L18 Innervation of the Eye Flashcards
What are the 3 types of nerves?
Sensory, motor, autonomic
What are cranial nerves?
Nerves that originate in thebrain, and innervate the head, neck, and upper trunk
Nuclei in the brain stem
12 pairs of nerves from 1-12
Which CN are important for vision?
CN2-7 (6 pairs)
List the names for each cranial nerve important for vision?
2 - optic nerve
3 - oculomotor nerve
4 - trochlear
5 - trigeminal
6 - Abducent
7 - Facial
Where does the ophthalmic branch (of CNV) innervate/branch out to?
Eye (pretty much all components) –> lacrimal glands, ends outside orbit, conjunctiva, mucous membrane of nasal cavity, skin of eyelids, eyebrows, forehead, and nose
Where do all the nerves enter the orbital area from?
Sphenoid bone through the superior or inferior fissure, then through the Annulus of Zinn. While, some nerves pass through the fissures but not the Annulus of Zinn
What is the significance of nerves that are above the ring (Annulus of Zinn)?
Free to move
What is the significance of nerves that pass through the ring (Annulus of Zinn)?
Cannot move around
What happens when there is inflammation in the area of Annulus of Zinn?
Compression of structures within it –> compression of optic nerve –> impair vision
Which nerves branch off from the trigeminal nerve (CNV)?
NVa - ophthalmic
NVb - maxillary
NVc - mandibular
Which nerves branch off NVa ophthalmic branch?
Lacrimal, nasociliary, frontal
Some nerves pass through near the walls of the Cavernous sinus of sphenoid bone, and some through the middle. Which nerves pass through where?
Walls: 3,4,5
Middle: 6 and internal carotid artery
Which nerves in the carvernous sinus are more likely to be damaged?
Nerves located closer to the sphenoid bones (in the cavernous sinus) are more likely to be damaged.
Thus, those near the walls - 3,4,5
What is the order of nerves in the orbit from top to bottom?
Lacrimal (NVa) > frontal (NVa) > trochlear (NIV) > Sup III > nasociliary> inf III > abducent (NVI).
Which nerves are above the ring?
Lacrimal, frontal, trochlear
Which nerves are in the ring?
Sup III, nasociliary III, abducent
Which nerve is the only nerve to exit the orbit?
CN2
Which intraocular muscles does CN3 innervate?
Iris (sphincter pupillae), ciliary muscle (accommodation) via parasympathetic nerve fibres
What else does CN3 innervate?
LPS (levator palpabrae superioris) - upper eyelid for blinking
What is the path of CN3?
Originates in the brainstem and passes through wall of c.sinus, above NIV. Then runs with sensory branch NVa and divide into superior and inferior branches within superior orbital fissure and Annulus of Zinn.
What does the superior division of CN3 innervate?
SR, levator palpebrae superioris
What does the inferior division of CN3 innervate?
Divides into three branches to supply the MR, IR, IO.
The nerve to inferior oblique gives rise to a thick branch (containing parasympathetic nerve fibres) which passes to the…
Ciliary ganglion.
What is the ciliary ganglion?
Short ciliary nerves which supply the ciliary muscle and sphincter pupillae.
What does CNIV innervate?
Supplies the SO muscle.
What nerve is the thinnest of cranial nerves?
NIV.
What is the pathway of NIV?
Leaves brainstem from dorsal (posterior) surface, wall of c.sinus below NIII above NV. Pass through superior orbital fissure above the tendinous ring.
What does the abducen (IV) supply?
LR muscle.
What is the pathway of the abducens nerve?
Originate in brainstem below NIII and NIV. Pass through the middle of c.sinus. Passes through the Annulus of Zinn.
Why is CNIV most affected ocular motor nerve in adults?
Could be due to its long trajectory (longest trajectory intracranially)
What are the two branches of the frontal branch?
Supraorbital, supratrochlear.
What are the branches of the nasociliary branch?
Long ciliary nerves for iris and cornea.
What nerve is commonly affected in diabetes?
NVI as it is the longest course through brain, sign of poor or untreated diabetes, resolves after treatment.
What are other signs of nerve abnormality?
Ptosis, pupil defects, sensation changes to face.
Where can abnormality in nerves occur?
Level of brain stem, course though brain cavernous sinus or within orbit.