Greater wing of sphenoid
The greater wing or ali-sphenoid of the sphenoid bone is a process which projects from either side of the lower part of the sphenoid body, at a common junction with the pterygoid process . It is a paired structure, which curves upward, backward and laterally from each side of the sphenoid body, which can be likened to the extended wings of a bat . Both wings also have a triangular process projecting inferiorly which is known as the spine of the sphenoid bone.
The greater wing of the sphenoid features superior, lateral and orbital surfaces.
The superior surface features:
- foramen rotundum: transmits the maxillary branch of the trigeminal nerve
- foramen ovale: transmits the mandibular division of the trigeminal nerve, accessory meningeal artery and (occasionally) the lesser petrosal nerve
- foramen spinosum: transmits the middle meningeal artery and meningeal branch of the mandibular nerve
- foramen Vesalii: variable presence, transmits small vein of cavernous sinus
The lateral surface features:
- infratemporal crest: a transverse ridge dividing the lateral surface in two parts
- spina angularis: serves as attachment for sphenomandibular ligament and the tensor veli palatini. Grooved by the chorda tympani, medially, and the auriculotemporal nerve, laterally
The orbital surface features:
- inferior margin: forms postero-lateral boundary of the inferior orbital fissure
- medial margin: forms lower boundary of the superior orbital fissure
- lateral margin: articulates with the zygomatic bone, inferiorly, and frontal bone, superiorly
The lateral margin of the posterior border of greater wing articulates with the anterior border of petrous temporal bone.
- sphenoidal emissary foramen (occasionally present) it is a small aperture medial to the foramen ovale, opposite the root of the pterygoid process; it opens below near the scaphoid fossa and transmits a small vein from the cavernous sinus
- foramen petrosum (occasionally present), a small opening between the foramen spinosum and foramen ovale, for transmission of the lesser petrosal nerve
- common variant of foramen spinosum where the meningeal artery passes through foramen ovale instead of foramen spinosum
The greater wings of the sphenoid are the only bony structures of the skull which undergo both intramembranous and endochondral ossification.
- injuries most commonly associated with fractures of the sphenoid are orbital fractures and mid-face fractures which usually occur following high energy trauma
- fractures of the greater wing of the sphenoid are relatively uncommon and mostly associated with lateral orbital wall fractures along the broad spheno-zygomatic suture
- lateral orbital decompression surgery for exophthalmos
- lateral orbital wall fracture repair
- emergent surgical relief of optic nerve compression