4) Cranial Nerves

Question 1

Name the 12 cranial nerves

Answer 1

I - Olfactory
II - Optic
III - Oculomotor
IV - Trochlear
V - Trigeminal
VI - Abducens
VII - Facial
VIII - Vestibulocochlear
IX - Glossopharnygeal
X - Vagus
XI - Spinal Accessory
XII - Hypoglossal

Question 2

Give the broad functions of each of the 12 CNs

Some Say…

Answer 2

I Some - Sensory
II Say Sensory
III Marry - Motor
IV Money - Motor
V But - Both
VI My - Motor
VII Brother - Both
VIII Says - Sensory
IX Big - Both
X Boobs - Both
XI Matter - Motor
XII Most - Motor

Question 3

Where does CN I exit the cranium?

Answer 3

Foramina in cribriform plate of ethmoid bone to reach nose

Question 4

What are the main actions of the Olfactory nerve?

Answer 4

Special sensory fibres:
uppermost part of nasal cavity
SMELL

Question 5

What is rhinorrhea?

Answer 5

Leakage of CSF from the nose

Associated with fractures of cribriform plate

Question 6

Where does CN II exit the cranium?

Answer 6

Optic canal

Question 7

What are the main actions of the Optic nerve?

Answer 7

Special sensory fibres:

VISION

Question 8

What is anosmia?

Answer 8

Loss of smell

Associated with fractures of cribriform plate

Question 9

Name some common nerve lesions of CN II

Answer 9

Loss of pupillary constriction &
Visual field defects
Due to: Direct trauma to eye or orbit
Fracture of optic canal
Pressure on optic pathway

Question 10

Where does CN III exit the cranium?

Answer 10

Superior orbital fissure

Question 11

What are the main somatic motor actions of the Oculomotor nerve?

Answer 11

Innervate: Superior, inferior, & medial rectus
Inferior oblique
LPS
(raise superior eyelid, turns eyeball sup, inf, & med.)

Question 12

What are the main visceral motor actions of the Oculomotor nerve?

Answer 12

Parasympathetic innervation:
Sphincter of pupil & ciliary muscle
(constricts pupil & accomodates lens of eye)

Question 13

Which nerve will be affected during a fracture or aneurysm involving the cavernous sinus?

Answer 13

Oculomotor CN III
Dilated pupil, ptosis
Eye turns DOWN & OUT
Pupillary reflex on side of lesion lost

Question 14

Where does CN IV exit the cranium?

Answer 14

Superior orbital fissure

Question 15

What are the main actions of the Trochlear nerve?

Answer 15

Motor:

Innervates Superior Oblique

Question 16

What nerve lesions may occur to the Trochlear nerve?

Answer 16

Stretching of nerve during its course around brainstem
Orbit fractures
Inability to look down when eye is adducted

Question 17

Name the 3 divisions of the Trigeminal nerve

Answer 17

Ophthalmic (Vi)
Maxillary (Vii)
Mandibular (Viii)

Question 18

Where does the Ophthalmic nerve (Vi) leave the cranium?

Answer 18

Superior orbital fissure

Question 19

Where does the Maxillary nerve (Vii) leave the cranium?

Answer 19

Foramen rotundum

Question 20

Where does the Mandibular (Viii) leave the cranium?

Answer 20

Foramen ovale

Question 21

What are the main actions of the Ophthalmic nerve?

Answer 21

Sensory:

cornea, skin of forehead, scalp, eyelids, nose & mucosa of nasal cavity & paranasal sinuses

Question 22

What are the main actions of the Maxillary nerve?

Answer 22

Sensory:

Skin of face over maxilla incl. upper lip, maxillary teeth, mucosa of nose, maxillary sinuses & palate

Question 23

What are the main actions of the Mandibular nerve?

Answer 23

Sensory:
skin, side of head over mandible incl. lower lip, mandibular teeth, TMJ, mucosa of mouth and ant. 2/3 of tongue
Motor:
muscles of mastication, mylohyoid, ant. belly of digastric, tensor veli palatini, tensor tympani

Question 24

What will lesions of the Trigeminal nerve lead to?

Answer 24

Paralysis of muscles (mastication)

Sharp, intense facial pain

Question 25

Where does CN VI exit the cranium?

Answer 25

Superior orbital fissure

Question 26

Which nerves exit the cranium via the superior orbital fissure?

Answer 26

Oculomotor (III) Trochlear (IV) Ophthalmic (Vi) Abducent (VI)

Question 27

What are the main actions of the Abducent nerve?

