Skull Base Reconstruction Using a Multilayer Pericranial Flap After Cranioendoscopic Resection of Sinonasal Adenocarcinoma: A Single-Center Experience

Background: Sinonasal adenocarcinomas are uncommon but locally aggressive malignancies with a marked tendency to invade the anterior skull base. Cranioendoscopic resection provides effective oncologic control while minimizing surgical morbidity. However, reconstruction of the resulting skull base defects remains technically demanding, particularly in cases where nasoseptal flaps are unavailable. In such scenarios, vascularized pericranial flaps (PCFs) offer a promising alternative, though data on their long-term performance in patients undergoing adjuvant radiotherapy remain limited. Objective: This study aimed to describe and evaluate the clinical, radiological, and oncological outcomes of multilayer anterior skull base reconstruction using a vascularized PCF following cranioendoscopic resection of sinonasal adenocarcinoma. Methods: A retrospective analysis was conducted on patients who underwent cranioendoscopic resection of sinonasal adenocarcinoma between 2010 and 2023. Skull base reconstruction was performed using a multilayer technique combining a vascularized PCF, dural substitute, and titanium plate. Collected data included demographics, surgical and radiological outcomes, and postoperative complications. Results: Thirteen male patients (mean age 59.6 ± 11.9 years) were included. The median anterior skull base defect area was 793 mm² (range: 600-950 mm²). One patient (7.7%) developed a postoperative cerebrospinal fluid (CSF) leak, successfully managed with conservative treatment. Two patients (15.4%) developed postoperative meningitis, which resolved with intravenous antibiotics. No surgical re-intervention or flap necrosis occurred. Radiological follow-up confirmed the integrity and stability of all reconstructions. All patients received adjuvant radiotherapy initiated within six weeks postoperatively, with no treatment delays or donor site complications. Conclusion: The multilayer reconstruction of anterior skull base defects using a vascularized PCF is a safe, reproducible, and highly effective technique. It provides durable, watertight closure, allows timely initiation of adjuvant radiotherapy, and demonstrates excellent outcomes even in irradiated surgical fields. In cases where nasoseptal flaps are not available or insufficient, the PCF should be considered a primary option for skull base reconstruction following cranioendoscopic tumor resection.