This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: ENT
Which is the MOST COMMON site for CSF Rhinorhoea? 
Select and explain. 
A. Ethmoid sinus, B. Frontal sinus, C. Sphenoid sinus, D. Tegmen Tympani
A: Ethmoid sinus
Answer: A: Ethmoid sinus 
Explanation: The most common site of CSF leak are the lamina cribrosa and fovea ethmoidalis. CSF rhinorrhea may result from trauma, congenital anomalies, septal surgery or sinus surgery. It is typically intermittent and tends to be position dependent. Diagnosis is made by estimating the level of glucose in the sample. Glucose level of more than 50mg per 100ml is typically diagnostic. Presence of beta or tau transferrin is most specific for CSF rhinorrhea.