6) Cranial Nerves

Question 1

How many cranial nerves are there?

Are they part of the CNS or PNS?

Answer 1

12

Part of peripheral nervous system

Question 2

What are the 3 parts of the brainstem?

Answer 2

Mid-brain, pons and medulla oblongata

Question 3

What is the role of the brainstem?

Answer 3

Regulation of cardio-respiratory functions and maintaining consciousness

Question 4

What is cranial nerve I?

Answer 4

Olfactory nerve

Question 5

What is the function of CN I?

Answer 5

Sense of smell

Question 6

How would you test CN I?

Answer 6

Test one nostril at a time using smelling salts

Question 7

What can damage to the olfactory nerve result in?

Answer 7

Anosmia (loss of sense of smell)

Question 8

What are the causes of anosmia?

Answer 8

URTI
Head injury e.g. basilar skull fracture
Neurodegenerative conditions e.g. Parkinson’s and Alzheimer’s

Question 9

Describe the route of CN I:

Answer 9

Through foramina of cribriform plate onto olfactory mucosa in roof of nose

Question 10

What is cranial nerve II?

Answer 10

Optic nerve

Question 11

What is the function of CN II?

Answer 11

Vision

Question 12

How would you test CN II?

Answer 12

Test one eye at a time 
Visual tests (acuity and fields) and puplis

Question 13

Describe the route of CN II:

Answer 13

Crossover at optic chiasm, through optic canal to retina

Question 14

What visual problems can a pituitary adenoma cause and why?

Answer 14

Bilateral visual problems due to compression of optic chiasm

Question 15

Which cranial nerves arise from the forebrain?

Answer 15

Olfactory and optic nerves

Question 16

What is cranial nerve III?

Answer 16

Oculomotor nerve

Question 17

What are the functions of CN III?

Answer 17

Innervate extra-ocular nerves (4/6)

PSNS to pupil causes constriction

Question 18

How would you test CN III?

Answer 18

Eye movements

Pupillary light reflexes

Question 19

Describe the route of CN III:

Answer 19

Through cavernous sinus and superior orbital fissure into orbit

Question 20

How does damage to the oculomotor nerve present?

Answer 20

Diplopia (double vision) and eye is in down and out position (blown pupil)
Due to damage to PSNS before cranial nerve

Question 21

What are the causes of oculomotor nerve lesions?

Answer 21

Raised intracranial pressure
Aneurysms
Cavernous sinus thrombosis
Diabetes/hypertension (pupil sparing)

Question 22

What is cranial nerve IV?

Answer 22

Trochlear nerve

Question 23

What is the function of CN IV?

Answer 23

Innervation of extra-ocular muscle - superior oblique

Question 24

How would you test CN IV?

Answer 24

Patient follows finger and reports double vision

Question 25

Describe the route of CN IV:

Answer 25

Arises from dorsal aspect of brainstem and travels through cavernous sinus and superior orbital fissure

Question 26

How does damage to the trochlear nerve present?

Answer 26

Diplopia, worse on downward gaze

Question 27

What are the causes of trochlear nerve lesions?

Answer 27

Head injury Raise ICP, stretching nerve Congenital palsies

Question 28

What is cranial nerve V?

Answer 28

Trigeminal nerve

Question 29

What are the functions of CN V?

Answer 29

Innervate muscles of mastication | Main sensory to face

Question 30

How would you test CN V?

Answer 30

Sensation to face Muscles of mastication Corneal reflex

Question 31

Describe the route of CN V:

Answer 31

V1 ophthalmic - superior orbital fissure V2 maxillary - foramen rotundum V3 mandibular - foramen ovale

Question 32

What can cause trigeminal nerve lesions?

Answer 32

Trigeminal neuralgia | Shingles

Question 33

How does damage to the trigeminal nerve present?

Answer 33

Absent corneal reflex Absent sensation Weakness/wasting of muscles of mastication

Question 34

What nerves can be damaged through facial trauma? | Hint: from trigeminal nerve

Answer 34

Intra-orbital (V2) and mental (V3) | Travel superficially

Question 35

What is cranial nerve VI?

