Abstract Introduction CRANIAL (CSF Rhinorrhoea After Endonasal Intervention to the Skull Base) is a prospective, multicentre observational study seeking determine: scope of skull base repair methods used, and corresponding rates postoperative CSF rhinorrhoea in endonasal transsphenoidal (TSA) expanded approaches (EEA) for tumours. Method A cohort pilot was carried out at eleven neurosurgical un...