The most important method to determine whether a person is suffering from meningitis or not, is through the analysis of cerebrospinal fluid (fluid extracted from the spinal chord). Other methods of detection include blood cultures and looking for markers of inflammation (such as C-reactive protein).
Fail-safe Method of Determining Meningitis
There are cases wherein the lumbar puncture can be contraindicative. It is not advisable to carry out lumber puncture if somebody has recently suffered from brain herniation caused by increased intracranial pressure or if there is a presence of cerebral mass lesion. In such a situation, the lumbar puncture can be preceded by a CT scan or an MRI scan. These can help eliminate non-meningitis possibilities.
How to Administer Lumbar Puncture
Causes other than meningitis make up to 45% of all adult cases. Hence, it is best to ensure that these causes are eliminated from the list of possibilities. A CT or MRI scan before performing Lumbar Puncture is the right way to go. If performing Lumbar Puncture is proving to be difficult then it is best to administer antibiotics. This would prevent any delay in treatment.
How Lumbar Puncture Method Helps Determine Meningitis
Before Taking out cerebrospinal fluid, the opening pressure is measured. If the reading turns out to lie in the region of 200 and 500 mm H2O (20-50 cm), presence of bacterial meningitis is ascertained. However, this value may be low in case of children.
The initial appearance of the fluid may also provide an indication about the nature of infection. If the fluid is cloudy in color, it indicates a higher level of c-protein, white and red blood cells and/or bacteria. This might indicate that the person is suffering from meningitis. However, such visual confirmation should be corroborated by proper laboratory analysis.
In laboratories a cerebrospinal fluid sample is analyzed to find out the level of protein, white and red blood cells and glucose. The presence of bacteria is ascertained with the help of the Gram staining method. However, if the results of this test are negative then this does not exclude meningitis as the cause. To find out more confirmed causes, the Gram staining method can be replaced by the method of microbiological culture.
Apart from Gram staining and Microbiological culturing, the other tests performed include limulus lysate test, polymerase chain reaction (PCR) test for bacterial or viral DNA and the latex agglutination test. The PCR test is a highly sensitive and specific technique that can give confirmed results. The other two come into picture only if Gram staining or microbiological culturation did not yield the desired results. The eventual treatment method to be employed would remain the same in both the cases.
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