Cranial Nerve Examination

Question 1

Cranial Nerve l: Olfactory Nerve

1. type: sensory/motor/parasympathetic? [1]
2. function? [1]
3. tract? [3]
4. how to examine? [1]

Answer 1

1. Sensory nerve
2. Smell
3. Olfactory cells of nasal mucosa → olfactory bulbs → pyriform cortex
4. Ask patient if there has been any changes in their sense of smell

Question 2

Cranial Nerve lI: Optic Nerve

1. type: sensory/motor/parasympathetic? [1]
2. function? [1]
3. tract? [4]
4. how to examine? [7]

Answer 2

1. Sensory nerve
2. Vision
3. Retinal ganglion cells → optic chiasm → thalamus → primary visual cortex in occipital lobe
4. Examination:
   
   • Optic discs with ophthalmoscope
   • Pupillary responses
   • Pupillary reflexes
   • Swinging light test
   • Visual acuity (using Snellen chart)
   • Visual fields and blind spot (tested by confrontation)
   • Eye muscles and movement

Question 3

What is the abnormality seen in the following ophthalmoscopic image and what features lead you to this diagnosis? [4]

Answer 3

• Papilloedema
  
  1. haemorrhage
  2. obscuration of blood vessels
  3. blurring of disc margins

Question 4

What is the abnormality seen in the following opthalmascopic image and what features lead you to this diagnosis? [2]

Answer 4

• optic atrophy/neuritis
  
  • pale optic disc

Question 5

What is used to test visual acuity? [1]

Answer 5

Snellen Chart

Question 6

Describe how each eye muscle moves the eye

Answer 6

Question 7

Cranial Nerve III: Oculomotor → the motor component:

1. Nucleus name & location? [2]
2. Functions? [2]
3. Structures innervated? [5]

Answer 7

1. Nucleus:
   
   • oculomotor nucleus
   • found in midbrain
2. Functions:
   
   • movement of eyeball
   • lens accommodation
3. Structures innervated:
   
   • inferior oblique muscle
   • superior rectus muscle
   • medial rectus muscle
   • inferior rectus muscle
   • levator palpebrae superioris muscle

Question 8

Cranial Nerve III: Oculomotor → the parasympathetic component:

1. Nucleus name & location? [2]
2. Function? [1]
3. Structures innervated? [2]

Answer 8

1. Nucleus:
   
   • Edinger-Westphal nucleus
   • found in midbrain
2. Function:
   
   • pupil constriction
3. Structures innervated:
   
   • ciliary muscle
   • pupillary constrictor muscles

Question 9

What is the diagnosis? [1]

Answer 9

Complete left oculomotor nerve palsy

Question 10

Cranial Nerve IV: Trochlear

1. type: sensory/motor/parasympathetic? [1]
2. functions? [2]
3. nucleus location? [2]
4. structure innervated? [1]

Answer 10

1. Motor nerve
2. Functions:
   
   • moves eyeball
   • depresses the adducted eye
   • intorts the abducted eye
3. Nucleus location:
   
   • inferior colliculus of midbrain
4. Structure innervated:
   
   • superior oblique muscle

Question 11

What is unique about cranial nerves II and IV? [1]

Answer 11

II and IV are only nerves to decussate to contralateral side

Question 12

Cranial Nerve VI: Abducens

1. type: sensory/motor/parasympathetic? [1]
2. functions? [1]
3. nucleus location? [1]
4. structure innervated? [1]

Answer 12

1. Motor nerve
2. Function:
   
   • eyeball movement to the side
3. Nucleus:
   
   • pons
4. Structure innervated:
   
   • lateral rectus muscles

Question 13

What is the diagnosis? [1]

Answer 13

left abducens nerve palsy

Question 14

What is internuclear ophthalmoplegia, what does it result from and what condition is it commonly associated with? [3]

Answer 14

1. Disorder of conjugate gaze which presents as failure of adduction of affected eye with nystagmus on lateral gaze in contralateral eye and can be unilateral or bilateral
2. Results from lesion of medial longitudinal fasciculus (connects 3rd and 6th nerve nuclei)
3. Commonly seen in multiple sclerosis

