ICL 6.4: Anatomical and Clinical Pearls of Cranial Nerves VIII, IX, X,XI & XII Flashcards
how does CN 9 exit the skull?
CN 9 exits the medulla and passes via the jugular foramen
the jugular foramen is also the location of its ganglia (superior and inferior)
what is the name of CN 9?
glossopharyngeal nerve
what are the components of CN 9?
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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what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVE fibers of CN 9?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVE fibers of CN 9?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GSA fibers of CN 9?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVA fibers of CN 9?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVA fibers of CN 9?
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
what is the gag reflex pathway?
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
what are the 3 sources that the afferent fibers carried in the glossopharyngeal nerve arise from?
- 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
- 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
- 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
what are the nuclei associated with CN 8?
CN 8 = vestibulocochlear nerve
vestibular nuclei fibers go to the saccule
cochlear nuclei fibers go to the cochlea
what are the components of CN 10?
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
what is the name of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVE fibers of CN 10?
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)
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVE fibers of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GSA fibers of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVA fibers of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVE fibers of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVE fibers of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GSA fibers of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the GVA fibers of CN 10?
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
what is the function, nucleus of origin, ganglion, foramen and signs of disfunction associated with the SVA fibers of CN 10?
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
what are the branches that the vagus nerve gives off?
- superior laryngeal nerve (branches into internal and external laryngeal)
- recurrent laryngeal nerve (becomes the inferior laryngeal nerve)
what is the pharyngeal plexus?
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)
what is the pathway of CN 11?
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which muscles are innervated by CN 11?
- sternocleidomastoid
2. trapezius
where do the cranial parts of CN 11 originate from?
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
where do the cranial parts of CN 11 originate from?
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
what deficits would you see if there’s a problem with CN 11?
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
what deficits would you see if there’s a problem with CN 11?
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
what is the name of CN 12?
hypoglossal nerve
where is the hypoglossal nuclei found?
in the dorsal medulla
what would happen if there is an UMN lesion involving CN 12?
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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what is the pathway of CN 12?
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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