Use of Intraoperative Fluorescent Indocyanine Green Angiography for Real-Time Vascular Evaluation of Pericranial Flaps

Intraoperative Indocyanine Green Angiography for Assessing Flap Perfusion in Skull Base Reconstruction: A Systematic Review

Objective This study was aimed to study the current use of intraoperative indocyanine green (ICG) angiography during skull base reconstruction and understand its efficacy in predicting postoperative magnetic resonance imaging (MRI) enhancement and flap.

Study Design The Embase, the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, and Google Scholar databases were searched from the date of inception until August 2020 for studies of ICG flap perfusion assessment during skull base reconstruction. The primary outcome of interest was the development of cerebrospinal fluid (CSF) leak after skull base reconstruction. Secondary outcomes of interest included postoperative meningitis, flap MRI enhancement, flap necrosis, flap perfusion measurements, and total complications.

Results Search results yielded 189 studies, from which seven studies with a total of 104 patients were included in the final analysis. There were 44 nasoseptal flaps (NSF), two lateral nasal wall flaps (LNWF), 14 pericranial flaps (PCF), and 44 microvascular free flaps. The rates of CSF leak and postoperative MRI enhancement were 11 and 94%, respectively. There was one case of postoperative meningitis. Pooled analysis of the available data showed that intraoperative ICG flap perfusion was associated with flap enhancement on postoperative MRI (p = 0.008) and CSF leak (p = 0.315) by Fisher's exact test.

Conclusion The available literature suggests intraoperative ICG enhancement is associated with postoperative MRI enhancement. Given the small sample sizes in the literature and the rarity of complications associated with skull base reconstruction, intraoperative ICG enhancement has not been predictive of flap necrosis or postoperative complications such as CSF leak or meningitis.

Level of Evidence This study presents level 3 evidence as a systematic review of case studies, case reports, and retrospective and prospective trials with no blinding, controls, and inconsistently applied reference standards.

Evaluation of Intranasal Flap Perfusion by Intraoperative Indocyanine Green Fluorescence Angiography

BACKGROUND

Vascularized intranasal flaps are the primary reconstructive option for endoscopic skull base defects. Flap vascularity may be compromised by injury to the pedicle or prior endonasal surgery. There is currently no validated technique for intraoperative evaluation of intranasal flap viability.

OBJECTIVE

To evaluate the efficacy of indocyanine green (ICG) near-infrared angiography in predicting the viability of pedicled intranasal flaps during endoscopic skull base surgery through a pilot study.

METHODS

ICG near-infrared fluorescence endoscopy was performed during endoscopic endonasal surgery for skull base tumors. Intraoperative and postoperative data were collected regarding enhancement of the flap body and pedicle. Fluorescence was rated qualitatively. Postoperatively, flap perfusion was evaluated via MRI-contrast enhancement in addition to clinical outcomes (cerebrospinal fluid leak and endoscopic flap appearance).

RESULTS

Thirty-eight patients underwent ICG fluorescence angiography. Both the body and pedicle enhanced in 20 patients (53%), while the pedicle only enhanced for 12 patients (32%), the body only for 3 (8%), and neither for 3 (8%). When both the pedicle and body enhanced with ICG, the rate of postoperative MRI contrast enhancement was 100% and the rate of flap necrosis was 0%. The sensitivity and specificity of flap pedicle ICG enhancement for predicting postoperative flap MRI enhancement were 97% and 67%, respectively. Two of 3 patients without enhancement developed flap necrosis.

CONCLUSION

ICG fluorescence angiography of intraoperative flap perfusion is feasible and correlates well with outcomes of postoperative MRI flap enhancement and flap necrosis. Additional study is needed to further refine the imaging technique and optimally characterize the clinical utility.

Optimizing Indocyanine Green Fluorescence Angiography in Reconstructive Flap Surgery: A Systematic Review and Ex Vivo Experiments

Background. Indocyanine green angiography (ICGA) offers the potential to provide objective data for evaluating tissue perfusion of flaps and reduce the incidence of postoperative necrosis. Consensus on ICGA protocols and information on factors that have an influence on fluorescence intensity is lacking. The aim of this article is to provide a comprehensive insight of in vivo and ex vivo evaluation of factors influencing the fluorescence intensity when using ICGA during reconstructive flap surgery. Methods. A systematic literature search was conducted to provide a comprehensive overview of currently used ICGA protocols in reconstructive flap surgery. Additionally, ex vivo experiments were performed to further investigate the practical influence of potentially relevant factors. Results. Factors that are considered important in ICGA protocols, as well as factors that might influence fluorescence intensity are scarcely reported. The ex vivo experiments demonstrated that fluorescence intensity was significantly related to dose, working distance, angle, penetration depth, and ambient light. Conclusions. This study identified factors that significantly influence the fluorescence intensity of ICGA. Applying a weight-adjusted ICG dose seems preferable over a fixed dose, recommended working distances are advocated, and the imaging head during ICGA should be positioned in an angle of 60° to 90° without significantly influencing the fluorescence intensity. All of these factors should be considered and reported when using ICGA for tissue perfusion assessment during reconstructive flap surgery.

