Second-Window Indocyanine Green for Visualization of Hemangioblastoma: A Case Report With Two-Dimensional Operative Video

Intraoperative visualization of cranial nerve schwannomas using second-window indocyanine green: A case series

BACKGROUND

Second Window Indocyanine Green (SWIG) is a novel intraoperative imaging technique that uses near-infrared (NIR) light for intra-operative tumor visualization using the well-known fluorophore indocyanine green (ICG). Because schwannomas often incorporate the nerve into the encapsulated tumor and impinge on surrounding neural structures, SWIG is a promising technique to improve tumor resection while sparing the nerve.

OBJECTIVE

To demonstrate the use of SWIG in resection of cranial nerve schwannomas.

METHODS

Three patients with cranial nerve schwannomas (i.e., trigeminal, vestibular, and vagus) underwent SWIG-guided resection. During surgery, NIR visualization was used intermittently used to detect fluorescence to guide resection. Signal-to-background ratio was then calculated to quantify fluorescence.

RESULTS

Patients were infused with ICG at a dose of 5.0 mg/kg 24 hours before surgery. Each patient achieved total or near-total resection and relief of symptoms with lack of recurrence at six-month follow-up. The average SBR calculated was 3.79, comparable to values for SWIG-guided resection of other brain and spine tumors.

CONCLUSION

This case series is the first published report of trigeminal and vagus nerve schwannoma resection using the SWIG technique and suggests that SWIG may be used to detect all schwannomas, alongside many other types of brain tumor. This paper also demonstrates the importance of preoperative ICG infusion timing and discusses the inverse pattern of NIR signal that may be observed when infusion occurs outside of the optimal timing. This provides direction for future studies investigating the administration of SWIG to resect cranial nerve schwannomas and other brain tumors.

Fluorescence-Guided Surgery: A Review on Timing and Use in Brain Tumor Surgery

Fluorescence-guided surgery (FGS) allows surgeons to have improved visualization of tumor tissue in the operating room, enabling maximal safe resection of malignant brain tumors. Over the past two decades, multiple fluorescent agents have been studied for FGS, including 5-aminolevulinic acid (5-ALA), fluorescein sodium, and indocyanine green (ICG). Both non-targeted and targeted fluorescent agents are currently being used in clinical practice, as well as under investigation, for glioma visualization and resection. While the efficacy of intraoperative fluorescence in studied fluorophores has been well established in the literature, the effect of timing on fluorophore administration in glioma surgery has not been as well depicted. In the past year, recent studies of 5-ALA use have shown that intraoperative fluorescence may persist beyond the previously studied window used in prior multicenter trials. Additionally, the use of fluorophores for different brain tumor types is discussed in detail, including a discussion of choosing the right fluorophore based on tumor etiology. In the following review, the authors will describe the temporal nature of the various fluorophores used in glioma surgery, what remains uncertain in FGS, and provide a guide for using fluorescence as a surgical adjunct in brain tumor surgery.