Cranial Nerves

Question 0

Name CN I and state its function

Answer 0

Olfactory

Sensory

Question 1

Name the cranial nerves

Answer 1

Olfactory
Optic
Oculomotor 
Trochlear
Trigeminal
Abducens
Facial
Vestibulocochlear 
Glossopharyngeal 
Vagus
Accessory
Hypoglossal

Question 2

Name CN II and state its function

Answer 2

Optic

Sensory

Question 3

Name CN III and state its function

Answer 3

Oculomotor

Motor

Question 4

Name CN IV and state its function

Answer 4

Trochlear

Motor

Question 5

Name CN V and state its function

Answer 5

Trigeminal

Both sensory and motor

Question 6

Name CN VI and state its function

Answer 6

Abducens

Motor

Question 7

Name CN VII and state its function

Answer 7

Facial

Both motor and sensory

Question 8

Name CN VIII and state its function

Answer 8

Vestibulocochlear

Sensory

Question 9

Name CN IX and state its function

Answer 9

Glossopharyngeal

Both sensory and motor

Question 10

Name CN X and state its function

Answer 10

Vagus

Both sensory and motor

Question 11

Name CN XI and state its function

Answer 11

Accessory

Motor

Question 12

Name CN XII and state its function

Answer 12

Hypoglossal

Motor

Question 13

Where does CN I innervate?

Answer 13

Uppermost part of the nasal cavity

Reaches the nasal cavity via the cribiform plate of the ethmoid bone

Question 14

What would the consequences of a fracture of the cribiform plate be?

Answer 14

Anosmia

Rhinorrhea if it involved the dura mater (leakage of CSF from the nose)

Question 15

How may optic nerve lessons occur and what are the consequences?

Answer 15

Direct trauma to the eye or orbit, fracture of the optic canal, pressure on optic pathway
Results in loss of pupillary constriction and visual field defects

Question 16

What does CN III innervate?

Answer 16

Extraocular muscles
Ciliary muscles
Sphincter pupillae

Question 17

How may lesions of CN III occur and what are the consequences?

Answer 17

Fractures involving the cavernous sinus or aneurysms

May result in dilated pupil, ptosis, eye turns inferolaterally, pupillary reflex on the side of the lesion is lost

Question 18

What does CN IV innervate?

Answer 18

Superior oblique of the eye

Question 19

How may lesions of CN IV occur and what are the consequences?

Answer 19

Stretching of the nerve around the brainstem or orbit fracture
May result in inability to look down when the eye is adducted

Question 20

What are the 3 divisions of CN V?

Answer 20

Opthalmic
Maxillary
Mandibular

Question 21

What does the Opthalmic division of CN V innervate?

Answer 21

Sensory innervation of the skin and cornea
Corneal reflex (involuntary blinking due to stimulus eg bright light)

Question 22

What does the maxillary division of CN V innervate?

Answer 22

Sensory innervation of the skin, mucous membrane of the nose, palate and upper dental arcade

Question 23

What does the mandibular division of CN V innervate?

Answer 23

Sensory innervation of the skin, lower teeth, cheek and anterior 2/3rds of the tongue
Motor innervation of the muscles of mastication

Question 24

What are the consequences of lesions of CN V?

Answer 24

Paralysis of muscles of mastication and sharp, intense facial pain

Question 25

What does CN VI innervate?

Answer 25

Motor innervation to the lateral rectus muscle

Question 26

How may lesions of CN VI occur and what are the consequences?

Answer 26

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

Question 27

What does CN VII innervate?

Answer 27

Special sensory to the anterior 2/3rds of the tongue General sensory to the external meatus and auricle Motor to the muscles of facial expression Parasympathetic secretomotor to submandibular and sublingual via chorda tympani Parasympathetic to glands of nasal mucosa, para nasal sinuses, palate and lacrimal gland

Question 28

Give 3 possible causes of CN VII lesion

Answer 28

Laceration of contusion in the parotid region Fracture of the Temporal Bone Intracranial Haematoma

Question 29

What are the consequences of laceration or contusion of CN VII in the parotid region?

Answer 29

Paralysis of facial muscles, eye remains open, angle of the mouth droops Bell's palsy

Question 30

What are the consequences of CN VII laceration by fracture of the Temporal bone?

Answer 30

Bell's Palsy | Loss of taste in the anterior 2/3rds of the tongue and dry cornea if it involves the cochlear nerve and chorda tympani

Question 31

What are the consequences of laceration of CN VII due to an intracranial haematoma?

Answer 31

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

Question 32

What does CN VIII innervate?

Answer 32

``` Special sensory (balance and hearing) Vestibular apparatus and cochlear of the ear ```

Question 33

How may lesions of CN VIII occur and what are the consequences?

Answer 33

Skull fractures, ear infections, acoustic neuroma Progressive unilateral hearing loss, tinnitus, vertigo Acoustic neuroma often impairs CN VII too

Question 34

What does CN IX innervate?

Answer 34

Sensory to: General and special to posterior 1/3rd of tongue Pharynx, oropharyngeal isthmus, dorsum of palate, auditory tube and related structures, mastoid antrum, mastoid air cells Carotid body and sinus Motor to: Stylopharyngeus Parasympathetic secretomotor to Parotid gland

Question 35

How may nerve lesions in CN IX occur and what are the consequences?

Answer 35

Deep lacerations of the neck | Loss of taste to posterior 1/3rd of tongue

Question 36

What does CN X innervate?

Answer 36

``` Sensory to: lower pharynx and larynx, external auditory meatus and back of auricle Special sensory (taste) to epiglottis ``` Motor to: All muscles of the pharynx except Stylopharyngeus All muscles of the airways, larynx, heart and GI tract All palate muscles except tensor veli palatine

Question 37

What may result in nerve lesions in the neck affecting the recurrent laryngeal branch of the vagus nerve and what are the consequences?

Answer 37

Hoarseness of voice due to paralysis of the vocal fold Due to: bronchial or oesophageal carcinoma Enlarged mediastinal lymph nodes Stretching over an aneurysm of the aortic arch Compression of the left nerve against the aortic arch due to mitral stenosis causing an enlarged left atrium pushing up the left pulmonary artery and compressing the nerve

Question 38

How can the superior laryngeal branch of CN X be damaged?

Answer 38

Thyroidectomy because the external branch lies close to the superior thyroid artery and can be damaged when ligating the blood vessel

Question 39

What does CN XI innervate?

Answer 39

Motor to Cranial compartment: pharynx, larynx and soft palate Spinal compartment (C2-4): trapezius and sternocleidomastoid

Question 40

How can lesions of CN XI occur and what are the consequences?

Answer 40

Surgery or lacerations to the neck | May result in paralysis of sternocleidomastoid and superior fibres of trapezius, shoulder drop

Question 41

What does CN XII innervate?

Answer 41

Motor innervation to all extrinsic and intrinsic muscles of the tongue, except palatoglossus

Question 42

How can lesions of CN XII occur and what are the cutest consequences?

Answer 42

Neck laceration and basal skull fractures | Results in protruded tongue deviating toward the affected side