Thrombus Visualization Using Low-Pressure Contrast Injection via a Small-Bore Aspiration Catheter in M2 Thrombectomy: A Technical Note

Objective: Accurate localization of thrombi in middle cerebral artery (M2) segment occlusions remains technically challenging but is essential for successful mechanical thrombectomy. We report a novel visualization technique that uses the aspiration catheter system itself to delineate the thrombus, thereby minimizing the risks associated with conventional microcatheter-based contrast injections. Case Presentation: An 81-year-old woman presented with acute ischemic stroke caused by an occlusion of the left M2 inferior trunk. Aspiration thrombectomy was performed using the described visualization technique. After positioning the aspiration catheter proximal to the thrombus, the inner microcatheter and guidewire were withdrawn, and contrast medium was gently injected at low pressure through the intermediate catheter. This approach produced a stagnant contrast column that clearly outlined the proximal surface of the clot as a meniscus sign, confirming direct catheter-thrombus contact. Complete reperfusion (thrombolysis in cerebral infarctions grade 3) was achieved after 2 aspiration passes, with no procedural complications observed. Conclusion: This novel technique offers a simple, safe, and effective method for direct thrombus visualization in M2 occlusions. By utilizing the intermediate catheter for controlled, low-pressure contrast injection, it may reduce the risk of distal embolization and simplifies the procedural workflow, potentially enhancing the rate of 1st-pass recanalization success. This technical note introduces the concept and provides preliminary evidence supporting further investigation and validation in larger patient cohorts.