This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2019, Subject name: ENT
Investigation used for CSF rhinorrhoea are all except 
Select and explain. 
A. CT cisternogram, B. Skull X-ray, C. beta2 transferrin, D. Nasal endoscopy
D: Nasal endoscopy
Answer: D: Nasal endoscopy 
Explanation: Advanced nasal endoscopic techniques can be used for CSF leak repair but not for investigation. CT cisternogram requires intrathecal injection of iohexol and a CT scan to localize the site. b 2 transferrin proteindetection by electrophoresis is asensitive and specific test for CSF.