CSF is preserved for examination in case of
## **Core Concept**
Cerebrospinal fluid (CSF) examination is crucial in diagnosing various neurological conditions. The preservation and handling of CSF samples are critical for accurate laboratory results. Different conditions require specific preservation methods to maintain the integrity of the sample for various tests.
## **Why the Correct Answer is Right**
The correct answer, **B. Viral encephalitis**, involves preserving CSF for examination to identify viral pathogens. In cases of suspected viral encephalitis, CSF is collected and sent for polymerase chain reaction (PCR) to detect viral genetic material. This requires careful handling and preservation to prevent degradation of the viral RNA.
## **Why Each Wrong Option is Incorrect**
* **Option A:** Bacterial meningitis - While CSF analysis is critical in bacterial meningitis, the focus is usually on Gram stain and culture, which do not require the same level of RNA preservation as viral PCR.
* **Option C:** Subarachnoid hemorrhage - In this case, the focus is on identifying blood in the CSF, which does not require special preservation techniques for RNA or cultures.
* **Option D:** Neurodegenerative diseases - These conditions often involve analysis of CSF proteins (like tau protein or beta-amyloid), but the preservation requirements are different and typically involve immediate freezing rather than specific viral transport media.
## **Clinical Pearl / High-Yield Fact**
For viral encephalitis, it's crucial to handle CSF samples carefully and store them in appropriate viral transport media to preserve the RNA for PCR testing. Delay or improper handling can lead to false-negative results.
## **Correct Answer:** B. Viral encephalitis