Long-Term Radiographic Changes of Vascularized Pedicled Nasoseptal Flaps After Endoscopic Endonasal Skull Base Surgery

Background: Endoscopic endonasal approaches (EEA) are widely used for a myriad of skull base pathologies. Although historically associated with high cerebrospinal fluid leak (CSF) rates, this risk has been largely mitigated with vascularized nasoseptal flaps (NSF). However, postoperative radiographic evaluation of NSF remains incompletely characterized. We aimed to characterize longitudinal changes in NSF appearance on MRI in a large cohort of patients undergoing EEA. Methods: We reviewed 71 patients who underwent EEA for tumor removal or CSF leak repair with MRI at least 24 months after surgery from July 2018 to December 2023. Fifty-seven percent of patients were female. Results: Among 71 patients with >24-month postoperative MRIs, 53 had immediate postoperative MRIs. Immediately after surgery, average flap and pedicle thickness measured 3.9±2.2 mm and 3.0±1.8mm, respectively. Collagen matrix inlay was used in 77.8% of cases, and a dural sealant in 96.3%. No postoperative CSF leaks occurred. NSF thickness (p=0.96), pedicle thickness (p=0.43), pedicle enhancement (p=0.97), and flap enhancement (p=0.5) remained stable across immediate, 12-month, and 24-month MRIs. Flap adherence increased significantly between immediate to 12-month MRI (p=0.001). The diaphragma sella showed significant descent between immediate and 12-month MRI (p<0.0001). 10 patients (18.9%) received adjuvant radiotherapy, which was associated with a significantly higher rate of pedicle enhancement at all time points (p<0.0001), with no other significant differences. Conclusions: The nasoseptal flap is an effective tool for skull base reconstruction after EEA. Nasoseptal flaps and their pedicles demonstrate characteristic long-term MRI features, and surgeons should recognize these changes when evaluating postoperative imaging.