BACKGROUND: CRANIAL (CSF Rhinorrhoea After Endonasal Intervention to the Skull Base) is a prospective multicenter observational study seeking to determine 1) the scope of skull base repair methods used and 2) corresponding rates of postoperative cerebrospinal fluid (CSF) rhinorrhea in the endonasal transsphenoidal approach (TSA) and the expanded endonasal approach (EEA) for skull base tumors. We sought to pilot the project, assessing the feasibility and acceptability by gathering preliminary data. METHODS: A prospective observational cohort study was piloted at 12 tertiary neurosurgical units in the United Kingdom. Feedback regarding project positives and challenges were qualitatively analyzed. RESULTS: A total of 187 cases were included: 159 TSA (85%) and 28 EEA (15%). The most common diseases included pituitary adenomas (n = 142/187), craniopharyngiomas (n = 13/187). and skull base meningiomas (n = 4/187). The most common skull base repair techniques used were tissue glues (n = 132/187, most commonly Tisseel), grafts (n = 94/187, most commonly fat autograft or Spongostan) and vascularized flaps (n = 51/187, most commonly nasoseptal). These repairs were most frequently supported by nasal packs (n = 125/187) and lumbar drains (n = 20/187). Biochemically confirmed CSF rhinorrhea occurred in 6/159 patients undergoing TSA (3.8%) and 2/28 patients undergoing EEA (7.1%). Four patients undergoing TSA (2.5%) and 2 patients undergoing EEA (7.1%) required operative management for CSF rhinorrhea (CSF diversion or direct repair). Qualitative feedback was largely positive (themes included user-friendly and efficient data collection and strong support from senior team members), demonstrating acceptability. CONCLUSIONS: Our pilot experience highlights the acceptability and feasibility of CRANIAL. There is a precedent for multicenter dissemination of this project, to establish a benchmark of contemporary practice in skull base neurosurgery, particularly with respect to patients undergoing EEA.