Session 4 - Cranial nerves

Question 1

What are the two mnemoics for cranial nerves?

Answer 1

Oh Oh Oh To Touch And Feel Very Girly Vaginas So Heavenly

Some Say Marry Money
But My Brother Says Big Boobs Matter Most

Question 2

Name the 12 cranial nerves

Answer 2

Olfactory - Sensory
Optic - Sensory
Oculomotor - Motor
Trochlear - Motor
Trigeminal - Both
Abducent - Motor
Facial - Both
Vestibulocochlear - Sensory
Glossopharyngeal - Both 
Vagus - Both 
Spinal accessory - Motor
Hypoglossal - motor

Question 3

Name and outline the sensory function of the CN I?

Answer 3

Olfactory nerve

Smell

Question 4

What pathology can be involved with the olfactory nerve?

Answer 4

Fracture of the cribiform plate associated with leakage of CSF from nose (rhinorrhea) and anosmia

Question 5

Name and outline the sensory function of the cranial nerve II

Answer 5

Optic nerve

Sight

Question 6

Outline the pathology of the optic nerve

Answer 6

Can be damaged due to
- Direct trauma to eye, orbit or optical canal
- Pressure on optic pathway
Causes a loss of pupillary constriction and visual field defects

Question 7

Name and outline the motor function of CN III

Answer 7

Oculomotor
Innervates
- Extraocular muscle
- Ciliary muscles
- Sphincter pupillae

Question 8

Outline pathology of the oculomotor nerve

Answer 8

Fracture of cavernous sinus or anurysm

Causes - Dilated pupils, ptosis, eyes turned down and out, loss of pupillary reflex on affected side

Question 9

Name and outline motor innervation of CN IV

Answer 9

Trochlear

Innervates the superior oblique of the eye

Question 10

Name a pathology of the trochlear nerve

Answer 10

Stretching of the nerve during its course around the brainstem OR orbit fractures
Causes inability to look down when eye adducted

Question 11

Name CN V and its three branches

Answer 11

Trigeminal nerve
Opthalmic
Maxillary
Mandibular

Question 12

What does the opthalmic branch do?

Answer 12

Sensory for skin and cornea

Question 13

How can the opthalmic branch be tested?

Answer 13

Corneal reflex (poking sclera)

Question 14

What does the maxillary branch innervate?

Answer 14

Skin, mucous membrane of nose, palate and upper dental arcade

Question 15

What does the mandibular branch do?

Answer 15

Sensory - Skin, lower teeeth, cheek and anterior 2/3rd of toung
Motor - Innervates muscles of mastication

Question 16

What do lesions of trigeminal nerve lead to?

Answer 16

Paralysis of muscles and sharp, intense facial pain

Question 17

What is CN VI? What is its motor function?

Answer 17

Abducens

Motor - Innervates the lateral rectus muscle

Question 18

What occurs in pathology of abducens?

Answer 18

Fractures involving cavernous sinus or orbit

Eye fails to move laterally, diplopia on lateral gaze

Question 19

What is cranial nerve VII and what are its sensory and motor functions?

Answer 19

Facial nerve
Sensory
Taste - Anterior 2/3 tongue 
Supplies part of external acoustic meatus and auricle
Motor
Muscles of facial expression 
Submandibular and sublingual glands
Nasal mucosa, paranasal sinuses and lacrimal gland

Question 20

Name three ways in which facial nerve can be injured

Answer 20

Laceration in parotid region
Fracture of temporal bone
Intracranial haematoma

Question 21

What symptoms are there in laceration of in parotid region facial nerve damage?

Answer 21

 Paralysis of facial muscles, eye remains open, angle of mouth droops, forehead does not wrinkle
(Bell’s palsy)

Question 22

What occurs in fracture of temporal bone injury to facial nerve?

Answer 22

Bell’s palsy

Involvement of cochlear nerve and chroda tympani - Dry cornea, loss of taste in anterior 2/3rds of tounge

Question 23

What are the symptoms of facial nerve damage due to intracranial haematoma?

Answer 23

 Forehead wrinkles because of bilateral innervation of frontalis muscle
 Paralysis of contralateral facial muscles

Question 24

What is bell’s palsy?

