Cranial Nerves

Question 1

What kind of nerve is the olfactory nerve CN1 and what is its central connection.

Answer 1

The olfactory nerve is a special visceral afferent ( SENSORY) nerve

It’s central connection is with the olfactory bulb

Question 2

Where does CN1 exit the skull?

Answer 2

Olfactory foramina in the cribriform plate

Question 3

What is CN1 function and how do we test it

Answer 3

Function - Sense of smell which come form the receptors cells in the nasal mucosa

To test this - a pungent smell is applied to each nostril ( scratch and sniff cards sometimes used)

Question 4

What type of nerve is the Optic nerve CN2 and what is its central connection

Answer 4

It is a special sensory afferent nerve and its central connection is the thalamus

Question 5

Where does CN2 exit from the skull

Answer 5

Optic canal

Question 6

What is the function of CN2 and how do we test this

Answer 6

Function - vision, from the retina of the eye to the brain

To test this - use a visual acuity test, ASMLER grid to record visual defects/ muscular function

Question 7

Nerve CN3 is the oculomotor nerve, what kind of neuron is this and what is its central connection

Answer 7

CN3 is both general somatic efferent ( motor) as well as general visceral efferent ( parasympathetic motor)

It’s central connection is the midbrain

Question 8

Where does CN3 exit the skull

Answer 8

Superior orbital fissure

Question 9

Since CN3 has both motor and parasympathetic fibres what are the two functions and how can we test these?

Answer 9

General somatic efferent - innervates levator palpebrae, med/inf/sup rectus and inf oblique
- to test this we would use visual filed test = LID LAG

General visceral efferent - innervates sphincter pupillae and ciliary muscles for pupil contraction and accommodation
- to test this we would use direct, consensual light and accommodation relfexes

Question 10

The Throchlear nerve is CN4, name the type of neuron that it is and where its central connection is

Answer 10

It is a general somatic efferent neuron

It’s central connection is the midbrain

Question 11

Where does the trochlear nerve exit the skull

Answer 11

Superior orbital fissure

Question 12

Which nerve functions to innervates the superior oblique muscle and how would this be tested

Answer 12

The Trochlear nerve CN4 and to test this use a visual field test

Question 13

What are the three divisions of the trigeminal nerve, what kind of neuron is each and where do they exit the skull

Where is the central connection

Answer 13

The trigeminal nerve CN5 has three Diviosns

• the ophthalmic division which is a general somatic afferent neuron and exits the skull via the superior orbital fissure
• the maxillary division which is general somatic afferent nerve and it exits the skull at the foramen rotundum
• the mandibular branch is the last division and is a mixed neuron with both general somatic afferent and brachial motor, this exits the skull via the foramen ovale.

There central connection is PONS

Question 14

The trigeminal nerve supplies sensations to the face and innervates the muslces of mastication, what are some ways you can test this nerve

Answer 14

Reaction to touch with eyes closed in each area the divisions supply

CNV1 - corneal reflex

CNV3 - jaw jerk reflex and open jaw against resistance, clench teeth together

Question 15

The facial nerve CN7 contains three different types of neurones, which all have the same central connection and exit from the skull.

Name them

Answer 15

Special visceral afferent

General visceral efferent ( parasympathetic motor)

Special visceral efferent ( branchial motor)

The central connection is the pontomedullary junction and they exit the skull via the internal acoustic meatus > facial canal> stylomastiod foramen.

Question 16

If a nerve is branchial motor what does this mean

Answer 16

Innervate skeletal muscle derived form brachial arches, including the muscles of mastication, facial expression and the palatal, laryngeal, trapezius and sterncleidmastiod muslces

Question 17

What are the branches of the facial nerve

Answer 17

Frontal

Zygomatic

Buccal

Marginal Mandibular

Cervical

Posterior auricular

Question 18

What are the functions of the facial nerve

Answer 18

Special visceral afferent - sensation from auricle and external acoustic meatus. Taste from anteior 2/3 of tongue

General visceral efferent ( parasympathetic motor) - secrete motor for submandibular and sublingual glands( via the submandibular ganglion). Innverates the lacrimal gland and nasal/oral cavity mucosal lining ( via pterygopalatine ganglion)

Special visceral efferent ( branchial Motor) - innervates muslces of facial expression, posteiror belly of diagastric and stylohyoid and stapedius

Question 19

The sensory neuron of the facial nerve is rarely tested, how can you carry out tests for the other two function

Answer 19

General visceral efferent - assessment of dry mouth

Special visceral efferent - raise eyebrows, show teeth, blow out cheeks, close eye against resistance

Question 20

The vestibulocohclear nerve is the 8th cranial nerve, it is a special somatic afferent nerve.

