Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Lateral Supraorbital Approach with Expanded Indications.

 The lateral supraorbital (LSO) approach is a less-invasive alternative to the pterional craniotomy that provides rapid transsylvian access. Establishing familiarity with the LSO technique and its features as compared with other anterolateral approaches is an important component of advanced skull base training. We present a step-by-step demonstration of the LSO approach using cadaveric dissection in a manner that is digestible for trainees at various levels.  This is anatomic step-by-step dissection and representative case series.  This study was carried out in the cadaveric dissection laboratory.  A formalin-fixed, latex-injected cadaveric head specimen was dissected under microscopic magnification by a neurosurgery resident under faculty supervision. Following dissection, representative case applications were reviewed.  Dissection and case illustration were the main outcome measures.  A single-layer myocutaneous flap is developed, and a single-burr-hole technique is used, followed by extensive drilling of the sphenoid wing. The dura is opened in a C-shaped fashion centered on the Sylvian fissure, exposing the inferior frontal and superior temporal lobes. Labeled photographs of dissections with pertinent anatomical structures are presented. Three case examples illustrating the versatility of the LSO approach, including the resection of a large pituitary adenoma, an inferior frontal melanoma metastasis presenting to the Sylvian surface, and a frontoinsular low-grade glioma, are reviewed.  As compared with the pterional craniotomy, the LSO approach involves a shorter incision, smaller craniotomy, and faster exposure; it can be conveniently tailored to various indications. Understanding the step-by-step dissection and indications of the LSO approach is of paramount importance to neurosurgery trainees.