Cranial Nerves (Motor)

Question 1

Name and Location of Motor Nuclei for the Trigeminal Nerve.

Answer 1

Motor Nucleus V

mid pons level

Question 2

Name and Location of Motor Nuclei for the Facial Nerve.

Answer 2

Facial Nucleus

mid pons level

Question 3

What do the facial nucleus axons create on the floor of the 4th ventricle?

Answer 3

Facial Colliculus (bulge)

Question 4

Name and Location of Motor Nuclei for the Glossophayngeal Nerve.

Answer 4

Nucleus Ambiguus

near junction of pons and lateral medulla

Question 5

What is interesting about the motor fibers of X?

Answer 5

some fibers go through proximal portion of CN XI before rejoining the CN X

Question 6

Name and Location of Motor Nuclei for the Vagus Nerve.

Answer 6

Nucleus Ambiguus

near junction of pons and lateral medulla

Question 7

Name and Location of Motor Nuclei for the Accessory Nerve.

Answer 7

Spinal Accessory Nucleus

(Intermediolateral gray area between dorsal and ventral roots of C1-C5)→

Question 8

How do the fibers of the Accessory enter the calvarium?

Answer 8

Ascend in the spinal cord and enter through the foramen magnum

Question 9

Name and Location of Motor Nuclei for the Hypoglossal Nerve.

Answer 9

Hypoglossal Nucleus

near midline in mid to posterior medulla

Question 10

Brainstem exit of CN V.

Answer 10

Middle of anterior pons

Question 11

Brainstem exit of CN VII.

Answer 11

Cerebellopontine Angle: after passing dorsal medially and looping over abducens nucleus

Question 12

Brainstem exit of CN IX.

Answer 12

Junction between pons and medulla

Question 13

Brainstem Exit of X.

Answer 13

Between interior olive and inferior cerebellar peduncle

Question 14

Brainstem exit of XI.

Answer 14

Lower medulla and upper spinal cord.

Question 15

Brainstem exit of XII.

Answer 15

Ventrally between the inferior olive and the pyramid

Question 16

Calvaria exit of CN V.

Answer 16

V3 exits the foramen ovale

Question 17

Calvaria exit of CN VII.

Answer 17

Auditory canal→ facial canal→ exit via stylomastoid foramen

Question 18

Calvaria exit of CN IX.

Answer 18

Jugular foramen

Question 19

Calvaria exit of CN X.

Answer 19

Jugular Foramen

Question 20

Calvaria exit of CN XI.

Answer 20

Jugular Foramen

Question 21

Calvaria exit of CN XII.

Answer 21

Hypoglossal foramen (posterior aspect of petrous temporal bone)

Question 22

Motor Targets of CN V

Answer 22

Masseter and Temporalis- muscles of mastication
Tensor tympani muscle- dampens sound
Tensor Veli Palatini- opens eustacian tube
Mylohyoid- elevates hyoid bone
Anterior Belly of Digastric- elevates hyoid bone

Question 23

Motor Targets of CN VII

Answer 23

Muscles of facial expression

Stapedius muscle- dampens sound

Question 24

Motor Target of CN IX

Answer 24

Stylopharyngeus muscle- raise pharynx when talking or swallowing

Question 25

Motor Targets of CN X

Answer 25

Pharyngeal and Palate Muscle- swallow, gagging | Laryngeal Muscle- voice

Question 26

Motor Targets of CN XI

Answer 26

SCM- head turning in opposite direction | Trapezius- elevation of shoulders

Question 27

Motor Targets of CN XII

Answer 27

Intrinsic tongue muscles

Question 28

Location of the GVE nucleus for Nervus Intermedius (CN VII)

Answer 28

Superior Salivatory | near midline of the rostral medulla

Question 29

Location of the GVE nucleus for CN IX

Answer 29

Inferior Salivatory | mid-portion of pons

Question 30

Location of the GVE nucleus for CN X

Answer 30

Dorsal Motor Nucleus of X | near midline of the medulla

Question 31

Parasympathetic Target for the Nervus Intermedius (CN VII)

Answer 31

Sphenopalatine and Submandibular ganglia → Lacrimal and all salivary glands except parotid

Question 32

Parasympathetic Target for CN IX

Answer 32

Lesser petrosal nerve→ Otic Ganglion→ Parotid Gland

Question 33

Parasympathetic Target for CN X

Answer 33

Intermural ganglia → Heart (slow HR), lung, and GI tract (increase digestion)

Question 34

What type of lesion causes unilateral weakness of jaw closure, reduced jaw jerk, and atrophy of the temporalis and masseter muscles? What nerve?

