Bone Inferonasally (Meeting at the Zygomaticomaxillary Suture)

Home , Anterior lacrimal crest, Frontal bone, Frontoethmoidal suture, Lacrimal sac, Palatine bone, Posterior lacrimal crest

Frontal bone

Lesser wing of sphenoid bone

Superior orbital Optic canal fissure

Greater wing of Ethmoidal bone sphenoid bone Lacrimal bone Zygomatic bone Lacrimal fossa

Inferior orbital Maxillary bone fissure

Lesser wing of sphenoid bone

Optic canal Anterior clinoid Sphenoid body Optic strut Superior orbital fissure

8 ● Neuro-Ophthalmology B Superior rectus muscle Trochlear nerve Levator muscle Frontal nerve Superior Lacrimal nerve oblique muscle Superior Annulus of Zinn ophthalmic vein Oculomotor nerve Optic nerve (superior division) Nasociliary nerve Medial rectus Abducens nerve muscle Lateral rectus Ophthalmic muscle artery Oculomotor nerve (inferior division) Inferior rectus muscle Zygomatic nerve Inferior C ophthalmic vein

Frontal nerve Levator muscle

Superior CN IV rectus muscle Nasociliary Superior CN III nerve Superior ophthalmic vein Optic nerve Ophthalmic Optic nerve artery sheath CN VI Inferior CN III Lateral rectus muscle Inferior rectus Inferior muscle ophthalmic vein D Figure 1-2 (continued) C, Anatomy of the orbital apex. The 4 rectus muscles arise from the annulus of Zinn. CNs II, III (superior and inferior branches), and VI and the nasociliary nerve all course through the annulus of Zinn. CN IV, the frontal and lacrimal nerves, and the ophthalmic veins are located outside the annulus. D, Anatomical dissection just anterior to the superior orbital fissure. (Parts A and C illustrations by Dave Peace; parts B and D courtesy of Albert L. Rhoton Jr, MD.) bone inferonasally (meeting at the zygomaticomaxillary suture). Medially, the orbital rim consists of the maxillary and lacrimal bones, which join the frontal bone superiorly. An additional 3 bones contribute to the orbit: (1) the ethmoidal bone medially, (2) the palatine bone inferiorly in the posterior orbit, and (3) the sphenoid bone laterally and superiorly in the orbital apex. The orbit is surrounded by several important structures. The 4 paranasal sinuses sur- round the floor (maxillary sinus) and the medial wall (ethmoidal and sphenoid sinuses) of the orbit (Fig 1‑4). The frontal sinus has a variable relationship to the anterior orbital roof. The other major structures around the orbit are the anterior cranial fossa superiorly (containing the frontal lobe) and the temporal fossa laterally (containing the temporalis muscle). The roof of the ethmoidal complex, delineated by the frontal ethmoidal suture (top of the ethmoidal bone, or lamina papyracea), marks the inferior boundary of the anterior cranial fossa. It is important to realize that surgical intervention above this anatomical Chapter 1: Neuro-Ophthalmic Anatomy ● 9

Frontosphenoid suture Supraorbital notch Greater wing, Frontal bone sphenoid bone Frontal bone Anterior clinoid Frontozygomatic Frontozygomatic process suture suture Zygomatic bone Zygomatic bone Superior Greater wing, Inferior orbital fissure orbital fissure sphenoid bone Maxillary bone Palatine bone Lesser wing, Maxillary sinus sphenoid bone A (Roof) B (Lateral)

Nasolacrimal duct Frontoethmoidal suture Frontal bone Ethmoidal bone Infraorbital foramen Lacrimal bone Zygomatic bone Lacrimal Maxillary bone bone (orbital plate) Post. lacrimal crest Inferior orbital groove Ant. lacrimal crest Lacrimal fossa Inferior orbital fissure Ethmoidal bone Maxilloethmoidal Greater wing, Sphenoid suture bone sphenoid bone Maxillary bone Palatine bone Palatine bone Maxillary sinus C (Floor) D (Medial) Figure 1-3 Bony anatomy of the right orbit. A, The orbital roof is composed of 2 bones: (1) the frontal bone and (2) the lesser wing of the sphenoid bone. The frontal sinus lies within the anterior orbital roof. The supraorbital notch, located within the medial one-third of the superior orbital rim, transmits the supraorbital nerve, a terminal branch of the frontal nerve of the ophthalmic division of CN V. Medially, the frontal bone forms the roof of the ethmoidal sinus and extends to the cribriform plate. B, The lateral orbital wall is formed by the zygomatic bone and the greater wing of the sphenoid bone. The junction between the lateral orbital wall and the roof is represented by the frontosphenoid and frontozygomatic sutures. Posteriorly, the wall is bordered by the inferior and superior orbital fissures. The sphenoid wing makes up the posterior portion of the lateral wall and separates the orbit from the middle cranial fossa. Medially, the lateral orbital wall ends at the inferior and superior orbital fissures. C, The orbital floor is composed of 3 bones: (1) the orbital plate of the maxillary bone, (2) the maxillary process of the zygomatic bone, and (3) the palatine bone. The nasolacrimal duct sits in the anterior medial area of the orbital floor, medial to the origin of the inferior oblique muscle. D, The medial orbital wall is formed by 4 bones: (1) maxillary (frontal process), (2) lacrimal, (3) sphenoid, and (4) ethmoidal. The largest component of the medial wall is the lamina papyracea of the ethmoidal bone. Superiorly, the anterior and posterior foramina at the level of the frontoethmoidal suture transmit the anterior and posterior ethmoidal arteries, respectively. The anterior medial orbital wall includes the lacrimal sac fossa, formed by the maxillary and lacrimal bones. The lacrimal bone is divided by the posterior lacrimal crest. The anterior part of the lacrimal sac fossa is formed by the anterior lacrimal crest of the maxillary bone. (Illustrations by Dave Peace.) landmark—as occurs, for example, during endoscopic sinus surgery—can result in entry into the anterior cranial fossa or a cerebrospinal fluid (CSF) leak. The sphenoid sinus forms the medial wall of the optic canal (Fig 1‑5). Surgery within the sphenoid sinus has the potential to damage the optic nerve; alternatively, the sphenoid sinus is a surgical route facilitating decompression of the optic chiasm. In approximately