ICL 6.4: Anatomical and Clinical Pearls of Cranial Nerves VIII, IX, X,XI & XII

Question 1

how does CN 9 exit the skull?

Answer 1

CN 9 exits the medulla and passes via the jugular foramen

the jugular foramen is also the location of its ganglia (superior and inferior)

Question 2

what is the name of CN 9?

Answer 2

glossopharyngeal nerve

Question 3

what are the components of CN 9?

Answer 3

SVE

GVE

GSA

GVA

SVA

so the glossopharyngeal nerve comes from multiple nuclei in the brainstem and collectively they form the glossopharyngeal nerve! there’s 5 fiber types conveying different information whether that be efferent or afferent

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Question 4

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVE fibers of CN 9?

Answer 4

SVE fibers of CN 9 provide motor function to the stylopharyngeus muscle

the efferent motor fibers originate from the nucleus ambiguus and are not associated with any ganglion

the fibers pass through the jugular foramen and there are no clinically significant signs of disfunction

Question 5

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVE fibers of CN 9?

Answer 5

the GVE fibers of CN 9 provide parasympathetic fibers to the parotid gland so that’s able to secrete fluid

these fibers originate from the inferior salivatory nucleus and associated with the otic ganglion

the fibers pass through the jugular foramen

signs of disfunction associated with the GVEs of CN 9 would be decreased salivation

Question 6

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GSA fibers of CN 9?

Answer 6

the GSAs of CN 9 convey sensation from the back of the ear

the fibers synapse in the spinal nucleus of CN V and pass through the superior ganglion

the fibers pass through the jugular foramen

signs of dysfunction associated with the GSA fibers of CN 9 would be decreased sensation in the back of the ear

Question 7

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVA fibers of CN 9?

Answer 7

the GVA fibers of CN 9 convey sensation from the pharynx, tongue and carotid receptors and synapse in the nucleus solitarius after synapsing in the inferior ganglion

signs of dysfunction associated with the GVA fibers of the glossopharyngeal nerve would be decreased gag reflex

Question 8

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVA fibers of CN 9?

Answer 8

the SVA fibers of CN 9 convey taste from the posterior 1/3 of the tongue and they synapse in the nucleus solitarius

the fibers are associated with the inferior petrosal ganglion and pass through the jugular foramen

signs of dysfunction associated with the SVA fibers of the glossopharyngeal nerve would be decreased taste

Question 9

what is the gag reflex pathway?

Answer 9

you’re activating the general sensory receptors in the pharyngeal wall that then send information back to the brainstem where it is going to connect with other nuclei right next door through internuclei

they first synapse in the spinal trigeminal nucleus and then the interneurons are going to synapse with the nucleus ambiguous which is a motor nucleus which goes and constricts the pharynx –> so the general sensory information coming in from CN 9 is then passed to the nucleus ambiguous which constricts the pharynx via CN 10

so CN 9 and 10 work together to create the gag reflex

Question 10

what are the 3 sources that the afferent fibers carried in the glossopharyngeal nerve arise from?

Answer 10

1. general somatic afferent fibers (GSA) carrying sensation from behind the ear have cell bodies in the superior ganglion; their central processes terminate in the spinal nucleus of the trigeminal nerve
2. general visceral afferent (GVA) fibers carry sensation from the pharynx and information from the carotid body baroreceptors and synapse in the nucleus solitarius after passing through the inferior ganglion
3. special visceral afferent fibers (SVA) carry taste sensation from the posterior tongue and synapse in the nucleus solitarius after passing through the inferior ganglion

2 and 3 arise from cell bodies in the inferior (petrosal) ganglion and have central processes that terminate in the nucleus solitarius

Question 11

what are the nuclei associated with CN 8?

Answer 11

CN 8 = vestibulocochlear nerve

vestibular nuclei fibers go to the saccule

cochlear nuclei fibers go to the cochlea

Question 12

what are the components of CN 10?

Answer 12

SVE

GVE

GSA

GVA

SVA

so there are a number of nuclei which are associated with building the vagus nerve just like the hypo pharyngeal nerve

Question 13

what is the name of CN 10?

Answer 13

vagus nerve

the vagus is the most posterior structure in the carotid sheath in the neck which is important because if they have to do an arterial line, they have to know where the vagus is

Question 14

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVE fibers of CN 10?

Answer 14

The SVE fibers of the vagus nerve provide motor function to the muscles of the soft palate, pharynx and larynx

The fibers originate from the nucleus ambiguus and do not pass through any ganglion — they do pass through the jugular foramen

Signs of dysfunction of the SVE fibers include hoarseness, dysphasia and decreased gag reflex (CN 9 glossopharyngeal nerve provides sensation to the pharynx but CN 10 vagus nerve is actually causes the muscles to move and produce a gag)

Question 15

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVE fibers of CN 10?

Answer 15

The GVE fibers of the vagus nerve provide parasympathetic innervation to the thoracic and abdominal viscera

They originate from the dorsal motor nucleus of CN X and do not have an associated ganglion — they do pass through the jugular foramen

Signs of dysfunction of the GVE fibers would be visceral disturbance and tachycardia

Question 16

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GSA fibers of CN 10?

Answer 16

The GSA fibers of the vagus nerve convey sensation from the external auditory meatus

They terminate in the spinal nucleus of CN V after passing through the superior/jugular ganglion and the jugular foramen

Dysfunction of the GSA fibers would cause decreased sensation in the external auditory meatus

Question 17

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVA fibers of CN 10?

Answer 17

The GVA fibers of the vagus nerve convey sensation from the pharynx, larynx, and the thoracic and abdominal viscera

The fibers terminate in the nucleus solitarius after passing through the inferior/nodose ganglion and the jugular foramen

Dysfunction of the GVA fibers would cause decreased sensation of the pharynx

Question 18

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVE fibers of CN 10?

