The skull base has an intimate relationship with visually essential structures (Fig 1-1). The skull base is connected to the lower facial skeleton by 3 sets of pillars formed by the maxillary and zygomatic bones anteriorly and the pterygoid process of the sphenoid bone posteriorly. Superiorly, the vault of the skull is made up of the parietal bones, which meet at the sagittal suture; the frontal bone, which adjoins them at the coronal suture; and the occipital bone, which meets the parietal bones at the lambdoid suture.
The sella turcica, located posteriorly and medially to the 2 orbits, is a skull-based depression within the body of the sphenoid bone. The lesser wing of the sphenoid bone is pierced by the optic canal, which allows the optic nerves to exit from the orbit. The superior orbital fissure, which transmits the ocular motor cranial nerves (CNs) (oculomotor nerve or CN III, trochlear nerve or CN IV, and abducens nerve or CN VI), the ophthalmic division of the sensory trigeminal nerve (CN V1), the sympathetic fibers, and the superior ophthalmic vein (Fig 1-2), represents the gap between the lesser and greater wings of the sphenoid bone. The parasellar region is connected laterally to the petrous and temporal bones and inferiorly to the clivus, extending to the foramen magnum and the exit of the spinal cord. The posterior skull base is enclosed by the occipital bones.
Figure 1-1 Bony anatomy of the skull base. A, General view of the skull base. The cavernous sinuses are located on each side of the sella turcica. Important openings within the skull base include the cribriform plate (transmits branches of the olfactory nerve, also known as cranial nerve [CN] I), optic canal (transmits the optic nerve, CN II), foramen ovale (transmits the mandibular division [CN V3] of the trigeminal nerve, CN V), foramen rotundum (transmits the maxillary division [CN V2] of CN V), superior orbital fissure (transmits CNs III, IV, VI, and V [ophthalmic division, CN V1]), and the foramen spinosum (transmits the middle meningeal artery, a branch of the external carotid artery). B, View of the parasellar bony anatomy demonstrates the relationship of the pituitary fossa to the cavernous sinus, including the foramina of the skull base. The foramen lacerum is filled with cartilage and contains the artery of the pterygoid canal, the nerve of the pterygoid canal, and venous drainage structures. The carotid artery enters the skull base through the carotid canal.
(Courtesy of Albert L. Rhoton Jr, MD.)
Excerpted from BCSC 2020-2021 series: Section 5 - Neuro-Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.