8. The Trigeminal and Facial Nerves

Question 1

What gives cranial nerves their name?

Answer 1

Emerge through foramina or fissures in the cranium and are covered by tubular sheathes derived from cranial meninges.

Question 2

What are the roles of the trigeminal nerve CN V?

Answer 2

Sensation for head, motor.

Question 3

What are the branches of the trigeminal nerve?

Answer 3

CN V1 - opthalmic
CN V2 - maxillary
CN V3 - mandibula

Question 4

Where does the trigeminal nerve arise from?

Answer 4

The lateral aspect of the pons by a large sensory root and small motor root. Ganglion sits in dural recess (trigeminal cave, lateral to cavernous sinus).

Question 5

What is the course of the opthalmic nerve (CN V1)?

Answer 5

Exits skull through superior orbital fissure.

Question 6

What is the role of the opthalmic nerve (CN V1)?

Answer 6

Sensory to: cornea, upper conjunctiva, nasal cavity, frontal sinus, ethmoid sinus, external nose, upper eyelids, forehead and scalp.

Question 7

How is the opthalmic nerve CN V1 tested?

Answer 7

Corneal reflex.

Question 8

What are the three branches of the CN V1 opthalmic nerve?

Answer 8

Frontal, nasociliary, lacrimal (-> lacrimal gland, conjunctiva, post ganglionic parasympathetic fibres to lacrimal).

Question 9

What is the route of the maxillary nerve CN V2?

Answer 9

Exits skull through foramen rotundum.

Question 10

What is the role of the maxillary nerve CN V2?

Answer 10

Sensory to: conjunctiva, posteroinferior, lateral external nose, maxillary sinus, superior palate, inferior eye lid, upper lip.

Question 11

How many terminal branches does the maxillary nerve CN V2 have?

Answer 11

14.

Question 12

What is the route of the mandibular nerve CN V3?

Answer 12

Exits skull through the foramen ovale.

Question 13

What are the roles of the mandibular nerve CN V3?

Answer 13

Sensory to: mucous membranes, lower lip, chin, external ear, anterior two thirds of tongue.
Motor to: masseter, temporalis, medial and lateral pterygoids, mylohyoid, digastric, tensor tympani, tensor vele palatini.

Question 14

What parasympathetic ganglia are associated with mandibular nerve CN V3?

Answer 14

Submandibular ganglion - submandibular salivary gland, sublingual salivary gland.
Otic ganglino - parotid salivary gland.

Question 15

Where does the facial nerve CN VII exit the skull?

Answer 15

Through the stylomastoid foramen.

Question 16

What are the functions of the facial nerve CN VII?

Answer 16

Motor to: muscles of facial expression, digastric, stylohyoid, stapedius.
Sensory to: general to small area of skin close to external acoustic meatus; special sensory taste to corda tympani from lingual nerve to anterior 2/3 of tongue.
Parasympathetic: pterygopalatine parasympathetic ganglion -> lacrimal gland, submandibular gland, sublingual gland.

Question 17

What is the course of the facial nerve?

Answer 17

Motor cortex -> pons -> internal acoustic meatus within petrous temporal bone -> facial canal within temporal bone, gives rise to great petrosal nerve, nerve to stapedius, chorsa tympani nerve -> stylomastoid foramen to exit temproal bone and give rise to posterior auricular branch -> branches to face and neck through parotid gland.

Question 18

What are the branches of the facial nerve?

Answer 18

Ten sulus buggered my cat.

Temporal, zygomatic, buccal, narginal mandibular, cervical.

Question 19

What does the temporal nerve innervate?

Answer 19

Occipitofrontalis and orbicularis oculi (superior).

Question 20

What does the zygomatic nerve innervate?

Answer 20

Orbicularis oculi (inferior).

Question 21

What does the buccal nerve innervate?

Answer 21

Orbicularis oris, buccinator, zygomaticus.

Question 22

What does the marginal mandicular nerve innervate?

Answer 22

Mentalis.

Question 23

What does the cervical nerve innervate?

Answer 23

Platysma.

Question 24

How is the facial nerve examined?

Answer 24

Observation for symmetry, ask about changes, examination of facial muscles.

Question 25

How are the facial muscle examined?

Answer 25

Occipitofrontalis - raise eyebrows against resistance.
Orbicularis oculi - scrunch up eyes against resistance.
Buccinator - puff out cheeks against resistance.
Levator labii superioris.
Depressor labii inferioris - show teeth against resistance.

Question 26

What are non-traumatic causes of facial nerve palsy?

Answer 26

Inflammation, infection (viral Herpes, parotitis from S. aureus), compression by parotid tumour.

Question 27

What are traumatic causes of facial nerve palsy?

Answer 27

Fractures of temporal bone, stabbing, gunshots, childbirth.

Question 28

What are iatrogenic causes of facial nerve palsy?

Answer 28

Surgery - parotidectomy.

Question 29

How is Bell’s palsy distinguished from stroke?

Answer 29

Bell’s - all muscles of facial expression paralysed.

Stroke - frontal sparing, occipitofrontalis and orbicularis oculi not paralysed due to bilateral innervation.