• Christos Koutsarnakis, Evangelos Drosos, Spyridon Komaitis, Nektarios Mazarakis, Eleftherios Neromyliotis, Aristotelis Kalyvas, Theodore Troupis, and George Stranjalis.
• Athens Microneurosurgery Laboratory, Athens, Greece; Department of Neurosurgery, Evangelismos Hospital, National and Kapodistrian University of Athens, Athens, Greece. Electronic address: ckouts@hotmail.co.uk.
• World Neurosurg. 2022 Feb 1; 158: 174-179.

ObjectiveThere is a lack of definite anatomical landmarks for the inferior extension of the standard retrosigmoid approach. In this study, we evaluated whether the posterior condylar emissary vein (PCEV) can be used as an intraoperative landmark for optimizing the surgical corridor.MethodsWe performed the standard retrosigmoid approach on 5 formalin-fixed and latex-injected cadaveric specimens and measured the distance between the PCEV near its bony canal and the vertebral artery (VA). In addition, vascular reconstructions of thin-sliced preoperative computed tomography (CT) scans were studied in 40 patients and the relationship between these 2 vessels was evaluated. An illustrative case is also included.ResultsThe PCEV was consistently identified on both sides of cadaveric specimens and in 87.5% and 82.5% of the left and right sides of the included CT scans, respectively. The average distance between the part of the PCEV near its osseous canal and the VA was measured to be between 8.4 mm and 8.6 mm in the specimens and between 9.2 mm and 9.3 mm in the CT scans. This distance offers a safe and effective plane of dissection during the standard retrosigmoid approach and allows easy access to the foramen magnum.ConclusionsThe PCEV near its bony canal proved to be an easy, straightforward, safe, and effective operative landmark with which the surgeon can extend the soft tissue dissection and bony exposure towards the foramen magnum. This maneuver provides ample access to the cisterna magna for cerebrospinal fluid drainage and increases visibility and surgical maneuverability to the entire cerebellopontine angle.Copyright © 2021 Elsevier Inc. All rights reserved.

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