Answer 18

the special visceral efferent fibers of the vagus nerve provide motor innervation to the muscles of the soft palate, pharynx and larynx and originate from the nucleus ambiguus

there is no associated ganglion and the fibers pass through the jugular foramen

signs of dysfunction associated with the SVEs of CN 10 would be hoarseness dysphagia and decreased gag reflex

Question 19

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVE fibers of CN 10?

Answer 19

the general visceral efferent fibers of the vagus nerve provide parasympathetic innervation to the thoracic and abdominal viscera and originate from the dorsal motor nucleus of CN X

there is no associated ganglion and the fibers pass through jugular foramen

signs of dysfunction associated with the GVEs of CN 10 would be visceral disturbance and tachycardia

Question 20

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GSA fibers of CN 10?

Answer 20

the general somatic afferent neurons of the vagus nerve convey sensation from the external auditory meatus and they synapse in the spinal nucleus of CN V

they pass through the superior jugular ganglion and the jugular foramen

signs of dysfunction associated with the GSA fibers of CN 10 would be decreased sensation in the external auditory meatus

Question 21

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVA fibers of CN 10?

Answer 21

the general visceral afferent fibers of the vagus nerve convey sensation of the pharynx, larynx and thoracic and abdominal viscera

they synapse in the nucleus solitarius and pass through the inferior nodose ganglion and jugular foramen

signs of dysfunction associated with the GVAs of CN 10 would be decreased sensation of the pharynx

Question 22

what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVA fibers of CN 10?

Answer 22

the somatic visceral afferent fibers of the vagus nerve convey taste from the posterior pharynx and synapse in the nucleus solitarius

the pass through the inferior nodose ganglion and the jugular formanen

signs of disfunction associated with the SVA fibers of CN X are not clinically significant

Question 23

what are the branches that the vagus nerve gives off?

Answer 23

1. superior laryngeal nerve (branches into internal and external laryngeal)
2. recurrent laryngeal nerve (becomes the inferior laryngeal nerve)

Question 24

what is the pharyngeal plexus?

Answer 24

a branch of the vagus nerve that is given off after the vagus nerve enters the carotid sheath

it provides motor function to the muscles of the pharynx and the soft palate EXCEPT the stylopharyngeus (CN IX) and tensor vela palatini (V3)

Question 25

what is the pathway of CN 11?

Answer 25

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Question 26

which muscles are innervated by CN 11?

Answer 26

1. sternocleidomastoid

2. trapezius

Question 27

where do the cranial parts of CN 11 originate from?

Answer 27

CN XI arises mainly from cell bodies in the ventral gray horn of the upper 5 cervical cord segments

the nerve ascends in the spinal canal enters the skull through the foramen magnum, where it is joined by the minor accessory component that originates in the nucleus ambiguous (CRANIAL PART), and leaves the cranial cavity through the jugular foramen to innervate the sternocleidomastoid and trapezius muscles

Question 28

where do the cranial parts of CN 11 originate from?

Answer 28

CN XI arises mainly from cell bodies in the ventral gray horn of the upper 5 cervical cord segments

the nerve ascends in the spinal canal enters the skull through the foramen magnum, where it is joined by the minor accessory component that originates in the nucleus ambiguous (CRANIAL PART), and leaves the cranial cavity through the jugular foramen to innervate the sternocleidomastoid and trapezius muscles

Question 29

what deficits would you see if there’s a problem with CN 11?

Answer 29

CN 11 may be compressed by lesions in the region of the foramen magnum or in the region of the jugular foramen

signs of dysfunction include weakness of head rotation (sternocleidomastoid muscle) and inability to elevate or shrug the shoulder (trapezius muscle) on the side of the lesion (ipsilaterally)

the sternocleidomastoid muscle rotates the face to the opposite side so that damage to the accessory nerve results in weakness in turning the head away from the side of the lesion

Question 30

what deficits would you see if there’s a problem with CN 11?

Answer 30

CN 11 may be compressed by lesions in the region of the foramen magnum or in the region of the jugular foramen

signs of dysfunction include weakness of head rotation (sternocleidomastoid muscle) and inability to elevate or shrug the shoulder (trapezius muscle) on the side of the lesion (ipsilaterally)

the sternocleidomastoid muscle rotates the face to the opposite side so that damage to the accessory nerve results in weakness in turning the head away from the side of the lesion

Question 31

what is the name of CN 12?

Answer 31

hypoglossal nerve

Question 32

where is the hypoglossal nuclei found?

Answer 32

in the dorsal medulla

Question 33

what would happen if there is an UMN lesion involving CN 12?

Answer 33

the corticobulbar input to the Hypoglossal Nucleus is primarily crossed –> so similar to the facial nucleus, the input is crossed; it synapses on the contralateral hypoglossal nucleus! this is what helps you differentiate between an upper vs. lower motor neuron lesion

so when you have a unilateral lesion high up in an UMN, if you ask someone to stick out their tongue the tongue will stick out to the opposite direction that the lesion is on –> the tongue will deviate to the side contralateral to the lesion

if a patient has a lower motor neuron lesion so if effects the hypoglossal nucleus or the fascicle coming out of the nucleus, you will see atrophy of the muscle tissue, fasiculations and the tongue will deviate to the same side as the lesion

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Question 34

what is the pathway of CN 12?

Answer 34

the hypoglossal nucleus is located in the paramedian area of the caudal medulla in the floor of the fourth ventricle

fibers course ventrally and exit from the ventral aspect of the medulla, between the medullary pyramids and the olive.

after exiting from the brainstem, the fibers pass through the hypoglossal canal in the occipital condyle and innervate the striated muscles of the tongue

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