Background The use of vascularized intranasal flaps has become essential in skull base reconstruction in endoscopic endonasal surgery (EES). However, necrosis of these flaps has the potential for CSF leak or devastating infection if not diagnosed early.
As indocyanine green (ICG) allows visualization of tissue perfusion, lack of intraoperative ICG fluorescence of flaps may correlate with postoperative flap necrosis.
Methods Patients undergoing EES for skull base tumor resection between September 2015 and August 2016 were prospectively enrolled. Each flap was evaluated intraoperatively with ICG endoscopy after administration of 12.5 or 25 mg of ICG. Pedicle and body were evaluated by three blinded observers with two possible grades: high or moderate (“positive enhancement”) and low or no enhancement (“no enhancement”). To evaluate postoperative MRI enhancement of the flap, the earliest postoperative image studies were used. Diagnosis of flap necrosis was confirmed with surgical revision of the reconstruction.
Results A total of 73 vascularized intranasal flaps were evaluated: 34 nasoseptal flaps (NSF), 29 extended NSF, 4 reused NSF, 1 reused extended NSF, and 5 inferior turbinate/lateral nasal wall flaps. Mean follow-up interval was 28 weeks (range: 2–76 weeks).
Flap pedicles had the same or higher degree of enhancement than flap bodies in all cases. 96.9% (32/33) of those flaps with enhancement of the body survived, with 1 case of partial necrosis. Among those cases with no body enhancement but enhancement of the pedicle, 90.6% (29/32) survived (2 cases of partial and 1 complete flap necrosis). Of those cases with neither body nor pedicle enhancement, 37.5% (3/8) developed flap necrosis (1 partial and 2 complete).
Pedicle and body ICG enhancement was inversely related to complete flap necrosis (p = 0.058) with a lower association with partial and complete necrosis (p = 0.068).
When compared with the enhancement of the flap in the earliest postoperative MRI available for the same patients (postoperative weeks 0–3), body and pedicle enhancement with ICG had a lower correlation with flap necrosis than postoperative MRI enhancement (p = 0.009). A greater number of cases with no MRI enhancement developed flap necrosis than with no ICG (NPV: 60 vs. 37.5% for the pedicle and 15% for the body). However, a higher amount of flaps survived when the body enhanced with ICG than when the flap enhanced on postoperative MRIs (PPV: 97 vs. 92.5%). Lack of enhancement of the body with ICG also covered more cases of flap necrosis than postoperative MRI (specificity: 85.7 vs. 42.8%), though this includes more flaps that did not enhanced but survived.
Conclusion Intraoperative pedicle and body ICG enhancement correlates with complete flap necrosis. Lack of ICG pedicle enhancement best predicts partial and complete flap necrosis, and ICG enhancement of the body predicts flap survival better than ICG pedicle enhancement or even postoperative MRI flap enhancement. Postoperative MRI enhancement of the flap remains the standard for identifying those cases that will develop flap necrosis but pedicle and body ICG enhancement had a good correlation with flap necrosis and allows intraoperative flap assessment.
