The investigation of choice for meningeal carcinomatosis in CNS is:
**Core Concept**
Meningeal carcinomatosis is a condition where cancer cells spread to the meninges, the protective layers of tissue covering the brain and spinal cord. The investigation of choice should accurately diagnose this condition, ideally through imaging or sampling of cerebrospinal fluid (CSF).
**Why the Correct Answer is Right**
The correct investigation for diagnosing meningeal carcinomatosis involves analyzing the CSF for malignant cells, which can be done through lumbar puncture. This procedure allows for the collection of CSF, which can then be examined cytologically for cancer cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Is not typically used for diagnosing meningeal carcinomatosis.
**Option B:** May show some abnormalities but is not the most direct method for diagnosing meningeal carcinomatosis.
**Option C:** Involves imaging and can show signs suggestive of meningeal carcinomatosis but is not as specific as CSF analysis.
**Clinical Pearl / High-Yield Fact**
Meningeal carcinomatosis is a serious condition that requires prompt diagnosis and treatment. CSF cytology is a crucial diagnostic tool, offering a direct method to detect malignant cells in the CSF.
**Correct Answer:** D. CSF cytology.