Answer 27

Motor: Lateral Rectus (turns eye laterally)

Question 28

How might the abducens nerve be lesioned?

Answer 28

Fractures involving cavernous sinus or orbit Eye fails to move laterally Diplopia on lateral gaze

Question 29

Where does CN VII exit the cranium?

Answer 29

Internal acoustic meatus; Facial canal; Stylomastoid foramen

Question 30

What are the main actions of the Facial nerve?

Answer 30

``` Special Sensory: Taste, ant. 2/3 tongue & palate Motor: Muscles of facial expression Scalp, stapedius, stylohyoid & post. belly of digastric Visceral Motor: Parasympathetic innervation to submandibular & sublingual salivary gland (chorda tympani) lacrimal gland & glands of nose & palate ```

Question 31

What may be the consequences of a laceration or contusion in the Parotid region?

Answer 31

CN VII Paralysis of facial muscles Eye remains open, angle of mouth droops, forehead doesn't wrinkle Bell's palsy

Question 32

What might happen to someone who fractures their temporal bone?

Answer 32

Bell's palsy Involvement of cochlear nerve & chorda tympani Dry cornea, loss of taste ant. 2/3 of tongue

Question 33

What effects will an intracranial haematoma have on CN VII?

Answer 33

Forehead wrinkles because of bilateral innervation of frontalis muscle Paralysis of contralateral facial muscles

Question 34

Where does CN VIII exit the cranium?

Answer 34

Internal acoustic meatus

Question 35

What are the main actions of the Vestibulocochlear nerve?

Answer 35

Vestibular: Controls BALANCE Cochlear: HEARING

Question 36

What may lesions of CN VIII cause?

Answer 36

Progressive, unilateral hearing loss, tinnitus, vertigo Caused by: tumour of nerve (acoustic neuroma), skull fractures, ear infections Acoustic neuroma frequently impairs CN VII too

Question 37

Where does CN IX exit the cranium?

Answer 37

Jugular foramen

Question 38

What are the main actions of the Glossopharyngeal nerve?

Answer 38

Special sensory: Taste to post. 1/3 tongue Visceral sensory: Parotid gland, carotid body & sinus, pharynx & middle ear General sensory: Cutaneous external ear Motor: Stylopharyngeus Parasymp. to parotid gland

Question 39

What nerve lesions may occur to CN IX?

Answer 39

Glossopharyngeal Deep lacerations of neck Loss of taste to post. 1/3 tongue

Question 40

Where does CN X exit the cranium?

Answer 40

Jugular foramen

Question 41

What are the main sensory actions of the Vagus nerve?

Answer 41

Visceral sensory: Lower pharynx & larynx, trachea, oesophagus, bronchi, heart, stomach, intestine General sensory: External auditory meatus, back of auricle Special sensory: Taste from epiglottis & palate

Question 42

What are the main motor actions of the Vagus nerve?

Answer 42

Innervates all muscles of pharynx except stylopharyngeus All muscles of airways, larynx, heart, GI tract All palate muscles except tensor veli palantini (parasymp. to trachea, bronchi, digestive tract, cardiac muscle)

Question 43

How might hoarseness of the voice occur?

Answer 43

Damage to Recurrent laryngeal branch of Vagus carcinoma, enlarged lymph node, aneurysm

Question 44

How will a brainstem lesion or deep laceration of the neck affect CN X?

Answer 44

Sagging of soft palate Deviation of uvula to normal side Hoarseness - paralysis of vocal cord

Question 45

How might the superior laryngeal nerve be damaged?

Answer 45

Thyroidectomy External branch lies close to sup. thyroid artery Damaged when ligating blood vessel

Question 46

Where does CN XI exit the cranium?

Answer 46

Jugular foramen

Question 47

What are the main actions of the Spinal accessory nerve?

Answer 47

Motor: Spinal - SCM & Trapezius Cranial - Innervates pharynx, larynx & soft palate

Question 48

How will nerve lesions caused by surgery or laceration to CN XI present?

Answer 48

Paralysis of SCM & superior fibres of Trapezius | Should droop

Question 49

Where does CN XII exit the cranium?

Answer 49

Hypoglossal canal

Question 50

What are the main actions of the Hypoglossal nerve?

Answer 50

Motor: | Innervates all extrinsic & intrinsic muscles of tongue except palatoglossus

Question 51

How would a nerve lesion of CN XII be caused and how would it present?

Answer 51

Neck laceration or basal skull fracture Protruded tongue deviates towards affected side (due to arrangement of muscles)