute and Chronic Meningitis
Spinal tap and analysis of cerebrospinal fluid Doctors ask about factors that increase the risk of chronic meningitis, such as a Overview of Immunodeficiency Disorders (as may be caused by HIV infection or AIDS) and travel to areas where Lyme disease or certain fungal infections are common. Doctors also ask about and look for symptoms that may suggest a cause. To confirm the diagnosis, doctors do a Spinal Tap (lumbar puncture) to obtain a sample of cerebrospinal fluid, which is then analyzed. The cerebrospinal fluid is sent to a laboratory to be examined and analyzed. In people with meningitis, the number of white blood cells in cerebrospinal fluid is higher than normal. The results can usually enable doctors to distinguish between chronic and acute meningitis. Some infectious organisms that cause chronic meningitis, such as the fungusCryptococcus neoformans, are visible under a microscope, but many, such as the bacteria that cause tuberculosis, are difficult to detect. The cerebrospinal fluid is also cultured. Organisms, if present, are grown so that they can be identified. However, culturing may take weeks. Special techniques, which may provide results more quickly, may be used to identify fungi and the bacteria that cause tuberculosis and syphilis. For example, tests may be done to detect proteins released byCryptococcus neoformans(called antigen testing). The polymerase chain reaction (PCR) technique, which produces many copies of a gene, may identify the unique DNA sequence of the bacteria that cause tuberculosis. Doctors may also use an automated test called Xpert MTB/RIF, recommended by the World Health Organization (WHO) for the diagnosis of tuberculous meningitis, to detect the genetic material (DNA) of tuberculosis bacteria in samples of cerebrospinal fluid. Other tests may be done on samples of cerebrospinal fluid to document prior exposure to the bacteria that cause tuberculosis. Chest x-rays or computed tomography (CT) of the chest may detect evidence of prior or current tuberculosis. Other tests on cerebrospinal fluid are done, depending on which disorders are suspected. For example, the fluid may be analyzed for cancer cells if cancer is suspected. The cause of chronic meningitis may be difficult to determine, partly because detecting microorganisms in cerebrospinal fluid can be difficult. Thus, spinal taps may be repeated to obtain more cerebrospinal fluid for culture. If available, tests that can rapidly analyze large stretches of genetic material can be used to identify otherwise undetectable microorganisms in cerebrospinal fluid. To identify the cause, doctors may also need to culture samples of blood and urine or to biopsy infected meninges or other tissues, which are identified using magnetic resonance imaging (MRI) or CT. Sometimes MRI or CT is done when the cause of symptoms is unclear. Even after extensive testing, the cause often cannot be determined. 