Cranial Nerves

Question 1

What does the CN III innervate

Answer 1

Extraocular muscles except LR and SO
Sphincterpupillae and ciliary muscles via parasympathetic

Question 2

Where is the third nerve nuclei?

Answer 2

Midbrain level of the superior colliculus

2 nuclei:

Motor nucleus - in atnieorr grey matter around cerebral aqueduct

Edinger Westphal (parasympathetic nucleus) - posterior to main motor

Question 3

Where do preganglionic and postganglionic fibres from the Edinger WEstphal nucleus travel?

Answer 3

Preganglionic to orbit to synapse in the ciliary ganglion

Postganglionic along short ciliary nerves to ciliary muscles and pshincter pupillae

Question 4

What other fibres does the edinger westphal nucleus receive?

Answer 4

Coriconuclear fibres for accommodation
Fibres from the pretectal nucleus for the direct and consensual light reflex

Question 5

What is the path of third nerve?

Answer 5

Emerges anterior from midbrain, medial to cerebral peduncles
Subarachnoid space
Anterior between posterior cerebral artery and superior cerebellar arteries
Runs parallel with posterior communicating artery
Perforates dura materand enters cavernous sinus in lateral wall above CNIV

Question 6

What nerves does the CN III receive prior to dividing?

Answer 6

Sensory communicating branch from the ophthalmic division of the trigeminal nerve

Sympathetic branch from the nerve plexus around the ICA

Question 7

What is the path of the superior division of the CNIII

Answer 7

Through SOF within CTR

Upwards and lateral to optic nerve

Enters superior rectus at junction of proximal and middle thirds

Through superior rectus and to levator palpebrae superioris

Question 8

Pathway of CNIII inferior division

Answer 8

SOF via CTA

Divides into three branches
MEdial rectus branch - passes medially below optic nerve to enter lateral surface of muscle

Inferior rectus branch - runs forward on upper surface of IR and enters between proximal and middle third

Inferior oblique branch - close to orbital floor and lateral to inferior rectus - enters posterior border
- Gives short branch to ciliary ganglion
= short ciliary nerves to sphincter pupillae and ciliary muscles

Question 9

Whatis the levator supplied by?

Answer 9

Single central group of cells (central caudal nucleus) via both third nerve nuclei

Question 10

Which muscle is supplied by contralateral CNIII nucleus?

Answer 10

Superior rectus

Others have ipsilateral supply

Question 11

What artery puts the CNIII at risk

Answer 11

Posterior communicating artery aneurysm

Superior cerebellar artery

Question 12

What does CNIV supply

Answer 12

Contralateral SO

Question 13

What is the path of the CNIV

Answer 13

Fourth nere nuclei at inferior colliculus of bmidbrain
Entirely motor

Coriconuclear fibres from cerebral hemispheres
Tectobulbar fibres connecting visual cortex via superior colliculus

Fibres from medial longitudinal fasciculus - connect to the third, sixth and eighth nerves

Fibres decussate before midbrain

Rund forward in subarachnoid space
Enters carvernous sinus in lateral wall inferior to CNIII - exits above CNIII

Nerve passes through SOF outside CTR

Passes medially in orbit superior to root of levator to SO

Question 14

What is the course of abducens

Answer 14

6th nucleus - near floor of fourth ventricle
Exits anteriorly - in subarachnoid space

To drosum sellae of sphnoid bone
Cavernous sinus
Inferonasally to internal carotid artery
SOF within CTR to orbit
To LR

Question 15

What are the nuclei of the trigmeinal nucleus

Answer 15

Main sensory - posteiror pons
Spinal - continues down to C2 of spinal cord
Mesencephalic - lateral grey matter around cerebral aqueduct
Motor nucleus - posterior pons

Question 16

Where is the trigeminal ganglion?

Answer 16

Apex of petrous part of temporal bone

Question 17

What nerve runs through the cavernous sinus

Answer 17

Abducens CNVI

Question 18

What is Gradenigo’s sydnrome?

Answer 18

PEtrous part of temporal bone breached in middle ear causing CNVI and CNVII palsy

Question 19

What re the branches of the ophthamlic nerve

Answer 19

Frontal nerve
Lacrimal nerve
Nasocilliary nerve

Divides then enter the orbit by SOF

Question 20

Where odes the lacrimal nerve enter the orbit

Answer 20

Through SOF external to CRT with frontal and trochlear

Question 21

What provids the larimal nerve with parasympathetic fibres

Answer 21

Zyogmaticotemporal branch of V2 - maxillary

Question 22

What is the function of lacrimal nerve

Answer 22

Provides secretomotor of lacrimal gland
Sensory to upper eyelid skin and conjunctiva

Question 23

Path of the frontal nerve

Answer 23

Enters orbit between lacrimal and trochlear nerve within SOF external to CTR

Supraorbital branch - upper lid, conj, forehead skin, mucous membrane of frontal sinus

Supratrochlear branch - medial upper lid and medial forehead skin

Question 24

What nerve supplies tip of nose

Answer 24

Nasociliary nerve

Question 25

What are the branches of the nasocilairy nervw

Answer 25

Ramus communicans (to cilairy ganglion) - sensory fibres Long ciliary nerves - forward from ciliary ganglion to pierce the eyeball near optic nerve - supply iris cilairy body and cornea - sensory to cornea, symapthetic fibres to dilator pupillar Infratrochlear nerve - larcimal sac,conj, emdial aspect of both eyelids, lateral nose

Question 26

What is the path of maxillary nerve CNV2

Answer 26

Trigeminal ganglion Wall of cavernous sinus beneath V1 Most infeiror nerve in wall Foramen rotundum PTerygopalatine fossa - pterygopalatine ganglion Inferior orbital fissure Infraorbital nerve Floor of orbit

Question 27

What are branches of V2

Answer 27

MEningeal - supplies dural mater in medial cranial fossa Ganglionic - susptend pterygopalatine ganglion from lower border of maxillary nerve - sensory nerves from oribtal periosteum and mucous membranes (nose, palate, pharynx) Contain postganglionic fibres from facial nerve to lacrimal gland Zygomatic - arises in pterygopalatine fossa, through SOF - zygomaticotemporal and zygomaticofaical - supply skin of forehead and cheek Posterior superior alveolar Middle superior alveolar Anterior superior alveolar FAcial nerves

Question 28

What CN pass through SOF

Answer 28

CN III CN IV CN V1 CN VI

Question 29

What CN passes through forament rotundum

Answer 29

CN V2 - maxillary

Question 30

What CN passes through foramen ovale

Answer 30

CNV3 - mandibular

Question 31

What CN passes through internal acoustic meatus?

Answer 31

VII VIII

Question 32

What cranial nerves pass through jugular foramen

Answer 32

CN IX - glossopharyngeal CN X - vagus CNXI - accessory

Question 33

What does CN IX supply

Answer 33

Stylopharyngeus msucle Parotid General sensation and taste from posterior third of tongue Pharyns Carotid sinus (baroreceptor) Carotid body (chemoreceptor)