Answer 34

unilateral LMN lesion of CN V or its nucleus

Question 35

Why do unilateral UMN lesions to CN V not cause the symptoms that LMN lesions do?

Answer 35

UMN input to trigeminal motor nuclei is largely bilateral

Question 36

What type of lesion (commonly caused by a stroke) results in weakness of contralateral lower facial muscles (spares forehead)?

Answer 36

unilateral UMN lesion to CN VII

Question 37

Why do UMN lesions of CN VII spare the forehead?

Answer 37

UMN input to CN VII is largely bilateral for forehead muscles but unilateral for lower face

Question 38

What type of lesion may produce some dysphagia (difficulty swallowing)?

Answer 38

unilateral UMN lesion to CN IX

Question 39

In what type of CN XII lesion does the tongue deviate away from the lesion?

Answer 39

unilateral UMN lesion

Question 40

Why do UMN CN XII lesions cause the tongue to point away from the lesion?

Answer 40

Corticobulbar fibers from motor cortex cross over to control contralateral genioglossus (others get bilateral innervation)

Question 41

What type of lesion causes ipsilateral weakness of lower face and forehead muscles + possible ipsilateral hyperacusis and dry eye?

Answer 41

unilateral LMN lesion of CN VII or its nucleus

Question 42

What is a common cause of LMN lesions to CN VII?

Answer 42

Bell's Palsy

Question 43

What type of lesion causes weakness of contralateral shoulder elevation and weakness of ipsilateral SCM muscle (turning head away from lesion)?

Answer 43

unilateral UMN lesion of CN XI

Question 44

Why do UMN lesions to CN XI affect the trapezius and SCM of different sides?

Answer 44

UMNs for the SCM descend ipsilaterally to the spinal accessory nucleus while the UMNs for the trapezius muscle cross the midline in the pyramidal decussation to synapse in the contralateral spinal accessory nucleus

Question 45

What type of lesion causes hoarseness, dysphagia, inability to elevate palate on ipsilateral side as well as a reduced gag reflex?

Answer 45

unilateral LMN lesion to CN X or its nucleus

Question 46

Why do UMN lesions to CN X not cause the same symptoms as LMN lesions?

Answer 46

Substantial bilateral upper motor neuron innervation of CN X nuclei

Question 47

What would you expect to see with a unilateral LMN lesion to CN XI?

Answer 47

Weakness and atrophy of both muscles ipsilateral to lesion—weakness elevating the shoulder and turning head away from lesion side.

Question 48

What would you expect to see with a unilateral LMN lesion to CN XII?

Answer 48

Tongue protrusion towards the side of the lesion, unilateral atrophy and fasciculations

Question 49

How do you test for CN V?

Answer 49

Test by having patient bite down on tongue depressor and test jaw strength; palpate masseter and temporalis bilaterally.

Question 50

What does the "jaw jerk reflex" test for?

Answer 50

assess function of motor nucleus of V and mesencephalic nucleus as well as the third branch of the trigeminal nerve (mandibular) carrying the fibers

Question 51

What is the "jaw jerk reflex"?

Answer 51

* Chin tapped (stimulate proprioceptors) * Project to mesencephalic nucleus and synapse * Fibers leave as interneuron and synapse on motor nucleus of V * Motors fibers occlude jaw (masseter contracts

Question 52

How do you test for CN VII?

Answer 52

Test by having patient wrinkle forehead, close eyes tightly, and show you their teeth. Look for symmetric furrowing of forehead, ability to symmetrically close eyes, and symmetric retraction of the corners of the mouth.

Question 53

How do you test for CN IX and X?

Answer 53

Integrity tested via the gag reflex ( IX carries afferent/sensory arm of the reflex but shares efferent part of the reflex with CN X). Stimulate reflex by gently touching posterior pharynx on left and right side separately and watching for the motor, or gag response and elevation of soft palate

Question 54

After synapsing in the nucleus solitarius, where do the secondary neurons from the Gag Reflex go?

Answer 54

secondary fibers project to the nucleus ambiguous where they synapse so that visceral efferents (traveling with the vagus nerve) can reach the pharynx and mediate the gag reflex

Question 55

How do you test for CN XI?

Answer 55

Test by getting patient to raise shoulder and look in opposite directions bilaterally.

Question 56

How do you test for CN XII?

Answer 56

Test by getting patient to stick tongue out (make sure it is sticking straight out at midline)