Intraoperative Indocyanine Green Fluorescence in Canine Meningioma: Macroscopic Visualization, Immediate MRI Verification, and Clinical Outcomes: A Case Series

Background Meningioma is the most common primary intracranial neoplasm in dogs, frequently presenting with seizures and neurological deficits. While indocyanine green (ICG) near-infrared (NIR) fluorescence is increasingly used in human neurosurgery, systematic data regarding its macroscopic expression in canine meningioma remain scarce. This case series aimed to evaluate the qualitative macroscopic expression of ICG, verify intraoperative findings using exceptionally early immediate post-operative contrast-enhanced magnetic resonance imaging (MRI), and report the clinical outcomes and complication management following fluorescence-guided surgery (FGS). Case presentation: Six client-owned dogs (median age: 13 years) with histologically confirmed meningiomas were evaluated. ICG was administered intravenously (median dose: 4.46 mg/kg) 6 to 24 hours prior to surgery. FGS was performed using an ultrasonic aspirator and a dedicated fluorescence imaging system. Distinct index-margin fluorescence was observed in all 6 cases (100%), allowing for real-time differentiation between tumor tissue and normal brain parenchyma during resection. Immediate post-operative T1-weighted contrast-enhanced MRI demonstrated 100% concordance with intraoperative wound bed fluorescence assessments when thin reactive rims (≤ 1–2 mm) were appropriately excluded. No adverse reactions were associated with ICG. The median follow-up was 6.25 months (range: 1.5 to 30.0 months), with favorable neurological control. Conclusions Under a standardized delayed-window protocol with dynamic working distance control, ICG effectively demarcated macroscopic canine meningiomas in this small cohort. Immediate post-operative MRI supported the surgeon’s qualitative assessments. Ultimately, FGS may serve as a viable surgical option to help minimize damage to normal brain tissue and potentially improve surgical outcomes in canine meningioma.