Sphenoid Bone's Lesser Wing

Description

Sphenoid bone lesser wing (ala minor) forms a thin, smooth bony shelf projecting anterolaterally from the sphenoid body, terminating medially as the pointed anterior clinoid process. Along its posteroinferior margin, the lesser wing defines the superior boundary of the superior orbital fissure, while its superior surface contributes to the anterior cranial fossa and its inferior surface helps form the posterior part of the orbital roof. Medially, the root of the lesser wing participates in the optic canal, where the canal’s walls sit immediately adjacent to the tuberculum sellae and the chiasmatic sulcus on the sphenoid body. A sharp landmark. Clinically, the anterior clinoid process and optic canal are constant reference points in skull base surgery and neuro-ophthalmology, because the optic nerve and ophthalmic artery traverse the canal and lie close to the paraclinoid segment of the internal carotid artery and the cavernous sinus. This illustration is well suited for explaining anterior clinoidectomy planning and the bony constraints around optic nerve decompression in traumatic optic neuropathy, compressive meningioma, or fibrous dysplasia involving the sphenoid. The clean bony surfaces and crisp edges make the margins of the optic canal and the relationship to the superior orbital fissure easy to teach without soft-tissue distraction. Use this illustration in neuroanatomy and head and neck anatomy courses when covering the anterior cranial fossa, orbital apex, and skull base foramina, and in operative atlases discussing the pterional or frontotemporal approaches to paraclinoid aneurysms. It also fits radiology teaching files as a companion to CT bone-window interpretation of the sphenoid, emphasizing how small variations in the anterior clinoid and optic strut can change the surgical corridor. Anatomical accuracy verified by SciePro's Medical Advisory Board.