The nasociliary nerve is a branch of the ophthalmic nerve (CN V₁) (which is in turn a branch of the trigeminal nerve (CN V)). It is intermediate in size between the other two branches of the ophthalmic nerve, the frontal nerve and lacrimal nerve.

Structure

Course

The nasociliary nerve enters the orbit via the superior orbital fissure, through the common tendinous ring, and between the two heads of the lateral rectus muscle and between the superior and inferior rami of the

oculomotor nerve The oculomotor nerve, also known as the third cranial nerve, cranial nerve III, or simply CN III, is a cranial nerve that enters the orbit through the superior orbital fissure and innervates extraocular muscles that enable most movements o ...

. It passes across the optic nerve (CN II) along with the ophthalmic artery. It then runs obliquely beneath (inferior to) the

superior rectus muscle The superior rectus muscle is a muscle in the orbit. It is one of the extraocular muscles. It is innervated by the superior division of the oculomotor nerve (III). In the primary position (looking straight ahead), its primary function is elevatio ...

and superior oblique muscle to the medial wall of the orbital cavity whereupon it emits the

posterior ethmoidal nerve The posterior ethmoidal nerve is a nerve of the head. It is a branch of the nasociliary nerve (itself a branch of the Ophthalmic nerve, ophthalmic nerve (CN V1)). It provides sensory innervation to the sphenoid sinus and ethmoid sinus, and part o ...

, and the anterior ethmoidal nerve.

Branches

Branches of the nasociliary nerve include: *

* anterior ethmoidal nerve * long ciliary nerves * infratrochlear nerve * communicating branch to ciliary ganglion

Function

The branches of the nasociliary nerve provide sensory innervation to structures surrounding the eye such as the cornea, eyelids, conjunctiva, ethmoid air cells and mucosa of the nasal cavity.

Clinical significance

Clinical assessment

Since both the short and long ciliary nerves carry the afferent limb of the

corneal reflex The corneal reflex, also known as the blink reflex or eyelid reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea (such as by touching or by a foreign body), though it could result from any peripheral stimulus ...

, one can test the integrity of the nasociliary nerve (and, ultimately, the

trigeminal nerve In neuroanatomy, the trigeminal nerve (literal translation, lit. ''triplet'' nerve), also known as the fifth cranial nerve, cranial nerve V, or simply CN V, is a cranial nerve responsible for Sense, sensation in the face and motor functions ...

) by examining this reflex in the patient. Normally both eyes should blink when either cornea (not the conjunctiva, which is supplied by the adjacent cutaneous nerves) is irritated. If neither eye blinks, then either the ipsilateral nasociliary nerve is damaged, or the

facial nerve The facial nerve, also known as the seventh cranial nerve, cranial nerve VII, or simply CN VII, is a cranial nerve that emerges from the pons of the brainstem, controls the muscles of facial expression, and functions in the conveyance of ta ...

(CN VII, which carries the efferent limb of this reflex) is bilaterally damaged. If only the contralateral eye blinks, then the ipsilateral facial nerve is damaged. If only the ipsilateral eye blinks, then the contralateral facial nerve is damaged.

Additional images

File:Gray776.png, Nerves of the orbit. Seen from above. File:Gray778.png, Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion. File:Gray787.png, Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure. File:Ciliary ganglion pathways.png, Pathways in the ciliary ganglion. File:Slide4abab.JPG, Extrinsic eye muscle. Nerves of orbita. Deep dissection.

References

External links

* - "A deeper dissection of the right orbit from a superior approach." * () * () * {{Authority control Ophthalmic nerve Medical mnemonics Otorhinolaryngology