<prompt> Investigation used for CSF rhinorrhoea are all exceptCT cisternogramSkull X-raybeta2 transferrinNasal endoscopy  <response>: 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. 