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

Background: Endoscopic endonasal approaches to sellar and parasellar lesions have emerged as the primary treatment modality. These approaches have historically been associated with a high rate of cerebrospinal fluid (CSF) leak; however, this risk has been successfully mitigated by the advent of the vascularized nasoseptal flap (NSF). Radiographic evaluation of flap appearance and integrity is a process that is still being understood. We aimed to describe long-term changes in flap appearance on magnetic resonance imaging (MRI) in a large cohort of patients undergoing endoscopic endonasal surgery for various lesions.

Methods: We reviewed 71 patients who underwent endoscopic endonasal surgery for tumor resection with no postoperative CSF leak, with MRI at least 24 months after index surgery from July 2018 to December 2023. Variables included average NSF pedicle thickness/enhancement, flap thickness/enhancement, flap adherence to the skull base, and diaphragm sellae descent on immediate postoperative MRI, 12-month postoperative MRI, and 24-month postoperative MRI. Patients were stratified by adjuvant radiotherapy to assess for radiation-induced radiographic changes.

Results: Out of 71 patients with 24-month postoperative MRIs, 54 had immediate postoperative MRIs available. The last follow-up MRI available was 33 months (standard deviation [SD] 15.4). Immediately after surgery, the average flap and pedicle thickness were 3.9 mm (SD 2.2) and 3.0 mm (SD 1.8), respectively. Fifty-one of 54 patients (94.4%) had an intraoperative CSF leak. No patients had a CSF leak post-operatively. NSF thickness (p = 0.96), pedicle thickness (p = 0.43), pedicle enhancement (p = 0.97), and flap enhancement (p = 0.50) were similar on immediate postoperative, 12-month, and 24-month MRIs. Flap adherence to the skull base increased significantly between immediate postoperative and 12-month MRI (75.9 vs. 97.9%, p = 0.001), and remained adherent at 24 months (97.8%). The diaphragm sella showed significant descent between immediate and 12-month postoperative MRI (54% versus 9.1% were above the tuberculum sella-dorsum sella line, p < 0.0001), and remained descended at 24 months (9.1%). There were no significant differences in flap thickness, pedicle thickness, flap enhancement, diaphragm descent, or flap adherence at any time point. The adjuvant radiotherapy group had a significantly higher rate of pedicle enhancement at all time points (immediate: 80% versus 19%; 12-month: 100% versus 21%; 24-month: 87.5% versus 16.2% full pedicle enhancement, p < 0.0001)

Conclusion: The nasoseptal flap is an effective tool for skull base reconstruction after endonasal skull base approaches. Nasoseptal flaps and their respective pedicle have a characteristic appearance on postoperative MRI, with long-term stability.

Publication History

Article published online:
07 February 2025