Lecture 8 - CN I - V

Question 1

Which 2 cranial nerves arise from the forebrain ?

Answer 1

CN I - Olfactory

CN II - Optic

Question 2

Purely special sensory cranial nerves

Answer 2

CN I- Olfactory
CN II - Optic
CN VIII - Vestibulocochlear

Question 3

Motor cervical nerves

Answer 3

CN III - Occulomotor 
CN IV - Trochlear 
CN VI - Abducens
CN XI - Spinal accessory
CN XII - Hypoglossal

Question 4

Cervical nerves that carry autonomics

Answer 4

CN III - occulomotor
CN VII - facial nerve
CN IX - glossopharyngeal
CN X - vagus

Question 5

Brain stem

Answer 5

Joins the brain to the spinal cord

Regulates cardio- resp function and maintains consciousness

Contains ascending sensory fibres and descending motor fibres

Question 6

What makes up the brainstem?

Answer 6

Midbrain
Pons
Medulla

Question 7

Course of the olfactory nerve

Answer 7

1. Olfactory nerve in the roof of the nasal canal
2. Enters the cribriform plate of the ethmoid bone
3. Olfactory bulbs to olfactory tracts
4. To temporal lobe

Question 8

Function of the olfactory nerve

Answer 8

Olfaction (smell)

Question 9

CN I test

Answer 9

Change in sense of smell

Anosmia - loss of sense of smell

Question 10

Commonest cause of anosmia

Answer 10

URTI (cold)

Question 11

Causes of anosmia

Answer 11

URTI
Head injury - basilar skull fracture
Tumour at base of frontal lobe

Question 12

Route of the optic nerve

Answer 12

1. Retinal ganglion cells at the optic disc have axons that converge into the optic nerve
2. Enters the optic canal
3. Fibres cross at the optic chiasm
4. Optic tracts enter the primary visual cortex in the occipital lobe

Question 13

Sight when there is a lesion in 1 optic nerve?

Answer 13

Only the ipsilateral eye sight is affected

Question 14

Sight when there is a lesion in the optic chiasm

Answer 14

Sight in both eyes are affected

Question 15

What can pituitary tumours course?

Answer 15

Compression on the optic chiasm

• Bitemporal hemianopia

Question 16

CN II tests

Answer 16

Visual acuity test - Snellen test
Visual field test
Pupillary light response
Optic disc visualised by a opthalmoscope

Question 17

CN II function

Answer 17

Sight

Afferents of the pupillary light response

Question 18

Papillodema

Answer 18

Swollen optic disc

Question 19

Photophobia

Answer 19

The optic nerve carries extensions of the meninges

Raised intracranial pressure can cause disruption to the nerve causing photophobia - trait of meningism

Question 20

Communication of the optic nerve with the midbrain

Answer 20

Communication from the optic tract with the brainstem midbrain to allow the pupillary reflex to light

• Occulomotor nerve is stimulated to constrict the pupil

Question 21

Route of the occulomotor nerve

Answer 21

1. Midbrain
2. Lateral wall of the cavernous sinus
3. Superior orbital fissure
4. To the extra-ocular muscles except the superior oblique and lateral rectus muscles, levator palbebrae superioris

Question 22

Muscles that CN III control

Answer 22

Superior rectus
Inferior rectus
Medial rectus
Inferior oblique

Levator palpebrae superioris

Parasympathetic innervation to the sphincter pupillae muscle

Question 23

CN III role

Answer 23

Eye movements
Raise eyelids
Constrict the pupil

Efferent limb of the pupillary light response

Question 24

Why is the occulomotor nerve vulnerable to compression

Answer 24

During raised intracranial pressure, the uncus can herniate and compress the nerve.

Between the tentorium cerebelli and uncus

Question 25

What can happen in CN III external compression

Answer 25

Pupil dilation as the parasympathetic fibres are on the periphery of the nerve that innervate the sphincter pupillae

Question 26

CNIII tests

Answer 26

Eye movements - follow finger Inspect eyelids and pupil size Pupillary light reflex

Question 27

Presentation of CNIII lesion

Answer 27

Eye in down and out position Pupil dilation Complete ptosis Diplopia

Question 28

Causes of CN III injury

Answer 28

``` External compression: Raised intracranial pressure: -tumour -haemorrhage Aneurysm Cavernous sinus thrombosis ``` Internal compression: Vascular secondary to: - diabetes - hypertension (pupil sparring)

Question 29

Route of the trochlear nerve

Answer 29

1. Mid brain 2. Through the lateral wall of the cavernous sinus 3. Through the superior orbital fissure 4. To the superior oblique extraocular muscle

Question 30

Role of CN IV

Answer 30

Eye movement - superior oblique muscle

Question 31

CN IV test

Answer 31

Eye movement test - follow finger

Question 32

Why is the trochlear nerve most susceptible to damage

Answer 32

Arises from the dorsal aspect of the brain stem and hooks around therefore has a long intracranial course

Question 33

Presentation of CN IV lesion

Answer 33

Up and in eye position | Diplopia

Question 34

3 branches of the trigeminal nerve

Answer 34

Opthalmic Maxillary Mandibular

Question 35

Role of the trigeminal nerve

Answer 35

``` General sensation to the: - face - part of scalp - paranasal air sinuses - nasal cavity - oral cavity - anterior 2/3rds of tongue meninges ``` Motor innervation to the muscles of mastication

Question 36

Opthalmic general sensory structures

Answer 36

Forehead Upper eyelid Medial nose

Question 37

Maxillary general sensory structures

Answer 37

Cheek Lower eye lid Lateral nose

Question 38

Mandibular general sensory structures

Answer 38

Lower lip Jaw and chin Lateral head and ear

Question 39

Route of Va

Answer 39

1. Pons 2. Trigeminal ganglion 3. Va through the superior orbital fissure 4. To orbit

Question 40

Route of Vb

Answer 40

1. Pons 2. Trigeminal ganglion 3. Vb through foramen rotundum 4. To the pterygopalatine fossa

Question 41

Route of Vc

Answer 41

1. Pons 2. Trigeminal ganglion 3. Vc through the foramen ovale 4. To the infratemporal fossa

Question 42

Which branch of the trigeminal nerve supplies motor innervation to the muscles of mastication?

Answer 42

Vc - Mandibular

Question 43

CN V test

Answer 43

Sensation in dermatomal areas of Va, b and c Check the function of the muscles of mastication Check the corneal reflex - blinking (afferent limb)

Question 44

Conditions involving the trigeminal nerve

Answer 44

Trigeminal neuralgia Shingles - sight threatening with vesicle scars Orbital/facial trauma - can affect the inferior orbital and superior alveolar nerve

Question 45

Branches of the opthalmic nerve

Answer 45

``` Frontal nerve: - Supraorbital - Supratrochlear Lacrimal nerve Nasociliary ```

Question 46

Branches of the maxillary nerve

Answer 46

Infraorbital nerve - cheek and lower eyelid Superior alveolar nerve - upper lip, teeth and gums (nerve blocker used by dentists)

Question 47

Branches of the mandibular nerve

Answer 47

Inferior alveolar nerve - Lower lip, teeth and gums (continues as the mental nerve) - Auricotemporal - ear, temples and TMJ - Lingual - anterior 2/3rds of the tongue

Question 48

Which nerve is susceptible to damage in a mandibular fracture

Answer 48

Inferior alveolar nerve