Risk analysis for delayed cerebrospinal fluid leak as a late complication of endoscopic transnasal surgery: effects of irradiation and insights into reconstruction methods.

Aggressive skull base tumors such as chordomas and high-grade meningiomas often exhibit resistance to treatment, highlighting the need for improved management combining endoscopic transnasal surgery (ETS) with adjunctive radiation therapy (RT). However, repeated ETS and RT may lead to delayed cerebrospinal fluid (CSF) leaks, posing clinical challenges. This study aimed to assess the incidence and risk factors for delayed CSF leaks. From November 2016 to October 2023, a total of 287 patients who underwent ETS for skull base lesions were analyzed, with the median follow-up of 45 months. Delayed CSF leaks were defined as leaks occurring six months or more after the last ETS procedure. Among these patients, 69 (24%) underwent multiple ETS procedures, and 102 (36%) received RT. Skull base reconstruction methods involved simple closure with fat grafting (with or without sphenoid mucosal flap) in 46%, non-vascularized multilayer closure in 50%, and pedicled mucosal flap-based reconstruction in 5%. Delayed CSF leaks occurred in 5 patients (1.7%), with cumulative incidence rates of 0.6%, 1.2%, and 3.7% at 3, 5, and 10 years, respectively. Notably, all leaks occurred exclusively in RT patients, showing significantly higher incidence rates compared to those without RT (2.6% at 5 years, 7.0% at 10 years vs. 0% at 10 years; p = 0.030). Cox proportional hazards analysis identified chordoma pathology, increased ETS procedures, and RT sessions as independent risk factors. Mucosal flap-based reconstruction effectively prevented recurrence, indicating its potential advantage for managing delayed CSF leaks following ETS combined with RT.