1149 NIR Indocyanine-White Light Overlay Visualization Mode for Neuro-Oto-Vascular Preservation in the Anterior Transpetrosal Approach: Technical Note for Tailored MDK Rhomboid Drilling

INTRODUCTION: We describe our preliminary investigation on microscopic real-time near-infrared indocyanine (NIR-ICG) fluorescence and white light overlay modality in anterior transpetrosal approaches for enhancing the intraoperative real-time and flow-dependent visualization of critical vascular structures. METHODS: We used robotic microscope (ZEISS KINEVO 900Ò) and the built-in FLOW800 and INFRARED800 functions with fluorescence capabilities to provide simultaneous ocular overlay of NIR indocyanine and white light images. The surgical procedure was recorded, and technical nuances, surgical time, operator feedback, and outcomes were discussed. The procedure was replicated in an uninjected adult specimen receiving an ICG bolus injection to examine the visualization properties and in a silicon-injected adult specimen to review critical landmarks. We described our experience using NIR indocyanine and white light overlay technology for subtemporal anterior petrosectomy in a single case (petroclival meningioma). RESULTS: ICG administration in the non-injected specimen was feasible, and NIR fluorescence noted. However, a thicker middle fossa floor and a bone layer covering GSPN required additional drilling that led to proper fluorescent ICA visualization. ICG fluorescence allowed consistent tracing of the ICA course from posterior genu to the petrolingual ligament. In the clinical scenario, it represented a valuable adjunct in enhancing the surgeon's ability to identify or confirm the location of the carotid canal, derive critical landmarks (Cochlear line and distance, Cochlear safety line), superior petrosal sinus, greater superficial petrosal nerve, Gasserian ganglion and trigeminal branches with improved precision and safety. CONCLUSIONS: This technique offers a comprehensive and real-time view of the overall surgical field and petrous ICA, contributing to safer surgical planning of posteromedial rhomboid drilling beyond static anatomical landmarks, favoring neuro-oto-vascular preservation in selected cases. However, further investigation is required to justify a wider adoption.