Investigation of choice for leptomeningeal carcinomatosis:
Ans is 'c' i.e. Gd-enhanced MRI Leptomeningeal carcinomatosis is a special form of metastasis where the tumor cells are widely disseminated throughout the meninges and the ventricles. Common sources are - adenocarcinoma of breast, lung, and gastrointestinal tract; melanoma; childhood leukemia; and systemic lymphoma. (Ref: Adam and Victor's Principles of Neurology 8/e p563)Haaga writes- "The greater sensitivity of MRI for detecting leptomeningeal tumor spread has established this technique as the diagnostic modality of choice for the evaluation of possible leptomeningeal carcinomatosis."Harrison writes- "Leptomeningeal metastases are particularly challenging to diagnose as identification of tumor cells in the subarachnoid compartment may be elusive. MR imaging can be definitive in patients when there are clear tumor nodules adherent to the cauda equina or spinal cord, enhancing cranial nerves, or subarachnoid enhancement on brain imaging. Imaging is diagnostic in approximately 75% of patients and is more often positive in patients with solid tumors. Demonstration of tumor cells in the CSF is definitive and often considered the gold standard. However, CSF cytologic examination is positive in only 50% of patients on the first lumbar puncture and still misses 10% after three CSF samples."
PET
SPECT
Gd enhanced MRI
CT scan