brain, spinal cord, and nerve disorders
Viral Meningitis
Diagnosis of Viral Meningitis
Spinal tap and analysis of cerebrospinal fluid Sometimes culture and testing of blood, other body fluids, or stool Doctors suspect meningitis when people have a headache, fever, and stiff neck. They then try to determine whether meningitis is present and whether it is caused by bacteria (requiring immediate treatment) or a virus. Viral meningitis is more likely when the symptoms are less severe. A Spinal Tap (lumbar puncture) is done to obtain a sample of cerebrospinal fluid. However, if doctors suspect that pressure within the skull is increased, computed tomography (CT) or magnetic resonance imaging (MRI) may be done first to check for causes of the increased pressure (such as a tumor or another mass in the brain). Doing a spinal tap when pressure within the skull is increased may cause a life-threatening disorder called The sample of cerebrospinal fluid is sent to a laboratory to be examined and analyzed. Sugar and protein levels and the number and type of white blood cells in the fluid are determined. The fluid is cultured to check for bacteria and thus rule out or confirm bacterial meningitis. The fluid is not usually cultured for viruses because doing so is technically difficult. The polymerase chain reaction (PCR) technique, which produces many copies of a gene, is used to identify enteroviruses, herpesviruses (such as HSV and varicella-zoster virus), and some other viruses. Doctors also test cerebrospinal fluid for the presence of antibodies to certain viruses. For example, detecting antibodies to West Nile virus in cerebrospinal fluid indicates infection with that virus. Doctors sometimes also take a sample of blood, nasal or throat secretions, or stool for culture, examination, and/or, if available, PCR testing. HIV can be diagnosed based on the results of antibody tests and PCR. Levels of antibodies to other viruses are measured and sometimes remeasured a few weeks later. An increase in the level of antibodies to a particular virus indicates that the virus caused a recent infection and so probably was the cause of recent meningitis. 