Question 15

Describe Horner’s Syndrome:

1. symptoms? [4]
2. causes? [9]

Answer 15

1. Symptoms:
   
   • Miosis
   • Ptosis
   • Apparent enophthalmos
   • Anhidrosis
2. Causes/Pathogenesis:
   
   • Results from ipsilateral disruption of cervical/thoracic sympathetic chain:
     
     • Congenital
     • Brainstem stroke
     • Cluster headache
     • Apical lung tumour
     • Multiple sclerosis
     • Carotid artery dissection
     • Cervical rib
     • Syringomyelia

Question 16

Cranial Nerve V: Trigeminal → the sensory component:

1. Nucleus locations? [2]
2. Structures innervated? [4]

Answer 16

1. Nucleus:
   
   • pons
   • medulla
2. Structures innervated:
   
   • face → ophthalamic, maxillary + mandibular divisions
   • anterior 2/3rds of tongue

Question 17

Cranial Nerve V: Trigeminal → the motor component:

1. Nucleus location? [1]
2. Function? [1]
3. Structures innervated? [4]

Answer 17

1. Nucleus:
   
   • pons
2. Function:
   
   • mastication
3. Structures innervated:
   
   • masseter
   • temporalis
   • medial pterygoids
   • lateral pterygoids

Question 18

1. What is the diagnosis?
2. What nerve is affected?
3. Who is at increased risk of developing this?
4. How do you treat it?

Answer 18

1. Diagnosis:
   
   • Herpes zoster ophthalmicus
2. What nerve does it affect?
   
   • Affects V1 of trigeminal nerve
3. Who is at increased risk?
   
   • Elderly
   • Immuno-compromised
4. Treatment:
   
   • Oral acyclovir

Question 19

Cranial Nerve VII: Facial → the motor component:

1. Nucleus location? [1]
2. Function? [1]

Answer 19

1. Nucleus:
   
   • pons
2. Function:
   
   • innervates muscle of facial expression

Question 20

Cranial Nerve VII: Facial → the sensory component:

1. Nucleus location? [1]
2. Function? [1]
3. Structures innervated? [1]

Answer 20

1. Nucleus:
   
   • medulla
2. Function:
   
   • taste
3. Structures innervated:
   
   • anterior 2/3rds of tongue

Question 21

Cranial Nerve VII: Facial → the parasympathetic component:

1. Nucleus location? [1]
2. Functions? [2]
3. Structures innervated? [2]

Answer 21

1. Nucleus:
   
   • medulla
2. Function:
   
   • salivation
   • lacrimation
3. Structures innervated:
   
   • salivary glands
   • lacrimal glands

Question 22

How do you distinguish between an upper motor neurone lesion (UMN lesion) and lower motor neurone lesion (LMN lesion)? [2]

Answer 22

1. Upper motor neurone lesions will present as weakness of inferior facial muscles
   
   • The forehead is spared
2. Lower motor neurone lesions will present as weakness of superior and inferior facial muscles
   
   • = Bell’s palsy

Question 23

The Corneal Reflex:

1. how do you test it?
2. what nerves are you testing?
3. what is it a test of?

Answer 23

1. How to test it?
   
   • lightly touch cornea with cotton wool
2. What nerves are you testing?
   
   • afferent: CN V
   • efferent: CN VII
3. What is it a test of?
   
   • test of pontine function

Question 24

Cranial Nerve VIII: Vestibulocochlear

1. type: sensory/motor/parasympathetic? [1]
2. functions? [2]
3. nucleus location? [2]
4. structure innervated and tracts? [4]

Answer 24

1. Sensory nerve
2. Functions:
   
   • hearing
   • balance
3. Nucleus location:
   
   • pons
   • medulla
4. Structure innervated:
   
   • cochlear → auditory cortex in the temporal lobes
   • nerve endings within semi-circular canals → cerebellum and spinal cord

Question 25

**Cranial Nerve IX: Glossopharyngeal →** the **sensory** component: 1. Nucleus location? [1] 2. Functions? [3] 3. Structures innervated? [3]

