Flashcards in Cranial Nerves (Motor) Deck (56):
Name and Location of Motor Nuclei for the Trigeminal Nerve.
Motor Nucleus V
(mid pons level)
Name and Location of Motor Nuclei for the Facial Nerve.
(mid pons level)
What do the facial nucleus axons create on the floor of the 4th ventricle?
Facial Colliculus (bulge)
Name and Location of Motor Nuclei for the Glossophayngeal Nerve.
(near junction of pons and lateral medulla)
What is interesting about the motor fibers of X?
some fibers go through proximal portion of CN XI before rejoining the CN X
Name and Location of Motor Nuclei for the Vagus Nerve.
(near junction of pons and lateral medulla)
Name and Location of Motor Nuclei for the Accessory Nerve.
Spinal Accessory Nucleus
(Intermediolateral gray area between dorsal and ventral roots of C1-C5)→
How do the fibers of the Accessory enter the calvarium?
Ascend in the spinal cord and enter through the foramen magnum
Name and Location of Motor Nuclei for the Hypoglossal Nerve.
(near midline in mid to posterior medulla)
Brainstem exit of CN V.
Middle of anterior pons
Brainstem exit of CN VII.
Cerebellopontine Angle: after passing dorsal medially and looping over abducens nucleus
Brainstem exit of CN IX.
Junction between pons and medulla
Brainstem Exit of X.
Between interior olive and inferior cerebellar peduncle
Brainstem exit of XI.
Lower medulla and upper spinal cord.
Brainstem exit of XII.
Ventrally between the inferior olive and the pyramid
Calvaria exit of CN V.
V3 exits the foramen ovale
Calvaria exit of CN VII.
Auditory canal→ facial canal→ exit via stylomastoid foramen
Calvaria exit of CN IX.
Calvaria exit of CN X.
Calvaria exit of CN XI.
Calvaria exit of CN XII.
Hypoglossal foramen (posterior aspect of petrous temporal bone)
Motor Targets of CN V
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
Motor Targets of CN VII
Muscles of facial expression
Stapedius muscle- dampens sound
Motor Target of CN IX
Stylopharyngeus muscle- raise pharynx when talking or swallowing
Motor Targets of CN X
Pharyngeal and Palate Muscle- swallow, gagging
Laryngeal Muscle- voice
Motor Targets of CN XI
SCM- head turning in opposite direction
Trapezius- elevation of shoulders
Motor Targets of CN XII
Intrinsic tongue muscles
Location of the GVE nucleus for Nervus Intermedius (CN VII)
(near midline of the rostral medulla)
Location of the GVE nucleus for CN IX
(mid-portion of pons)
Location of the GVE nucleus for CN X
Dorsal Motor Nucleus of X
(near midline of the medulla)
Parasympathetic Target for the Nervus Intermedius (CN VII)
Sphenopalatine and Submandibular ganglia → Lacrimal and all salivary glands except parotid
Parasympathetic Target for CN IX
Lesser petrosal nerve→ Otic Ganglion→ Parotid Gland
Parasympathetic Target for CN X
Intermural ganglia → Heart (slow HR), lung, and GI tract (increase digestion)
What type of lesion causes unilateral weakness of jaw closure, reduced jaw jerk, and atrophy of the temporalis and masseter muscles? What nerve?
unilateral LMN lesion of CN V or its nucleus
Why do unilateral UMN lesions to CN V not cause the symptoms that LMN lesions do?
UMN input to trigeminal motor nuclei is largely bilateral
What type of lesion (commonly caused by a stroke) results in weakness of contralateral lower facial muscles (spares forehead)?
unilateral UMN lesion to CN VII
Why do UMN lesions of CN VII spare the forehead?
UMN input to CN VII is largely bilateral for forehead muscles but unilateral for lower face
What type of lesion may produce some dysphagia (difficulty swallowing)?
unilateral UMN lesion to CN IX
In what type of CN XII lesion does the tongue deviate away from the lesion?
unilateral UMN lesion
Why do UMN CN XII lesions cause the tongue to point away from the lesion?
Corticobulbar fibers from motor cortex cross over to control contralateral genioglossus (others get bilateral innervation)
What type of lesion causes ipsilateral weakness of lower face and forehead muscles + possible ipsilateral hyperacusis and dry eye?
unilateral LMN lesion of CN VII or its nucleus
What is a common cause of LMN lesions to CN VII?
What type of lesion causes weakness of contralateral shoulder elevation and weakness of ipsilateral SCM muscle (turning head away from lesion)?
unilateral UMN lesion of CN XI
Why do UMN lesions to CN XI affect the trapezius and SCM of different sides?
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
What type of lesion causes hoarseness, dysphagia, inability to elevate palate on ipsilateral side as well as a reduced gag reflex?
unilateral LMN lesion to CN X or its nucleus
Why do UMN lesions to CN X not cause the same symptoms as LMN lesions?
Substantial bilateral upper motor neuron innervation of CN X nuclei
What would you expect to see with a unilateral LMN lesion to CN XI?
Weakness and atrophy of both muscles ipsilateral to lesion—weakness elevating the shoulder and turning head away from lesion side.
What would you expect to see with a unilateral LMN lesion to CN XII?
Tongue protrusion towards the side of the lesion, unilateral atrophy and fasciculations
How do you test for CN V?
Test by having patient bite down on tongue depressor and test jaw strength; palpate masseter and temporalis bilaterally.
What does the "jaw jerk reflex" test for?
assess function of motor nucleus of V and mesencephalic nucleus as well as the third branch of the trigeminal nerve (mandibular) carrying the fibers
What is the "jaw jerk reflex"?
•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
How do you test for CN VII?
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.
How do you test for CN IX and X?
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
After synapsing in the nucleus solitarius, where do the secondary neurons from the Gag Reflex go?
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
How do you test for CN XI?
Test by getting patient to raise shoulder and look in opposite directions bilaterally.