Quiz Form

Question Date: 24/06/2023

Question: Which of the following tests is most likely to be normal in a patient with cauda equina syndrome due to leptomeningeal spread of acute leukemia?

Options:

• Lumbosacral MRI
• Cerebrospinal fluid flow cytometry
• Cerebrospinal fluid protein
• Lumbosacral fluorodeoxyglucose positron emission tomography (FDG-PET)

Correct Answer: Lumbosacral fluorodeoxyglucose positron emission tomography (FDG-PET)

Explaination: FDG-PET imaging of the CNS in instances of leptomeningeal disease is rarely helpful with respect to lesion detection in the CNS. In contrast, some cerebrospinal fluid abnormality is always present, although the abnormality is often nonspecific, typically an elevated protein concentration or opening pressure. The false-negative rate for cerebrospinal fluid cytology is nearly 50%; in patients with a leptomeningeal metastasis from hematologic cancers, flow cytometry is two to three times more sensitive than cytology. False-negative rates for spinal MRI range from 30% to 70%.

Reference: Page 137, Chamberlain MC. Neoplastic myelopathies. Continuum (Minneap Minn). 2015 Feb;21(1 Spinal Cord Disorders):132-45. doi: 10.1212/01.CON.0000461089.02113.1b. PMID: 25651222.