Nasociliary nerve

The nasociliary nerve is a branch of the ophthalmic nerve, itself 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.

Nasociliary nerve
Nerves of the orbit, and the ciliary ganglion. Side view. (Nasociliary is at center.)
Nerves of septum of nose. Right side. (Nasociliary is rightmost yellow line.)
Details
From	Ophthalmic nerve
To	posterior ethmoidal nerve, anterior ethmoidal nerve, long ciliary nerves, infratrochlear nerve, communicating branch to ciliary ganglion
Identifiers
Latin	nervus nasociliaris
TA	A14.2.01.025
FMA	52668
Anatomical terms of neuroanatomy

Structure

The nasociliary nerve enters the orbit between the two heads of the lateral rectus muscle and between the superior and inferior rami of the oculomotor nerve. It passes across the optic nerve (CN II) and runs obliquely beneath the superior rectus muscle and superior oblique muscle to the medial wall of the orbital cavity. It passes through the anterior ethmoidal opening as the anterior ethmoidal nerve and enters the cranial cavity just below the cribriform plate of the ethmoid bone. It supplies branches to the mucous membrane of the nasal cavity and finally emerges between the inferior border of the nasal bone and the side nasal cartilages as the external nasal branch.

Branches

• posterior ethmoidal nerve
• 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

Testing

Since both the short and long ciliary nerves carry the afferent limb of the corneal reflex, one can test the integrity of the nasociliary nerve (and, ultimately, the trigeminal nerve) 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 (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

• 
  Nerves of the orbit. Seen from above.
• 
  Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion.
• 
  Dissection showing origins of right ocular muscles, and nerves entering by the superior orbital fissure.
• 
  Pathways in the ciliary ganglion.
• 
  Extrinsic eye muscle. Nerves of orbita. Deep dissection.

References

This article incorporates text in the public domain from page 888 of the 20th edition of Gray's Anatomy (1918)

External links

• Anatomy figure: 29:03-08 at Human Anatomy Online, SUNY Downstate Medical Center - "A deeper dissection of the right orbit from a superior approach."
• lesson9 at The Anatomy Lesson by Wesley Norman (Georgetown University) (nasalseptumner)
• cranialnerves at The Anatomy Lesson by Wesley Norman (Georgetown University) (V)
• MedEd at Loyola GrossAnatomy/h_n/cn/cn1/cnb1.htm