Near-Infrared Fluorescence with Second-Window Indocyanine Green as an Adjunct to Localize the Pituitary Stalk During Skull Base Surgery

A potential application of near-infrared (NIR) fluorescence imaging using second-window indocyanine green (SWIG) is demonstrated. We hypothesized that because the pituitary lacks a blood-brain barrier, we might visualize the pituitary stalk using SWIG. A 52-year-old, right-handed man presented to our clinic for evaluation of progressive loss of vision. Physical examination was significant for loss of right peripheral vision and near-complete loss of left field vision. Prolactin was high-normal at 16.2 mg/dL. Brain magnetic resonance imaging demonstrated a 36-mm sellar mass extending superiorly and laterally crossing the intracranial left internal carotid artery, consistent with a nonfunctional pituitary macroadenoma. We elected to pursue left pterional craniotomy for resection. The patient was eligible for our SWIG clinical trial and consented to the study. SWIG is a novel, investigational technique using Food and Drug Administration-approved indocyanine green to enhance visualization of neoplastic tissue intraoperatively.(1-7) The patient received 2.5 mg/kg of indocyanine green intravenously approximately 24 hours preoperatively. Intraoperatively, under white-light microscopy, the tumor was easily identified and distinguished from the optic nerves and internal carotid artery. After debulking of the gross tumor, NIR visualization using a laser-equipped endoscope(8) demonstrated strong MR fluorescence in the pituitary stalk. Despite the distorted anatomy, this technique enabled us to confidently identify and preserve the pituitary stalk. Postoperatively, the patient had persistently high urine output that normalized in 24 hours without desmopressin (sodium 139-140 mmol/L); after uneventful recovery, he was discharged with mild improvement in visual function. This case demonstrated a potential use of our SWIG protocol. As the stalk demonstrates strong MR fluorescence after high-dose indocyanine green administration, surgeons may be able to better localize and preserve the stalk even in complex skull base tumor cases where the anatomy may be significantly distorted.