Answer 24

Form of facial paralysis resulting from dysfunction of facial nerve. Most common mononeurpathy. Inflammatory condition leads to swelling of facial nerve, especially in narrow bone canal beneath ear.
Eye on affected side cannot be closed, which leads to dry cornea and there may be a loss of taste in anterior 2/3 tongue.

Question 25

What three pathologies must be excluded before a diagnosis of bell's palsy can be made?

Answer 25

Stroke Lyme disease Herpes zoster virus

Question 26

How is Bell's palsy treated?

Answer 26

Corticosteroids

Question 27

What is CN VIII and what are its main functions?

Answer 27

Vestibulocochlear nerve Vestibulo branch - controls balance Cochlear branch - Hearing

Question 28

What are some possible pathologies of the vestibulocochlear nerve and their symptoms?

Answer 28

o Skull fractures, ear infections, tumour of the nerve (acoustic neuroma) may all cause nerve lesions  Progressive, unilateral hearing loss, tinnitus, vertigo  Acoustic neuroma frequently impairs Facial Nerve (CN VII) too

Question 29

What is CN IX and what are its sensory and motor functions?

Answer 29

``` Glossopharyngeal nerve Sensory - Taste to posterior 1/3rd of tongue General sensory widely distributed to the pharynx, oropharyngeal isthmus, dorsum of palate, auditory tube - CAROTID BODY AND SINUS ``` Motor - Innervates stylopharngeus - PAROTID

Question 30

How can the glossopharngeal nerve be damaged?

Answer 30

Loss of taste to posterior 1/3rd tongue

Question 31

What is CN X and what are its sensory and motor function?

Answer 31

Vagus nerve Sensory  General Sensory lower pharynx and larynx, external auditory meatus and back of auricle  Special Sensory (taste) to epiglottis Motor  Innervates all muscles of the pharynx, except Stylopharyngeus  Innervates muscles of airways, larynx, heart and GI tract  Innervates all of the palate muscles, except tensor veli palatine

Question 32

How can pathology of vagus nerve cause hoarseness of voice?

Answer 32

 Hoarseness of voice due to paralysis of vocal fold o Left recurrent laryngeal nerve is lower than the right o Bronchial or oesophageal carcinoma o Enlarged mediastinal lymph nodes o Stretched over an aneurysm of the aortic arch

Question 33

How can mitral stenosis cause hoarseness of voice?

Answer 33

o Mitral stenosis  Enlarged LA  Pushed up left pulmonary artery, compressing the left recurrent laryngeal nerve against the aortic arch

Question 34

How can a thyroidectomy cause damage to superior laryngeal nerve?

Answer 34

 External branch lies close to superior thyroid artery and may be damaged when ligating the blood vessel

Question 35

What is CN XI? What are its motor functions?

Answer 35

Accessory nerve Innervates pharync, larynx and soft palate Trapezius and SCM

Question 36

What can cause lesions of accesory nerve?

Answer 36

Surgery or lacerations to the neck can cause parlysis of SCM and superior trapezius and shoulder drop

Question 37

What is CN XII and what are its motor functions?

Answer 37

Innervates extrinsic and intrinsic muscles of the tounge, except for palatoglossus

Question 38

How can hypoglossal nerve be damaged?

Answer 38

Neck lacerations and basal skull fractures | Protruded tongue will deviate towards affected side due to arrangement of muscles

Question 39

What are the muscles of facial expression?

Answer 39

Three groups Orbital Group - Obicularis Oculi - Corrugator supercilli Nasal group Oral Group - Orbicularis Oris - Buccinator - risorius, zygomaticus major, zygomaticus minor, levator labii superioris, levator labii superioris alaeque nasi and levator anguli oris

Question 40

Danger of facila nerve damage in terms of orbital group

Answer 40

The eye cannot shut - this can cause the cornea to dry out. This is known as exposure keratitis. The lower eyelid droops, called ectropion. Lacrimal fluid pools in the lower eyelid, and cannot be spread across the surface of the eye. This can result in a failure to remove debris, and ulceration of the corneal surface.`