15 Motor Cranial Nerves

Question 1

Where does CN V exit the brainstem?

Answer 1

mid pons level

Question 2

Where does CN V3 exit the calvarium?

Answer 2

via the foramen ovale

Question 3

In what nucleus do the muscle spindle nuerons excited by a jaw jerk reflex synapse in?

Answer 3

mesencephalic nucleus of CN V. Then an interneuron connects it to motor nucleus of V to send an impulse to contract masseter

Question 4

Is UMN input to trigeminal motor nuclei ipsilaters, contralaterl, or bilateral?

Answer 4

bilateral. Unilateral UMN lesions do not produce unilateral weakness. Jaw jerk may be increased.

Question 5

What would a LMN lesion of CN V or nuclei present as?

Answer 5

unilateral weakness of jaw closure, reduced jaw jerk, atrophy of masseter

Question 6

Where does CN VII exit brainstem?

Answer 6

pontomedullary junction (cerebellopontine angle)

Question 7

Where does CN VII exit calvarium?

Answer 7

exits via auditory canal, then bends into facial canal and exits skull through stylomastoid foramen

Question 8

What CN innvervates the superior salivatory nucleus?

Answer 8

CN VII

Question 9

Is UMN input to CN VII ipsilateral, contralateral, or bilateral?

Answer 9

Largely bilateral for forhead muscles, BUT unilateral for muscles of lower face (contralaterally).

UMN lesion will spare forehead muscles due to bilaterallity, and cause contralateral lower face weakness

Question 10

How will a LMN lesion of CN VII present?

Answer 10

ipsilateral weakness of lower face AND forehead along with dry eye and hyperacusis (commonly due to Bell’s palsy). Test corneal reflex by storking cornea

Question 11

What will stroking the cornea test?

Answer 11

corneal close reflex by CN VII

Question 12

What CN innervates stylopharyngeus muscle? Where is the motor nucleus located?

Answer 12

CN IX (glossopharyngeal) and its motor component is in the nucleus ambiguus near the pontomedularry junction

Question 13

What CN do parasympathetic fibers from the inferior salivatory nucleus run through?

Answer 13

CN IX to the lesser petrosal nerve to synapse in otic ganglion and innvervate parotid gland

Question 14

Where does CN IX exit the brainstem?

Answer 14

near pontomedullary junction

Question 15

Where does glossopharyngeal nerve exit the calvarium?

Answer 15

via jugular foramen

Question 16

Which CN innervates parotid gland?

Answer 16

CN IX

Question 17

What is motor component of CNX, that innervates muscles of soft palate, pharynx and larynx, served by?

Answer 17

nucleus ambiguus

Question 18

What nucleus sends preganglionic, parasympathetic fibers to the intramural ganglia of heart, lung and digestive tract? Where is it located

Answer 18

dorsal motor nucleus of vagus near the midline of medulla

Question 19

What CN exits the the brainstem as a series of rootlets between inferior olive and inferior cerebellar peduncle?

Answer 19

CN X

Question 20

Where does CN X exit the calvarium?

Answer 20

jugular foramen

Question 21

What CN serves as the dominant efferent component of gag reflex?

Answer 21

CN X. CN IX is mostly afferent componenet

Question 22

How will a CN X LMN or nucleus ambiguous lesion present?

Answer 22

ipsilateral inability to elevate palate, dysphagia and hoarsensess

Question 23

How will a UMN CN X lesion present?

Answer 23

hardly at all since UMN innervation of X is largely bilateral

Question 24

How would a lesion of dorsal motor nucleus of vagus present?

Answer 24

loss of parasympathetics to heart, lungs and GI.

tachycardia, GI immotility

Question 25

Where do motor axons for CN XI originate from?

Answer 25

caudal portion of nucleus ambiguus and spinal accessory nucleus

Question 26

Through what foramina of the calvarium does CN XI pass?

Answer 26

enters calvarium through foramen magnum, exits through jugular foramen

Question 27

How will a LMN lesion of CN XI present?

Answer 27

ipsilateral weakness of BOTH trapezius and sternocleidomastoid. Weakness elevating ipsilateral shoulder and turning head away from lesion

Question 28

How will a UMN lesion of CN XI present?

Answer 28

weakness of contralateral shoulder elevation and ipsilateral SCM. –> weakness elevating contralatereral shoulder and turnign head away from lesion.

Question 29

Where does CN XII exit calvarium?

Answer 29

hypoglossal foramen

Question 30

Which direction will contration of left tongue muslces push tongue out of mouth?

Answer 30

left tongue muscle contraction pushes tongue out to right

Question 31

How will a LMN CN XII lesion present?

Answer 31

ipsilateral weakenss of tongue muslces, so tongue will protrude to ipsilateral side (lick the wound)

Question 32

How will a UMN lesion of CN XII present?

Answer 32

UMN corticobulbar fibers from motor cortex cross over to control contralateral CN XII motor nuclei. UMN lesions cause tongue to deviate away from lesion