Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Modified One-Piece Orbito-pterional Craniotomy and Pretemporal Approach with Clinical Application for Posterior Circulation Aneurysms

Objective To provide an educational, stepwise description of the microsurgical anatomy and technical nuances of the orbito-pterional craniotomy, with anatomical illustration through cadaveric dissection and clinical correlation via illustrative cases of posterior circulation aneurysm surgery. Methods An orbito-pterional craniotomy was performed bilaterally on four silicone-injected embalmed cadaveric heads (eight sides) using standard microsurgical instrumentation under operative magnification. A standardized stepwise protocol was followed, encompassing extradural osteotomies and intradural dissection targeting the basilar apex region. Clinical correlation was provided through two operative cases of posterior circulation aneurysms treated via the orbito-pterional approach. Results The orbito-pterional craniotomy reliably provided a lowered basal trajectory and expanded pretemporal corridor while preserving the zygomatic arch. Key steps are detailed for laboratory and intra-operative reproduction by trainees, including interfascial temporalis dissection, single-piece orbito-pterional osteotomy, anterior clinoidectomy, yielding enhanced exposure of the interpeduncular cistern and posterior circulation with minimal brain retraction. Illustrative cases demonstrated that this approach facilitates perforator preservation, multiple angles of attack, and a safe operative corridor for clipping complex posterior circulation aneurysms, while avoiding the additional bone work and less favorable cosmetic outcomes associated with a full orbitozygomatic craniotomy. Conclusion The one-piece orbito-pterional craniotomy offers distinct advantages for complex cranial operations. Learning and internalizing its key steps, anatomical nuances, and nuanced clinical applications are critical for trainees, particularly those with interest in skull base or cerebrovascular neurosurgery.