[ESTABLISHING A NEW TEAM FOR ENDOSCOPIC ENDONASAL SKULL BASE SURGERY: THE LEARNING CURVE FROM BASIC TO ADVANCED COMPLEXITY LEVEL].

Introduction: Establishing a new team for endoscopic endonasal skull base surgeries (EES) requires a period of adjustment. Our team was established 4 years ago and consists of surgeons with previous experience. Our objective was to examine the learning curve associated with the establishment of such a team.

Methods: All patients who underwent EES between January 2017 and October 2020 were reviewed. The first 40 patients were defined as the 'early group' and the last 40 as the 'late group'. Data was retrieved from electronic medical records and surgical videos. Study groups were compared in terms of the level of surgical complexity, (II to V according to EES complexity level scale; level I cases were excluded), surgical outcome and complication rate.

Results: 'Early group' cases and 'late group' cases were operated on in 25 and 11 months, respectively. Complexity level II surgeries, which mainly included pituitary adenomas, were the most common in both groups (77.5% and 60%, respectively); of these, functional adenomas and reoperations were more common in the 'late group'. The rate of advanced complexity surgeries (III - V) was higher in the 'late group' (40% vs. 22.5%); level V surgeries were performed only in the 'late group'. No significant differences were observed in terms of surgical outcomes or complications; postoperative cerebrospinal fluid (CSF) leaks were less common in the 'late group' (2.5% vs. 7.5%).

Conclusions: Our findings indicate that the establishment of a new EES team, even if it includes experienced skull base surgeons, is associated with a learning curve, which requires about 40 cases.