nasociliary

Nasociliary refers to the nasociliary nerve and the structures it supplies within the orbit and nose. In anatomical terminology, it describes components and regions that receive sensory innervation from this branch of the ophthalmic division (V1) of the trigeminal nerve.

Anatomy and course: The nasociliary nerve arises from the ophthalmic nerve as it enters the orbit through the superior orbital fissure. It travels along the medial wall of the orbit, between the medial rectus and the superior oblique muscles, giving off several branches. Major branches include the posterior ethmoidal nerve, the anterior ethmoidal nerve, and the infratrochlear nerve. The anterior ethmoidal nerve exits the skull via the anterior ethmoidal foramen and becomes the external nasal branch, supplying the skin of the nose. The posterior ethmoidal nerve passes through the posterior ethmoidal foramen to innervate the posterior ethmoidal air cells and adjacent nasal mucosa. The infratrochlear nerve provides sensation to the medial canthus region, eyelids, and nearby skin. The nasociliary nerve also gives rise to the long ciliary nerves, which extend forward to the eyeball and supply sensory innervation to the cornea and contribute to the iris and ciliary body.

Clinical relevance: The nasociliary nerve carries sensory fibers to both the nasal mucosa and the eye, including corneal sensation via the long ciliary nerves. Because of its sensory distribution, injuries or blocks of the nasociliary nerve can affect corneal sensation and nasal sensation and are considered in regional anesthesia for ocular procedures. Conditions such as herpes zoster ophthalmicus may involve nasociliary fibers, producing characteristic facial and ocular pain.