Endoscopic ICG in Pituitary Adenoma: Advantages, Limitation, and Selection Criteria for Beneficial Usage

Background: Endoscopic-indocyanine green (E-ICG) has been used in endoscopic skull base surgery using specific high gain camera and near-infra-red (NIR) light source. Accumulation of the ICG in skull base tumors is still a new technique that is undergoing multiple studies. Pituitary adenomas are one of the most common lesions operated endoscopically in skull base surgery. Introducing the E-ICG as a useful tool in better visualization of the pituitary adenoma and the gland is a promising tool in maximizing the efficiency of these procedures. However, selecting the cases that will benefit from this technology is still under investigation. With our experience gained using this technology, correlation with the radiological T1 post gadolinium sequences seem to be one of the hallmarks in expecting the pattern of fluorescence of the gland and the tumor in these cases.

Objective: To better understand and propose criteria for selecting the pituitary adenoma cases that will benefit from the E-ICG based on the clinical experience gained from utilization of this technology.

Methods: A prospective study enrolling nine patients ([Table 1]) with pituitary adenoma undergoing endoscopic endonasal surgery was conducted. The study was approved by the Institutional Review Board with a consent obtained from each patient enrolled in the study. Exclusion criteria included; pregnancy, age less than 18 years old, allergy to sulfa, iodide, or penicillin. For visualization of ICG fluorescence, separate 5.8 mm, 0 and 45 degrees, 19 cm length endoscopes attached to a Cold Light Fountain D-LIGHT P and an IMAGE1S H3-Z FI Three-Chip FULL HD in addition to the standard endoscopes for normal scenes (all Karl Storz Endoscopy America, Inc.). Full-length videos were obtained from all surgeries and are interpreted postoperatively in relation to the fluorescence pattern. The videos are assessed to obtain the required information to put guidelines in selecting the patients amenable for the technology based on our and previous experiences. The postgadolinium sequences and pathological specimens of these patients are interpreted versus the scenes obtained.

Results: A strong correlation was found between the T1 postgadolinium sequences and the fluorescence pattern ([Fig. 1]). The more differential enhancement between the gland and the tumor on T1 postcontrast enhancement, the more differential fluorescence can be found. The main advantages of this technique were to identify the ICA to maximize the exposure; detection of the tumor–gland interface for maximum preservation of glandular tissue and identification of residual nonenhancing tumor against the fluorescent pituitary gland. Some of the negative aspects of the technique were presence of excessive leaky fluorescent blood during the dissection of the tumors in the early phase of fluorescence and overlapping fluorescent structures in the surgical field. Based on these findings, a proposed flowchart ([Fig. 2]) is attached to propose steps for selecting the cases for E-ICG.

Conclusion: Presentation of the pituitary adenomas to the sellar surface, the period of fluorescence of each structure in the inspected field that may overlap and radiological postcontrast T1 images are the main criteria in selecting the cases amenable for E-ICG.