Lecture 9 - Cranial Nerves

Question 1

What is CN 1

Answer 1

Olfactory - S

Question 2

What is CN 2

Answer 2

Optic - S

Question 3

What is CN 3

Answer 3

Oculomotor - M

Question 4

CN IV

Answer 4

Trochlear - M

Question 5

CN V

Answer 5

Trigeminal - B

Question 6

CN VI

Answer 6

Abducens - M

Question 7

CN VII

Answer 7

Facial - B

Question 8

CN VIII

Answer 8

Acoustic - S

Question 9

CN IX

Answer 9

Glossopharyngeal - B

Question 10

CN X

Answer 10

Vagus - B

Question 11

CN XI

Answer 11

Accessory - M

Question 12

CN XII

Answer 12

Hypoglossal - M

Question 13

Where does the optic nerve go

Answer 13

retina –> optic chiasm –> joins to lateral geniculate nucleus of the thalamus –> forms optic radiation –> joins onto posterior internal capsule –> finishes at visual cortex of occipital lobe

Question 14

How can an anterior lobectomy impact vision

Answer 14

can take out some of the meyer’s loop

Question 15

How is the PMC organised?

Answer 15

retinotopically

the PMC is located on the banks of the calcarine fissure.

The superior (upper) parts of the visual field is represented on the lower bank of the calcarine fissure, and vice versa.

it is also organised contralaterally

the closer to the retina, the area is represented closer to the occipital pole, and a larger area is dedicated to it than regions in the periphery.

Question 16

what is the difference between lesions of the meyers loop and optic radiation?

Answer 16

the Meyers loop/lower portion of optic radiation projects to the lower banks of the calcarine fissure –> cause loss of upper field of vision

The optic radiation/upper portion of optic radiation projects to the upper banks of calcarine fissure –> causes loss of lower field of vision;

both will be losses of contralateral fields of vision, and only one quadrant (upper or lower)

you can lesion the ENTIRE optic radiation (includes both upper and lower) to create contralateral homonymous hemianopia

Question 17

What are the two pathways for visual processing

Answer 17

WHERE? pathway - dorsal pathway (goes up) analyses motion and spatial infor

WHAT? pathway - ventral pathway (goes down) - analyses form, etc.

Question 18

pathological features that can occur for CN III?

Answer 18

Ptosis caused by loss of levator palpebrae function
 Eye deviated laterally and down
 Diplopia
 Dilated non reactive
pupil
 Loss of accommodation

Question 19

pathological features that can occur for CN IV?

Answer 19

 Inability to move eye downward
and laterally
 Diplopia
 Patients tilt head toward unaffected eye to overcome inward rotation of affected eye

Question 20

Which nerves control eye movement?

Answer 20

CN III, CN IV, and CN VI

OCULOMOTOR, TROCHLEAR AND ABDUCENS

they move the extraocular muscles

Question 21

What does CN V do?

Answer 21

trigeminal nerve

face, mouth and meningial sensation

motor innervation for mastication muscles!!

meninges - v1 - opthalmic
mouth - v2 - maxillary
face - v3 - mandibular.

Question 22

What does the aducens nerve do

Answer 22

CN VI

abducts the eye
motor

Question 23

What does the facial nerve do

Answer 23

it is both sensory and motor

sensory - taste for anterior 2/3 of tongue

motor - movement of facial expressions for the face

unilateral lesions will not paralyse above eyes because it is bilaterally innervated

Question 24

What is the difference between UMN and LMN damage causing hemifacial paralysis?

Answer 24

UMN - preserves forehead movement - damage is above the pons

LMN - whole side of face is paralysed

Question 25

What is bell’s palsy

Answer 25

unilateral face paralysis, acute..

no known reason, possibly viral.

abrupt LMN paresis, from 1-7 days onset.

go on corticoseroids.

Question 26

What does the acoustic nerve do?

Answer 26

vestibular and hearing

• crosses midline multiple times so unilateral lesion does not cause significant hearing loss

SENSORY ONLY

Question 27

What does the accessory nerve do?

Answer 27

CN XI

Motor

innervates the sternomastoid and trapezius muscles - MOVES HEAD AND NECK

lesions will cause weakness in head turning TO THE opposite opposite side of the lesion

Question 28

What is bulbar palsy

Answer 28

LMN lesion of CN IV, V, and VII.

pseudo bulbar palsy is an UMN lesion of CN IX, X, and XII.

Question 29

what does the glossopharyngeal nerve do

Answer 29

both sensory and motor

motor - innervates part of tongue and pharynx and salivary gland

sensory - taste and sensory impulses from tongue and pharynx

Question 30

What does the vagus nerve do?

Answer 30

both sensory and motor

• parasympathetic innervation!!!!! - goes to heart, lungs and vesceral organs

motor - pharynx (swallowing) and larynx (voice)

sensory - travel from aortic arch to innervate the pharynx, larynx, outer ear and meninges of the posterior fossa to the trigeminal nuclei

this is the only CN that extend BEYOND HEAD AND NECK

emerges from MEDULLA via jugular foramen