Long-Term Survival and MRI Enhancement of Nasoseptal Flaps in Endoscopic Endonasal Skull Base Surgery

Objective: As endoscopic endonasal surgery is gaining more widespread acceptance in skull base surgery, the use of vascularized nasoseptal flaps is increasing. There are few studies looking at long-term viability and vascularity of these flaps. We reviewed our experience with nasoseptal flaps and examined their survival rate and perfusion based on long-term follow-up MRI.

Method: Between 2008 and 2012, we performed nasoseptal flaps in 147 patients. Seventy-four patients who had preoperative, immediate postoperative, and long-term postoperative MRI scans with contrast were analyzed for flap enhancement, thickness, location, and survival. Sagittal MRI scans were examined to determine flap location, degree of coverage of craniectomy site, and degree of flap migration or retraction. Flap survival was correlated with lumbar drain placement, intraoperative and postoperative CSF leak, and mucocele formation.

Results: Of the total 147 patients, 93% had a unilateral nasoseptal flap and 7% had bilateral flaps. The most common tumor pathologies were pituitary adenoma (48%), meningioma (14%), and craniopharyngioma (13%). A transsphenoidal/transsellar approach was performed in 22% of cases, and an extended approach was used in 78%. Four cases were revised for flap failure (2.7%); two of these revisions were for CSF leak (1.36%) and two for mucocele formation (1.36%). Immediate (median follow-up of 2 days) and long-term (median follow-up of 8 months) postoperative MRIs with contrast were available in 74 patients, with a flap survival rate of 91%, as determined by the presence of enhancement on the long-term contrast MRI. Additionally, at immediate and long-term imaging, 74% and 84%, respectively, of this cohort had flaps that appeared at their initial intended location, with complete coverage of the skull base defect. There was no association between postoperative CSF leak or mucocele formation and flap enhancement, thickness, or location on the immediate postoperative MRI.

Conclusion: Nasoseptal flaps have a high rate of viability over time and provide a stable vascularized barrier between the intracranial and nasal spaces. Flap coverage improves over time as the flap progressively adheres to the skull base. Although mucocele formation is rare, ensuring complete removal of sphenoid mucosa and proper placement of the flap would further reduce this relatively uncommon complication.