Technological and Ideological Innovations in Endoscopic Skull Base Surgery

BACKGROUND

Endoscopic skull base surgery has evolved over the last several decades due to technological advances and operative techniques. Several innovations that are not yet mainstream may have significant impact on the future of endoscopic skull base surgery.

METHODS

Current literature pertaining to innovations in endoscopic skull base surgery was retrieved using PubMed, Embase, Web of Science, and Google Scholar.

RESULTS

Several recent innovations may play an influential role in the advancement of endoscopic skull base surgery, including fluorescent dyes such as indocyanine green fluorescence, fluorescein, and 5-aminolevulinic acid, 3-dimensional endoscopes, robotic surgery, and intraoperative magnetic resonance imaging.

CONCLUSIONS

Several technologies are under current investigation with the hope to improve future outcomes in endoscopic skull base surgery. Additional research and evolution are necessary and will require intense scrutiny before becoming standard of care.

Clinical Experience with Secondary Endoscopic Reconstruction of Clival Defects with Extracranial Pericranial Flaps

Objectives  The aim of this study is to report the clinical outcome of extracranial pericranial flaps (ePCF) used for reconstruction of clival dural defects following failure of primary repair. Design  Retrospective review of skull base database. Setting  Academic medical center. Participants  Patients undergoing reconstruction of clival defects with ePCF following endoscopic endonasal surgery (EES). Main outcome measures  Postoperative cerebrospinal fluid (CSF) leak, meningitis, and flap necrosis. Results  Seven patients (five males and two females) who underwent ePCF reconstruction for clival defects following EES were included. All patients (ages 8-64 years) had a postoperative CSF leak due to a failed primary clival reconstruction (five had one, one had two, and one had three failed CSF leak repairs prior to ePCF reconstruction). Nasoseptal and inferior turbinate (lateral nasal wall) flaps were not available for secondary reconstruction due to prior surgeries. The immediate success rate of ePCF for the reconstruction of clival defects in patients with multiple flap failures was 58%. Two patients developed CSF leaks that were successfully repaired endoscopically with the addition of free tissue grafts; one patient had partial flap necrosis that required debridement; none required an additional vascularized flap. Width of the defect, length of the defect, properties of the ePCF, and age did not demonstrate significance ( p  > 0.05) for adverse outcome. Conclusion  An ePCF is a reconstructive option for high-risk, large clival defects when other local and regional vascularized flaps are not available or fail. ePCFs can be used for reconstruction of clival defects in all populations, including pediatric patients.

Prediction of Skin Necrosis after Mastectomy for Breast Cancer Using Indocyanine Green Angiography Imaging

Background:

In immediate tissue expander reconstruction following total mastectomy for breast cancer, indocyanine green angiography (ICGA)–guided skin trimming is useful for the prevention of complications. However, instances of unclear ICGA contrast can occur with this method, which are difficult to judge as to whether preventive trimming is warranted. To further improve the mastectomy flap necrosis rate, more accurate objective parameters are necessary.

Methods:

The degree of clinical improvement was compared between 81 patients trimmed according to the surgeon’s judgment (non-ICGA group) and 100 patients with ICGA-guided trimming (ICGA group). We then retrospectively measured 3 parameters [relative perfusion (RP); time (T) to reach RPmax; and slope (S = RP/T) reflecting the rate of increase to RPmax] by using region of interest analysis software and examined their relationships with skin necrosis.

Results:

The rate of grade III necrosis (reaching the subcutaneous fat layer) was significantly lower in the ICGA group (4.8%) than in the non-ICGA group (17.8%; P < 0.05). The specificity of RP for the diagnosis of skin necrosis was high (98.5%; cutoff value, 34). However, the sensitivities of slope parameters were higher than RP.

Conclusions:

ICGA-guided trimming decreased the rate of deep skin necrosis requiring additional surgical treatment. Region of interest analysis indicated that a relatively low percentage luminescence (RP < 34) was indicative of the need for skin trimming, combined with a slow increase in the perfusion of the mastectomy skin flaps.