Anatomy and Borders
The superior orbital fissure is formed by bony structures of the sphenoid bone (os sphenoidale). It represents the cleft situated between the lesser wing (ala minor) and the greater wing (ala major).
The inferior surfaces of the lesser wings form the roof of the orbit (facies orbitalis), terminating posteriorly and medially in the anterior clinoid processes. At the base of the lesser wing lies the optic canal (canalis opticus). The superior orbital fissure serves as a communication pathway between the middle cranial fossa (fossa cranii media) and the orbit (orbita).
Contents of the Superior Orbital Fissure
This aperture serves as a primary entry point for nerves entering the orbital cavity. It transmits motor nerves innervating the extraocular muscles of the eye, along with a major sensory branch:
- Oculomotor nerve (n. oculomotorius) — cranial nerve III.
- Trochlear nerve (n. trochlearis) — cranial nerve IV.
- Abducens nerve (n. abducens) — cranial nerve VI.
- Ophthalmic nerve (n. ophthalmicus) — the first division of the trigeminal nerve (CN V). It is strictly sensory (sensoria). The peripheral processes of the trigeminal ganglion (gasserian ganglion) traveling within this nerve mediate pain, temperature, and tactile sensation from the face and forehead.
Cranial nerves III, IV, and VI drive extraocular movements by innervating the muscular apparatus of the eye and eyelids: the levator palpebrae superioris, rectus, and oblique muscles. Together, they coordinate conjugate eye movements.
In addition to neural trunks, the fissure transmits venous and arterial vessels:
- Superior ophthalmic vein (v. ophthalmica superior).
- Occasionally, anterior meningeal branches from the ophthalmic artery (r. meningeus anterior ex a. ophthalmica).
Topography and Surrounding Structures
The orbit communicates with the cranial cavity via the optic canal and the superior orbital fissure. The optic canal transmits the optic nerve (CN II). Additionally, the orbit communicates with the pterygopalatine and infratemporal fossae through the inferior orbital fissure (fissura orbitalis inferior).
From the intracranial perspective, the superior orbital fissure opens into the middle cranial fossa. This same fossa houses other critical foramina for the branches of the trigeminal nerve: the foramen rotundum for the maxillary nerve (V2) and the foramen ovale for the mandibular nerve (V3).
Clinical Significance
When performing regional anesthesia for structures innervated by the maxillary nerve (V2), an orbital approach may be utilized. In this technique, a needle is inserted at the inferolateral angle of the orbit and advanced along the lateral wall posteriorly to a depth of 4–5 cm.
If the needle deviates and penetrates the superior orbital fissure, mechanical trauma to the wall of the cavernous sinus (sinus cavernosus) may occur. Within the lateral wall of the cavernous sinus, the oculomotor, trochlear, abducens, and ophthalmic nerves course in close proximity to the internal carotid artery. Injury to the sinus can lead to cavernous sinus thrombosis, a life-threatening complication.