Cranial Nerves

Question 1

CN 1 Olfactory

Answer 1

Pure sensory
MC contoused
Shortest CN
Involved c TBI (3, 7, 1)
Lesion: Anosmia
Exit: Cribriform plate of ethmoid

Question 2

CN 2 Optic

Answer 2

Pure sensory
CN c thickest myelin sheath
Not a true peripheral nerve (myelination is from oligodendrocytes)
Involved c increased ICP
Involved c MS (2)
Lesion: I/L Monocular blindness
Exit: Optic canal

Question 3

CN 3 Oculomotor

Answer 3

Pure motor
Involved with the following:
DM (3, 6)
TBI (3, 7, 1)
PD (3, 7, 9)
Botulism and MG (3, 4, 6)
Lesion: External strabismus
Exit: Superior orbital fissure

Question 4

Argyll Robertson Pupil

Answer 4

CN 3
impaired pupillary light reflex c intact accomodation

Question 5

Levator palpebrae is innervated by?

Answer 5

CN 3
80% eye opening

Question 6

Mueller’s muscle is innervated by?

Answer 6

Sympathetic NS
Involved c horner’s
20% eye opening
Lesion: Ptosis

Question 7

CN 4 Trochlear

Answer 7

Motor only
Only crossed CN; Stupid nerve
Thinnest CN
Longest intracranially
Only CN arising from the dorsum of the brainstem
Involved with:
MG and Botulism (3, 4, 6)

Question 8

Lesion in CN 4 leads to?

Answer 8

Vertical diplopia
I/L tilt to compensate

Question 9

CN 5 Trigeminal

Answer 9

Mixed CN
Largest CN
Involved with:
Leprosy (5, 7)
Tic douloureux/Trigeminal neuralgia

Question 10

3 Sensory Nuclei of CN 5

Answer 10

At the brainstem
Midbrain: Mesencephalic nucleus (Proprioception )
Pons: Main sensory nucleus (light touch)
Medulla: Spinal nucleus (pin prick, pain and temp)

Question 11

CN 5 motor fxn

Answer 11

Mastication:
TIME mm
Mouth closing: temporalis, internal pterygoid, mentalis
Mouth opening: external pterygoid
Other mm: tensor tympani, tensor valu palatini, ant. digastric, mylohyoid

Question 12

CN 5 sensory fxn

Answer 12

Facial sensation plus general sensation on the anterior tongue

Question 13

CN 6 Abducens

Answer 13

Pure motor (LR6)
Involved c:
DM (3, 6)
MG and Botulism (3, 4, 6)
Lesion: Horizontal diplopia; to compensate: I/L rotate
Lesion: Internal strabismus / Esotropia

Question 14

CN 7 Facial

Answer 14

Mixed CN
Involved with:
TBI (3, 7, 1)
PD (3, 7, 9)
GBS (7)
Sjogren syndrome (7, 9)
Leprosy (5, 7)
Bell’s palsy

Question 15

CN 7 sensory fxn

Answer 15

Ant 2/3 taste of tongue

Question 16

CN 7 motor fxn

Answer 16

Facial expressions;
innervates: posterior digastric and stapedius (lesion: hyperacusis)

Question 17

Zygomaticus major action

Answer 17

True smile

Question 18

Risorius action

Answer 18

Grimace

Question 19

Corrugator supercilii action

Answer 19

Frowning

Question 20

Procerus action

Answer 20

Distaste

Question 21

Frontalis action

Answer 21

Surprise

Question 22

Orbicularis oris action

Answer 22

Kissing

Question 23

Orbicularis oculi action

Answer 23

eye closing

Question 24

CN 8 Vestibulocochlear

Answer 24

Pure sensory
Involved with:
Meniere’s disease
Vertigo

Question 25

CN 8 Vestibular part is responsible with?

Answer 25

Balance; Lesion: disequilibrium

Question 26

CN 8 Cochlear part is responsible with?

Answer 26

Hearing; Lesion: Sensorineural hearing loss (irreversible)

Question 27

CN 9 Glossopharyngeal

Answer 27

Mixed CN Swallowing and gag reflex (afferent) Lesion: difficulty c swallowing

Question 28

CN 9 motor fxn

Answer 28

innervates stylopharyngeus

Question 29

CN 9 sensory fxn

Answer 29

general sensation and taste of the posterior 2/3 of tongue

Question 30

CN 10 Vagus nerve

Answer 30

Mixed CN Longest CN extracranially Lesion: dysphagia, dysphonia Gag reflex (efferent)

Question 31

CN 10 motor fxn

Answer 31

pharyngeal (palatoglossus) and laryngeal (phonation) mm

Question 32

CN 10 sensory fxn

Answer 32

back of the ear, external pinna of the ear, throat

Question 33

Lesion to CN 10 tongue deviation towards?

Answer 33

I/L to the lesion

Question 34

Lesion to CN 10 uvula deviation towards?

Answer 34

C/L to the lesion

Question 35

Uvula deviation (central/peripheral)

Answer 35

Central (I/L) Peripheral (C/L)

Question 36

CN 11 Spinal Accessory

Answer 36

Pure motor Traps and SCM

Question 37

Radical neck dissection results to?

Answer 37

Lateral winging of the scapula (sliding door paralysis)

Question 38

MC form of dystonia

Answer 38

Torticollis

Question 39

CN 12 Hypoglossal

Answer 39

Pure motor Lesion: Dysarthria

Question 40

CN 12 motor fxn

Answer 40

Innervates intrinsic mm of the tongue. Extrinsic mm (genioglossus, hyoglossus, styloglossus)