Use of Second Window ICG in spinal cord biopsy of a mildly contrast-enhancing lesion: Technical note and review of the literature

Abstract

Introduction: Indocyanine green (ICG) is commonly used to visualize cerebral vasculature, particularly in the management of cerebral aneurysms. There have also been attempts to use ICG for visualization of tumors. Injection of ICG followed by immediate fluorescence microscopy is limited by the short time window for imaging and administration and restricted depth of imaging. Second Window Indocyanine Green (SWIG) addresses these issues by allowing for longer contrast times and the imaging of deeper regions of brain tissue. Biopsy of spinal cord lesions is often difficult for a variety of reasons, including the delicate nature of the tissue and differentiating normal from lesional tissue visually, especially in lesions with heterogeneous enhancement.

Methods: In this case report, we describe the use of second window ICG to facilitate the visualization of a spinal cord lesion and subsequent biopsy of the lesion.

Results: This patient is a 24-year-old female who had recurrence of a suprasellar germinoma. An MRI of the rest of the neuraxis was performed to assess for the presence of drop metastases. The spinal cord from C2-5 was expanded with areas of patchy enhancement; however, this lesion was asymptomatic. The patient's oncologist requested a biopsy of this lesion to help direct subsequent care of her recurrent germinoma. The day before surgery, the patient had an intravenous injection of ICG dye. She then underwent a C3-5 laminectomy for biopsy of her cervical intramedullary lesion. After opening of the dura, no visible abnormality of the spinal cord could be identified. A Stryker endoscope showed an area of ICG uptake in the cord at approximately the C3-4 level. A midline myelotomy was centered over the ICG demarcated area and several samples were taken for pathology. Final biopsy results determined the lesion to be spinal cord parenchyma with perivascular and intraparenchymal lymphocytes - not consistent with spinal cord tumor or germinoma.

Conclusion: Second Window ICG is effective in visualizing otherwise visually unremarkable spinal cord lesions. This technology can facilitate biopsy of these lesions and possibly their surgical resection.

Keywords: Cancer; Fluorescence; Fluorescent imaging; ICG; Intramedullary tumor; Neurosurgery; Spinal lesion.