Nasoseptal Flap Enhancement on Early Postoperative MRI Does Not Predict 3-Month Enhancement nor Postoperative Cerebrospinal Fluid Leak Risk.

Abstract

Background and objectives: The nasoseptal flap (NSF) has been a versatile reconstructive option for extended endonasal skull base surgery, significantly decreasing postoperative cerebrospinal fluid (CSF) leakage rates. One failure mechanism of concern is NSF necrosis. It has been postulated that immediate postoperative MRI flap enhancement can predict flap necrosis. This retrospective study analyzes NSF enhancement to assess for flap viability and CSF leakage.

Methods: Patients from 2012 to 2020 who underwent extended endoscopic endonasal surgery with NSF reconstruction were assessed. Immediate postoperative MRI and delayed 3-month MRI were compared for NSF enhancement. Enhancement was graded as no enhancement, partial, or complete enhancement. Patient demographics, tumor type, intraoperative CSF leak grade, and postoperative CSF leakage were assessed based on flap enhancement patterns.

Results: Of 713 patients who underwent endoscopic endonasal surgery, 64 required NSF reconstruction. On the immediate postoperative MRI, 45 patients (70%) had complete flap enhancement, 9 (14%) had partial, and 10 (16%) no enhancement. On the 3-month MRI, 59 patients (92%) had complete flap enhancement and 5 (8%) had partial enhancement. There was significant improvement of flap enhancement between immediate postoperative and 3-month MRI (P = .002). All patients with no initial enhancement had complete enhancement at 3 months. Of those with partial enhancement, 2 remained partial and 7 had complete enhancement at 3 months. Overall, 44 patients (69%) had no change between MRI scans, 17 (27%) improved, and 3 (5%) had decreased enhancement. There was no correlation between intraoperative CSF leak rates and flap enhancement. Four patients had postoperative CSF leaks, 2 having complete immediate enhancement, 1 partial, and 1 without enhancement (P = .85).

Conclusion: Overall, immediate postoperative MRI NSF enhancement (or lack thereof) did not predict enhancement at the 3-month MRI and did not correlate with postoperative CSF leakage. Hence, one should not rely solely on postoperative flap enhancement to assess the viability of the dural reconstruction.