Postoperative cerebrospinal fluid (CSF) leak is a significant complication of endoscopic endonasal approaches (EEA) to the skull base. The use of tissue sealants such as fibrin glue (Tisseel) or synthetic agents (PEI/PEG) is widespread in surgical practice, however, recent high-quality evidence challenges their clinical benefit and cost-effectiveness. This study aims to investigate whether the routine use of sealants in patient with peri-operatively assessed low CSF leak risk, significantly improves outcomes over no sealant use, to guide more cost- effective, evidence-based closure strategies. To the best of our knowledge, the present study is the first randomized clinical trial to evaluate the necessity and comparative effectiveness of fibrin and synthetic sealants versus no sealant in preventing postoperative CSF leaks following endoscopic endonasal surgery in low-post operative CSF leak risk patients.

Introduction Postoperative cerebrospinal fluid (CSF) leak is a significant complication of endoscopic endonasal approaches (EEA) to the skull base. The use of tissue sealants such as fibrin glue (Tisseel) or synthetic agents (PEI/PEG) is widespread in surgical practice, however, recent high-quality evidence challenges their clinical benefit and cost-effectiveness. This study aims to investigate whether the routine use of sealants in patient with peri-operatively assessed low CSF leak risk, significantly improves outcomes over no sealant use, to guide more cost- effective, evidence-based closure strategies. To the best of our knowledge, the present study is the first randomized clinical trial to evaluate the necessity and comparative effectiveness of fibrin and synthetic sealants versus no sealant in preventing postoperative CSF leaks following endoscopic endonasal surgery in low-post operative CSF leak risk patients. Materials and Methods This is a prospective, randomized, controlled, single-center clinical trial conducted at the Maria Skłodowska-Curie National Research Institute of Oncology in Warsaw, Poland.

Adult patients scheduled for endoscopic endonasal surgery (EES) will first undergo screening based on medical history and detailed radiological evaluation. Those who meet all predefined inclusion and exclusion criteria will be enrolled and randomized preoperatively using a computer-generated allocation sequence into one of three treatment arms: (1) no sealant (standard multilayer closure), (2) fibrin glue application (Tisseel®), or (3) synthetic polyethylene glycol-based sealant (Adherus®). Following randomization, surgery will be performed in accordance with the assigned intervention. The primary endpoint is the incidence of postoperative cerebrospinal fluid (CSF) leak within 3 months. Secondary outcomes include endoscopic evaluation of mucosal healing at 6 weeks and 3 months, postoperative complication rates (e.g., meningitis, pneumocephalus), reoperation rate, patient-reported quality of life, and a cost-effectiveness analysis comparing sealant use to standard closure. The study is designed and will be reported in accordance with the SPIRIT 2025 (Standard Protocol Items: Recommendations for Interventional Trials) guidelines to ensure methodological transparency and reproducibility. Results Initial enrollment includes a target of 225 patients (75 per arm). Interim data analysis focuses on early healing parameters, safety profiles, and cost metrics. Hypothesis testing will determine if either sealant significantly reduces CSF leak rates compared to no sealant and whether the marginal benefit justifies routine use in all patients. Exploratory endpoints include biomaterial handling characteristics and surgeon-reported usability. Conclusion The NoSeal Trial addresses a critical gap in evidence regarding the necessity and comparative performance of sealants in skull base reconstruction. By evaluating both clinical outcomes and economic impact, the study seeks to optimize surgical protocols and improve the safety and efficiency of endonasal neurosurgical procedures.

Inclusion Criteria:

• Age ≥ 18 years
• Scheduled for endoscopic endonasal surgery involving standard skull base reconstruction
• Informed written consent obtained prior to enrollment
• Hemodynamic and electrolyte stability before surgery
• Procedure expected to be completed without use of high-flow intraoperative CSF diversion techniques

Exclusion Criteria:

• Revision surgery or extended endoscopic approaches requiring complex reconstruction (e.g., clival or cribriform defects)
• Tumors requiring complex sella reconstruction from the start
• Preoperative hydrocephalus
• Known allergy to fibrin-based or synthetic sealant components
• Active sinus infection or systemic inflammatory disease
• Prior radiotherapy to the sellar or parasellar region
• Uncontrolled diabetes mellitus (HbA1c > 7.0%)
• Participation in another interventional trial that may influence wound healing or CSF assessment
• Radiologic signs of chronic intracranial hypertension or hypotension

De-identified individual participant data (IPD) to be shared will include:

Demographics (age, sex) Preoperative imaging risk features Intraoperative findings (CSF leak grade, reconstruction technique) Treatment allocation (sealant type or no sealant) Primary and secondary outcomes (e.g., CSF leak occurrence, mucosal healing scores, complication rates, SNOT-22 and VAS scores) Follow-up data at 4 and 12 weeks Reoperation status Adverse events

De-identified individual participant data (IPD) and supporting documentation will be available beginning 6 months after publication of the primary results and will remain accessible for up to 36 months.

Access will be granted to qualified researchers affiliated with academic or non-commercial institutions who submit a methodologically sound research proposal. Access will include de-identified IPD and supporting documents (protocol, SAP, ICF, CSR, analytic code). Requests should be sent to the corresponding author. Data will be shared via secure institutional data-sharing platforms upon approval of the proposal and execution of a data use agreement.