Nasoseptal Flap Enhancement on Immediate Postoperative MR Imaging Does Not Predict Three-Month Imaging Rates Nor Postoperative CSF Leak Risk

 

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

Methods: Patients from 2012 to 2020 who underwent extended endoscopic endonasal skull base surgery with nasoseptal flap reconstruction were assessed. Immediate postoperative MRI and delayed 3 month MRI were assessed for nasoseptal flap enhancement. Enhancement was graded as no enhancement, partial enhancement 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 endonasal operations, 64 required nasoseptal flap reconstruction. Tumor types in this cohort included: craniopharyngioma (34%), meningioma (28%), pituitary adenoma (11%), chordoma (9%), and other pathologies (18%). On the immediate postoperative MRI, 45 patients (70%) had complete flap enhancement, 9 patients (14%) had partial enhancement, and 10 patients (16%) had no enhancement. On the 3-month MRI, 59 patients (92%) had complete flap enhancement and 5 patients (8%) with partial enhancement. There was significant improvement of flap enhancement between immediate postoperation and 3-month MRI (p = 0.002). Of the patients with no initial enhancement, all ten patients had complete enhancement at 3 months. Of the patients with partial enhancement, two remained partial at 3 months and seven had complete enhancement at 3 months. Overall, 44 patients (69%) had no change between MRI scans, 17 patients (27%) improved, and 3 patients (5%) had decreased enhancement at 3 months. There was no correlation between intraoperative CSF leak rates and flap enhancement. Four patients had postoperative CSF leaks (all with Grade 3 intraoperative defects), with two having complete immediate enhancement, one partial enhancement and one without enhancement (p = 0.85).

Conclusion: Overall, the immediate postoperative MRI nasoseptal flap enhancement (especially the lack of enhancement) did not predict flap enhancement at the 3-month MRI and also 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 ([Figs. 1] and [2]).

Publication History

Article published online:
15 February 2022

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