• Tomotaka Ohshima, Aichi Niwa, Reo Kawaguchi, Naoki Matsuo, and Shigeru Miyachi.
• Neuroendovascular Therapy Center, Aichi Medical University, Nagakute, Aichi, Japan. Electronic address: tmtkoh@gmail.com.
• World Neurosurg. 2020 May 1; 137: 229-234.

BackgroundWhen endovascular clot retrievals are performed using a stent retriever and/or an aspiration catheter, identifying the accurate position of a clot is extremely important for a successful immediate recanalization. Herein, we report a new technique called microcatheter withdrawing angiography, which facilitates the identification of the precise position of a clot. The negative shadow appearance of the clot on angiography was referred to as the actual crab claw sign.MethodsWhen a 0.027-inch microcatheter penetrated the clot after inserting a 0.014-inch microwire, selective angiography was conducted using the microcatheter. Simultaneously, the microcatheter was slowly withdrawn with continuous contrast media injection, while the microwire was kept in the distal vessel. The precise position of the clot was found, which was referred to as the actual crab claw sign. Next, we conducted in vitro and in vivo analyses.ResultsThe actual crab claw sign could be identified in the vascular model and in actual clinical settings. Therefore the sweet spot of the stent retriever could be set over the clot, and an accurate contact aspiration could be performed using an aspirator.ConclusionsMicrocatheter withdrawing angiography can help identify the actual crab claw sign. This technique has a higher success rate and faster recanalization than conventional strategy, particularly in challenging cases of unsuccessful recanalization during the first attempt.Copyright © 2020 Elsevier Inc. All rights reserved.

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