4. Cranial Nerves I-VI

Question 1

what are cranial nerves?

Answer 1

Supplying tissues and structures of head and neck region including special sense organs
(Except vagus which supplies other areas too)

Question 2

Which nervous system are cranial nerves part of?

Answer 2

Peripheral

Question 3

Where can cranial nerves be damaged?

Answer 3

Cranial nerve during its route outside the CNS
The brainstem where nuclei are located
The tracts within forebrain which communicate with cranial nerves

Question 4

What are the first 2 cranial nerves?

Answer 4

Extension of the forebrain

Question 5

Where do the cranial nerves arise from?

Answer 5

2 from forebrain
2 from midbrain
4 from pons
4 from medulla

Question 6

What is CN1?

Answer 6

Olfactory nerve

- special sense smell

Question 7

What are the causes for damage to CN1?

Answer 7

Upper respiratory tract infection
Head/facial injury
Anterior cranial fossa tumours

Question 8

Where do CN1 extensions pass through?

Answer 8

Cribiform foramina in ethmoid bone

Question 9

What is CNII?

Answer 9

Optic

- special sense vision

Question 10

How do you test CNII?

Answer 10

Pupillary size and response to light
Visual acuity (Snellen chart) and visual fields
Ophthalmoscopy

Question 11

What are the signs and symptoms of damage to optic nerve?

Answer 11

Blurred vision involving one eye or complete absence of vision in one eye
On clinical examination: abnormalities in pupillary size and reflex, poor visual acuity, pathology involving optic nerve

Question 12

What diseases or conditions can involve the optic nerve?

Answer 12

Optic neuritis
Anterior ischaemic optic neuropathy
Papilloedema due to raised intracranial pressure

Question 13

What is CNIII?

Answer 13

Oculomotor (motor and parasympathetic)

Question 14

What does CNIII innervate?

Answer 14

Extra ocular muscles
Levator palpebrae superioris
Sphincter pupillae (muscle in iris)

Question 15

How do you test for CNIII?

Answer 15

Inspection of resting gaze

Eye movements, pupils and pupillary light reflexes, eyelid position

Question 16

What would be present on examination of CNIII if damaged?

Answer 16

Ptosis
Abnormal position of eye (down and out)
Pupil may or may not be dilated
Double vision

Question 17

What are the causes of a CNIII lesion?

Answer 17

Micro vascular ischaemia: >50 years, diabetes/hypertension
Compressive: aneurysmal posterior communication artery (headache/retroorbital pain), head injury, tentorial herniation secondary to increased ICP

Question 18

Where can CNIII be damaged?

Answer 18

Brainstem
By free edge of tentorium cerebelli
Cavernous sinus

Question 19

What is CNIV?

Answer 19

Trochlear (motor)

Question 20

What does CNIV innervate?

Answer 20

Superior oblique muscle

Question 21

How do you test for CNIV?

Answer 21

Inspection of resting gaze, eye movements

Question 22

What signs or symptoms can you get with CNIV lesion?

Answer 22

Double vision
Abnormal eye position
Head tilt

Question 23

What can cause CNIV lesion?

Answer 23

Congential
Micro vascular ischaemia (diabetes, hypertension)
Trauma
Tumour

Question 24

Where can CNIV be damaged?

Answer 24

Midbrain

Cavernous sinus

Question 25

What is CNVI?

Answer 25

Abducens (motor)

Question 26

What does CNVI innervate?

Answer 26

Lateral rectus

Question 27

How do you test for CNVI?

Answer 27

Inspection of resting gaze, eye movements

Question 28

What can lesion of CNVI present as?

Answer 28

Double vision - worsen in lateral always gaze
Abnormal eye position
Difficulty/unable to move affected eye laterally

Question 29

What can cause a CNVI lesion?

Answer 29

Micro vascular ischaemia (diabetes/hypertension)
Head injury, tumour
Raised ICP

Question 30

Which cranial nerves take a very similar pathway and what is the pathway?

Answer 30

Oculomotor
Trochlear
Abducens
Exit brainstem, pass through cavernous sinus, enter into orbit via superior orbital fissure

Question 31

What is CNV?

Answer 31

Trigeminal (motor and general sensory)

Question 32

Where does the trigeminal nerve generally supply?

Answer 32

Branches have an extensive distribution supplying skin of the face and scalp and deep structures of the face
Muscles of mastication

Question 33

Where does the trigeminal nerve originate?

Answer 33

Pons

Question 34

What are the 3 divisions of the trigeminal nerve?

Answer 34

Ophthalmic
Maxillary
Mandibular

Question 35

How do you test for CNV?

Answer 35

Light touch on dermatomes, muscles of mastication and corneal reflex

Question 36

What will patients with trigeminal nerve lesion present with?

Answer 36

Sensory deficits within the dermatomal regions
Weakness in muscles of mastication
Absent corneal reflex

Question 37

What are some conditions associated with trigeminal nerve lesion?

Answer 37

Trigeminal herpes zosta (shingles) - in subdivisions
Trigeminal neuralgia (compression from blood vessel)
Orbital and mandibular fractures
Posterior cranial fossa tumours

Question 38

Where do subdivisions of trigeminal nerve run through?

Answer 38

Ophthalmic - cavernous sinus, superior orbital fissure
Maxillary - cavernous sinus, foramen rotundum, infra-orbital foramen
Mandibular - foramen ovale

Question 39

What are the distal brands of the ophthalmic division of the trigeminal nerve?

Answer 39

Frontal nerve - gives rise to supraorbital/supratrochlear
Nasociliary nerve
Lacrimal nerve

Question 40

What are the distal branches of the maxillary division of the trigeminal nerve?

Answer 40

Infra-orbital

Superior alveolar nerves

Question 41

What are the distal branches of the mandibular division of the trigeminal nerve?

Answer 41

Auriculotemporal nerve
Lingual nerve (tongue)
Inferior alveolar nerve and mental nerve

Question 42

Which nerve is vulnerable in mandibular fractures?

Answer 42

Inferior alveolar nerve