Answer 25

1. Nucleus: * medulla 2. Functions: * taste * proprioception for swallowing * blood pressure receptors 3. Structures innervated: * posterior 1/3rd of tongue * pharyngeal wall * carotid

Question 26

**Cranial Nerve IX: Glossopharyngeal →** the **motor** component: 1. Nucleus location? [1] 2. Functions? [2] 3. Structures innervated? [2]

Answer 26

1. Nucleus: * medulla 2. Functions: * swallow and gag reflex * lacrimation 3. Structures innervated: * pharyngeal muscles * lacrimal glands

Question 27

**Cranial Nerve IX: Glossopharyngeal →** the **parasympathetic** component: 1. Function? [1] 2. Structure innervated? [1]

Answer 27

1. Function: * saliva production 2. Structure innervated: * salivary glands

Question 28

What is the diagnosis and how do you know? [2]

Answer 28

1. left glossopharyngeal nerve palsy 2. glossopharyngeal palsy causes deviation of uvula **away** from the side of the lesion

Question 29

**Cranial Nerve X: Vagus →** the **sensory** component: 1. Nucleus location? [1] 2. Functions? [3] 3. Structures innervated? [3]

Answer 29

1. Nucleus location: * medulla 2. Function: * chemoreceptors * pain receptors * sensation 3. Structures innervated: * chemoreceptors on carotid bodies → monitoring blood oxygen concentration * pain receptors → respiratory and digestive tract * sensation in external ear, larynx and pharynx

Question 30

**Cranial Nerve X: Vagus →** the **motor** component: 1. Nucleus location? [1] 2. Functions? [4] 3. Structures innervated? [4]

Answer 30

1. Nucleus location: * medulla 2. Functions: * heart rate and stroke volume * peristalsis * air flow * speech and swallowing 3. Structures innervated: * pacemaker and ventricular muscles * smooth muscles of the digestive tract * smooth muscles in bronchial tubes * muscles of larynx and pharynx

Question 31

**Cranial Nerve X: Vagus →** the **parasympathetic** component: 1. Structures innervated? [2]

Answer 31

1. smooth muscles and glands of the same areas innervated by motor component 2. as well as thoracic and abdominal areas

Question 32

**Cranial Nerve XI: Spinal Accessory** 1. type: sensory/motor/parasympathetic? [1] 2. functions? [2] 3. nucleus location? [1] 4. structures innervated? [2] 5. how to test it? [2]

Answer 32

1. Motor nerve 2. Functions: * shoulder shrugging * head rotation 3. Nucleus location: * medulla 4. Structure innervated: * sternocleidomastoid muscle * trapezius muscle 5. How to test CN XI: * Turn your head to the side and resist my hand * Shrug your shoulders up and resist my hand

Question 33

**Cranial Nerve XII: Hypoglossal** 1. type: sensory/motor/parasympathetic? [1] 2. functions? [2] 3. nucleus location? [1] 4. structure innervated? [1]

Answer 33

1. Motor nerve 2. Functions: * speech * swallowing 3. Nucleus location: * medulla 4. Structure innervated: * tongue

Question 34

What is the diagnosis and how do you know? [2]

Answer 34

1. left-sided hypoglossal nerve palsy 2. tongue deviates **towards** the side of the lesion

Question 35

**Multiple Cranial Nerve Syndromes** What cranial nerves would be affected by a lesion in the: 1. cavernous sinus? [5] 2. superior orbital fissue? [4] 3. cerebellopontine angle? [3] 4. jugular foramen? [3] 5. bulbar/pseudobulbar palsy? [4]

Answer 35

1. Cavernous sinus? * III * IV * V (1st and 2nd divisions) * VI * Horner's syndrome 2. Superior orbital fissure? * III * IV * V (1st division) * VI 3. Cerebellopontine angle? * V * VII * VIII 4. Jugular foramen? * IX * X * (and XI) 5. Bulbar/pseudobulbar palsy? * IX * X * XI * (and XII)