The 3 divisions of CN V are the ophthalmic (V1), the maxillary (V2), and the mandibular (V3).
Ophthalmic division (CN V1)
The ophthalmic division enters the cavernous sinus lateral to the ICA and courses beneath CN III and CN IV (see Figs 3-24, 3-25). Within the sinus, it gives off a tentorial–dural branch, which innervates the cerebral vessels, dura mater of the anterior fossa, cavernous sinus, sphenoid wing, petrous apex, Meckel cave, tentorium cerebelli, falx cerebri, and dural venous sinuses. CN V1 passes into the orbit through the superior orbital fissure and divides into 3 branches: frontal, lacrimal, and nasociliary (see Fig 3-17).
Frontal nerve The frontal nerve (see Fig 3-19) divides into the supraorbital and supratrochlear nerves, which provide sensation to the medial portion of the upper eyelid and the conjunctiva, forehead, scalp, frontal sinuses, and side of the nose. The supratrochlear nerve exits the orbit 17 mm from midline, whereas the supraorbital nerve exits at 27 mm from midline, through either a notch or a true foramen.
Lacrimal nerve The lacrimal nerve innervates the lacrimal gland and the neighboring conjunctiva and skin. The lacrimal gland receives its parasympathetic supply from the retro-orbital plexus (discussed later, in the section Facial Nerve [Seventh Cranial Nerve]). Occasionally, the lacrimal nerve exits the orbit via a lacrimal foramen to supply the lateral forehead. Otherwise, that area is supplied by branches of the supraorbital nerve.
Figure 3-21 Divisions of the nasociliary nerve. The nasaociliary nerve is a branch of V1, the ophthalmic division of CN V. The posterior ciliary nerves supply sensation to the globe. The paired long ciliary nerves innervate the anterior structures; the short ciliary nerves, posterior structures. The short posterior ciliary nerves also carry sympathetic and parasympathetic fibers to the iris dilator and sphincter muscles, respectively. In addition, they carry parasympathetic fibers to the ciliary muscle, where they induce accommodation.
(Modified with permission from Levin LA, Nilsson SFE, Ver Hoeve J, Wu SM. Adler’s Physiology of the Eye. 11th ed. Philadelphia: Elsevier/Saunders; 2011:91.)
Nasociliary nerve Branches from the nasociliary nerve supply sensation to the middle and inferior turbinates, septum, lateral nasal wall, and tip of the nose. The infratrochlear branch serves the lacrimal drainage system, the conjunctiva, and the skin of the medial canthal region. The ciliary nerves (short and long) carry sensory fibers from the ciliary body, the iris, and the cornea. The short ciliary nerves also carry the sympathetic and parasympathetic fibers from the ciliary ganglion to the iris dilator and sphincter, respectively, and the parasympathetic fibers to the ciliary muscle (Fig 3-21). The sensory short ciliary fibers pass through the ciliary ganglion to join, along with the long ciliary fibers, the nasociliary nerve. Thus, the short ciliary nerves carry sensory (V1), sympathetic, and parasympathetic fibers (see Fig 3-19).
Maxillary division (CN V2)
The maxillary division leaves the trigeminal ganglion to exit the skull through the foramen rotundum, which lies below the superior orbital fissure (see Fig 3-1). CN V2 courses through the pterygopalatine fossa into the inferior orbital fissure and then passes through the infraorbital canal as the infraorbital nerve. After exiting the infraorbital foramen, CN V2 divides into an inferior palpebral branch, a nasal branch, and a superior labial branch, supplying the lower eyelid, the side of the nose, and the upper lip, respectively. The teeth, maxillary sinus, roof of the mouth, and soft palate are also innervated by branches of the maxillary division. These branches can be damaged after fractures of the orbital floor.
Mandibular division (CN V3)
The mandibular division contains sensory and motor fibers. It is the only division of CN V that contains motor fibers. It exits the skull through the foramen ovale (see Fig 3-1) and provides motor input for the masticatory muscles. Sensation is supplied to the mucosa and skin of the mandible, lower lip, tongue, external ear, and tympanum.
Excerpted from BCSC 2020-2021 series: Section 2 - Fundamentals and Principles of Ophthalmology. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.