Answer 35

Abducens nerve

Question 36

What is the function of CN VI?

Answer 36

Innervation of extra-ocular muscle - lateral rectus

Question 37

How would you test CN VI?

Answer 37

Patient follows finger and reports double vision

Question 38

Describe the route of CN VI:

Answer 38

Through cavernous sinus and superior orbital fissure into orbit

Question 39

What can cause damage to abducens nerve?

Answer 39

Nerve can be easily stretched in raised ICP due to running under surface of pons

Question 40

How does damage to abducens nerve present?

Answer 40

Diplopia | Eye can't be abducted past midline

Question 41

What nerves arise from the midbrain?

Answer 41

Oculomotor and trochlear nerves

Question 42

What nerves arise from the pons?

Answer 42

Trigeminal, abducens, facial and vestibulocochlear nerves

Question 43

What nerves arise from the medulla oblongata?

Answer 43

Glossopharyngeal, vagus, spinal accessory and hypoglossal nerves

Question 44

What is cranial nerve VII?

Answer 44

Facial nerve

Question 45

What are the functions of CN VII?

Answer 45

Muscles of facial expression Anterior 2/3rd of tongue (taste) PSNS to lacrimal and salivary glands

Question 46

How would you test CN VII?

Answer 46

Muscles of facial expression

Question 47

Describe the route of CN VII:

Answer 47

Through petrous part of temporal bone via internal acoustic meatus, gives off branches and travels through stylomastoid foramen to give off terminal branches

Question 48

What can cause damage to facial nerve and how does it present?

Answer 48

Bell's palsy Parotid tumours Ipsilateral paralysis of muscles

Question 49

What is cranial nerve VIII?

Answer 49

Vestibulocochlear nerve

Question 50

What are the functions of CN VIII?

Answer 50

Hearing and balance

Question 51

How would you test CN VIII?

Answer 51

Hearing test | Rinne's and Weber's test

Question 52

Describe the route of CN VIII:

Answer 52

Through internal acoustic meatus and terminates in ear

Question 53

What is an acoustic neuroma?

Answer 53

Benign tumour growing on nerve

Question 54

How does damage to vestibulocochlear nerve present?

Answer 54

Hearing loss | Vertigo/tinnitus

Question 55

What is cranial nerve IX?

Answer 55

Glossopharyngeal nerve

Question 56

What are the functions of CN IX?

Answer 56

Sensation or soft palate, tonsils and oropharynx Taste and sensation of posterior 1/3rd of tongue Sensory from carotid body and sinus Autonomic to parotid gland Innervates stylopharyngeus

Question 57

How would you test CN IX?

Answer 57

Gag reflex

Question 58

Describe the route of CN IX:

Answer 58

Through jugular foramen

Question 59

What is cranial nerve X?

Answer 59

Vagus nerve

Question 60

What are the functions of CN X?

Answer 60

Sensory to laryngopharynx and larynx Innervates muscles of soft palate, pharynx and larynx PSNS to thoracic and abdominal viscera

Question 61

How does damage to the vagus nerve present?

Answer 61

Deviation of uvula when soft palate is elevated (say Aaah) | Recurrent laryngeal branch - hoarseness and dysphonia

Question 62

What is cranial nerve XI?

Answer 62

Spinal accessory nerve

Question 63

What are the functions of CN XI?

Answer 63

Innervate SCM and trapezius

Question 64

How would you test CN XI?

Answer 64

Shrug shoulder | Turn head against resistance

Question 65

Describe the route of CN XI:

Answer 65

Through jugular foramen

Question 66

What anatomical area does the spinal accessory nerve run through and how can it be damaged?

Answer 66

Posterior triangle | Lymph node biopsies and stab wounds

Question 67

What is cranial nerve XII?

Answer 67

Hypoglossal nerve

Question 68

What are the functions of CN XII?

Answer 68

Innervate muscles of the tongue

Question 69

How would you test CN XII?

Answer 69

Inspection and movement of the tongue

Question 70

Describe the route of CN XII:

Answer 70

Through hypoglossal canal

Question 71

How does damage to the hypoglossal nerve present?

Answer 71

Weakness and atrophy of the tongue muscles on same side