Review of Cranial Nerves

Question 1

What is neuropathy vs neuritis vs neuralgia vs palsy?

Answer 1

Neuropathy - damage to a nerve
Neuritis - inflammation of a nerve
Neuralgia - pain along a nerve
Palsy - paralysis of a nerve

Question 2

What is the geniculate ganglion?

Answer 2

The sensory ganglion for CN7

Question 3

What is the trigeminal ganglion?

Answer 3

The sensory ganglion for CN5

Question 4

What is the spiral ganglion?

Answer 4

The sensory ganglion for the cochlea (CN8)

Question 5

What is the vestibular ganglion?

Answer 5

The sensory ganglion for the semicircular ducts (CN8)

Question 6

What are the rostral and petrosal ganglia? Where are they located?

Answer 6

Superior and inferior sensory ganglia of CN9. Both located in brain before CN9 leaves jugular foramen

Question 7

What are the jugular and nodose ganglia?

Answer 7

Superior and inferior sensory ganglion of CN10. Superior is in jugular foramen, nodose ganglion is just behind pharynx inferior to styloid process

Question 8

What is somatic vs visceral?

Answer 8

Somatic - refers to somite derivatives i.e. body wall, skeletal muscles, joints
Visceral - refers to visceral organs, smooth + cardiac muscles, and glands

Question 9

What is special sensory?

Answer 9

Senses: taste(Chorda tympani, CN7), smell(CN1), hearing(CN8), balance(CN8), vision (CN2)

Question 10

What is special motor?

Answer 10

Refers to pharyngeal arch muscular derivatives:
1st: mastication
2nd: facial expression
3rd: Stylopharyngeus muscle
4th+6th: Pharyngeal + laryngeal constrictors

Question 11

How does the olfactory nerve work?

Answer 11

Special visceral sensory - There are olfactory receptor cells within the olfactory epithelium. Odors bind the smell receptors called cilia on the dendrites. When these cells die, there is an olfactory stem cell to replace them. They sit within the olfactory epithelium. The receptor cells’ axons travel through the cribriform plate, synapse on olfactory bulb of brain.

Question 12

What is anosmia and what can it be a sign of?

Answer 12

Anosmia - loss of smell
Sign of developing Alzheimer’s or Parkinsons.

Smell can also decrease with age and nasal pulps (growth along nasal passages)

Question 13

How does the optic nerve work?

Answer 13

Special somatic sensory

• Cell body: Retinal ganglioncells
• Axons: Bundles of GC neurons pass thru optic canal, partial crossing of axons anterior to infundibulum in optic chiasm. Thus, the tract contains axons from opposite visual field

Question 14

What can damage the optic nerve?

Answer 14

Diabetic neuropathy, glaucoma, neuritis from MS, or even an Epstein-Barr Herpes infection causing neuritis and vision loss via autoimmune response

Question 15

How does the oculomotor nerve work?

Answer 15

General somatic motor. CN3 passes thru cavernous sinus and enter eye through superior orbital fissure and CTR. Also has visceral effect to pupillary muscles and ciliary muscles after synapsing in ciliary ganglion

Question 16

How does CN3 damage present?

Answer 16

Eye is turned down and out (only SO and LR are working), ptosis, dilated pupil, blurred vision for near objects (no accommodation)

Question 17

How does the trochlear nerve work?

Answer 17

General somatic motor. CN4 travels in lateral wall of cavernous sinus inferior to CN3. Longest intracranial nerve course

Question 18

How does CN4 damage present?

Answer 18

Person tilts head away from affected side to prevent double vision (since inferior oblique is overworking to extort the eye on other side, and eyes need to be straight up and down)

Question 19

What type of motor innervation does trigeminal give?

Answer 19

Special motor (probably somatic)

Question 20

What is trigeminal neuralgia?

Answer 20

Tic douloureux - Stabbing pain caused by neurovascular compression

Question 21

How does trigeminal nerve affect sensation to the eye?

Answer 21

Loss of corneal reflex when touched - important when protecting eyes. Sensation provided by long and short ciliary nerves

Question 22

What is the only nerve that goes directly through the cavernous sinus and not the lateral wall?

Answer 22

Abducent nerve

Question 23

What can damage to the vestibular nerve cause?

Answer 23

Nystagmus, vertigo

Question 24

What can damage to the cochlear nerve cause?

Answer 24

Hearing loss and tinnitus

Question 25

What sensations does CN9 innervate?

Answer 25

Posterior 1/3 of tongue taste and sensation, visceral sensory from sinus nerve, upper pharynx and palatine tonsils for gag reflex

Question 26

What is the course of CN9?

Answer 26

Has rostral and petrosal ganglion in brain, exits thru jugular foramen after giving tympanic branch for autonomics and middle ear sensation. Passes posteromedial to styloid process to innervate stylopharyngeus

Question 27

What can damage to CN9 cause?

Answer 27

Sudden pain that begins in throat, radiates down side of neck in front of ear.
Lesion often happens at jugular foramen.

Question 28

What are the major branches of the vagus nerve at this level?

Answer 28

1. Auricular branch - to auricle
2. Pharyngeal branch - enters superior border of middle constrictor, innervates all soft palate muscles and pharynx muscles (minus stylopharyngeus and tensor veli palatini).
3. Superior laryngeal
4. Recurrent laryngeal

Also carries taste from epiglottis!!

Question 29

Where are the cell bodies of the accessory nerve? What does it do? How does it travel?

Answer 29

C1-C5. Innervates SCM + Trapezius

Enters thru foramen magnum and exits thru jugular foramen

Question 30

Where does the hypoglossal nerve travel?

Answer 30

Through the hypoglossal canal, across the internal and external carotid, then deep to the mylohyoid and superficial to hyoglossus

Question 31

What happens what you have damage to CN12?

Answer 31

Small involuntary muscle contractions or twitch initially (fasciculation) and then paralysis and atrophy. Sticking out tongue will curl it towards the lesion side