Near-Infrared Fluorescence Imaging With Indocyanine Green for Intraoperative Nerve Root Visualization in Spinal Surgery: From Preclinical Studies to a Pilot Randomized Controlled Trial

Study DesignPilot randomized controlled trial.ObjectivesIatrogenic nerve injury is a major complication in endoscopic spinal surgery, potentially causing serious neurological deficits. Near-infrared (NIR) fluorescence imaging with indocyanine green (ICG) has shown promise for intraoperative nerve root identification. This study assessed the feasibility, optimal dosing, safety, and mechanism of ICG fluorescence for nerve root visualization, transitioning from preclinical to clinical phases.MethodsIn the preclinical phase, 36 rabbits were assigned to ICG dose groups (1.4, 2.8, or 5.5 mg/kg, corresponding to 0.5, 1, or 2 mg/kg in humans) and observation times (3, 6, 12, or 24 hours). Fluorescence signals in lumbar nerve roots were quantified by signal-to-background ratio (SBR) and mean fluorescence intensity (MFI). Histological analyses explored ICG retention mechanisms. In the clinical phase, 40 patients undergoing unilateral biportal endoscopic surgery for lumbar disc herniation were randomized into different ICG dose groups (0, 0.5, 1, or 2 mg/kg), administered 1.5 hours preoperatively. Intraoperative fluorescence parameters, nerve root identification time, and perioperative outcomes (VAS and ODI scores) were assessed.ResultsIn preclinical studies, the 2.8 and 5.5 mg/kg groups showed peak SBR and MFI at 3 hours post-injection. Histology revealed ICG accumulation in nerve root microvascular regions. In the clinical study, the 2 mg/kg group had the highest SBR and MFI, reducing nerve root identification time without significant adverse events.ConclusionICG fluorescence imaging is a feasible and safe technique for intraoperative nerve root visualization, with ICG accumulation attributed to the enhanced permeability and retention effect.