Nasociliary nerve

The nasociliary nerve is a sensory nerve that is a branch of the ophthalmic nerve (CN V1), which is a division of the trigeminal nerve (CN V).^[4] It is an important nerve in the head and face, as it supplies sensation to a large area of the face and head and also serves as a conduit for other cranial nerves. In this article, we will explore the structure, location, function, and clinical significance of the nasociliary nerve.

Structure

The nasociliary nerve arises from the ophthalmic nerve, which is the first division of the trigeminal nerve.^[5]The ophthalmic nerve divides into several branches, including the nasociliary nerve, the frontal nerve, and the lacrimal nerve. The nasociliary nerve is a small nerve that is located within the orbit (eye socket) of the skull. It begins at the apex of the orbit, just above the optic nerve, and travels downward and forward through the orbit.^[3] Along its course, it gives off several branches, including the long ciliary nerves, which supply the ciliary muscles and the iris, and the short ciliary nerves, which supply the sclera and the conjunctiva.

Location

The nasociliary nerve is located within the orbit of the skull, which is a bony cavity that surrounds and protects the eye. It is located at the apex of the orbit, just above the optic nerve, and travels downward and forward through the orbit. As it travels through the orbit, it gives off branches that supply various structures within the eye and surrounding tissues.^[6]

Function

The nasociliary nerve is a sensory nerve that supplies sensation to a large area of the face and head.^[2]It innervates the skin of the forehead, the upper eyelid, and the side of the nose. It also supplies sensation to the conjunctiva, the transparent membrane that lines the inner surface of the eyelids and covers the sclera (white part of the eye). In addition to its sensory function, the nasociliary nerve also serves as a conduit for other cranial nerves.^[8] It carries the autonomic fibers of the oculomotor nerve (CN III), which supplies the muscles of the eye, and the parasympathetic fibers of the facial nerve (CN VII), which innervate the lacrimal gland and the glands of the nasal mucosa.

Clinical Significance

The nasociliary nerve is an important nerve in the head and face, and any damage to this nerve can lead to sensory deficits and other complications. Damage to the nasociliary nerve can occur due to trauma, inflammation, or compression. It can also be damaged during surgery, such as during an orbital decompression or a blepharoplasty (eyelid surgery).^[1] Symptoms of nasociliary nerve damage may include numbness or tingling in the forehead, upper eyelid, or side of the nose, as well as difficulty moving the eye or problems with the secretion of tears or nasal mucus.