Cranial Nerves

Question 1

What is the pathway of the olfactory nerve?

Answer 1

Receptors in olfactory epithelium, fibres pass through foraminifera in cribriform plate of ethmoid bone and enter olfactory bulb in anterior cranial fossa

Question 2

What are the components of the olfactory nerve?

Answer 2

Special sensory - smell

Question 3

What are clinical applications of the olfactory nerve?

Answer 3

Fractured cribriform plate may tear olfactory nerve fibres causing anosmia

Question 4

What is the pathway of the optic nerve?

Answer 4

Enters via optic canal, nerves join to form optic chiasm

Fibres from medial half of each retina cross to form optic tract

Question 5

What are the components of the optic nerve?

Answer 5

Special sensory - vision

Question 6

What are the clinical applications of the optic nerve?

Answer 6

Increase in CSF pressure can cause papilloedema
Section of right optic nerve causes blindness through right eye
Section of optic chiasm causes loss of peripheral vision
Section of right optic tract causes blindness in left temporal and right nasal fields

Question 7

What is the pathway of the oculomotor nerve?

Answer 7

Emerges from midbrain and exits via superior orbital fissure

Question 8

What are the components of the oculomotor nerve?

Answer 8

Somatic motor - extraocular muscles

Visceral motor - parasympathetic to pupil causing constriction and to ciliary muscle causing accommodation of lens

Question 9

What are the clinical applications of the oculomotor nerve?

Answer 9

Drooping of upper eyelid (ptosis)
Eyeball abducted and pointing down
No pupillary reflex
No accommodation of lens

Question 10

What is the pathway of the trochlear nerve?

Answer 10

Emerges from dorsal surface of mid brain and exits via superior orbital fissure

Question 11

What are the components of the trochlear nerve?

Answer 11

Somatic motor - superior oblique muscle

Question 12

What are the clinical applications of the trochlear nerve?

Answer 12

Diplopia when looking down

Question 13

What is the pathway of the opthalmic branch of the trigeminal nerve?

Answer 13

Emerges from pons, travels through trigeminal ganglion and exits via superior orbital fissure

Question 14

What are the components of the opthalmic branch of the trigeminal nerve?

Answer 14

General sensory - from cornea, forehead, scalp, eyelids, nose and mucosa of nasal cavity and sinuses

Question 15

What are the clinical applications of the opthalmic branch of the trigeminal nerve?

Answer 15

Loss of corneal or sneezing reflex

Trigeminal neuralgia - gentle touch becomes painful or there is constant pain

Question 16

What is the pathway of the maxillary branch of the trigeminal nerve?

Answer 16

Emerges from the pons, travels through trigeminal ganglion and exits via foramen rotunda

Question 17

What are the components of the maxillary branch of the trigeminal nerve?

Answer 17

General sensory - from face over maxilla, maxillary teeth, TMJ, mucosa of nose, maxillary sinus and palate

Question 18

What are the clinical applications of the maxillary branch of trigeminal nerve?

Answer 18

Loss of sensation in face

Trigeminal neuralgia

Question 19

What is the pathway of the mandibular branch of the trigeminal nerve?

Answer 19

Emerges from pons, travels through trigeminal ganglion and exits via foramen ovale

Question 20

What are the components of the mandibular branch of the trigeminal nerve?

Answer 20

General sensory - from face over mandible, mandibular teeth, TMJ joint, mucosa of mouth and 2/3rds of tongue
Somatic motor - muscles of mastication, part of digastric, tensor veil palatine and tensor tympani

Question 21

What are the clinical applications of the mandibular branch of the trigeminal nerve?

Answer 21

Paralysis of muscles of mastication

Trigeminal neuralgia

Question 22

What is the pathway of the abducens nerve?

Answer 22

Emerges between pons and medulla and exits via superior orbital fissure

Question 23

What are the components of the abducens nerve?

Answer 23

Somatic motor - lateral rectus muscle

Question 24

What are the clinical applications of the abducens nerve?

Answer 24

Medial deviation of affected eye causing diplopia

Question 25

What is the pathway of the facial nerve?

Answer 25

Emerges between pons and medulla and exits via internal acoustic meatus, facial canal and stylomastoid foramen

Question 26

What are the components of the facial nerve?

Answer 26

Somatic motor - muscles of facial expression and scalp, stapedius of middle ear, part of digastric muscle Visceral motor - parasympathetic innervation of submandibular and sublingual salivary glands, lacrimal glands, glands of nose and palate Special sensory - taste from anterior 2/3rds of tongue and soft palate General sensory - external acoustic meatus

Question 27

What are the clinical applications of the facial nerve?

Answer 27

Most frequently injured due to long pathway through bone | Bells palsy - can't frown, close eyelid or bare teeth

Question 28

What is the pathway of the vestibulocochlear nerve?

Answer 28

Emerges from between pons and medulla and exits via internal acoustic meatus

Question 29

What are the components of the vestibulocochlear nerve?

Answer 29

Special sensory - vestibular sensation from semicircular ducts, utricle, saccule gives sense of position and movement Hearing from spiral organ

Question 30

What are the clinical applications of the vestibulocochlear nerve?

Answer 30

Tinnitus Deafness Vertigo Nystagmus

Question 31

What is the pathway of the glossopharyngeal nerve?

Answer 31

Emerges from medulla and exits via jugular foramen

Question 32

What are the components of the glossopharyngeal nerve?

Answer 32

Special sensory - taste from posterior 1/3rd of tongue General sensory - cutaneous sensation from middle ear and posterior oral cavity Visceral sensory - sensation from carotid body & carotid sinus Visceral motor - parasympathetic innervation of parotid gland Somatic motor - to stylopharyngess, helps with swallowing

Question 33

What are the clinical applications of the glossopharyngeal nerve?

Answer 33

Loss of gag reflex | Associated with injuries to CNs X and XI - jugular foramen syndrome

Question 34

What is the pathway of the vagus nerve?

Answer 34

Emerges from medulla and exits via jugular foramen

Question 35

What are the components of the vagus nerve?

Answer 35

Special sensory - taste from epiglottis and palate General sensory - sensation from auricle, external acoustic meatus Visceral sensory - pharynx, larynx, trachea, bronchi, heart, oesophagus, stomach Visceral motor - parasympathetic innervation muscle in bronchi, gut, heart Somatic motor - pharynx, palate and oesopahgus

Question 36

What are the clinical applications of the vagus nerve?

Answer 36

Damage to pharyngeal branches cause difficulty in swallowing Damage to laryngeal branches causes difficulty in speaking Prominent notice of damage is to somatic motor component

Question 37

What is the pathway of the accessory nerve?

Answer 37

Small cranial and large spinal roots exit via jugular foramen

Question 38

What are the components of the accessory nerve?

Answer 38

Somatic motor - striated muscle of soft palate, pharynx and larynx and to sternocleidomastoid and trapezius

Question 39

What are the clinical applications of the accessory nerve?

Answer 39

Weakness in turning head and shrugging shoulders

Question 40

What is the pathway of the hypoglossal nerve?

Answer 40

Emerges from medulla and exits through the hypoglossal canal

Question 41

What are the components of the hypoglossal nerve?

Answer 41

Somatic motor - to muscles of tongue

Question 42

What are the clinical applications of the hypoglossal nerve?

Answer 42

Vulnerable to damage during tonsillectomy | Causes paralysis and atrophy of ipsilateral half of tongue - tip deviates towards affected side