Question

All of the following statements about CSF leak are true, except:

• A. The most common site of CSF leak is the fovea ethmoidalis
• B. Beta-2 transferrin estimation is highly specific for diagnosis
• C. Fluorescein dye can be used intrathecally for localising the site of leak
• D. MRI (gadolinium enhanced) T1 images are best for diagnosis of the site of leak

Hint:

For finding the leak site, think thin-section CT and cisternography, not contrast T1 MRI.

Answer 1

The Correct Option is D

Step 1: A CSF leak (rhinorrhoea) needs the site of the skull base defect to be found before repair. Each option tests a fact about diagnosis and localisation.
Step 2: Option A is true. The cribriform plate and the fovea ethmoidalis region of the anterior skull base is the commonest site of spontaneous and traumatic CSF rhinorrhoea because the bone there is thin and the dura is adherent.
Step 3: Option B is true. Beta-2 transferrin (and beta-trace protein) is found almost only in CSF, perilymph and aqueous humour. Detecting it in nasal fluid is highly specific for confirming that the fluid is CSF.
Step 4: Option C is true. Intrathecal fluorescein, given via lumbar puncture, stains the CSF green and lets the surgeon see the exact leak point endoscopically. It is used in low doses with caution.
Step 5: Option D is false and is the exception. The best imaging for localising a CSF leak is high-resolution CT of the skull base to show the bony defect, often combined with CT cisternography or heavily T2-weighted MR cisternography to show the fluid tract. Gadolinium-enhanced T1 MRI does not show the CSF tract well and is not the best test.
Hence the false statement, and the answer, is Option D.