What is its central connection and where does it exit the skull

Answer 20

Central connection is the pontomedullary junction and it exits the skull via internal aucostic meatus

Question 21

What is the function of CN8 ( it has two branches)and how can we test this

Answer 21

Vestibular branch - sensation of equilibrium and balance
- fistula test
Cochlear brach - sensation of hearing
- whispered voice test

Question 22

Name some functions of the glossopharyngeal nerve

Answer 22

Sensory imput from the posterior one 1/3 of the tongue palatine tonsils, oropharynx, mucosa of middle ear

Taste from from the posterior 1/3 of tongue

Sensory information from carotid body

Secretomotor for parotid gland

Innervates stylopharyneus, pharyngeal constrictor. Assists in phonation and swallowing

Question 23

Via what ganglion does CN9 innervate the parotid gland

Answer 23

Otic ganglion

Question 24

What are the functions of the vagus nerve which is a mixed sensory and Motor nerve

Answer 24

Sensory information from larynx, auricle, external acoustic meatus and dura mater of posterior cranial fossa

Special sensory - taste from palate and epiglottis

Information from aortic body, oesphagous, lungs, bronchi, heart and intestines

Innervates thoracic and intraabdominal viscera including all smooth muscle and glands

Innervates laryngeal and pharyngeal muscles ( expect stylopharngeus)

Permits phonation and swallowing

Question 25

What reflex is the vagus nerve responsible for

Answer 25

The gag reflex

Question 26

The glossopharnygeal nerve and the vagus nerve are tested together, how is this carried out

Answer 26

Speech assessment for dysarthria and dysphonia
Patient says ‘ah’ to move palate and uvula

Patient puffs out cheeks with lips closed ( in dysfunction air will escape out of the nose)

Assess strength of cough, swallow test - observe of absent swallow or cough

Question 27

What kind of nerve is the accessory nerve and where is the central connection and the exit from the skull

Answer 27

CN11 is an a general somatic efferent, its central connection is the medullar oblongata and it exits the skull via the jugular foramen

Question 28

What is the function of CN11 and how do u access its function

Answer 28

Innervates the sternocleidmastiod and trapezius muslces and muslces of the soft palate

To test this - shrug shoulders or turn head against resistance on one side

Question 29

The final cranial nerve CN12 is the hypoglossal nerve it is a general somatic efferent nerve.

Where is this nerves central connection and where does it exit the skull

Answer 29

It’s central connection is the medulla oblongata and the exit is the hypoglossal canal

Question 30

What does the CN12 innervate and how do you test this function

Answer 30

Innervates all intrinsic and extrinsic muscles of the tongue .

This is tested by assessing the tongue for wasting/ deviation when push out. Say ‘’ yellow lorry’’ to assess speech

Question 31

What is the one tongue muscle that isn’t innervated by the glossophrnygeal nerve and what nerve is it instead innervated by

Answer 31

The palatoglossal nerve is not innervated byCN9 instead by the vagus nerve

Question 32

A patient comes in complain of loss of pupillary constriction what nerve would be affected here

Answer 32

CN2 the optic nerve

Question 33

Anosmia( loss of smell) ; cerebrospinal fluid rhinorrhea is an abnormal finding from what kind of lesion

Answer 33

Fracture of cribriform plate which has affected CN1

Question 34

A Patient comes in following laceration of the neck. What symptoms would they show and what nerve would be affected

Answer 34

Patient would come in complaining of drooping of shoulder
This would be from paralysis of the sternocleidomastiod and descending fibres.

The accessory nerve would have been affected

Question 35

Your patient comes in complaining that their lower jaw is deviating when they open and that there is loss of pain and touch in face

What nerve has been damaged here?

Answer 35

The trigeminal nerve has been affected in this case

Injury to terminal branches (particularly CNV2) in the roof of the maxillary sinus ; pathological processes affecting trigeminal ganglion.

Question 36

The parotid gland has been lacerated, what will the patient complain of and subsequently which nerve will have been affected?

Answer 36

The patient will have paralysis of the facial muscles, they will say that this eye still remains open yet they cannot wrinkle their forehead

Question 37

Patient has said that their facial muscles are paralysed however they are still able to wrinkle their forehead. Explain what is happening hear with relation to cranial nerves.

Answer 37

The most common cause here is a intracranial hematoma ( a stroke) due to injury of the facial nerve

Question 38

TEST

Answer 38

TET

Question 39

Loss of taste on posterior third of the tongue and loss of sensation of the soft palate on the affected side.

These are symptoms which would be presented if what cranial nerve was affected

Answer 39

Glossopharyngeal CN9

Question 40

Which foramen does the facial nerve pass

Answer 40

Stylomastiod foramen

Question 41

Which foramen of the skull do the 3 divisions of the trigeminal nerve exit via

Answer 41

Ophthalmic - supra orbital fissure
Maxillary - Foramen rotundum
Mandibular - Foramen ovale

Question 42

The foramen spinsosum allows passage of which artery

Answer 42

Middle meningeal artery

Question 43

Which foramen is not present in life as it is filled with cartilage

Answer 43

Foramen lacerum

Question 44

Which pharyngeal arch does the facial nerve embryologically come from

Answer 44

2nd pharyngeal arch

Muslces of facial expression

Question 45

Which pharyngeal arch does the trigeminal nerve arise from

Answer 45

1st pharyngeal arch