Evaluation of Intranasal Flap Perfusion by Intraoperative ICG Fluorescence Angiography

Introduction: Vascularized intranasal flaps have become the primary reconstructive option for the endoscopic endonasal approach (EEA) to the skull base. Indocyanine green (ICG) fluorescence angiography can be utilized to visualize vascularity and tissue perfusion. The aim of our proof-of-concept study was to evaluate the efficacy of intraoperative ICG fluoresce in evaluating the perfusion of intranasal flaps used in skull base reconstruction.

Methods: ICG fluorescence endoscopy was performed on patients during endoscopic endonasal surgery for a skull base tumors. Intraoperative and post-operative data was collected regarding enhancement of the flap body and pedicle. Fluorescence of the flap body and/or pedicle was rated qualitatively as high, medium and low. Post-operatively, MRI enhancement of the flap was recorded in addition to clinical outcomes (CSF leak and flap necrosis).

Results: Twenty-seven patients underwent flap fluorescence angiography at the conclusion of their procedures. A nasal septal flap (NSF) was utilized in 16 patients while extended NSF and lateral wall flaps were used in 7 and 3 patients respectively. In one patient, a prior NSF was dissected free and re-utilized. Median time to visualize fluorescence was 25 seconds (range of 14–98s). There was no association between the degree of flap fluorescence and the time to fluorescence. Twenty-five patients had data recorded about the body of the flap and twelve patients had data recorded about the flap pedicle. The flap pedicle fluoresced to the same degree (17%) or more (83%) than the body of the flap in all patients. Seventeen flap bodies had medium or high fluorescence, and all 17 enhanced on post-operative MRI. Eight flap bodies were found to have low fluorescence and 6 enhanced on MRI. Eleven pedicles had med/high fluorescence, 10 of which enhanced on MRI. One pedicle had low fluorescence and did not enhance on MRI. This patient later developed flap necrosis and was the only individual with low fluorescence of both the flap pedicle and body. Fluorescence of the flap body predicted post-operative MRI enhancement with a sensitivity and specificity of 89% and 100%, respectively, and a positive and negative predictive value of 100% and 75%, respectively. Florescence of the flap pedicle predicted MRI enhancement with a sensitivity and specificity of 100% and 50%, respectively, with a PPV and NPV of 91% and 100%, respectively.

Conclusion: ICG fluorescence angiography of intranasal flap perfusion is feasible and correlates well with post-operative MRI flap enhancement. Strong fluorescence of the flap body and pedicle correlates with post-operative MRI enhancement. Similarly, low fluorescence of the flap body and pedicle may predict a lack of MRI enhancement, but the flap pedicle has a stronger negative predictive value. Flap necrosis was predicted by low fluorescence of both the flap body and pedicle. Additional study is needed to further refine the imaging technique and optimally characterize the clinical utility.