Ocular Anatomy 13 Cranial Nerves

Question 1

Where are the nuclei of the oculomotor nerve?

Answer 1

Adjacent to the superior colliculus in the midbrain
2 2 4 4

Question 2

What is the path of the oculomotor nerve?

Answer 2

Runs anterior passing red nucleus and emerges on ventral sruface of midbrain between PCA and superior cerebellar arteries
Runs anteriorly int he lateral wall of the cavernous sinus and enters the orbit (after dividing into superior and inferior branches) via SOF

Question 3

CN3 is at risk from aneurysm of which artery

Answer 3

Posterior communicating artery aneurysm which lies parallel

Question 4

Which msucle is supplied by contralateral oculomotor nerve nucleus

Answer 4

Superior rectus

Question 5

What does the inferior branch of oculomotor nerve carry??

Answer 5

IR, MR, IO, parasympathetic fibres to ciliary ganglion

Question 6

Where is the trochlear nerve nucleus?

Answer 6

Inferior colliculus

Question 7

What is the path of the trochlear nerve?

Answer 7

Decussate before emerging from the dorsal aspect of the brainstem
Runs forward in subarachnoid space around the cerebral peduncle to enter the lateral wall of the cavernous sinus
Initially lies inferior to CN3 but then moves to lie superior and lateral on leaing the cavernous sinus.
Enters the orbit through the SOF outside the tendinous ring
Innervates contralateral SO

Question 8

What does damage to CN4 result in?

Answer 8

SO paralysis and contralateral headtilt

Question 9

Nucleus of CN6

Answer 9

Abducens

Floor of fourth centrical where CN7 passes over it froming faical colliculus

Question 10

Path of Abducens

Answer 10

Emerges from the brain stem in the CPA where it may be damaged by tumours e.g. acoustic neuroma
Passes up clivus in subarachnoid space
Passes over apex of petrous temporal bone.
Lies within cavernous sinus
Enters orbit through SOF inside CTR and pierces lateral rectus

Question 11

What nerve lies wholly within the cavernous sinus?

Answer 11

Abducens nerve - first to be damaged in cavernous sinus thrombosis

Question 12

What are the branches of the CNV1 ophthalmic nerve

Answer 12

Lacrimal nerve
Frontal nerve
Nasociliary nerve

Question 13

What are the paths of the lacrimal and frontal nerve

Answer 13

Ophthalmic nerve in lateral wall of cavernous sinus divides
Lacrimal and frontal nerves enter the orbit outside the tendinous ring
Lacrimal receives parasympathetic fibres (for lacrimal gland) from the zygomaticotemporal branch of the maxillary nerve

Frontal nerve supplies the frontal sinuses via supraorbital and supratrochlear divisions

Question 14

What is the path of the nasociliary nerve?

Answer 14

Largest branch enters the orbit thought the tendinous ring
It is also the major snesory nerve to the globe
Receives fibres from teh long ciliary nerves and the short ciliary nerves that travel via the ciliary ganglion

Question 15

What is the anterior ethmoidal nerve?

Answer 15

Terminal branch of nasociliary nerve
Supplies lateral wall of the nose and parts of nasal septum
Terminates on the tip of the nose as external nasal nerve

HZO lesions - signal ocular involvement by nasociliary nerve (Hutchinson’s sign)

Question 16

What is the path of CNV2 trigeminal maxillary nerve

Answer 16

From trigeminal ganglion lies in the lateral wall of the cavernous sinus
Passes through the foramen rotundum and into the pterygopalatine fossa (supplies pterygopalatine ganglion)
Exits fossa as infraorbital nerve
This lies in infraorbital canal in floor of orbit
Innervates maxillary sinuses, upper incisor, canine, premolar teeth, skin of cheek, lower eyelid, upper lip