Case Lessons: Application of Second-window ICG in Intra-axial Neoplasm Resection

Introduction: Neurosurgeons rely on subjective tissue discrimination to pursue radical intra-axial neoplasm resection but not at the expense of patients’ quality of life. Technology can help localize tumor and define extent of resection. Indocyanine green (ICG) is a near-infrared (NIR) fluorophore with increased tissue penetration. In 2016, second-window ICG (SWIG) technique was firstly applicated in glioma resection. Gadolinium-enhancing neoplasms and necrosis can be localized through brain parenchyma. Recent evidence demonstrates postresection residual fluorescence can be a powerful tool to evaluate extent of resection in conjunction with magnetic resonance imaging (MRI) for patients with brain metastasis. We present clinical experience from a single institute about SWIG in intra-axial neoplasm resection.

Methods: Patients were infused intravenously with 5 mg/kg ICG (C43H47N2O6S2⋅Na) over a 1-hour period the day before surgery. In the operating room, all cases were imaged using the Haag-Streit (Hi-R 1000) microscope with an 800nm emission filter. Real-time videos were captured in 1280p resolution. In seven patients, the resection was carried out with intraoperative cortical and/or subcortical mapping, because these lesions were either located in the central lobe or near corticospinal tract. All intra-axial neoplasm resection were performed via microsurgical technique.

Results: Between Mar. 2024 and Oct. 2024, there were three gliomas, seven metastases, one primary CNS lymphoma and three cases of radiation necrosis. CSF releases after craniotomy, durotomy, and arachnoid dissection. This makes brain shift. Furthermore, tumor debulking leads to re-expansion of compressed brain and changes in cerebral blood volume. Navigation which is based on preoperative neuroimaging can sometimes be confusing due to brain shift and change of conformation. In ten cases, SWIG can serve as adjunct and provide real-time information for tissue discrimination. In six cases, residual NIR signal correlates with Gadolinium-enhancement in MRI within 48 hours after operation.

Conclusion : This case-series study demonstrates that neurosurgeons can coordinate microsurgical techniques, intraoperative visual clues from SWIG, and anatomy-imaging correlation, to achieve maximal safe resection. Large-scale randomized trials are required to prove benefits of SWIG in intra-axial neoplasm resection.